What happened in physics this week. LHC first beams, nuclear dating leads to weddings, holes blocking light, quark news, muon colliders, and more.

Beam 1 circulated for several minutes and before that we were able to take a a few splash events.  Then after they managed to circulate Beam 2 and they are ready to capture it…

The BBC was here for most of the Beam 2 episode.

-Edgar Carrera (Boston University)

These are really different times and so exciting! I am sitting at home in Hamburg, actually supposed to work on a talk. But I am constantly staring at the online version of the LHC beam display, any other online feed I could find, and also Pauls comments here on QD. And this is really exciting! Also my husband is asking all the time what the status is and how many turns were done.
You can also follow all the details on Twitter, as anounced earlier today by the DG. Hope you all stay tuned to follow this in the next days, weeks, months and years to come!!

As reported on the CERN twitter, http://twitter.com/CERN, the beam has been captured!!
They are now attempting the second beam.

This is showing a huge amount of faith in this machine. The LHC operators clearly feel that they are ready to start understanding their accelerator, this is confidence boosting and exiting news. I should note at this point that the LHC isn’t strictly accelerating these beams. It is storing the beams and circulating them from the SPS, where the LHC receives injected beam as part of a complex accelerator system.
The SPS can be seen on the previous post where I showed an overview of the LHC ring.

I’m back at my home in France now and can hear several cars all beeping their horns very loudly. I sincerely hope this is related to the great work of the LHC operators.

CERN just issued a press release announcing the first circulating beams of 2009 in the Large Hadron Collider. At 10 o'clock this evening, CERN local time, the first beams circulated for several minutes in the clockwise direction. The LHC operations team is now working to circulate a beam in the counter-clockwise direction.

Full description and pictures from the evenings achievements can be found here

ATLAS event displays and related information from the LHC restart in Nov 2009. We recorded today, Friday Nov 20, the first so-called “Beam Splash” events. For these events the beam in one arm of the LHC was dumped onto closed collimators located 140 meters upstream and downstream of ATLAS. The collision leads to a large number of detectable secondary particles longitudinally traversing the detector.

All displays shown here are produced very shortly after the data were taken, using unprocessed raw events from the ATLAS detector.

These guys are amazing, and they mean business.

Beams being circulated now. This is impressive stuff………

If we capture the beams this will be an amazing achievement in my opinion.

I have few regrets in life, but if there’s one, it’s that I didn’t have access to all this amazing technology when I was a teenager and figuring out just how I was going to tackle my love for astronomy. How I would have loved podcasts, programmable telescopes, CCDs, websites with satellite pass information…

But that’s the way things are now, and lots of people are putting this tech to good use. Like, for example, Sirius Stargazing, a new YouTube channel with info on how to observe various astronomical objects. It’s just starting out but off to a good start. Here’s one video on the Pleiades. And who’s the dork in the tie introducing it?

If you have a YouTube account and are interested in observing the skies, then consider subscribing to Sirius Stargazing. They may just give you ideas.

The first beam of 2009 has passed through ATLAS! Follow the events at http://twitter.com/cern.

I think the CERN twitter update summarizes the current situation better than I can.
http://twitter.com/cern. For those who don’t like clicking on links:
“Beam 1 has made more than 500 turns of the LHC. The beam orbit is improving fast.”

Scientists at CERN are in the process of restarting the Large Hadron Collider at this very moment! Here's a handy guide for following their minute-by-minute progress over the Internet.

When I was a nipper ‘Splash’ was a movie starring a rather lovely looking Daryl Hannah as a mermaid and Tom Hanks as some bloke. Nowadays, splash is what we call events when particle literally splash into the detectors.
So we are pleased to bring you the first splash event of 2009.

This is what data looks like going through ATLAS.
Gorgeous!

The champagne has been released. Beam has been circulated, making 2 turns (the two spots you can see in the picture I showed in my last post). Everyone is happy. There’s phone calls and text messages (it’s an ‘SMS’ in Europe but whatever) and emails being sent around.

The guys operating the LHC deserve a hearty round of applause. This has been smooth and impressive.

Now, the fun, and the real hard work starts.

Beam makes 2 turns!
Need I say more……you can clearly see the points on the plot above. We’re back!!!!

Beautiful!!!

OK, I hope my insisting to post on ATLAS’s progress towards seeing beam isn’t boring you. But like as not, if you’re reading this you’re probably mildly interested. So the scoop is we’re close, very close, and we could be ready for business soon.

Last year there were people trying to explain to every BBC reporter that the beam wasn’t just “slow” but it was being sent around each portion of the ring in turn. So we’re at point 8 now…….and I see an update coming in on this page that reads “Beam to point 1″.
You know what’s at point 1 don’t you: ATLAS!!

Alright, finger’s crossed. Here goes!

Cautious optimism continues. The scene in the ATLAS control room is, shall we say, busier than normal. As you can see from these pictures:

It’s all looking quite positive as I write this. It’s almost 8pm and I couldn’t make it into the control room myself (the last meeting of my day was ongoing until about 7.30pm so I was out of luck) but I’m of the opinion that too many cooks spoil the broth on this one. Plus, I am far from necessary to make the dream a reality at this point. Still, I’m a little jealous of these very excited people. So I am hearing from friends, via text message and facebook updates how things are going in the ACR. It sounds like a good time, but a nervous time, is being had by all.

I’m also keeping track of the beam progress here where we can nicely see that things are progressing smoothly.

A screenshot for those interested is below:

One thing I like very much is to look at the *actual* ATLAS web cams. Not the control room, with all the people milling around, most of whom are pretending to look important in case they get caught on camera yawning. The *actual* detector which you can see here.
There’s a screenshot at the bottom part of the page.

I love looking at these pictures of the detector, because it reminds me of one thing. Nobody is down there. Trust me, I’ve looked. I keep checking these webcams expecting to see some joker who’s trying to get a better view, or making a political statement, but of course that’s not possible, the protection and safety systems simply would not allow it. So while we all look at our screens on the surface, the real action is quite a lonely interaction, between beam and detector. It is that separation, the fact that we can’t really be down there when “it” happens, when anything happens, that is really quite poetic. The fact that one can look side-by-side at these actual shots of the detector, and of the people controlling it is a very interesting thing, and something I’m finding to be an amusing experiment. When some activity occurs in the detector, that is beam related, this counting room will explode into life. People will be cheering, there will be champagne, back slapping, who know, maybe the odd high-five, and all of that good stuff. Might I add, this is very well deserved as some of these people work extremely hard to see such things, and have been waiting for this moment for many many years. However, contrast that with the picture of the detector at that very same moment. She will be a picture of tranquility and calm, almost oblivious to what has gone on; and as people celebrate above her, drinking and cheering, ATLAS will still sit there with a look of, “was that it?” slapped all over her muon chambers.

Aspiring physicist Heidi Baumgartner is certainly destined for physics fame after successfully finding the Higgs boson on October 31, 2009. While the rest of the scientific community toils away building multi-billion dollar machines like the Large Hadron Collider to search for the much coveted Higgs in the wreckage of particle collisions, Baumgartner says she found it quite by accident in New York City's Greenwich Village.

I am the secondary on-call expert for the High Level Trigger system, therefore I am backing up the primary expert at P5.

Everyone is so excited around here.  We are waiting for the beams to reach P5.  They will eventually circulate around the LHC ring and that will allow their alignment, etc.  The monitor that shows the beam status from the LHC machine reads “Injection Probe Beam”.

It is a great feeling to be here, to make history, to contribute a little bit to the improvement of our knowledge, to the improvement of our own humanity.

http://cmsdoc.cern.ch/cms/performance/FirstBeam/cms-e-commentary09.htm (I am the guy typing standing in one of the pics )

Edgar Carrera (Boston University)

09:37 PST: Like many of my colleagues, I’ve been eagerly awaiting word that the LHC has successfully threaded the proton beam around the whole ring. In recent days they have gotten it half way around the 27 km circumference, and within hours, they should be able to circulate it and I assume “capture” it with the RF, which creates stable bunches in the synchrotron. Everything has gone very smoothly to this point, so I expect success shortly!

Once beam has circulated stably in both rings, some time next week the LHC team will attempt to collide protons at the injection energy of 450 GeV (a total center of mass energy of 900 GeV). While this is much less than the Tevatron is colliding presently, it could provide some sorely needed initial data for the detectors to do timing and calibration of the various subsystems. There will even hopefully be a few collision events recorded with clear “dijet” structure – collisions where quarks and/or gluons inside the protons hit head on and effectively bounce sideways into the detector, giving two back-to-back collimated sprays of particles. Pictures of such events will be great to see, at long last!

You can follow progress live on twitter: http://twitter.com/cern and I will update this post as I learn more.

10:32 PST: The LHC has gotten beam around clockwise, to Point 6! Woo hoo!

10:45 PST: Magnet quench – should be recovered soon…

11:25 PST: Beam has reached Point 7!

11:30 PST: Point 8! Next beam will be sent past Point 1 where ATLAS is…

11:39 PST Beam all the way around the ring! WOO HOO!! It’s baaaaaack! The LHC Page 1 display shows that the injection probe beam made it more than once around the machine:

11:54 PST: Next goals: do the same with the counterclockwise beam. Will they attempt RF capture tonight? Trying to find out…

13:11 PST: Turns out (no pun intended) they decided to go for RF capture of the clockwise beam rather than probe counterclockwise. They are up to 10 million turns with the RF on! Fantastic!

13:30 PST: Having captured the beam for several minutes, the LHC will now switch to counterclockwise.

14:53 PST: About to go for a full orbit of the counterclockwise beam…done!! Now to RF capture!

15:30 PST: Counterclockwise beam is RF captured! The LHC is operational…colliding beams within a week? Stay tuned.

News brief from the ATLAS Detector at the LHC:

Dear Colleagues,

ATLAS has recorded successfully the first beam-splash events of 2009. You can admire them at the following sites:

http://atlas.web.cern.ch/Atlas/public/EVTDISPLAY/events.html
https://atlas-live.cern.ch

Keep an eye on these sites, as they will be refreshed regularly.

This very exciting moment and great achievement for the machine and our experiment are the results of the outstanding work of many people !

Kind regards

Fabiola Gianotti

Well done! We look forward to more progress from this re-start.

Zz.

Students at Cambridge voted Newton as the greatest Cambridge student of all time. He was followed closely by Charles Darwin, which isn't a slouch himself in the history of science.

The physicist and mathematician, who went to Trinity College, won 23.6 per cent of the vote in the poll by student newspaper Varsity.

Charles Darwin, who attended Christ's College, came a close second with 20.6 per cent and poet Lord Byron, who was a student at Trinity College, came third with 10.8 per cent.

Zz.

As you can see in the picture I took this morning, it is foggy here at CERN today as we await the first circulating beam of protons in the LHC since last year.  When this will happen exactly is a little foggy as well.  There will probably be protons put into the LHC sometime this evening, so perhaps overnight we will have a circulating beam.

At the ATLAS detector, we are excited for the first beam to ATLAS this year, which will happen first (the way the LHC is configured, the beam has to go almost all the way around the LHC’s ring from where it is injected to get to the ATLAS detector).

The beam will first be made to stop before ATLAS by moving the beam collimator in its way.  This will cause a huge cascade of particles to hit the ATLAS detector (similar to what was done recently at the CMS detector ), and it will be quite useful for us at ATLAS to detect all these particles and check our timing.

After that the collimator is removed and beam will pass through the ATLAS detector, at which point is has just about made one revolution around the LHC.  This will be repeated for the beam going in the other direction around the LHC.  Then in the coming days or weeks we will have two beams of protons in the LHC at the same time…and finally collisions!

I had a lot of time to kill in Philadelphia's International Airport on Sunday (I was changing planes), and I must say that is not a bad airport in which to be in such a situation. I like the city a lot, and so am not surprised that its main airport is to my liking. First of all, who can not like an airport that supplies you with... (you're expecting free wireless, and they had that, sure, but no, I mean)... with... Rocking Chairs!!! I saw some excellent art as well. And lots of displays of various types. I'll share a couple more in a post or two, but look at some of the pieces I snapped pictures of for you. They are done with packing tape! Yes, packing tape. That brown thin stuff you know well... It was part of a series of scenes from noir films, rendered in this way. Very effective indeed, I felt. The series name is "Tape Noir". [...]

I missed out on posting this a couple of days ago but it’s a nice summary of the LHC commissioning status. The key features, as of Wednesday November 18th, are these:
* All 8 LHC Sectors are now under the responsibility of the beam operation group

* All 1572 superconducting circuits have been commissioned and now READY FOR THE FIRST BEAM RUN

* The Hardware Commissioning team wish the Operation Crew a terrific success with the challenging Beam Commissioning.

The eagle-eyed (wanted to try and squeeze EAGLE into this post as a tip-of-the-cap to one of the early ATLAS efforts) among you will have noticed the big words, “READY”, “FOR”, “THE”, “FIRST”, “BEAM” and “RUN”.

The LHC is ready! But wait, we’ve been here before right? Last year? This thing doesn’t work, there are birds with baguettes trying to ruin our fun, and, it gets cold in the winter, and, “Handball!” (do the right thing France), and,
was that Tom Hanks?, and, oh wait you mean you tested it now, and, oh the QPS is functioning well, and, oh, it’s ready.

LHC latest news can be followed here and there is word of beams circulating the machine before the end of the weekend.

Today it’s the turn of ATLAS to experience some beam and I’ll report on that a bit later.
CMS have already recorded “splash” events as you can see from the image here. Let’s hope that by this time next week things are still as positive and upbeat as they are today.

There is a very good review article in the latest issue of Science[1] that compiles all of our experimental and theoretical understanding of light propagation in a medium.

Abstract: It is now possible to exercise a high degree of control over the velocity at which light pulses pass through material media. This velocity, known as the group velocity, can be made to be very different from the speed of light in a vacuum c. Specifically, the group velocity of light can be made much smaller than c, greater than c, or even negative. We present a survey of methods for establishing extreme values of the group velocity, concentrating especially on methods that work in room-temperature solids. We also describe some applications of slow light.

Zz.

[1] R.W. Boyd and D.J. Gauthier, Science v.326, p.1074 (2009).

A mathematician has discovered two entirely new arrangements of rowers in a racing eight in which the rowing forces cancel to make the boat wiggle-free.

They take their rowing seriously at the University of Cambridge. So seriously, in fact, that the university has press-ganged John Barrow at the Center for Mathematical Sciences to study the serious problem of oscillating non-zero transverse moment in racing boats, otherwise known as wiggle.

The placement of the rowers, the "rig" of the boat, obviously has consequences for the motion of the boat. The question is how best to arrange an even number of crew members in a coxless racing boat in a way that minimizes or eliminates wiggle.

The traditional way of rigging a boat places rowers alternately pulling oars on each side of the boat. "The traditional rig appears symmetrical and simple in ways that might tempt you into thinking it is in every sense optimal. However, this is not the case," says Barrow who goes on to show that the balance of forces in this rig as the oars are pulled through the water always produces a wiggle.

But there is an arrangement in which the transverse forces cancel. This rig consists of one rower pulling on the port side of the boat followed by two on the starboard with a final rower on port. In the rowing world, this arrangement is known as the Italian rig because it was discovered by the Moto Guzzi Club team on Lake Como in 1956. The Moto Guzzi crew went on to win gold representing Italy at the Melbourne Olympic Games later that year.

Barrow next considers a crew of eight and identifies four possible rigs that have a zero transverse moment. These are shown above. The interesting thing is that only two of these rigs are known to the racing world. Rig b is called the "bucket," or "Ratzeburg rig," first used by crews training at the famous German rowing club of the same name in the late 1950s.

Rig c is simply the Italian rig repeated twice. It was used by the Italian Eights in the 1950s after their success with the Fours. It's also known as the triple tandem rig.

The other two, rigs a and d, are brand spanking new and don't seem to have ever been discussed. However, rig d is a combination of a zero-moment Italian Four with its mirror image.

Barrow goes on to generalize the idea for any number of crew, proving along the way that only crew numbers divisible by four can be wiggle-free. (Assuming that they are evenly spaced.)

He also goes on to show that unbalanced boats in which there are unequal numbers of oars on each side, can also be wiggle free if the spacing between the rowers can be altered. As an example, he shows how a Three could have a zero transverse moment.

Barrow ends by saying that his work is not intended to revolutionize rowing tactics. That seems overly modest. Clearly, Barrow's paper should be recognized as a master stroke.

What's the betting that that we'll see at least one of the new rigs at the 2012 Olympics in London?

Ref: arxiv.org/abs/0911.3551: Rowing and the Same-Sum Problem Have Their Moments

I wrote recently about a couple of theory groups who claim to have discovered intriguing signals in the gamma-ray data acquired by the Fermi satellite. The Fermi collaboration hastened to trash both these signals, visibly annoyed by pesky theorists meddling in their affairs. Therefore a status update is in order. Then I'll move to realizing the holy mission of yellow blogs, which is spreading wild rumors.

The first of the theorist's claims concerned the gamma-ray excess from the galactic center, allegedly consistent with a 30 GeV dark matter particle annihilating into b-quark pairs. The relevant data are displayed on this plot released recently by Fermi, which shows the gamma-ray spectrum in the seven-by-seven degrees patch around the galactic center. There indeed seems to be an excess in the 2-4 GeV region. However, given the size of the error bars and of the systematic uncertainties, not to mention how badly we understand the astrophysical processes in the galactic center, one can safely say that there is nothing to be excited about for the moment.

The status of the Fermi haze is far less clear. Here is the story so far. In a recent paper, Doug Finkbeiner and collaborators looked into the Fermi gamma-ray data and found an evidence for a population of very energetic electrons and positrons in the center of our galaxy. These electrons would emit gamma rays when colliding with starlight, in the process known as inverse Compton scattering. They would also emit microwave photons via synchrotron radiation, of which hints are present in the WMAP data. The high-energy electrons could plausibly be a sign of dark matter activity, and fit very well with the PAMELA positron excess, although one cannot exclude that they are produced by conventional astrophysical processes. But Fermi argues that there is no haze in their data. During the Fermi Symposium last week the collaboration was chanting anti-haze songs and tarred-and-feathered anyone humming Hazy shade of winter. Interestingly, it seems that each collaboration member has a slightly different reasons for doubts. Some say the haze is just heavy cosmic-ray elements faking gamma-ray photons. Some say the haze does exist but it can be easily explained by tuned-up galactic models without invoking an energetic population of electrons. Some say the haze is LOOP-1 - a nearby supernova remnant that happens to lie roughly in the direction of the galactic center. But none of the above explanations seems to be on a firm footing, and the jury is definitely out. In the worst case, the matter should be clarified by the Planck satellite (already up in the sky) who is going to make more accurate maps of photon emission at lower frequencies that will lead to a better understanding of astrophysical backgrounds.

And now wild rumors... which, let's make it clear, are likely due to daydreaming over-imagination of data-hungry theorists. The rumors concern Fermi's search for subhalos, which is one of the most promising methods of detecting dark matter in the sky. Subhalos are dwarf galaxies orbiting our Milky Way who are made almost entirely of dark matter. Two dozens of subhalos have been discovered so far (by observing small clumps of stars that they host) but simulations predict several hundreds of these objects. The darkest of the discovered subhalos has a mass-to-light ratio larger than a thousand, indicating large concentration of dark matter. Because of that, one expects dark matter particles to efficiently annihilate and emit gamma rays (typically, via final state radiation or inverse Compton scattering of the annihilation products). Although the resulting gamma-ray flux is expected to be smaller than that from the galactic center, the subhalos with its small visible matter content offer a much cleaner environment to search for a signal.

So, Fermi is searching for spatially extended object away from the galactic plane that steadily emit a lot of gamma rays but are not visible in other frequencies. The results based on 10-months data have been presented in this poster. Apparently, they found no less than four candidates at the 5-sigma level!!! However, according to the poster, these candidates do not fit the spectra of three random dark matter models. For this reason, the conclusion of the search is that no subhalos have been detected, even though it is not clear what astrophysical processes could produce the signal they have found.

Well, I bet an average theorist would need fifteen minutes to write down a dark matter model fitting whatever spectrum Fermi has measured. On the other hand, the collaboration must have better reasons, not revealed to us mortals, to ditch the candidates they have found. On yet another hand, the fact that Fermi is not revealing the positions and the measured spectra of these four candidates makes the matter very very intriguing. So, we need to wait for more data. Or for a snitch :-)

You know, other people talk a lot about time, too — it’s not just me. Here’s a great video from Nature, featuring a conversation between David Gross and Itzhak Fouxon about the existence of time. (Via Sarah Kavassalis.) Itzhak plays the role of the starry-eyed young researcher — he opens the video by telling us how he originally went into physics to impress girls, although apparently he has stuck with it for other reasons. Gross, of course, shared a Nobel Prize for asymptotic freedom, and has become one of the most influential string theorists around. David plays the role of the avuncular elder statesman (I’ve seen him be somewhat more acerbic in his criticisms) — but he’s one of the smartest people in physics, and his admonitions are well worth listening to. He gives some practical advice, but also advises young people to think big.

Unfortunately the video doesn’t seem to be embeddable, but you can go to the video page and click on the “David Gross” entry. (The others are good, too!)

You all know my perspective here — time probably exists, and we should try to understand it rather than replace it. But I’ll agree with David — let’s not ignore more “practical” problems, but not be afraid to tackle the big ideas!

You know what "galaxy" means in Latin Greek, don’t you?

Yeah, it’s Saturn, not the Milky Way, but still. That is made of awesome. I want to go to that coffee shop!

Via Reddit.

It happens in the best families, so they say. Two experiments work 24/7 to produce an improved result on the Higgs search, and the result is disappointing, to say the least.

I am talking about the Tevatron, of course. For a little while longer, CDF and D0 will have the exclusive on Higgs boson searches. Last March, we all rejoyced when we saw that the Tevatron was starting to become sensitive to a high-mass Higgs, and indeed it excluded its existence in a range of masses between 160 and 170 GeV. We were waiting for more exclusions for the winter conferences of 2010, when more data would be used to produce improved results. Instead, no improvement, but actually, a retractatio. How is that possible ??

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As you may know from earlier posts, I love markets, a place where people come together with lots to see, talk about, interact over, and of course to taste. Community. One of my favourite things. Here's a lovely stall at Granville Island in Vancouver when I was there briefly a short while ago. (Click for larger view.) I can't resist showing you this display: (Click for larger view.) [...]

At this week’s Hadron Collider Physics Symposium, the CDF and D0 experiments at the Tevatron announced their newest results on the search for a standard-model Higgs boson.  You can find documentation from the two experiments here, and this is what the “money plot” looks like:

The mass range 163-166 GeV is excluded at 95% confidence level.  Now, for comparison, here is what this plot looked like in March:

At that time, the exclusion range was stated as 160-170 GeV.  More data, but the excluded range got smaller?  Indeed so.  However, the real figure of merit for the reach of the search is indicated by the dotted line on both plots, which indicates how well you expect to do.  This is what is used to design the data analyses — not what you get from the data themselves, as looking at the actual data can bias your results.  As of March, we would have expected not to be able to exclude any Higgs production at all, and lucky (or unlucky?) fluctuations made the data look more background-like than Higgs-like, and thus the experiments were able to set a limit.  But now the dotted line is lower on the plot, and below the standard-model line over a small region, so now it is expected that we set a limit, and the data are consistent with that…but the actual observed limit has gotten worse.  As we like to say, you get what you get.

Fermilab will continue to take data and improve these limits — or, for all we know, discover a standard-model Higgs.  The turn-on of the LHC, which is expected to continue this weekend, will bring more players into the game.

I’m getting word there will be circulating beams as early as tomorrow evening – another LHC milestone!  (As mentioned on CERN twitter)  First collisions are not too far away after that.

This image above is an almost-live updated image of the CMS control room – this is one of the two general-purpose detectors at CERN. (See image correctly at the US LHC blog site) Using some fancy CSS I overlaid some text of the different areas in the room.

I’ll be on shift in the Trigger area starting next week.  There’s about 6 wide-screen monitors back there that I’ll be watching to keep track of (too) many things.  (The Trigger decides what collision events to record or throw away.)

Feel free to spy on people in there.  Geneva is +6 hours from New York and +9 hours from Seattle, so it might be late there compared to your time, but people are on shift 24 hours a day!

Following up on our story about a meeting to discuss ideas for a muon collider program in the United States, here is a schematic image of what the accelerator complex would look like.

One of the secondary goals of the Fermi gamma ray satellite is to look for the signature of dark matter. One idea for dark matter is that it’s composed of weird (and as yet undetected) particles called WIMPs (weakly interacting massive particles). A very odd property about them is that they are self-annihilating: when two of them touch, they turn into energy (and other, more easily detectable particles). When I first read about this several years ago I was pretty excited, because this is finally a testable hypothesis about dark matter.

My fellow Hive Overmind blogger and astronomer Sean Carroll writes that it’s possible Fermi has done just this. The data are not conclusive, but very provocative nonetheless. He has the details.

But I can’t resist adding that on The Big Bang Theory a few weeks ago, Raj and Sheldon were investigating building a detector to look for this very type of dark matter. I wrote David Saltzberg, the science advisor (whom I met on the set last month when I was visiting LA; more on him and that at a later date) and told him this, and he noted that I was right. Well, how about that! It had to happen sometime. Now, to publish…

I once witnessed a physicist explain the universe to an artist. The artist had approached the physicist to learn how to understand extra dimensions, a concept, so he explained, that would undoubtedly enhance the depth of his artwork, and be of great inspirational value for his quest to capture the contextuality of essence. Or maybe essence of contextuality. Or something like that. Either way, the physicist took a piece of chalk and drew a line on the blackboard. "That is our universe," he said. It took several minutes before the artist stopped laughing and said "Now THAT is what I'd call an abstraction."

You see, the fact that our universe is at least 4-dimensional and infinitely large (or damned close to that) creates some problem with visualization. The average blackboard is 2-dimensional, somewhat smaller than infinite, and my female brain already finds 3d plots messy and confusing. Add to this that most physicists aren't particularly great in drawing the universe.

Thus arises the need to picture 4 dimensions in an intuitive and illuminating way. Penrose-Carter diagrams, also called "causal diagrams," do exactly that. Though they do not work for the most general space-times, but only when additional symmetries simplify the scenario, they capture the essence of a 4-dimensional space-time. Or maybe the essence of 4-dimensional contextuality.

Understanding causal diagrams is one of the most basic skills you need if you want to work in General Relativity.

It works like this.

First, we have the problem of getting 4 dimensions down to 2, where one of the 4 dimensions is time. That's not so complicated. We will assume that space is spherically symmetric, such that when you sit in one point, all directions from that point look similar. This would be the case for example if you sat in the middle of a ball or, to reasonably good precision, if you sat in the middle of the Earth. The only interesting information is then in the change of scenery as a function of the distance from you, who you are sitting in the center of symmetry. We can thus capture the full 3 space dimensions by just considering what happens with the distance to the center of symmetry. This distance is of course just the radial coordinate r. Besides that, we will draw the time-coordinate t, which is usually depicted vertically, whereas r is horizontally. This is shown in the picture below, left. You've seen that before.

An infinitely flat 4-dimensional space-time is then just a half-plane. Note that a flat space is spherically symmetric around every point. (If you want to nitpick, what I mean with "flat" is that the curvature tensor identically vanishes.)

Next thing we do is to notice that if we had a particle moving towards the center of symmetry at r=0, passing through it, and moving away from it again, it would look on the half-plane like a reflection instead. Sometimes we thus mirror the half-plane to the other side, such that the curves of particles just go through. Keep in mind though that r increases in both directions. The world-lines of particles with a fixed velocity move on straight lines in that plane. Don't try to draw curves for particles that do not approach the center radially because the symmetry doesn't allow it. We now adopt the first convention for causal diagrams:

Light moves on 45° angles.

Curves on which light moves are called "lightlike," or, due to their property of having zero length in a Minkowski-metric, "null curves."

The next step is more tricky, because now we have to deal with the infinitely large space. How do we get it to fit on a blackboard? If you have ever done perspective drawing, you know the answer already. The "horizon line" and the "vanishing points" depict the infinite distance on a finite sheet of paper. The price to pay is that what is equally spaced far away, moves closer and closer together on the 2-dimensional picture. An example is the photo with railroad tracks to the right.

To draw a picture of an infinite space-time, we do exactly the same: we make infinity finite by squeezing together what is far away. Since the space-time is infinite in more than one direction an additional assumption is that we

Squeeze infinity equally in all directions.

The resulting squeeze is also called a "conformal transformation," and has the merit of preserving angles, such that most importantly null curves still move on 45°, no matter which such transformation you used. There are many different squeezes, though qualitatively they look all similar. An example for an often used squeeze is the tangent function in the interval [-π/2,π/2], shown to the left. If you take equal spaces on the vertical axis, the corresponding values on the horizontal axis produce a no longer evenly spaced representation of that infinite vertical axis.

If we now go and squeeze our flat space-time what we get is a diamond.


In this diagram, spacelike curves always have angles less than 45°, and timelike curves on which particles can move have angles more than 45° (in every point). All spacelike curves come from and end in the side corners, called "spacelike infinity," whereas timelike curves all come from the bottom corner and end in the upper corner, called "past timelime infinity" and "future timelike infinity," rspt. Light comes from the lower V-shaped boundary and end at the upper Λ-shaped boundary, called "past null infinity" and "future null infinity." The null infinities are usually denoted with an I in a script font, and are thus for short often called "scri minus" for past null infinity and "scri plus" for future null infinity.

So far so good, but flat Minkowski space is admittedly somewhat boring. Let us thus look at something more interesting. The causal diagram of the maximally analytically extended Schwarzschild-solution, describing a static black hole. You have seen it thousands of times in the header of this website.


It is futile trying to explain how to obtain the diagram without telling you what a metric is and what to do with it, but the big advantage of these diagrams is exactly that you can learn something about the space-time properties without bothering with tensor equations, so let's see.

The growing evidence that cells communicate with photons is generating an exciting new field of research.

Last year, researchers at the Rush University Medical Center in Chicago showed that human cells in culture could synchronize their internal chemical processes even though they were mechanically, chemically, and electrically isolated from one another. The cells, it seemed, were communicating through the exchange of photons.

Various other groups have shown similar effects. Many cells seems to produce optical and UV photons at about 10 photons per square cm/s, a rate that cannot be explained by ordinary thermodynamic emissions. Other evidence indicates that this form of optical communication can increase the rate of mitosis in cells by up to 50 percent.

So how do they do it? Today Sergei Mayburov at the Lebedev Institute of Physics in Moscow puts forward the idea that optical communication is a natural process in many cells that can be explained by the way we already know many cells to function.

He points out that biologists have long known that photons play a central role in the biochemistry of many plant and bacterial cells. The basic idea, laid out in the 1960s, is that optical or UV photons enter a cell and stimulate the creation of excitons, electron-hole pairs, on certain long chain molecules. The exciton travels along the molecule, influencing the way it reacts with other species within the cell. This is the basic theory behind photosynthesis.

Mayburov's idea is that this process is, first, reversible, second, not limited to photosynthetic cells and third, possible to modulate for communication.

Let's unpack those ideas. Take the first: if photons can create excitons in cells, it seems reasonable to assume that the process can occur in reverse (exactly this happens in semiconductors to create light).

The second idea is also plausible. If excitons form in photosynthetic molecules, why not in other types of biological molecules, too. The problem with Mayburov's hypothesis is that it's not immediately obvious which other biological molecules may be capable of this and neither does he make any suggestions.

Finally, is it possible for cells to modulate the way they generate photons to transmit information and for others to receive it? It's certainly conceivable that photon production could be switched on and off by a change in some internal state of a cell. Certainly, if we're to explain the experimental evidence, something like that must be going on. But Mayburov leaves us wondering how this might happen on the molecular scale.

This is a rapidly emerging field which overturns some well entrenched thinking in biology so it's hardly surprising that it generates more questions than answers. For example, how do cells discriminate between biophotons and background light? And what to make of other evidence that the photons can sometimes be coherent?

These are exciting problems. But Mayburov's broad claim that the phenomena is closely related to photosynthesis is an important step that should bring this emerging field to the attention of a much wider audience.

Ref: arxiv.org/abs/0909.2676: Coherent and Noncoherent Photonic Communications in Biological Systems

Well, you then go to your back up plan and be a CALL GIRL!! :)

This is way too hysterical to make up, or maybe it is made up, who knows?

The more complete story on this can be found at Times Online. The part I found to be quite hilarious was this:

How did she become a prostitute? She studied anthropology and mathematics in Florida: “I wanted to be a physicist, but that just didn’t work out.” After Florida, her family lived in Sheffield, where she studied some more: “By the time I got to Sheffield it was for doctoral study at the department of forensic pathology.”

I would say that was a drastic alternative indeed! :)

Zz.

Ah, a name from the past!

Paul Chu, after serving as president of the Hong Kong University of Science and Technology, returns to the scene of his triumph at the University of Houston. Back in the heyday of high-Tc superconductors, he discovered YBCO after the publication of Bednorz and Müller's LACO, the first high-Tc superconductor. What was significant about YBCO was that it was the first superconductor discovered that has a Tc above liquid nitrogen temperature. This is important because it allows one to have a superconductor using a relatively cheap cooling source, rather than using liquid helium.

This, of course, was the trigger for the "Physics Woodstock" at the 1987 APS March Meeting in New York. Ah, the good old days!

Zz.

Greetings from Down Under! Current at the CosPA conference in Melbourne, after spending a couple of days in Sydney — a brief fling through Adelaide up next.

It’s been a mixed bag so far; while I’ve had great fun interacting with people here in Australia, I’ve also been struggling with a nasty cold I picked up on the flight over. Spent yesterday mostly in bed, too fogged up to even work on my talk for Friday. But when I’ve had the strength to be up and about, it’s been a treat. Here’s an iPhone snap of the University of Sydney; that clocktower in the middle houses, appropriately enough, the Centre for Time.

One of the perks of civilization that hasn’t quite caught on in these parts is affordable internet access in hotel rooms, so don’t expect a lot of blogging over the next week or two. Instead, I can point you to a couple of recent videos. One is an extended interview for Edge, entitled Why Does the Universe Look the Way it Does? It is an interview (presented in text and video), not a carefully pre-planned document, so not all thoughts are arranged as elegantly as one might like. Here is some of the flavor:

We are in a very unusual situation in the history of science where physics has become slightly a victim of its own success. We have theories that fit the data, which is a terrible thing to have when you are a theoretical physicist. You want to be the one who invents those theories, but you don’t want to live in a world where those theories have already been invented because then it becomes harder to improve upon them when they just fit the data. What you want are anomalies given to us by the data that we don’t know how to explain.

The other one is a panel discussion on Time Since Einstein, from the World Science Festival. As the description there says, it features Roger Penrose, David Albert, and some other people it would be too exhausting to list individually. Here’s part 1 of 5:

World Science Festival 2009: Time Since Einstein, Part 1 of 5 from World Science Festival on Vimeo.

Now if only my immune system would finish off the little viral buggers inside me, I could get out and see a bit of this interesting country.

Sorry I didn’t include this in my last entry. Literally as soon as I posted it, I got another email about the LHC Schedule… which said so far things are going well and that the restarting of the LHC is imminent. That means beams should be circulating soon. Things are changing very quickly and as things are happening we’ll try to keep you up-to-date.

For the public, there will be some quasi-live event displays will be posted here

Once there are events, you should be able to see them. So check it out

-Regina

This week I’m attending an analysis Jamboree at Brookhaven National Lab. When I was little, the word Jamboree always conjured up images of country bears playing banjos (maybe that’s because my grandparents would take us to Disneyland…).

Unfortunately this Jamboree doesn’t include singing bears, instead it’s a discussion of different analyses to do with the first data from the ATLAS. BNL is one of the major hubs in the US for ATLAS, so about twice a year they host analysis meetings. Different running conditions sometimes warrant different analyses and with data coming hopefully soon, we need unite our efforts and make sure all the things – like software – is standard.

A bit about calibration

I’m giving a presentation on a calibration study I’ve been doing. Calibration is one of the first things we’ll have to do with first data. Like any tool, we’ll need to make sure we understand what we’re getting out of the detector once the data starts rolling in. It’s not as glamorous as a search for an unknown particle, but it is definitely important.  Particles like J/psi and Z have distinct mass peaks (at 3 GeV and 91 GeV respectively) when the energy from their decay products is reconstructed and combined. So we’ll take the reconstructed electrons, and look for a peak at around the Z mass and then tweak our algorithms so the peak lines up with the known peak. This type of calibration for example can be done using only one piece of the detector (like the calorimeter).

Another type is calibration between detector pieces. I’m looking at a study which compares what you read as the energy in the calorimeter and the momentum in the tracker. If you take the ratio, you should get about one, (since the mass of the electron is so small… you all remember E^2=(pc)^2+(mc^2)^2, right?)

But other than calibration

For lunch today we ventured off the BNL site to eat at a staple in American cuisine: Taco Bell. My friend and former roommate was back at BNL from CERN to participate in the Jamboree festivities, so we were celebrating America by getting refills on our super-sized drinks and cheesy Gorditas (sure I know what you’re thinking… Taco Bell is “Mexican” food… right). The culture shock is always a little surprising when going to CERN or coming back.

So now it’s after lunch, so back to work.

-Regina

I recently discussed here the Tevatron results of searches for new Z bosons in electron-positron or dimuon samples collected by CDF and DZERO, pointing out that there seem to be a couple of intriguing upward fluctuations in the data. One of the dielectron fluctuations sits at a mass of 240 GeV, the other, also in the dielectron spectrum, is at about 720 GeV. Neither is compelling.

read more

Fermilab took the next step in ensuring that the high-energy physics community has choices for the path to discovery beyond the energy range of the Large Hadron Collider. The laboratory hosted a three-day workshop last week as a precursor to a new national muon collider R&D program.

Several weeks ago it was brought to my attention that some of our readers via Facebook wanted to hear my take on the EPR paradox, so I figured I ought to get around to saying something. It turns out, further, that this is an appropriate thing to discuss since it has some applications to particle physics in how we are able to decipher what goes on inside our particle colliders.

So let’s start with the basic idea. The Einstein-Podolsky-Rosen paradox is a thought experiment that was originally proposed to highlight the inadequacies of quantum mechanics. What ended up happening was that the phenomenon of quantum entanglement became the foundation for real-life applications of quantum mechanics, e.g. quantum cryptography.

A fair warning: I’m not going to give a proper, formal treatment of the paradox nor will I further discuss the original motivation. Instead, I’ll give a heuristic description and jump into an application to B mesons.

First, let’s start off by reminding ourselves that we assume that information cannot travel faster than the speed of light. This related to the fundamental principle of causality: if things could travel faster than the speed of light, then in some reference frame, it’s moving backwards in time.

Alright, now onto the EPR paradox. The idea is this:

• You have a particle (the blue guy in the picture above) that decays into two other particles, A and B.
• There is a conservation law that constraints some property of A and B relative to one another. For example, conservation of electric charge says that if the original particle has no charge and A has charge +1 (e.g. positron), then B must have charge -1 (e.g. electron).
• Quantum uncertainty tells us that until we make an observation, the state of the particle is unknown. For example, we don’t know if A is an electron or a positron until we actually check. Further, quantum mechanics tells us that the particles must actually be in some “superposition” of states.
• If, after A and B travel a long distance in this “superposition,” someone checks particle A, then the conservation law determines the state of particle B. In our example, if someone in Fermilab observes that A is an electron, then we can instantly deduce that someone at CERN (which is where B happens to be zooming past at the moment) will observe B to be a positron.
• But the Fermilab scientist could just as likely have observed A to be the positron and thus B would be an electron; until the person at Fermilab actually measured A, it was in some intermediate state. Thus the moment A is measured, it instantly fixes what B must be.
• To be clear: before A is measured, B really is a mixture of states and can be observed to be anything. After A is measured, B can only be observed to be the correct state to satisfy the conservation law.
• So here’s the paradox: how the heck did B know how to behave if it’s so far away from A? (Instead of CERN, B could have been at a distant galaxy when A was measured.) It appears that information travels from A at the point of measurement at a speed faster than light to B. (In fact, at an infinite velocity.)  Einstein called this “spooky action at a distance.”

First, let me say that the effect is real. Indeed, the particles A and B are said to be entangled. (This entangled state is actually rather fragile, since you can’t let the particles interact with any other matter that would allow them to disentangle.) Second, this is not really a paradox. The point is that there is no actual “information” being transmitted since there’s no way to impose a state on A, the initial observation is always random. You can try to think up clever ways around this, but they always fail. There is no paradox. Particles can be entangled and can have weird correlations across long distances, but that’s just a prediction of quantum mechanics that is fully consistent with causality.

Before anyone complains that I’ve oversimplified the problem, let me note that we’ve been very informal about a lot of details. First of all, we haven’t provided a rigorous definition of “information.” For our purposes it’s fine to take an intuitive definition, e.g. can I encode a simple binary message. We also haven’t talked about the specifics of what conservation law we’re using. The EPR paradox usually is described in terms of particle spins so that the conserved quantity is angular momentum. This allows one to think about subtleties regarding spins relative to different axes (x-direction vs. y-direction) that are important for a full discussion, but that we’ll gloss over here. Finally, we won’t say anything about why the related question of why A and B should exist in a superposition when they’re flying away undetected (i.e. what “eigenstate” is produced and detected).

What we’re described is the ‘essence’ of quantum entanglement; we’ve skipped the details, but as usual, the physics is more in the intuition rather than the details. A neat real-life application for this is quantum cryptography, which is a way for two parties to share a secure “key” while being able to check if a third party is eavesdropping. The idea is that information is sent via entangled particles, with one particle of each pair saved by the sender. If a third party tries to view the packets of information, then this would lead to an observable non-correlation of the would-be entangled particles. [Again, we omit the details.]

Application to B Physics. Now we get back to particle physics! Above is a picture of the BaBar detector at the Stanford Linear Accelerator Center (”SLAC National Laboratory”). It’s an experiment that finished data taking last year whose purpose was to examine the decays of B mesons and their antiparticles. The antiparticles are written with a line over the B so that people usually call them “B-bar,” hence the name of the experiment: “B, B-bar” became “BaBar.” They even got official permission to use BaBar the elephant as a mascot.

There are a few types of B meson. Like all mesons, they are made up of a quark and an antiquark. B-mesons are those which contain an (anti)-bottom quark. A neat thing about neutral mesons is that they have well defined, distinct anti-particles (e.g. a down/anti-bottom meson would have a bottom/anti-down anti-meson) even though these particles have the same charge. The charges of the constituent quarks change, but the total B meson system doesn’t change charge. This means, for reasons that I won’t go into, neutral mesons and their antiparticles can mix quantum mechanically. The B-meson, in particular, have the nice property of ‘oscillating’ on roughly the same time scale as they decay. This means that we can produce a B meson and it’ll wiggle between wanting to be a B and an anti-B about once before eventually annihilating into other stuff.

Now here’s the point: we’ve discussed in a previous post that matter and antimatter are related by CP symmetry. We know that this symmetry must be broken because our universe is made up of a whole lot of matter and practically no antimatter. So there’s something different about matter and antimatter, and it would be very interesting to see how these differences appear. Naively, if CP symmetry were exact (e.g. if matter and antimatter were truly mirror images) then whenever a neutral B meson decays into something (say, a muon, anti-muon pair) then we would expect the anti-meson to also decay into that something with the same probability. (See why this only works with neutral mesons? If the mesons were charged then the anti-meson could not decay into the same final state without violating conservation of charge.) It would be really great, then, if we could just look and see how often B mesons decayed into these states versus B-bar mesons.

Unfortunately life isn’t that simple. Because the B decays very quickly (i.e. before it reaches the detector instrumentation), all we actually see are the remnants of its decays. That means that we can observe a large sample of events that decayed into muon, anti-muon (and, realistically, some pions) that point to the center of the beam pipe where we expect the B’s to come from. There appears to be no way to figure out which of these events came form B’s and which came from B-bars!

Now this is where entanglement comes in. I should apologize in advanced to my experimental colleagues for my simplified explanation. What the clever physicists at BaBar (and its Japanese counterpart, Belle) do is to collide electrons and positrons at just the right energy to produce lots of a particle called the Upsilon-4S. This funny-named particle then decays to an entangled B and B-bar pair. Each of these particles will “oscillate” quantum mechanically between actually being a B and a B-bar, but once one of them is identified as a B (or B-bar), the other is uniquely identified as well. Most of the time both of the particles decay into things like the muon signal that we want to compare. As stated above, this is unhelpful because we can’t figure out how to count each event as coming from a B or a B-bar decay.

However, some of the time one of the particles will decay into something that only a B can decay into. We don’t care about the rate for those decays, but observing it means—via entanglement—that the other particle must be a B-bar (or vice versa). In the case where one particle undergoes such a “signature” decay and the other particle decays into the muon/anti-muon decay of interest, we can definitively count that muon/anti-muon as coming from the appropriate B or B-bar meson.

In this way, the so-called B-factories (because they produce lots of B-mesons) were able to measure differences in the decay rates of B and B-bar mesons to these muon/anti-muon final states. In other words, they directly observed CP violation: a difference between the behavior of matter and antimatter. The information gleaned from these experiments help us constrain the source of matter/antimatter asymmetry that eventually allowed the universe to form things like galaxies and planets instead of annihilating into a big mess of photons. And we were able to do this using a strange property of quantum mechanics that Einstein originally dismissed as “spooky action at a distance.”

Before I sign-off, this whole question of information traveling at superluminal velocities reminds me of my favorite string theory joke:

These days there are so many string theory papers being written that one might be concerned that they are being written at a rate that is faster than the speed of light. One needn’t worry, however, since no information is actually being transmitted.

Zing! (I hope my string theory friends don’t read this blog.)

Cheers!
Flip

When you poke the Pillsbury dough boy in his bulging tummy, he giggles. When you poke the bulge in NGC 4710, however, you get the history of how galaxies form. Voila!

Awesome. And you really need to embiggen this one to get a sense of the incredible beauty and resolution of the picture. Try the 4000 x 2000 pixel one on for size!

NGC 4710 is an edge-on spiral galaxy located about 60 million light years away in the Virgo Cluster. That puts it in the next town over, cosmically speaking, so it’s a rich target for something like Hubble Space Telescope. This image, newly released (but taken in 2006 before the last servicing mission), reveals spectacular details in the sideways galaxy. Views like this really accentuate the huge sprawling dust complexes littering spiral galaxies.

But it isn’t the dust astronomers are interested in here. Spirals have three main parts: a more-or-less spherical bulge in the center, the disk (which has the spiral arms), and a giant halo of stars surrounding them both. We understand a lot about spirals, but lots of big questions remain, including how and when the bulge forms. A galaxy is born out of a vast, collapsing cloud of gas. It’s possible that the bulge forms straight away, with the infalling gas of the protogalaxy making stars which build up in the galactic center. It’s also possible that the bulge forms later, well after the galaxy itself takes shape, as stars in the inner part of the galactic disk interact gravitationally and fall to the center, building up the bulge.

It turns out there might be a way to distinguish these formation mechanisms, even billions of years after the fact. Globular clusters are small (well, a couple of dozen light years across or so) balls of hundreds of thousands of stars. They orbit bigger galaxies; the Milky Way has well over 100 orbiting it. We know that many globulars formed at the same time as their parent galaxies; the stars in the clusters can be incredibly old. This means that perhaps the formation of the galaxy and its attendant clusters are connected.

In fact, it’s thought that the same process that creates the bulge in the "forms at the same time as the galaxy itself" scenario also creates globular clusters, but the other process (stars from the disk falling inward) does not create globulars.

That’s where NGC 4710 comes in. Being edge-on, we can see the bulge clearly, so it can be studied. But it also presents a good view of its globulars, so scientists can look at pictures like this one and simply count up the number of globular clusters near the galaxy and then figure out if the number is consistent with one of the two formation mechanisms.

In this case, NGC 4710 sports very few globulars, indicating the bulge formed after the galaxy itself. But NGC 4710 is only one of many galaxies being studied this way. Will they all show the same sluggish beginnings to their central bulges?

Time will tell. But I hope that as more of these galaxies are studied more images as lovely as this one become available.

Image credit: NASA & ESA

My mom came up with a very bright (and simple) idea on how to explain to very small kids (toddler level) that mommy will not be back for days. And I would like to share it.

So I was absent from home more than half of a  month in the last month due to two collaboration meetings and a conference. Does not happen every month luckily. My mom, who was babysitting my children (2 and 4 years old) devised an ingenious way of telling them that there is no point in asking couple of times a day when is mommy coming back home. And here it is:

“Mommy went to work by airplane so she can not be back quickly (solid proof is a car left at home). Mommy only comes back quickly if she went to work by car! ”

And it worked! Simple enough:).

This is an excellent review article by John Pendry on left-handed material and its application to "cloaking". Pendry, as everyone should already know, revived this field of study with his work on metamaterial. So this article compliments quite well with the earlier article in Physics Today.

Zz.

The news is up. We had election results announced for the spokesperson for the Long Baseline Neutrino Experiment at DUSEL. This is the first time I witnessed proper elections. Three excellent candidates, extremely dedicated to the project. They came up with their vision and how they see project priorities and future.  It was interesting to tune into scientific elections. I am sure that all three will lead this longterm collaboration (read: results not likely before 2020) at some point or another. In the end collaborators decided for Bob Svoboda from UC Davis and I wish him good luck.

It is an unbeleivable challenge keeping motivated, dedicated collaboration for a decade at least. The physics promise is unsurpassed, but it is a long way getting there. We all want to know if  the lepton CP-violation phase is large enough to fit in the answer to matter dominance that we observe.  We all want to know which neutrino mass is the heaviest, but again, it is a long way getting there. Everyone would love to see some of the relic supernova neutrinos, of even a real supernova blast, but the road is long with a lot of hurdless.

So, in the meantime we concentrate on more down to Earth questions – some fun like choosing a more exciting name for the LBNE. Vote counting is underway between:

NuGOLD
Neutrino Galactic Observatory and Long baseline Detector

BISON
Black hills Illinois Supernova, Oscillation, and Nucleon decay detector

HND
Homestake Neutrino Detector

Which one do you like?

There are planty of technical design questions (a lot of fun too)  such as how one efficiently calibrates a 100 kton detector (size of just 1 of three modules!)?  What are the things that must be calibrated if we want to reliably answer above mentioned physics questions?

Generally, one can never calibrate too much to  better understand detector data, but what is the minimum, we wonder?

Since we will use water (most likely), it needs to be transparent – by hundreds of meters ! So there should be away that water clarity is checked regularly. Do organisms tend to grow in water?  Of course. Do they make water blurry?  Probably. So elaborate water purification system will be designed.

We may add gadolinium to water to get powerful neutron tagging ability (which I would really like to see happen since it opens doors for various several  MeV level physics). Will Gd stay in water? How do we put it back in after purification of everything else? We need to care about environment as well. So, more open questions…

On top of that we will need to get accurate timing and charge gain calibration for around 150,000 photomultiplier tubes (PMTs). Even at the speed of 10 per minute it would take a full month just for that (assume normal working days). We need to be clever.

And finally the part that I really like is calibrating detector energy scale – namely, when we gather all the PMT signals, we go back and figure out the energy of particle interaction that caused the signal. It is sort of like a detective game. We know when each PMT produced the signal and how big was it and then we trace back and figure out what particles and at what energy caused the signal and where in the detector it took place. Fun! As real detectives we first use the known (facts) which is calibration and based on it, figure out the unknown  which are all the other data collected from the PMTs. The first option for calibration are muons – they come in all energies from various direction, but it an uncontrolled fashion and no independent cross-check of their energy. One can build small accelerator and get fast electron of know energies to study detector nergy response. Part that we have started looking into are radioactive sources. Because it turns out that most of typical radioactive sources produce gammas and or other particles up to several MeV, but nothing above 10 MeV. And it is this reion of 10-20 MeV that would be really nice to understand well for supernova neutrnos. And getting a nice neutrino spectrum of fresh supernova would indeed be precious. So we started looking into fission fragments and if anything can be done with it. We may end up with some quite exsotic radioactive sources. Will keep you posted.

DNA repair machines may home in on the electrical signals created by mutations

Here's a curious puzzle involving DNA molecules. DNA is regularly damaged by ordinary wear and tear and the constant buffeting of ionising radiation. However, cells possess an extraordinary collection of molecular machines such as repair enzymes that rapidly identify the defects and repair them.

The puzzle is how they do it. One idea is that repair enzymes simply float about for long enough and eventually find damaged regions. But the numbers just don't stack up. Genes are usually between 1000 and 1,000,000 base pairs long. By contrast, a typical mutation usually involves just a handful of base pairs. That's just too small to find using a random walk with any reliability. Some other form of active location finding must be going on.

One theory is that mutations change the electrical characteristics of a stretch of DNA and that this creates a signal that repair enzymes can home in on, like electricians locating a break in a circuit. The trouble is that DNA doesn't conduct electricity like a power cable and so it isn't clear how this would work.

Now Arkady Krokhin at the University of North Texas and few buddies have worked out how DNA may do it. The key turns out to be that different regions of DNA have different electrical characteristics. The group has calculated from first principles the way in which charge flows in different regions. They say that in exons--the information carrying parts of genes--the energy spectrum of the molecule allows delocalised electrons to exist. In these areas, charge can flow.

However the energy spectrum of the regions that do not carry information--the introns--does not allow for delocalised electrons. So introns are effectively insulators.

That sets up well defined regions within DNA that can be identified electronically.It also means that any change in electronic properties caused by a mutation would be largely confined too. That immediately suggests a way that repair enzymes can home in on damage.

Of course, this work is just one step towards a coherent theory that explains DNA repair (which actually involves many different processes).

But the beauty of this approach is that it could also explain why some damage goes unrepaired, leading to cell death and even cancer.

The thinking is that certain mutations cause less of an electrical change than others. These mutations are "electronically masked" and so go undetected by repair enzymes. There is even experimental evidence for this from resistance measurements done on DNA with cancer-causing mutations.

If this theory is true, one important question is how might it be possible to exploit DNA's electrical characteristics to detect and even prevent cancer in future?

Ref: arxiv.org/abs/0911.2953: Inhomogeneous DNA: Conducting Exons And Insulating Introns

This is rather “inside baseball”, but back when Cycle 17 Hubble Space Telescope (HST) proposals were being written, I plotted up the number of proposals as a function of time until deadline. Right now, a signficant fraction of the astronomical community is involved in crafting “multicycle” proposals for the telescope. The idea is that there are probably useful projects that are sooooo time consuming that you couldn’t possibly do them through normal proposal channels.

Well, the race is on! Here’s the data on what I know of so far. We’re up to 8 proposals at 24 hours before the deadline. With the enormous sample of two, count ‘em, two data points, we’re on the same curve as we were for Cycle 17 (plotted in black), but scaled down by a factor of 27. The blue line is extrapolating an exponential to the current rate of proposal submission. Both tracks argue for about 30 proposals going in. The scaling factor of 27 suggests that there will be an average of 27 people on each proposal, if Steinn’s argument that the number of proposals is set solely by the size of the community holds. The late-time development of this curve could be way off, however, because there is no way to put one of these together at the last minute. (On the other hand, the proposed experiments are so immensely complicated, that maybe the only way you get them done is waiting until the last minute).

I’ll update the plot if people give data in the comments! (Updated! I cut the blue exponential fit in the revised plot, as it was a lousy match.)

I did an interview with reporter Maria Sciullo of the Pittsburgh Post-Gazette a few days ago, and her article is now online. I’m glad she talked to Anthony Aveni; I’m reading his book The End of Time: The Maya Mystery of 2012 and it’s a great review of the Mayans, their astronomy, and their complete lack of predicting a doomsday in 2012.

I’m sure I’ll get some doomcriers in the comments. If you really think the Mayan calendar says the world will end in 2012, then I strongly urge you to read Aveni’s book. He’s an actual Mayan scholar, he knows his stuff, and he’s not out to either scare you or reassure you: he’s out to tell the truth.

When physicist Leon Lederman won the Nobel Prize for Physics in 1988, he found himself responsible for writing thank-you notes to a couple of hundred well-wishers. In his typical cheeky fashion, Lederman composed a form letter to cover his bases.

From a grad student in particle physics, these are my recommendations for learning a bit of French.

Before You Know It

I’ve tried out several language programs, including really expensive ones like Rosetta Stone.  Out of them all, this flash-card program has been my favorite. With each card there is a picture and sound recording of someone pronouncing the word or phrase. It quizzes you on cards and repeats ones you get wrong.

The free version lets you download sets made by other people from the main site, and also comes with a handful of card sets.  The paid version gives you a few thousand cards and lets you make & record your own flash cards and upload them to the site for others. It cost me about $50.

(I should find a native speaker and create a useful set of cards for physicists who come to CERN…)

http://www.byki.com/

Les Nombrils

As a comic book about girls in high school, I do feel a little weird buying these, but they’re so funny and filled with a lot of French I never learned in textbooks or class.

This has been my favorite source to learn modern slang or just informal phrases and such.  Words I’ve learned include: mec for “guy”, biche for “girl,” hyper-top for “cool” (I think?), and caleçon for “boxers (shorts).”  A mini-jupe is a mini-skirt.

So if you’d like to learn informal French related to relationships, clothing, teenage life, or the like, check out these comic books.

Alright, I’ll admit it: I own the whole series.

http://www.lesnombrils.com/

Coffee Break French

I download these podcasts and listen to these when I’m driving. They’re slow and clear and leave space for you to try pronouncing words and phrases yourself.  With this you can learn about simple things as well as more complicated topics like tense and grammar.

These are definitely more useful when you are alone and can talk out loud without looking weird.

http://radiolingua.com/category/shows/coffee-break-french/

What does a star on the edge of death look like? Perhaps not what you think:

This series of images [as usual, click to embiggen], from the European Southern Observatory’s Very Large Telescope, will take some ’splainin. Hang on.

A supernova — an exploding star — is among the brightest single objects in the known Universe. A supernova can release as much energy in a single second as the Sun will in a thousand years.

Most people think of supernovae as massive stars exploding at the end of their lives, but there is another kind. When the Sun finally dies in a few billion more years, it will shed most of the material making up its outer layers, revealing the white-hot, dense core. This superhot ball will have half the mass of the Sun in it, but only be the size of the Earth. We call such a thing a white dwarf.

If a white dwarf orbits a normal star like the Sun, it can draw material off. This matter piles up on the surface and can eventually detonate like a stellar thermonuclear bomb. We call these Type Ia supernovae.

The thing is, massive stars are bright, so we can see them a long way off. We know of many stars in our galaxy that can blow that way (though all too far away to hurt us). But a Type Ia progenitor is faint, and hard to spot. Usually, the first notice we get of one is when it explodes, and we see the sudden and vast increase in light in a distant galaxy.

But astronomers have spotted a potential Type Ia supernova in our own galaxy, a ticking time bomb about 25,000 light years away. Called V445 Puppis, in November 2000 it underwent an explosive event: not a supernova, but a regular nova, the detonation of small (in cosmic terms) amount of material. Still, it ejected a lot of matter — several times the mass of the entire Earth — at very high speed, about 24 million kilometers per hour (14 million mph). That would reach from the Earth to the Moon in one minute flat. Over the course of several years, astronomers have taken images of the expanding debris, and the change — seen in the picture above — is dramatic, lovely, and terrifying.

The debris did not expand spherically because the two stars are in a tight orbit, circling each other rapidly. The matter drawn off the normal star forms a thick disk around the white dwarf. When the material on the surface exploded, it couldn’t go through the disk, so it went up and down, above and below the disk. Over time it forms what’s called a bipolar structure, because it comes out of the poles of the star. We see lots of similar bipolar objects, but not usually in a system that’s about to go bye-bye.

Tellingly, there is no detectable hydrogen in the system. The surface of the white dwarf appears to be mostly helium, and the normal star looks to be dumping only helium on the white dwarf. Type Ia supernovae are hydrogen poor, even lacking it completely, so that fits.

Also, the mass of the white dwarf in V445 Puppis is on the thin hairy edge of the maximum it can be before it blows. When a white dwarf reaches 1.4 times the mass of the Sun, it goes kablooie (I had to calculate this as a homework problem in grad school). V445’s mass? 1.35 times that of the Sun.

Yikes.

So when will the system go off? Hard to say. It may not be for thousands of years, or even longer. At that distance, it will be very bright in the sky, brighter than Venus. It won’t hurt us; it’s way too far away to to do that. But a nearby supernova of this type would be a huge boon to astronomy! It’s this flavor of supernova we use to measure the expansion of the Universe (since they are so bright they can be seen very far away, and tend to blow up with the same brightness every time).

It’s a little funny to think that the death of a star so many quadrillions of kilometers away can actually be a benefit to us. But remember, the calcium in our bones and iron in our blood came from supernovae like the one V445 Puppis will eventually become, so not only do we learn more about the Universe from them, we owe our very existence to them as well.

After an unbelievable 8 years, I finally made it back to CERN. For a particle physicist, this is an incredibly long absence from the lab that now has evolved into the center of the particle physics universe. However, I have many good reasons for this long absence, since I’ve been working on non-CERN projects ever since leaving CERN after my diploma thesis in September 2001. And, where integrated time is concerned I’m still doing ok: Back then I spent a whole year here…

The reason for my trip was a look ahead to the future: CERN has recently joined the CALICE collaboration, and I’m hoping for a fruitful collaboration to solve at least some of the challenges for detectors at a possible future multi-TeV lepton collider, the CLIC machine  that Lucie already briefly mentioned. Here, also the hadron calorimeter brings up all sorts of new and interesting questions. To contain showers of much higher energy, a deeper detector, potentially with a much denser absorber such as Tungsten, is needed. And for Tungsten, the evolution of hadronic showers is still very poorly known. To address this issue, a new program within CALICE has been launched, and I’m happy to be a part of this newly developing initiative.

Here, I also can’t resist to slip in a comment on Lucie’s question if now is not the time to focus on getting the LHC running, instead of planning the next big machine. And I have to say that I strongly disagree: It is absolutely essential that we now focus also on what might lie ahead, how the next generation of accelerators will look like, otherwise particle physics might not have a future. The R&D and construction cycles for these big experiments are now measured in decades, so we have to have a future plan for projects which come after the LHC. And since it is not clear how the new physics will look like, we need to be prepared: For lower energies, we have the well-defined ILC as a precision machine to give us a thorough understanding, but if new stuff only shows up above many hundreds of GeV, then we need a different technology, which the CLIC concept can provide. Of course, this is not “shovel ready” yet, a lot of R&D, both on the machine and on the detectors, is still required.

Just to set the time scales here (and the are even longer nowadays): The discussions and studies of LHC began in the early 1980s (at that point, I was in Kindergarten!). First beams in LEP were in 1989. Then, in 1994, LHC was approved by the CERN council. And hopefully we get first collisions still in 2009. Now, if you extrapolate this good quarter of a century from the first studies and concepts to collisions it is immediately apparent: if particle physicists don’t now also work on the next big project, none of us, from the grad student level upwards, will see any new machine in their professional life. So while getting the LHC under way should absolutely be the top priority in particle physics right now, we have to already be well advanced with the planning for what might come afterwards right now (and luckily we are).

Of course, as Lucie also mentioned: It is an ambitious, risky program: We are betting on a spectacular physics output from the LHC experiments. Here, I am quite optimistic, but I guess that is obvious, otherwise I should have picked another field to work in. Without good, convincing results it will obviously be hard to justify a new, large scale project. On the other hand, I don’t think there is a risk that “LHC will find everything”. If we are lucky, it will answer some of our questions, and give us new ones to pursue, and maybe even send us into a totally unexpected, new direction.

German amateur astronomer Bernhard Christ was in the right place at the right time — due to very careful planning and foresight — and captured this astonishing scene:

[Click to embiggen.]

That’s the International Space Station crossing the face of the Moon, what astronomers call a transit (like an eclipse, but when something small goes in front of something big). This image is actually a composite of several images taken in a row, with some sharpening to make it cleaner looking.

The transit only lasted for 0.4 seconds, so Christ had to be on the ball to capture this. He used a digital astronomical camera that can take what is essentially video (really just rapid still shots, but after all that’s what video is), and processed the individual frames. It’s a gorgeous image, with the Moon looking really stunning.

And if you’re wondering why he only got four shots of the ISS, look again: there is a shot of it just inside the limb of the Moon, but it’s low contrast and hard to see. Just follow the path of the ISS as it crosses the Moon and you’ll find it.

My thanks to Herr Doktor Christ for allowing me to post this picture. Well done, and vielen Dank!

I’m putting in my fair share of work these days with the imminent arrival of something special into this world soon (just to nip it in the bud early, no I do not mean I’m becoming a father, not just yet at least). Beams are this years baby. Who knows, if we’re lucky, by the end of the year, birds and baguettes permitting, we may even collide them. If we do have collisions I would bet on one thing, they will be done very carefully and there will be no risks taken whatsoever. Stating the obvious there I suppose but, well, we are in a cautiously optimistic mood these days.

The ACR as I have mentioned previously is the ATLAS Control room and after a couple of weeks hiatus working on other worthwhile tasks I was back on shift this morning. A few things have changed in the past weeks.The ATLAS mural is to provide some visual excitement to an otherwise drab building. A great idea! You can see point 1 as you drive past CERN and actually being able to see what the experiment looks like as you drive past really adds to the mystery and excitement surrounding the place. It also saves parents having to convince their kids by saying,”hey Billy, there’s something really cool going on 100m below that large concrete building over there.” A exclamation that would likely be met with a, “whatever Dad/Mum”, or the equivalent in French perhaps.

Coupled with the exterior painting, is a rushed job to paint the interior areas of point 1 around the ATLAS control room. This is causing a bit of a problem as people are having more trouble getting in and out than usual, and since the traffic milling around the control room has unsurprisingly risen recently things are less than ideal. It made my getting to the coffee machine this morning a near gargantuan task which isn’t quite what I needed (what I needed was the coffee!). In a similar vein, a fancy revolving door was put in last year as ATLAS neared the business end of operations and all the world’s dignitaries were coming over for a gander. Hopefully the painters rush won’t be wasted.

From coloured walls to color charge (I should trademark that segueway) the detector is running smoothly. Very smoothly in fact. Collecting stable overnight runs, ironing out some minor problems along the way, testing new access methods to the computers at point 1, among many other things. This collaboration has really pulled it’s collective socks up, and the amount of hard work and long nights put in to make us ready to lovingly accept whatever beam is sent our way is always impressive to me. I’m not immune myself, far from it. I find it extremely inspiring and tend to do most of my best work in an intense and vital time as this one most assuredly is. I’m pulling together several aspects of the analysis I am planning to unleash on the data we collect, while also working to understand the current functioning of the ATLAS pixel detector to make it as efficient and safe as possible for the weeks ahead. But perhaps most importantly are the shifts: taking part, doing your share, pitching in, one of the crowd, waiting in the control room, champagne on ice.

I don't normally find reading papers on quantum gravity to be "entertaining". However, this is actually is, simply because the authors have to be rather concise due to limited space. Written by Sabine Hossenfelder Lee Smolin of the Perimeter Institute, it actually provides quite an overview of the phenomenological aspect of the search for the effects of quantum gravity. It focuses entirely on what we had measured and can possibly measure in the next decade or so. Reading this, one notices a lot of "negative result" experiments, especially on the search for possible violations of Special Relativity at those extreme scales.

Like I said, a very entertaining reading. :)

Zz.