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Archive for May, 2010

Hi there!

First, hello to the MIT Tech Review who made me famous for about 15 seconds this month. That’s one of my Facebook comment replies Singhal is pointing at (below) – and hi there Facebook users! It struck me when I saw that how strange the spread of information is, and how much information we read in a heavily digested format in a typical day…

Meanwhile, the LHC is running as normal. No news is good news, for the moment. If you want to hear about some (possibly) exciting physics, I highly recommend the NYT article on a possible hint of new physics from the Tevatron. They do a pretty good job explaining things there, so I won’t confuse you any further. There does seem to be something to it – and now the race is on to find what’s out there at the LHC!! Physicists or the very brave can read the full article here. Notice that their result is “evidence,” not “discovery” (or “observation”). That means they’re 99.7% sure the result is new physics – to claim discovery, they’d have to be 99.9999% sure (ok, there needs to be a little more mathematical definition of “sure” to make that precise, but I hope it gives you some idea of what I mean).

Note: Fixed my evidence / observation mix up. Thanks for the careful reading…

–Zach

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Me voila de retour du site de l’expérience à laquelle je participe : Dø à Fermilab. J’ai participé à une une semaine de collaboration, où la majeure partie des physiciens de Dø a travers le monde se rejoignent pour partager leurs progrès dans les différents sujets de recherche abordés par l’expérience.

Le monde de la physique des particules est aujourd’hui en pleine effervescence, le démarrage du LHC au CERN ouvre la voie a de nouvelles découvertes, mais le Tevatron n’a pas finit de repousser les limites de nos connaissances. Une analyse portant sur les données de Dø vient de montrer un résultat significatif dans la recherche d’une asymétrie matière/antimatière, autrement dit un élément de réponse à la question « pourquoi notre univers est composé de matière et pas d’antimatière? ».

Higgs WantedCes résultats impressionnants me conforte que le Tevatron reste plus que jamais en course pour une découverte majeure : le boson de Higgs (qui est en passant le sujet de ma thèse 🙂 ).
Le modèle standard de la physique des particules prévoit (dans sa version la plus simple) l’existence de cette particule ainsi que toutes ses propriétés, la seule inconnue étant sa masse. La technique utilisée pour sa recherche directe est une sorte de balayage de toutes les masses possibles, de cette manière il a déjà été exclu par le LEP (“l’ancêtre” du LHC au CERN) pour toute masse inférieure a 114GeV.
Le Tevatron a déjà frappe fort l’année dernière en excluant l’existence d’un boson de Higgs de masse comprise entre 150 et 160GeV réduisant encore la fenêtre de recherche. D’après nos observations, il est très probable qu’il ait une masse inférieure à 150GeV (ce qu’on appelle un Higgs “léger”), et c’est précisément là où le Tevatron compte bien frapper encore.
Les paris sont ouverts, qui du Tevatron ou du LHC mettra la main sur cette particule insaisissable? Je ne perd pas espoir d’être parmi les physiciens qui trouveront ce « Graal », mais d’une manière ou d’une autre, ce sera une découverte capitale pour notre compréhension du monde subatomique.

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A couple of my friends came up with this video that shows you what a heavy ion collision “sounds” like:

[youtube jF8QO3Cou-Q The sound of the little bang]

They base the sound on a power spectrum derived from measurements at RHIC.  The discussion is about the Relativistic Heavy Ion Collider, but everything they say is also true for the LHC.  You can find a great discussion of this on their web page.

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Matter and anti-matter

Tuesday, May 18th, 2010

Recently the D0 collaboration at the Tevatron announced an interesting result.  Having come from the BaBar experiment and worked on CP violation, I found it exciting.  Our universe is dominated by matter.  It’s everywhere and there is almost no anti-matter to be found.  This is one of the principle questions in our sub-atomic understanding of the universe.  The answer to this was put forward many years ago by Sakharov; there has to be CP violation, meaning that the swapping a particle with its anti-particle and looking at the interaction in a mirror can’t be the same as the original.

CP violation was discovered several years ago and has already won Nobel prizes.  The B-factories have measured many of the CP violating parameters of the Standard Model and come up with a rather coherent picture.  These measurements and constraints are embodied in the CKM triangle, where the height of the triangle is a measure of the amount of CP violation.


CKM Triangle

Recent CKM fitter result

It’s beautiful really.  Like a piece of fine art.


Kandinsky composition VIII

Kandinsky Composition VIII

There is just one problem; the amount of CP violation is insufficient by about 10 orders of magnitude. This means that there has to be more CP violation out there that we don’t know anything about.

This is where D0 comes in. They have been looking at CP violation in decays that aren’t accessible at the B-factories, and they found something. The Standard Model says they shouldn’t find much at all, but they did. I think it’s exciting. This isn’t the first sign of stress on the Standard Model, and there will undoubtedly be more coming in the next few years from LHC and other experiments. I think it is an exciting time to be involved in fundamental science research since we will be revising and rewriting many long held theories in the coming decades.


D0 result

D0 asymmetry result is separated from the Standard Model representing the blue point.
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The cost of money

Tuesday, May 18th, 2010

Now, here is a plot to make a principal investigator happy:

Swiss franc-dollar exchange rate
It is true that recent concerns about the sovereign debt in Greece is leading to uncertainties in financial markets that could hold back economic recovery around the world, which is hardly good. But one side effect has been the strengthening of the dollar against European currencies such as the Swiss franc (CHF), and that is good news for US people working at CERN.

CERN does all of its business in CHF and the costs of building and operating the experiment are calculated in CHF. However, US funding agencies of course distribute research funding in dollars. This gives the US LHC research program and researchers at US universities a significant sensitivity to exchange rates, as we receive dollars but must spend CHF. As the plot shows, the exchange rate has changed by about 13% over the past six months, which means that we now have 13% more purchasing power than we did in November. It’s not a small number. In addition, US people working at CERN are typically paid in dollars by their home institution but need to pay their living expenses in Geneva in CHF. So it is a boon to them if the exchange rate improves. (Or, if they are getting paid in CHF, then it is easier on their institutions to make payroll.)

What we don’t know, of course, is which way that graph is headed, and that makes it hard to plan and budget and so forth, especially on the timescale of years. More to the point, should I get cash out of the CERN ATM today, or wait until tomorrow?

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LHC Physics News

Monday, May 17th, 2010

By special request, here is an update on how the physics and machine are doing. Hope it helps!

Any results or new physics hints?

We don’t yet have enough data to see much new physics. Unless it’s something really strange, we expect only one “interesting” event for every thousand million collisions we see. We’ve seen hundreds of millions of collisions now, but it’s unlikely that we’ll say anything definitive until we’ve seen quite a bit. You can see my previous posts about being careful and errors for some of the reasons why.

As for the results we have seen, we’re progressing well. I liked the way one of my collaborators put it: a march through the history of physics. We’ve gone through the ’50’s, ’60’s, and some of the 70’s. We’ve gotten some of the ’80’s done as well. We probably need ten or one hundred times more data to get through the ’90’s. After that, the sky is the limit…

Why is the machine going so slow?

Truth is, the LHC is doing great. It feels as though every week we collect as much data as we had collected up to that point. Of course, the exponential growth won’t go on forever. But there are quite a few things that we can still do to get a lot more data out of the machine. In numbers: we are around one half of one thousandth of one percent of the “maximum” collision rate in the LHC. We know very well how to get thousands of times more collisions per second – but we want to go slowly. This machine has to be around for 20 years – it won’t do to get hasty and have an accident at this point! We can’t just go buy another one!!!

If you watch the LHC Page 1 obsessively, then you’ll see a lot of down time. It turns out that, if you’re in Europe particularly, it’s self-selecting. That is, when the experts are there during the day, we’ll spend a lot of time doing tests. At night, they often have stable runs (by “night” I mean midnight to 8am). But it’s those tests (during which we don’t have “stable beam,” and sometimes we don’t even have beam) that give us the confidence to raise the collision rate by quite a bit. Tonight, more tests – so that we can get a higher collision rate!

So when will we know more??

The collision rate will continue to increase, and I hope we hit the “magic number” – 100 inverse picobarns of data – around the end of the year. I say “magic number” because that’s around the time when we’ll start to really beat previous machines like the Tevatron in Chicago. To some, that’s when the fun starts – when we start looking for new physics, and we have reach well beyond any other machine in history.

We release a lot of results at conferences. The summer has several key conferences, so I fully expect several results from each experiment at every conference. They probably won’t be “discovery” results, but they will be the first key physics results. They’re exciting to some physicists, but, frankly, many will consider most of these “ho-hum” results (unless one of us does find something new!). Everyone recognizes how important it is to get some results, and what attitude is being expressed. We’re releasing physics results less than six months after the machine started! There are experiments that have taken years with their data before releasing any results!!

And as the exciting results roll in, we’ll keep you up-to-date here, as much as we can!

–Zach

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After a short stay in the US, I have returned back to CERN.

I flew on a Boeing 767 for about 9 hours.  That was not a comfortable flight.  An Airbus A330 has much more leg room.  Also, on the Airbus, each seat has it’s own personal screen to select from a couple dozen movies and shows to watch, whenever you want.

The science of a nicer airline flight isn't so complicated.

Airplanes could be more comfortable, but there are things you can do yourself to make trips better.  The best thing I ever did to make all my flights more comfortable was to buy noise-canceling headphones.

I was skeptical of noise-canceling headphones at first.  I didn’t have any friends that owned a pair, and most stores don’t have them out in the open for you to test.  I did research on them, all the way from the basic physics of noise-canceling headphones, to actual reviews of headphones.

Basically, noise-canceling headphones reduce low frequencies the most.  That means engine noise, low rumbles, wind, etc are reduced considerably, but you’ll still be able to hear a baby cry, cat meow, or a phone ring.  (I hope you never have to sit next to a cat on a flight.  I love cats, but I’ve found they’re not so pleasant on airplanes.)

I’ve been using noise-canceling headphones for two years now on all my flights, and I can’t recommend them enough for people that fly a lot.

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On Shift at CDF

Sunday, May 16th, 2010

The last few weeks have been absolutely crazy for me and are a great reflection of my life and times as a physics gradstudent. In the last three weeks I’ve managed to finally acquire the full data set that will be my thesis, give the first of a series of talks on the validation and calibration of this data set,  then have receive friends and family from all over the world for my wedding, then travel to Barcelona and Mallorca Spain for my honeymoon where I got to do some amazing climbing/cycling/ and relaxing before racing back to Chicago to be on shift at Fermilab

At "The Arch" in Mallorca

At "The Arch" in Mallorca doing some deep water soloing

So I’m back after a bit of a break and on shift here at CDF. Late last year I completed my first round of “ACE” shifts and now I’m back to do the much less stressful job of “consumer operator”. The ACE is the primary person in charge of running the data acquisition and high voltage systems for all of the components that make up the detector and having the proper experts contacted when something goes haywire. This can be a stressful job, since you don’t want to lose one second of colliding beams and often when things go wrong there are twenty errors, alarms going off, and you are only somewhat familiar (at best) with the way everything works.

My current job (the consumer operator) is much less stressful. I mostly check the data in the form of plotted histograms and compare them against what we expect them to look like. This is done to insure that the data we are recording and the ACE is working so hard to keep coming into the system isn’t tainted because of some piece of hardware acting strangely.

Snapshot of the CDF control room

Snapshot of the CDF control room

I really enjoy my time as CO since I get to meet the new Aces, talk with the Scientific Coordinator (SciCo), and see the experts as they get called in and learn something new about my experiment while a problem is being fixed. Additionally, there is really no feeling quite like that of being part of the team that is bringing in High Energy Physics (HEP) data that will eventually advance our understanding of our universe. Really quite a cool thing!

So while it is a bit of a shock to the system to go from data analysis to wedding to honeymoon to back on shift…it is one of the crazy aspects of being in the world of particle physics that you must wear many hats and I consider myself luck to be part of it all.

Me and my bride!

Me and my bride!

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CALICE at the Wall

Thursday, May 13th, 2010
A small subset of CALICE on the Great Wall of China at Badaling.

A small subset of CALICE on the Great Wall of China at Badaling.

After a few weeks break from QuantumDiaries, I’m back again, and again on travel: The CALOR2010 conference in Beijing, China. At this conference, all aspects of calorimetry in high energy physics are discussed in great detail. I already got a few useful ideas for new things to try out, so certainly a worthwhile event. In addition, this time my trip is “family neutral”, since my wife is with me to visit a mutual friend and to do some sightseeing. The consequence: No complaints from home, no minus points for being away so much this time :-).

While I’m spending long days in the auditorium listening to talks and participating in discussions, it is not all work here in Beijing: Yesterday afternoon we had the opportunity to visit the Great Wall at Badaling. We even took a group photo of a small subset of the CALICE collaboration (with a clear bias towards hadron calorimetry). Not such a big showing as for our beach event, but way more work: Some of us had quite a climb up the wall behind them at that point (others took the easy way by cable car).

The Wall is by far not the only thing to discover in Beijing, even given the very limited amount of free time. Every dinner is a new adventure, and one night we got to witness noodle making to make an Italian cry. Erika (front center in the Wall picture) certainly was deeply impressed…

A noodle making demonstration in a fancy restaurant in the center of Beijing. Even Italians were impressed...

A noodle making demonstration in a fancy restaurant in the center of Beijing. Even Italians were impressed...

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Congratulations, Dr. Dale

Wednesday, May 12th, 2010

Last weekend was graduation weekend here at Nebraska (did any of you notice that we have a new blogger with UNL ties?). If you want to see a bunch of happy people, go to graduation; I can’t think of anything to be glum about there. This was a particularly happy graduation for me, as my first PhD student, Dale Johnston, received his diploma. (Equal credit, if not more, goes to my colleague Aaron Dominguez; we co-advise graduate students.) Dale’s thesis was on the Higgs search at D0; his work was a piece of the puzzle in the first exclusion limits on a high-mass standard-model Higgs. At the ceremony I got to help put his doctoral hood on him — the first time I’ve done such a thing, and I hope to have many more opportunities.

That evening Aaron and I drove out to Seward, about twenty five miles west of Lincoln, where Dale’s in-laws live, to help celebrate with his family. Everyone was very proud of Dale’s achievements, and rightfully so. I will admit that you can lose perspective when you spend all of your working days with people who have a PhD or who will be getting one soon. You start to think that everyone has a PhD! (I have even less perspective, as I come home to my PhD wife at the end of the work day.) In fact, it is a rare achievement. Only about 1400 people in the US will earn a PhD in physics this year. This is only a tiny fraction of the population, of course, and not even a very big fraction of, say, high-school seniors who imagine that they will become physicists someday. It’s not an easy path. So it was very rewarding to me to see how excited Dale’s family was about his accomplishments.

So, graduate students — we have a lot of respect for what you are doing, and we know how hard it is. Hang in there! You’ll be rightfully proud of what you have done when you finish.

Meanwhile: the end of the academic term means a bit more time to think about my physics research. I’ll be back at CERN next week for the CMS “physics week,” where we’ll be taking a hard look at where we’ve gotten with the data so far, and what we are hoping to get figured out in time for upcoming conferences. This would all be wonderful except for the fact that I and my colleagues are also mired in the move to our new physics building. We have been waiting for this moment for three and a half years now, but the move itself has been quite chaotic and stressful. We’re trying to keep our eye on the big picture, which is that we will have a wonderful new facility for research and teaching. Want to have the rewarding experience of getting a PhD in physics? Come to Nebraska!

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