Updated: 6 March 2011

Northeastern University/CERN

2002 Research Experiences for Undergraduates Program

Calibration of the Compact Muon Solenoid Hadron Calorimeter

Advisors: Richard Kellogg and Pawel de Barbaro
CERN, Geneva, Switzerland


The particle physics world is striving to detect the Higgs Boson, the theorized last piece in the Standard Model puzzle. For this end, CERN is building the Large Hadron Collider (LHC), which will be the most powerful accelerator in the world when it goes online in 2008. The LHC is a proton-proton collider, as opposed to the particle-antiparticle collider that was its predecessor, the Large Electron Positron collider (LEP). Four detectors are being built for the new accelerator: the Compact Muon Solenoid (CMS); A Large Ion Collider Experiment (ALICE); LHC Beauty experiment (LHC-B); and A Toroidal LHC Apparatus (ATLAS). All four follow the same basic design. They measure the energy and position of particles via different layers designed to detect particles of increasing energies. These layers are called calorimeters and are referred to by the type of particles they stop: Electron Calorimeter (ECAL); Hadron Calorimeter (HCAL); solenoid; and muon chamber.

While at CERN, I assisted in the calibration of CMS HCAL. In order to simulate realistic working conditions, the HCAL crew had to make a small ECAL so that they could calibrate HCAL as it would appear behind ECAL. Thus, they also needed to calibrate their ECAL. I arrived during the first test beam run of ECAL. We systematically shot the electron beam into each crystal of ECAL; the data we collected were the results of these measurements. Since test beam time is limited, we made cursory analysis of the data to check that it was reasonable. The majority of the summer was spent completely analyzing this data and similar data gathered when HCAL was placed behind ECAL. In CMS, particles will pass through ECAL and hit HCAL at a variety of angles. To simulate this effect at the test site, ECAL was fixed while HCAL was placed on a movable table. The table could be rotated horizontally and pitched vertically. Systematically, we adjusted the table and measured the reaction of HCAL (through ECAL) at various angles and through different ECAL crystals.