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LHC sets world record

A cross section showing the 7 TeV collision as recorded by CMS
Courtesy of CMS

Today the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland has collided two beams of 3.5 TeV protons – producing 7 TeV, a new world record for energy produced in a collider. The (Compact Muon Solenoid) CMS experiment successfully detected these collisions, signifying the beginning of the 'first Physics" at the LHC.

"Today's achievement of collisions at 7 TeV has opened the door to what we hope is a vast hall full of new and deeper understandings about the universe and the interactions between particles," said University of Minnesota Professor Jeremiah Mans.

CMS was fully operational and observed around 200,000 collisions in the first hour. The data were quickly stored and processed by a huge array 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.

"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," said CMS Spokesperson Guido Tonelli. "If they exist, and LHC will produce them, we are confident that CMS will be able to detect them." Prior to these searches it was 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."

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 tons) 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.

The University of Minnesota has played a key role in the creation of the CMS detector. The Minnesota team, jointly supervised by professors Rusack, Mans and Kubota, currently consists of three postdoctoral researchers, five graduate students, and six undergraduates. Professor Roger Rusack, currently at CERN for a year as the leader for electromagnetic calorimeter, has been involved with the project since 1993. Professor Rusack first developed and tested the photodetectors for the calorimeter and in recent years has led work on the low-voltage system and data links in the detector. Professor Mans leads a group working on the hadron calorimeter and developed triggering electronics for the calorimeter. The group is also involved in upgrades designed to further improve the quality of data produced by the detector.

The Minnesota group is working on a number of physics analysis topics which are expected to yield results by midsummer. These include studies of the massive electroweak bosons (particularly the neutral Z boson) as well as studies of photons produced in the collisions at LHC. The group is also looking for possible new particles, such as possible heavy almost-stable charged particles which could have an important connection to the dark matter problem.

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