TOP 2012 – Part 1

Greetings from the TOP 2012 conference, Winchester UK! What’s a ‘Winchester’ I hear you asking? A type of gun? Indeed yes, though sadly not of the smoking variety that we’re all so keen to find. However in this particular case Winchester is a historical town in the south of England, complete with the typical rolling green fields, a cathedral, and the not so typical contingent of visiting physicists!

This is the highlight of the conference year if you’re a top quark physicist. Better than ICHEP (unless of course, you actually got to go to ICHEP) and more relaxed than Moriond QCD. Five full days in a four star hotel in the English countryside with only the top quark on our minds, bliss! There’s also a pool and a spa, but who cares about such trivialities…

The best ‘little’ particle there is!

In the year of the Higgs discovery, what might we expect to see in the top sector? Well intrepid reader, that’s a mighty fine question and one that has an agreeable sense of symmetry to it. Just as we’re beginning to probe the boson responsible for bestowing particles with mass, we’re well and truly entering into an era of precision measurements of the standard model’s (SM) most massive particle! In this year’s conference all four five[1] hadron collider experiments involved in top quark physics will present cutting edge, state of the art results on everything from cross sections and properties, to resonances and exotic particle searches. This aptly named particle is, for lack of a more articulate argument, AWESOME [2]!

Conference goody bag win!

Now it’s only the first day of the conference, and we’ve plenty of reason to expect some very exciting results over the next few days, but what has got me so excited on day one? Is it the promise of some ‘friendly’ games of football and croquet with the theorists? No of course not, it’s the simply amazing conference goody bag, in which you’ll find this little gem!

Not only is it a laser pointer (never again will I have to gesture wildly from the audience at a dubious data point on a plot that the speaker pretends not to be able to see), it is also a more retro mechanical pointer, with a pen on the end as a finishing touch! Take that ICHEP!

Why do we care?

So why should you care about top quark physics? If the particle found is indeed the fabled Higgs Boson, then the top quark is the highest mass particle known to exist and may play a special role in electroweak symmetry breaking. Furthermore, there’s barely a new physics model out there that doesn’t involve the top quark in one way or another and top events are fantastic probes for new physics particles such as Z’, axi-gluons and certain flavours of SUSY.

Aren’t you going to show us some plots?

Since many of the physics analysts are taking advantage of last minute editorial board approvals, some of the more interesting and controversial plots are not available for me to post (at least not yet). But there are a few highlights that we can be pretty sure are on the way. Almost certainly there will be a lot of interest in the latest and greatest LHC top cross section combination and time will surely be allotted to the most current forward-backward asymmetry results from CDF and DØ. But with the full 7TeV data sets under their belts, and 8TeV on the way, it will be exciting to see what ATLAS and CMS have been doing with the forward-central asymmetries and lepton charge asymmetries.

If you’re not familiar with these terms, I could easily spend several blog entries explaining why this is a really cool measurement, and why it tantalisingly offers hints of beyond the standard model physics. But I suspect if you’ve read this far on a blog entitled “TOP 2012” then you’ve probably already heard of it. For those that haven’t, the following link is a very nice summary paper.

It’s a theory paper but try not to panic, and stay tuned for the latest results as they are presented this week.

[1] Welcome to top physics LHCb!

[2] Christian Schwanenberger, DØ Physics co-ordinator – ad verbatim, too many times to count and in various accents.

James Howarth is an experimental PhD student studying at the University of Manchester, UK. His physics interests centre on Top Quark Physics in general and on Top Properties in particular.

Moriond day 1: The outer limits

Not many trips take you to all ends of the world in one day, but that was nevertheless how it felt after the first talks at Moriond. Sunday and Monday have mainly featured presentations on neutrino and dark matter physics. Many of these experiments are placed in remote regions or deep under ground. We have heard reports from the OPERA collaboration (of [perhaps] faster than light neutrino fame), Ice Cube, a wonderful neutrino detector located at the South-pole, the Japanese T2K neutrino experiment and many many others. For someone working on a LHC experiment it is very refreshing to learn about other experiments in the field, we might be the biggest game in town, but not the only one.

La Thuile, host of the 2012 Rencontres de Moriond

Monday morning was all about Dark Matter. A very interesting subject connecting astrophysics with particle physics. In short, we believe that some new, unexplained type of particle causes the galaxies to be five times heavier than expected from what we see from visible light alone. A possible explanation comes from Supersymmetry (SUSY), which predicts a stable particle that is supposed to interact only through the weak force and gravity, the lightest supersymmetric particle or LSP. Most of the dark matter experiments are reporting negative or inconclusive results, except one, DAMA. So the talks have been focused on how each experiment either confirms or disagrees with DAMA. With the ATLAS experiment, we also search for SUSY dark matter, but in a very different way than the dedicated experiments. In ATLAS, dark matter could show itself as “missing energy” that makes the rest of the particles coming from the collision not quite add up energy wise. Depending on the model, it is possible to search for dark matter indirectly by looking for this missing energy together with other particles decaying in a specific pattern.

The LHC talks have been moved to the end of the week to give us more time to approve the latests results from the 2011 run. Everyone I’ve talked to here (especially the theorists) are interested to learn what we might have discovered, patience can be difficult with potential discoveries just around the corner

Morten Dam Jørgensen is a PhD fellow at the Niels Bohr Institute in Copenhagen, Denmark. He is currently working on searches for long-lived particles and general model independent searches for deviations from the Standard Model. You can find more information at http://mdj.dk

Mystical Moriond

As a young physicist not many conferences have the same mystical status as Rencontres de Moriond. This gathering of physicists from all areas of particle physics is one of most anticipated events of the year. More a gathering than a conference, Moriond started in 1966 and has inspired many similar events. Presentations, time for discussion and recreation is combined to inspire and foster collaboration and new ideas. Another element is the meeting between young and more experienced scientists. Nearly half of the talks are given by young participants below 35 like myself.
I was invited by the ATLAS collaboration to present our latest results on a search for a type of long-lived particles that has meant a lot to me for the last two years.

The particles are called R-Hadrons, or perhaps they will be – because at the moment they are just an idea about what Nature can potentially give us if the world is super-symmetric or contains extra dimensions. These particles are pretty crazy, not only are they very very heavy (much heavier than the top quark or the yet to be discovered Higgs boson) but they also live longer than most particles. Even stranger they can “flip” their electrical charge if they pass through material. So all in all some very strange particles, but also very interesting to look for.

In ATLAS there are quite a few of us working on this kind of search, so presenting the work is not simply a personal effort; the results are made in collaboration between many people creating the analysis, not to mention all the work that goes into running the experiment. Because we always publish together, presentations like mine must be approved and agreed upon by the rest of the collaboration, meaning that they have to be thoroughly worked out before the talk. In the next post I will talk about the preparations and my first impressions of the place itself, now I have to catch my flight!

Morten Dam Jørgensen is a PhD fellow at the Niels Bohr Institute in Copenhagen, Denmark. He is currently working on searches for long-lived particles and general model independent searches for deviations from the Standard Model. You can find more information at http://mdj.dk