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Paul Jackson | CERN | Switzerland

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Results from the first published search for supersymmetry at ATLAS have arrived

Wednesday, April 6th, 2011

It’s been a little while since this was put out into the public domain and given the minor hoopla about the few events above background the CDF are showing I thought I’d post this rather nice recent publication from ATLAS. The analysis entitled “Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector in √s=7  TeV pp Collisions” was published in Phys. Rev. Lett. (106, 131802 (2011)) on March 28, 2011. Although the title may lack a certain verve and snap, the Letter was deemed interesting and perhaps even important enough to spawn a viewpoint entry from the PRL editors. You can access the publication from that same link. But the again what if Supersymmetry is wrong? We can never really rule it out, to paraphrase a much more famous physicist than I, SUSY can only be discovered, or abandoned. Depends how patient we’re willing to be I suppose.

The analysis shows no excess above expectation for events consistent with Supersymmetry, but it does, along with several recent analyses from both ATLAS and CMS, demonstrate the relative maturity of new physics searches at the LHC. This will only grow in the coming months as the dash to analyze the 2011 data reaches fever pitch before a suite of what promise to be fascinating conferences this summer. With many CDF/D0 analyses heading towards their final iterations and more statistics to try to underline or refute the existence of the excess seen by CDF covered in the New York Times article and given a detailed report on the US LHC blogs.

I’ll mention more about a selection of the various ATLAS and CMS new physics searches in another post I imagine, but as of yet we are yet to see any striking evidence of the failure of the Standard Model to describe the data collected at the LHC. Maybe this will be the year?


The last few weeks

Monday, April 4th, 2011

Well, it has been an awfully long time since I posted anything whatsoever here on QD and for that I must apologise. In fact I have been rather increasingly missing my opportunities to post good interesting blogs for a sweet while. So I’ll give you a brief run down of some of the things filling my last few weeks. Let’s start with…..

Yes we physicists love to travel. A couple of weeks ago I flew from Geneva all the way down to Australia for a whistle-stop tour of the antipodes. It was indeed a flying visit of only 5 days in total where I was afforded the opportunity (I should really say privilege) to interact and discuss physics for a few days with members of the ATLAS group in Melbourne initially. I presented a seminar talk there and met with some colleagues before flying on to Adelaide to discuss high energy physics with many members of their faculty, representing various physics disciplines, presented a colloquium on ATLAS and the LHC and showed some first results from searches for Stable Massive Particles using the ATLAS detector (a beautiful paper that you can read all about in this arXiv posting. It was a break from my everyday responsibilities but a real treat to interact with colleagues, meet new interesting people and discover a fun and vibrant part of the world for the first time (I’d been to Australia before but never Adelaide). The other remarkable thing of this is that through ATLAS I now have a good friend to visit in Melbourne and could combine a little relaxation time with my work ‘duties’.
This week I’ll be off to Rome for a few days to finish off what looks like being another week of meetings. Along with a colleague at “La Sapienza”, the main city University of Rome, I have organized a short workshop to study the potential synergies of some of ATLAS’s effort on Exotics and Supersymmetry searches. In a collaboration of so many people it can often be difficult to see the wood for the trees and so a few days of concentrated work and discussion away from the spotlight of CERN can be remarkably beneficial for productivity and inspiration. A smaller subset of us met up in Copenhagen last year to great effect, leading to some very informative work. Why have the meeting away from CERN? Why blag yourself a free couple of days in Rome you ask? Well, at CERN it is very difficult to get this atmosphere of everyone focused on a particular set of points, working in a team for a short period. We have the tendency to wander off, go back to our offices, work on other things, or more seriously, be on-call where we could be called away at any moment. These short workshops are like taking a little bit of research “me time”, and more often than not you learn a lot more in an informal setting chatting to people about their efforts than you do listening to talks or reading papers (“What exactly do you mean?”, “I’ve never understood that, could you tell me what it is?”, “Why does that work anyway?”………questions you would *never* ask in a public meeting but far easier to ask in a more informal remote setting).
After Rome it’s back to lovely CERN where springtime is starting to bloom if only we didn’t have to………

Yup, the other thing taking up my time. Not so bad, the winter conference rush is over (something I’ll hopefully mention briefly in an upcoming post) but physics never sleeps. Just as we’ve polished off the last of the champagne and smoked the last of our celebratory conference deadline meeting cigars the LHC is ready to roll into action again, and like any good action movie sequel, this time, it’s serious!
2011 promises to be a watershed year for the LHC. All of the experiments have demonstrated their impressive turn around to publish results at breakneck speed from when the data is available and the quality of those results is very good indeed. But this year, well, let’s try and put it in perspective. In a few good runs of the machine (a couple of days basically) the LHC has delivered around half of the data it did in the entirety of the 2010 running. She’s having a technical stop now (an oil change, but we’re buying her some rims and a sweet new sounds system to boot) and will be back in business colliding beams very soon. The perspective I mentioned, the size of last years dataset will be increased by greater than a factor of 10 in time for the big summer conferences (starting in July), and we may have that data even earlier for conferences coming up in June! That dataset increase alone could be enough statistical power to see an excess of events in some of the search channels for new physics. That’s 3 months from now. The future is now! By the end of the year, last years dataset could have been increased by almost a factor of 100. With that type of data there is possibility of even some precision measurements.
My work has not only been kept busy working on analyses to exploit this summers dataset (while still finishing up one from the past years data) but also in coordinating the use of a new type of ATLAS data storage type which until now had not been used very extensively but which we will rely on more so this year. In order to save disk space for the upcoming data deluge,
and to give us resources to analyse it, the decision was made to dispense with a detailed data format from ATLAS and we were charged to store this information for interested users, but only use 1% of the data volume that had previously been taken up. Quite a challenge, but an important one to meet, and we’re going at it head-on.

The only other things I had time for this weekend was……

I am lucky enough to have become friends with an elderly gent from Beaujolais who sells his wines (which he harvests and makes all on his own) in the locals markets on Saturday and Sunday. He stays over in one of the spare rooms I have on Saturday night in exchange for a few bottles of his delicious wine. He’s a jovial character and this Saturday he arrived at my place with a couple of dozen oysters and some chilled white wine to share. A great way to start a Saturday afternoon, then pop down to lake Geneva to hang out with some friends, back over to France for an afternoon/evening barbeque before dashing back into Switzerland for a few hours of band practice before the night unfolds.

So all-in-all it’s been a busy time, but we’re all busy, aren’t we?


CERN announces LHC to run in 2012

Monday, January 31st, 2011

The TeVatron conspiracy theorists thought it may have been a hoax to blind-side their own running aspirations, but today CERN announces that the LHC will continue apace into 2012. The run in 2011 will soon be upon us and this ambitious plan to continue well into 2012 shows great faith in the LHC’s ability to deliver and provides a clear path for the detectors to make serious inroads into new physics parameter space in the upcoming 18 months. Improved constraints on new physics are already coming out from the impressive suit of papers and conference notes either public or surely in the works for an exciting winter conference season which will be with us soon.

The decision to run into 2012, was taken by CERN management following their annual skiing trip/winter getaway planning workshop held in Chamonix last week.
Not only will the LHC continue to run, but the beams will remain at their now accustomed 3.5TeV, providing a 7TeV center-of-mass. In my opinion this is a wise choice. The potential gains in pumping the energy from 7 to 8TeV were there, for certain channels, but in many/most cases a steady and progressive increase in luminosity at this lower energy is more than sufficient to provide the necessary sensitivity. Perhaps the big-wigs also decided to err on the side of caution and thought that even if the machine could operate well with 4TeV beams is it really worth the risk?
We’ll find out soon enough as the management usually do an excellent job summarizing their decision making to the rest of us doing our day-to-day work.

You can read for yourself the full press release regarding the decision to run and energy choice. From an experiments perspective we just want to know as soon as possible. Changing energy means rerunning Monte Carlo’s, perhaps reevaluating triggers and checking cross sections again. Running into 2012 impacts the timing of the shutdown and activities related to that. The long shutdown, now in late 2012 and 2013, is required to replace the splices needs for the LHC to able to approach her 14TeV design center-of-mass energy. But not only that. The experiments have extensive upgrade activities planned for these months and need to arrange manpower, equipment and resources required to safely and successfully delve back into their detectors to replace or tweak the parts in need of a tune up. Knowing this news will provide a clearer path to the exact nature of the early upgrade work.

But before 2012 running we have 2011 running. And even before that, we have lots to do analyzing the 2010 data. Now we can push ahead doing that, safe in the knowledge it will not be the last data that we take at 7TeV!


Resonance: Music from the ATLAS experiment

Wednesday, November 17th, 2010

Good day,

As Jon Butterworth reports in his Guardian blog entry today, the ATLAS cd project, long in the making, is about to be released. The project, which is titled Resonance, will constitute a double cd and DVD. Commemorative mugs, t-shirts and baseball caps will undoubtedly follow. All the proceeds go to charity, in particular, to the Happy Children’s Home in Pokhara, Nepal to help them build their orphanage. So not only do you get the great music and fascinating insight into the scientific/sonic marriage, but also you can snuggle up with that warm fluffy feeling of having helped out those little blighters who aren’t as well off as you are. It’s win win. To the music. The compositions are a mixed bag, spanning many genres and styles which in some sense, I suppose, is meant to reflect the diversity of the collaboration it represents. So therefore, not everything will be to everyones tastes. But the quality is excellent
and will, we hope, impress and perhaps even shock a few people. I have my favourites of course, but I am a bit biased given that I wrote and performed one of the songs. On that front, I’d like to make a little mention that the band I’m with, AWESOME, are the only band on the cd composed entirely of ATLAS physicists! But there is a lot to enjoy, from Heavy metal to Celtic harp.

Heavy metal you say? That’s right, like lead. The ions of which we are now continuously bashing together to produce spectacular new results. This shows the flexibility and breadth of the LHC physics program to probe the moments after the big bang.

For a more complete description of the heavy ion collisions see this very nice piece in Symmetry magazine.

But back to the cd, and to all of you going through the usual annual struggle of finding an interesting Christmas present for their families and friends, what better than a music project guaranteed to satisfy all comers. After all, just like ATLAS, there’s something for everyone. Here’s a picture of three of the handsomest collaborators if you needed more convincing.

Posing. (left to right, Nick Barlow, myself, Christian Ohm).

Posing. (left to right, Nick Barlow, myself, Christian Ohm)

Bye for now.


Keeping it friendly

Monday, October 25th, 2010

I join you fresh from a weekend of two majestic parties at two ends of the spectrum of graduate student experience. Although that ship sailed for me more years ago than I care to admit, I do still have the odd young friend who has yet to weigh anchor and head for the island of postdoc-dom. And some who have just undertaken that voyage.
The first of whom we partied for this weekend was a man who recently graduated. He made the bold move, about one and half years ago to jump ship from ATLAS and go “back” to work on D0 at the TeVatron, whereupon he finished an analysis on real data in time to return back to ATLAS to triumphantly accept his new job. We celebrated his graduation and his upcoming post. While the party was ongoing we received news of another close friend successfully defending his thesis and, having already secured a postdoc job, graduating from student life with aplomb. He had also moved to the TeVatron from ATLAS to experience some real data and get a good thesis out. For these two chaps that move in “the wrong direction” has paid dividends.

Our Saturday night was spent celebrating the company one last time of another dear friend who is moving back from CERN to his institution in the US in order to finish up his thesis and proceed on with his own move to bigger and better. Less a going away party than a moment to take stock of the transient nature of the field and how friends and colleagues move on before our eyes.

Friendships at CERN are strange things. Thrown together, as we are, into the mix of work, the lines between social life and working life can become quite blurred. Often there are friends of convenience instead of true comradeship. But every now and then we make, through our work connections friends for life, not just for collisions.
One friend leaving and we wish him well, hoping for his safe return quite soon.

One other thing to report is the pending release of the ATLAS cd. It’s been about a year since it was supposed to be coming out and now we hear that they are doing the final mastering. I’ll report back with more news and some links when it’s out.

An early snippet of the band I’m involved with can be seen here. Enjoy!


Inspired Direction

Wednesday, May 26th, 2010

I’m on shift again, and my usual streak has hit the ATLAS control room again with a bout of quench protection system problems and dumping of beams the like of which I’m starting to think might not happen when I’m not here. After all, if I’m analyzing data we must be taking it at some point. I should probably bring my rabbit’s foot with me for tomorrows graveyard shift. This brief hiatus from the LHC’s otherwise monumental first data taking run does provide me the opportunity to post though, for the first time in a while (sorry ’bout that!).

So what to say. My title refers to a visitor we had at CERN last week. Persis Drell, the director of SLAC, was at CERN for a couple of days with the purpose of catching up with the SLAC/Stanford group based out here. She tacked the CERN trip onto other official business she had in Europe but it was a very worthwhile couple of days. Persis had a pretty packed agenda planned for her including visits with the ATLAS hierarchy, a long chat with CERN’s own director Rolf Heuer and lunch with some of the ATLAS management. Into this day she also managed to squeeze some time with the staff and students who nominally work for her, but in many cases she may never have met. So, last Friday I found myself in a dusty basement, surrounded by boxes and broken equipment trying to explain the delicate inner workings of the ATLAS pixel detector, accompanied by one of the students in our group. Forgoing the setting up of any look-at-how-clever-we-are presentation we just had a chat and showed Persis around a bit. It was relaxed and informative. She asked questions and showed a genuine interest and it made me think about the last time someone had looked me in the eyes and showed a marked interest in the research I was doing? Dunno. Of course, you get good at these things when you’re high up the food chain. But there is a moment of inspiration in the recognition of your work as something beyond the ordinary.

My pitch was over and I embarked on a relatively successful but not particularly bloggable afternoon of work before our Friday group meeting started. 5pm every Friday, mostly to accommodate our colleagues back in the bay area, is a bad time to have a meeting. Unless, that is, you have wine with the meeting. Labs in the US aren’t allowed alcohol on site. One occasionally gets the impression that CERN may grind to a halt if such a rule were imposed here. We get the uneasy looks from our head as she realizes the wine bottles aren’t just ‘for show’. She politely declines the offer of a plastic cup half filled with cote du rhone (or half emptied of air I suppose) and we go through our presentations and updates in the usual manner.

We had a rather enjoyable work dinner that evening. I’m sometimes skeptical of going out to work related functions, often robbing you of your free time only to force you into conversation with someone who wants to talk solely about what they did at work that week. This was one of the good ones though. Of course there’s the physics talk, but it’s interspersed with all types of topics, anecdotes, even jokes.
It’s great to see all members of a group getting along, regardless of position. The lab director and one of the students in heated argument.

Being geographically separated from the place where you work has it’s pitfalls, mostly from an administration standpoint but also in that it makes you forget the potential support network that exists. Out of sight, out of mind in a sense. But when the boss, the big boss, puts in the time and effort to make you realize that there are people in your corner, it inspires you to do that little bit more in return…..and sometimes a little bit more is all it takes.


Event Displays from 7TeV Collisions

Tuesday, March 30th, 2010

Event Displays from 7TeV collisions in ATLAS are now online.

Collision Event @ 7TeV

Collision Event @ 7TeV

Another lovely image


First 7 Tev collisions have been recorded in ATLAS

Tuesday, March 30th, 2010

Title says it all!

There is much excitement being tracked on the ATLAS blog and in and around
everyone associated with the experiment.

The real physics program begins


Half of something is better than all of nothing!

Tuesday, March 2nd, 2010


Apologies for my lack of quantum diatribe in recent weeks. Thus far 2010 has been a hive of activity at CERN with first papers coming out from the big experiments already, or imminently, and the results of the Chamonix workshop. This is the workshop where the very important people from CERN go and hang out in Chamonix for a week and decide on the direction of the lab, returning to CERN after what seems like a pretty long process of talks and discussion (with I’m sure a bit of relaxing thrown in for good measure), to then tell the rest of us what’s going on. There might be a bit more to it than that, but since it isn’t by open invitation most of the padawan learners and younglings are left waiting for the decision of the Jedi council. Joking aside, this is an important process, since it gives the experts from the detector and machine side time to
digest each others comments and provide feedback while the lab management can take on board all that is said and formulate a plan that works within budgetary constraints etc.

This year we received the news that the LHC will run for the 2010-2011 with 3.5+3.5TeV beams, so a center-of-mass energy of 7TeV, half of the design specification of LHC. This number is a trade-off. The machine can hopefully operate safely at this energy for the next two years and provide the experiments with some physics. There was the discussion of going up to 10TeV CM energy, but there are risks involved, and (quite rightly) the LHC operators felt it most prudent to get some operational experience at a point they felt most safe at, and where, the experiments will get some real data to play with, and a sample of 1fb-1 at 7TeV should allow us to have some fun for a couple of years.
The lower energy doesn’t make a huge difference to LHCb, ALICE will still get their ions, and ATLAS and CMS will still be able to probe a high-energy regime in search of new physics, or in the earliest papers, just show how awesomely timed in and aligned the detectors are.

From I personal perspective this is a very positive and upbeat response to the will-they, won’t-they situation of which energies we’ll run at, and for how long we will be running. This is best exemplified by the wotk being done on 10TeV
CM energy Monte Carlo for physics studies at an operating energy we may well never run at.

But for now, we are here in early March, spring is in the air, and there’s beam back in the machine. Things are looking rosy.


Mood swings

Tuesday, December 8th, 2009

It’s been a busy couple of weeks with many more highs than lows. If you’re reading this you probably know already of the recent successes of the LHC, from first beam, to first collisions, to acceleration. This last weekend won’t have seen the LHC hit the headlines in the popular press as much as others but rest assured this was a big one. What was achieved throughout the last weekend was that the LHC, and the experiments who benefit from it’s proton collisions, ran stably with full detectors turned on. In the case of ATLAS that means we turned on the pixel detector for the first time with beam. You might be thinking something along the lines of “well what’s the big deal, haven’t the other parts of the detector been running for weeks, doesn’t that just mean you’re behind schedule or something?” but the reality of the situation is that the innermost detectors of these big experiments need to be treated very carefully while the beams are in their commissioning phase. All it would take is a stray beam or two inconveniently directed into those sensitive beauties to wreak havoc with years of patient work put in my many people. Anyway, this is an excitable digression, I’m on shift RIGHT NOW and we have BEAM RIGHT NOW so you’ll have to forgive me if I’m a bit sidetracked.

What I wanted to put across with this post is something else that has occurred at CERN in the last 6 weeks or so and that is the clear and collective change of mood. You are no doubt aware of the major accident that happened last September very soon after the LHC turned on for the first time. During the 14 months that followed the schedule of many students has slipped a year, some funding agencies have lost a little faith or belief in the LHC programme, which has become the butt of some jokes, quips and commentaries in the press. It became very evident as 2009 wore on that the mood at CERN was slipping. Positivism was draining away and many people were clearly becoming, shall we say less than motivated with their work. This is understandable. But through this all people were still hoping that the (re-)turn-on of the LHC would be a smooth and successful period that would give us the promise of data to come.

In hindsight the timing of the LHC turn-on has been perfect, with stable beams and some useful data being collected before everyone will take a well earned break for Christmas. In this way, the staff will all return in the New Year ready for the challenge ahead after pushing hard for a few weeks before the holidays. Had the start-up been delayed a few weeks it would have slipped into the New Year and left everyone feeling rather deflated while pushing their Christmas dinner around their plates, pondering their futures.

CERN these days is a buoyant, happy place. People are excited to be on shift, excited to be at work, and eager to be involved. Personally I think this excitement will be building and continuing for some time yet and throughout 2010 when we start to get “real” first data. It serves to remind you just how much everyone cares about what they do and how much the success of the LHC means to people, professionally, and personally.