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Archive for July, 2010

End of Another Great 25×25 run

Saturday, July 31st, 2010

I’m on pixel shift in the ATLAS control room at the moment. We’ve had a very successful run, with stable LHC beams for about the past 12 hours. The luminosity of the detector is another step forward, because the past two nights have seen more bunches per beam than ever before. The lifetime of the beam is also excellent. You can see below that the luminosity of the beam has only been decaying very slowly for the past 9 or 10 hours.

The LHC reports that, after the dump, they will fill the LHC for another physics run. I’m actually not sure why they’re dumping so soon, given that it will likely take a few hours to dump and refill, and the beam still has a lot of oomph in it. Some ideas off the top of my head: maybe the LHC experts think it’s best to do the dump and refill during the day shift; maybe they think that the luminosity in the next run can be made even better; or maybe they want to get more practice and collect more data about the start of physics fills in this configuration. But the bottom line, for me and for ATLAS, is that when they dump the beam, we reset our detector and get ready for the next physics run.

Ok, gotta go, it’s time for the beam dump!

LHC Status from July 31, 2010 at 11:49 AM


As we speak there are 25 bunches of protons in both proton beams in the LHC.  See all those steps in the graph (red and blue lines)?  Each little step is one bunch being added, and each “big” step is 4 bunches being added.  So if you count the steps yourself you should get a total bunch count of 25 in each beam.  The red and blue lines correspond to the left-hand y-axis showing “Intensity”.

The energy of the proton beams is in black and goes with the right-hand y-axis, “Energy (GeV)”.  As I write this the protons are around 500-some GeV and being ramped up to 3500 GeV which should take about half an hour.

Once both beams are at 3500 GeV and they declare stable beams, it’s time to record some data with the most bunches in the LHC to date!


Visiting Nagoya

Thursday, July 29th, 2010

Two weeks after returning from our big European trip, we did a very short trip within Japan: we visited the string theorists at Nagoya University, or short, Meidai. (You may wonder how this abbreviation comes about. The Japanese name of Nagoya University is Nagoya Daigaku, 名古屋大学. The first kanji of the two words are 名大. The syllable “mei” is the alternative reading of the first Kanji, which is pronounced “na” in Nagoya.)
100727174224 Even though Nagoya is not a typical tourist destination and we were there for work, we managed to squeeze in some early morning sightseeing. The earlier the better, given the scorching summer heat that reached 37 degrees Celsius in the afternoon. The picture above was taken in Nagoya’s downtown, Sakae.
The campus itself is located at the eastern edge of town and looks very modern. And given the amount of construction that is going on there, it will continue to do so for a while.
More than for its sights, Nagoya is famous for its food. The spicy chicken wings, even though very tasty, are definitely a challenge for the digestive system.


ICHEP’s Biggest Day

Tuesday, July 27th, 2010

Yesterday was, I suppose, the biggest and most formal day here at the 35th International Conference of High Energy Physics. I wore my suit, and took some ribbing from some of my colleagues for dressing up so much, but I’ve worn it for far less excuse and am not sorry in the slightest. It’s not every day, or even every ICHEP, that one hears an address from the President of the French Republic!

Mr. Sarkozy’s speech was great to hear. He is a very emotive, enthusiastic, and informal speaker, which made him relatively easy to understand for those in the audience (like me) with limited French. He didn’t claim to know the details of our work, and seemed to think we’re all a little weird, but spoke mostly about the importance of fundamental questions about the universe and his support for basic research. This was very well received indeed. He also talked a bit about the contributions of the French labs to the LHC and other projects, which is fair: France plays one of the central roles at CERN, and the French particle physics community has made significant contributions throughout the field. This is reflected in the excellent and informative conference that they’re hosting here in Paris.

ICHEP BanquetIf there was one thing I would ask to be improved for the next ICHEP, however, I wish there had been a bit more food at the banquet! You can see the banquet, which was held in the National Natural History Museum, at right. It was a very impressive museum — the main hall reminds me of the ATLAS cavern, and seems to be just about the same size — and the food was certainly varied and interesting. But the lines were long to get even a little of it, and we had to go out to dinner afterwards to be full.

Yesterday was also the final talk on the combined Tevatron Higgs results. Fermilab sent out the press release while we were still on coffee break, so I saw the excluded mass range on Twitter before going into the talk. (I overcame the temptation to shout out the answer at the start.) It was still a very entertaining talk, and obviously the details of how the measurement was done were as important to see as the final numbers. Of course, we all wish there had been more to see than mass limits in the expected range and a few possible tantalizing hints. We also had talks from the CERN’s Director for Accelerators and Technology on the LHC and from the spokespeople of the LHC experiments. Although we haven’t seen anything really new at the LHC yet, it’s clear that the accelerator and experiments are all making great progress in getting ready to make the exciting discoveries that we’ll see at future conferences!


Particles and Searches

Friday, July 23rd, 2010

Lots of us bloggers have been talking about ICHEP which is going on this week. I’m not attending the conference, although some of the work I’ve been doing is :).
Now I’ve been turning my attention back to my physics analysis.  As of about a week ago we have 200 nb-1 (now closer to 300 nb-1) of data – which is about 1/50th of what I hope to get for an analysis.

I briefly mentioned that I’ll be doing a search in a previous post. Now I’d like to share a bit what this particle beast is. A leptoquark carries quantum numbers for both quarks and leptons. It would decay by generation such that it mixes families of quarks and leptons. So why do we think it exists? In a word: Symmetry.

Physicists love symmetry (and symmetry breaking :)). Symmetry in forces (like electricity and magnetism), symmetry in families and generations of particles, symmetries everywhere. Since the quarks and leptons in the Standard Model have the same family structure it seems like there should be something that ties them together, like leptoquarks.

Granted this is a bit of an oversimplification, theorists have put in lots of work into understanding how these particles work. And now I’m going to be looking for them.

I’ll be giving updates over the next few months explaining more about these particles over the coming weeks.



My First Day at ICHEP

Friday, July 23rd, 2010

This is my poster. There are many like it but this one is mine.
There are probably many blogs where you can read summaries of the ICHEP conference — or if not, there will be soon enough — so I’m going to limit myself to telling you about my day. Getting my poster printed and getting it to Paris in one piece was stressful, but uneventful in the end, and once I got to the conference things were easy. The poster session was the first evening, and you can see me at right standing in front of the thing, ready to explain what’s going on. (I will soon post more about the measurement shown in the poster, but here is the official ATLAS conference note, and here is an old summary of some of the concepts.) I didn’t get an overwhelming number of people asking questions — there were an awful lot of posters, which gave me a new perspective on how my work is one tiny facet of our overall effort to understand particle physics — but I did have a few good discussions with interested folks, and the psoter will be up all week.

As for the rest of the conference, I mostly went to the “early LHC experience” sessions, along with a few talks in the Standard Model session. I found the ATLAS and CMS measurments of the W and Z bosons interesting, but mostly because they show how the experiments are getting going. The theory of these particles is very well understood, and the experiments are consistent with it — in fact, if the experiments disagreed the theory at this point, we’d conclude that something had gone wrong with the experiments. When the detectors are solidly understood and working toward precision measurements, they may discover subtle differences from theoretical predictions in this area, but that will be years from now.

And now for another day of conference talks!


It has been a long time since my last blog. It has been, and will continue to be, a very busy time for me, with thesis progress, job searches and relocation plans. As is often true of summer, there are many weddings and other celebrations going on too. However, in the middle of this busy time we can always find a few minutes if it really matters, and I am writing this blog to urge you to take action.

Phil Chater, my partner, finally graduated with his Chemistry PhD last week, and during the ceremony Simon Singh (something of a role model of mine) was awarded an honorary doctorate. If you haven’t heard of him, he has done great things for the publicity of physics and mathematics in books and documentaries (I recommend “Fermat’s Last Theorem”, “Big Bang” and “Trick or Treatment: Medicine on Trial”) and he co-founded the STEM ambassador scheme that brings undergraduates into schools in outreach projects. In 2008 he began a fight against a lawsuit from the British Chiropractic Association because of an article he wrote in the Guardian questioning what evidence exists to support the effectiveness of certain treatments for children’s diseases. He was not the first to be targeted as a single person for simply speaking out and encouraging others to question and not blindly trust (he did not make any false accusations!). They were unsuccessful in their suit, but the case only recently ended and the effects were still very damaging for him. However, many people were enraged by this case and took action, writing to their MPs in a call for English Libel Reform, and hitting back at misleading chiropractic claims.

At the graduation, he gave an inspiring speech that illustrated that the action of one person can make a difference. Jack of Kent’s blog encouraged so many to sign a petition calling for the reform (sign it here) (read more here) that it is no longer something that can be sidelined or ignored. The blogger should be a role model to all of us – a sign that if you believe in something, you can make a difference if you take action. This was the confidence I needed after rallying so hard to save my experiment’s funding in the UK.

In the spirit of taking action I now write about the Early Day Motion 467, a document I am urging my MP to sign, and if you can relate to the issues I write below then please ask your MP to do the same. The document expresses concern at the current lack of specialist physics teachers (a quarter of all 11–16 schools in England have no specialist physics teacher) and the consequent drastic drop in the number of entrants to physics A-level (a sixth of these schools fail to send any students to study A Level Physics). It is a recognition of the threat that this poses to UK physics and engineering, and therefore to the UK economy. Every child should have access to high quality (and enthusiastic) physics teaching, and if anything can be done to break this cycle of rapidly evaporating physics teachers and physics students in the country, it should be done soon. I hope that in my future I can work to inspire students to undertake Physics A level and even a Physics degree – not only to save the economy and research in this country but because we need more Simon Singhs/Ben Goldacres in this world – those who will look at the world through skeptical, scientific eyes and encourage others to do the same.


ICHEP: what to watch for

Wednesday, July 21st, 2010

At long last, the 35th International Conference on High Energy Physics begins tomorrow. It’s the largest particle-physics conference of the year, and the first major conference since the start of LHC operations at 7 TeV, If the US LHC blog has seemed to be a bit quiet lately, it might be because so many bloggers have been working hard to get results ready. Now, it’s highly unlikely that there will be any surprising LHC discoveries announced there; we just don’t have nearly enough data yet. But that doesn’t mean that this conference will be boring! Here are a few things that you might want to be watching for:

  • How well are the experiments keeping up with the LHC? The LHC has now delivered about 350 nb-1 of integrated luminosity to the experiments. What fraction of that data will the experiments show? This is a measure of the operational efficiency of the experiments, and of their ability to get the data through reconstruction and analysis. If the experiments are able to show a large fraction of the delivered data, then we can be optimistic about how quickly results will come out as the collision rates rise.
  • How competitive is the LHC with the Tevatron? The Tevatron experiments have collected a huge amount of data over the past nine years, and have an excellent understanding of how their detectors work. They will still be in the lead on many, many physics topics. (Disclaimer: I also work on one of the Tevatron experiments.) However, because of the LHC’s higher collision energy, there might be a few measurements for which the LHC can produce stronger results, even with a tiny amount of data. Will there be any such results, and what will they be?
  • How competitive is the Tevatron with the LHC? Everyone is eager to hear the latest limits on the standard-model Higgs boson from the Tevatron. The excluded Higgs masses are the ones that would have been the easiest for the LHC to see too. How much harder will new Higgs limits make it to find a Higgs at the LHC?
  • Any surprises from elsewhere? Let’s not forget that this conference covers all of particle physics, and there’s a lot more going on out there than just the LHC!
  • How tired do the presenters look? A lot of that 350 nb-1 came at the last minute — did everyone stay up all night to finish their data analysis?

I won’t be attending the conference, but I’ll try to provide some commentary from lovely Lincoln as events unfold. Good luck to all involved — this is going to be a lot of fun!


“Get a life!” seems to be a tried and true TV line when talking to geeks, nerds and the like. I’d like to think I have one. It must be the birth of my third son that has me reflecting on a larger scale than usual, but I haven’t found that being a physicist has been a significant burden on my personal life.

I know there are stereo types of physicist spending day and night at the lab working. My wife often likes to tease me that when I get home late from work it isn’t because of anything she needs to worry about; I was engrossed in my work and lost track of time. I’ll admit that it has happened (ok more than once), but I don’t make a habit of it. Most of the people I work with keep regular, sane hours, and all have what seem to be normal personal/work lives. Sometimes we have to put in extra hours at the lab, like now as the ICHEP conference is upon us, but most jobs have deadlines and extra hours to meet them.

Physicists and scientists in general are often unfairly considered to lack a personal life. I’ll admit that I have met some, but the vast majority are able to relax and have some fun most days. In fact, I get to have fun just about all day everyday since I find physics fun most of the time in addition to having fun away from work, and isn’t that the measure of having a really good life.


Almost There

Monday, July 19th, 2010

The official ATLAS conference note describing the analysis I worked on was approved on Saturday morning. My poster was finalized, approved, and printed — possibly not in that order — just in the past few hours. Now the only challenge left is to get myself and my poster through a French air traffic controllers’ strike and to the Palais de Congrès by Thursday morning.