I work with crazy particles. Dark matter is pretty weird, so are neutrinos seemingly, but what I search for blows it all away. Tuesday was the day of my presentation. The format for these young scientist presentations are 5 minutes and time for a single question afterwards. Trying to present a full picture of any analysis in that short a time is impossible; instead the idea is more like handing out a business card telling the audience what you work on in the hope that some will be interested and contact you informally afterwards.

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.

Experimentalists and theorists are gathering once more in the Alps at La Thuile, Italy, March 3-17 for the annual "Rencontres de Moriond" to discuss latest results in particle physics and cosmology.

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.

This is continuing from the previous post, where I discussed how we convert data collected by ATLAS into usable objects. Here I explain the steps to get a Physics result. I can now use our data sample to prove/disprove the predictions of Supersymmetry (SUSY), string theory or what have you. What steps do I follow?

OK, so I’ll try to give a flavour of how the data that we collect gets turned into a published result. As the title indicates, it takes a while! The post got very long, so I have split it in two parts. The first will talk about reconstructing data, and the second will explain the analysis stage.

A very happy new year to the readers of this blog. As we start 2012, hoping to finally find the elusive Higgs boson and other signatures of new physics, an important question needs to be answered first - are we going to have collisions at a center of mass energy of 7 or 8 TeV?

“If it’s just a fluctuation of background, it will take a lot of data to kill.” Dr. Fabiola Gianotti, spokesperson for the ATLAS collaboration, made this statement on Dec. 13, 2011 during a special seminar I attended at CERN. Within the minute that followed, I hurriedly concocted a tweet, tacked on #Higgs and #CERN hashtags, and sent Fabiola’s weighty comment out onto the WWW.

The results on Standard Model (SM) Higgs searches that ATLAS reported at a CERN seminar on December 13, 2011, have now been submitted for publication in three papers.

The ATLAS collaboration has announced the discovery of the χ_b(3P), which is a bound state of a bottom quark and bottom antiquark (bbar).

The latest update of the ATLAS searches for the Standard Model Higgs boson was presented at a CERN seminar on December 13, 2011. As stated in the CERN press release, the new ATLAS and CMS results are "sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. Tantalising hints have been seen by both experiments in the same mass region, but these are not yet strong enough to claim a discovery."

The Higgs Boson is the only missing piece in the Standard Model of particle physics and its search is undoubtedly one of the most important searches in the history of physics. The Higgs boson is the generator of all elementary particle masses in nature. The mass of the Higgs boson itself is unknown, and before the LHC it was searched for in previous experiments but not found. LHC experiments have produced excellent results since the start of the data taking. In ATLAS and CMS a discussion was initiated about a year ago to combine the Higgs search results from both experiments. The framework and the procedure to combine results had to be defined and agreed upon before the combined analysis could proceed.

Physicists are confident they will soon be able to answer a fundamental question at the LHC: how do particles acquire mass? The simplest answer, the one given in the Standard Model of the fundamental particles, is that a single particle, the Higgs boson, endows the other particles and itself with mass. The Higgs boson does this by means of the "Higgs mechanism", which involves breaking a symmetry that would leave all Standard Model particles massless if it were not broken. However the Higgs boson is not the only way the Higgs mechanism might work.

Today we witnessed a landmark LHC first: At the HCP conference in Paris, friendly rivals, the ATLAS and CMS collaborations, came together to present a joint result! This ATLAS-CMS combined Higgs search was motivated by the fact that pooling the dataset increases our chances of excluding or finding the Higgs boson over those of a single experiment. This is the first example of this kind of scientific collaboration at the LHC, and the success of the whole endeavor hinged on a whole host of thorny issues being tackled…

Perhaps the most anticipated result of the LHC involves the search for the Higgs boson, the only particle predicted by the Standard Model (SM) that has not yet been seen by experiments. The Higgs boson helps explain how elementary particles acquire mass. If the SM Higgs boson exists it will be produced at the LHC and swiftly decay into various known and well-studied particles, with the dominant decay products depending on the actual Higgs mass. ATLAS and CMS search for the SM Higgs boson using a range of decay products: two photons; two tau leptons; two b quarks; two W bosons; and two Z bosons. Analysing all these channels ensures that the search is sensitive to observing the Higgs irrespective of its mass.

I’m writing from the annual Hadron Collider Physics Symposium, which began on Monday in Paris, France. It’s organised jointly by LPNHE and the University of Paris VI & VII, with an excellent location right in the heart of the Latin Quarter. HCP is a fun conference with only plenary talks, which means that I’ve had the chance to attend talks on a wide range of subjects including many quite remote from my usual areas of expertise.

If you ask a child to draw a physicist, they’ll usually draw you a disheveled man in a lab coat. But looking around the hundreds of physicists eating lunch at CERN today, I saw many women, only one or two that could be classified as disheveled, and zero lab coats. Yet this image persists.

The ATLAS Experiment presented its latest results at the Hadron Collider Physics Symposium 2011 in Paris, France (14-18 November). Many of the most recent searches and analyses are based on more than double the data available at the last big conference in August.

It’s not every day you get to explain ATLAS to a group of journalists with just a pop-up book as a prop. But, as some readers might already know, this is no ordinary pop-up book. ATLAS and the LHC leap from the page in incredible detail thanks to paper engineer Anton Radevsky’s wonderful designs. A new edition of the book has just been released in French, so at the end of last month I found myself travelling in to the centre of Paris from Orsay for the press launch.

Du 12 au 16 novembre, plus de 250 physiciens des particules se réuniront à Kyoto, au Japon, pour partager leurs plus récents résultats. L'une des conférences internationales de physique des particules les plus prisées de l'année, le Hadron Collider Physics Symposium 2012 (HCP 2012), aura lieu, cette année, au pays du Soleil levant.

The clock just turned 2:00 a.m., again, on LHC Page One – the machine’s online status viewer – and I’m pondering just how I ended up on the longest shift of the year. I normally love this evening, snuggling under a warm comforter for that extra hour of late-autumn sleep. But, this year, on the very hour we ‘fall back’, I am cuddling with the controls of ATLAS’s 46 meter long muon spectrometer, a bar of chocolate and an extra cup of coffee. So be it.

In an amazing year that has exceeded our expectations, the Large Hadron Collider has delivered, and ATLAS has recorded, over 5 inverse femtobarns (fb-1) of collisions. These units correspond to having 3.4 x 1014 or 340 000 000 000 000 total collisions. Most analyses presented at the last major conference (the Lepton Photon Symposium in August in Mumbai) made use of about 1 fb-1, so this is a big jump.

L'édition francophone de Voyage au Cœur de la Matière sortira le 25 octobre à Paris aux Editions Verlhac (diffusion Seuil). Ce livre animé dévoile une grande aventure scientifique moderne : l'extraordinaire quête menée par l'expérience ATLAS pour comprendre notre Univers.

A new French edition of the ATLAS pop-up book, Voyage au Cœur de la Matière (Voyage to the Heart of Matter), will be officially launched from the exhibition Entrée en Matière at Paris' Trocadéro on Tuesday, October 25th.

The first time I drove to Fermilab as a grad student, I got kind of lost. However, once I remembered my adviser’s words of advice, it was suddenly easy to find the strangely shaped Wilson Hall, a.k.a. “the highrise sticking out of the Prairies”. During my PhD years with the CDF Collaboration, I went there many a time – to attend meetings, to take shifts. The Chicago area summers were harsh, and so were the winters. On early morning shifts over the Christmas week, I realized that all too well. CDF had over five hundred collaborators at that time and this was my first introduction to a big experiment. Despite its size, everyone still seemed to know each other and it was one big happy family.