ATLAS: Exceeding all expectations

“One year ago it would have been impossible for us to guess that the machine and the experiments could achieve so much so quickly”, says Fabiola Gianotti, ATLAS spokesperson. The whole chain – from collision to data analysis – has worked remarkably well in ATLAS.


The first LHC proton run undoubtedly exceeded expectations for the ATLAS experiment. “ATLAS has worked very well since the beginning. Its overall data-taking efficiency is greater than 90%”, says Fabiola Gianotti. “The quality and maturity of the reconstruction and simulation software turned out to be better than we expected for this initial stage of the experiment. The Grid is a great success, and right from the beginning it has allowed members of the collaboration all over the world to participate in the data analysis in an effective and timely manner, and to deliver physics results very quickly”.

In just a few months of data taking, ATLAS has observed the known elementary particles, up to the heavy W and Z bosons and the even heavier top quark. The experiment has also established its first limits on new physics, some of which are already beyond those produced so far at Tevatron. “We are producing new results all the time now”, says Gianotti. “We plan to release a new wave of results early next year, for the 2011 winter conferences. Given the record luminosity achieved by the machine, by the end of 2011, combining ATLAS and CMS, we can expect to be able to exclude the existence of the Higgs boson over the full allowed mass range, or else to collect evidence for it if its mass is greater than 125 GeV. We could also discover Supersymmetry up to masses of almost 1 TeV and new forces up to masses of the carrier particles of 1.5 - 2 TeV. And who knows, perhaps (hopefully!) Nature has some nice surprises in store for us!”

In parallel to putting a lot of effort into the analysis of the rich harvest of data from the proton-proton collisions, ATLAS has also started to collect information from the ion-ion run, which started last week. “Heavy-ion physics is an integral part of the ATLAS scientific programme”, explains Fabiola Gianotti. “In particular, ATLAS has excellent calorimetry, with almost complete angular coverage, fine granularity and very good resolution. These features are an asset when looking for signatures of quark-gluon plasma formation such as jet quenching”.

The first LHC ion run will end a few weeks before Christmas. After such an intense and demanding year, the ATLAS collaboration will have a chance to catch its breath and recharge its batteries in preparation for the new run that will start in 2011. “During the LHC technical stop, we will carry out the yearly maintenance of the infrastructure and replace some failing components such as power supplies, calorimeter optical links, etc. Indeed, this year has been wonderful for our collaboration, but it was also very challenging, and we will take advantage of the Christmas break to have a well-earned rest! After so many years of hard work by the worldwide ATLAS community, we expected things to work well, but not as well as this! The dedication and enthusiasm of everyone, in particular our young colleagues (students and post-docs), have been fundamental to achieving these results. The successes of this year have also been made possible thanks to the outstanding performance of the LHC. We are extremely grateful to the whole machine team”, concludes Gianotti.

by CERN Bulletin