At 12:58:34 the LHC Control Centre declared stable colliding beams: the collisions were immediately detected in CMS. Moments later the full processing power of the detector had analysed the data and produced the first images of particles created in the 7 TeV collisions traversing the CMS detector.
CMS was fully operational and observed around 200000 collisions in the first hour. The data were quickly stored and processed by a huge farm of computers at CERN before being transported to collaborating particle physicists all over the world for further detailed analysis.
The first step for CMS was to measure precisely the position of the collisions in order to fine-tune the settings of both the collider and the experiment. This calculation was performed in real-time and showed that the collisions were occurring within 3 millimetres of the exact centre of the 15m diameter CMS detector. This measurement already demonstrates the impressive accuracy of the 27 km long LHC machine and the operational readiness of the CMS detector. Indeed all parts of CMS are functioning excellently – from the detector itself, through the trigger and data acquisition systems that select and record the most interesting collisions, to the software and computing Grids that process and distribute the data.
“This is the moment for which we have been waiting and preparing for many years. We are standing at the threshold of a new, unexplored territory that could contain the answer to some of the major questions of modern physics” said CMS Spokesperson Guido Tonelli. “Why does the Universe have any substance at all? What, in fact, is 95% of our Universe actually made of? Can the known forces be explained by a single Grand-Unified force”. Answers may rely on the production and detection in laboratory of particles that have so far eluded physicists. “We’ll soon start a systematic search for the Higgs boson, as well as particles predicted by new theories such as ‘Supersymmetry’, that could explain the presence of abundant dark matter in our universe. If they exist, and LHC will produce them, we are confident that CMS will be able to detect them.” But prior to these searches it is imperative to understand fully the complex CMS detector. “We are already starting to study the known particles of the Standard Model in great detail, to perform a precise evaluation of our detector’s response and to measure accurately all possible backgrounds to new physics. Exciting times are definitely ahead”.
Images and animations of some of the first collisions in CMS can be found on the CMS public web site http://cms.cern.ch
CMS is one of two general-purpose experiments at the LHC that have been built to search for new physics. It is designed to detect a wide range of particles and phenomena produced in the LHC’s high-energy proton-proton collisions and will help to answer questions such as: What is the Universe really made of and what forces act within it? And what gives everything substance? It will also measure the properties of well known particles with unprecedented precision and be on the lookout for completely new, unpredicted phenomena. Such research not only increases our understanding of the way the Universe works, but may eventually spark new technologies that change the world in which we live. The current run of the LHC is expected to last eighteen months. This should enable the LHC experiments to accumulate enough data to explore new territory in all areas where new physics can be expected.
The conceptual design of the CMS experiment dates back to 1992. The construction of the gigantic detector (15 m diameter by 21m long with a weight of 12500 tonnes) took 16 years of effort from one of the largest international scientific collaborations ever assembled: more than 3600 scientists and engineers from 182 Institutions and research laboratories distributed in 39 countries all over the world.