Heavy Ion Physics with the CMS detector at the LHC

Abstract

The Large Hadron Collider at CERN will collide protons at √ S = 14 TeV and lead ions at √ S NN = 5.5 TeV. The physics program of the Compact Muon Solenoid (CMS) includes the study of heavy ion collisions. The CMS detector consists of a 13 m long, 6 m wide superconducting solenoid providing a uniform 4 T magnetic field. Charged particles will be measured with a large acceptance, high resolution silicon tracker consisting of pixel and strip detector layers. The tracker is surrounded by electromagnetic and hadronic calorimeters located inside the magnet while the muon detector is positioned on the outside. The central detector will be complemented by CASTOR, a proposed forward calorimeter, and a Zero Degree Calorimeter (ZDC). The CMS data acquisition system, with its reliance on a multipurpose, high-level trigger system, is uniquely qualified for efficient triggering in high-multiplicity heavy ion events. The high energies available at the LHC will allow high statistics studies of the dense partonic system with hard probes: heavy quarks and quarkonia with an emphasis on the b and ϒ; high p T jets; photons and Z 0 bosons.

The high energy frontier of ultrarelativistic nucleus–nucleus collisions

“…Intriguing results on jet production at the LHC have been shown by ATLAS [41] (using the anti-k T algorithm [42]) and CMS [43] (based on the use of an iterative cone algorithm [44]). A strong increase in the di-jet unbalance is observed when comparing Pb-Pb to pp collisions [45,46], when jets are studied with jet radii R = (∆η) 2 + (∆ϕ) 2 ≃ 0.2 − 0.4.…”

Five years of tracking heavy ion collisions at RHIC

“…These RHIC data combined with SPS measurements extrapolate to a LHC Pb-Pb multiplicity of around 1000 -2000 at mid-rapidity. How the LHC experiment CMS is preparing for the Table 1 RHIC operating modes and total integrated luminosity delivered to the experiments [6] heavy ion program can be found in [11]. Heavy ions are extended objects and their collisions is not always head-on, the degree of geometrical overlap, or centrality, is described by the impact parameter, b, or perpendicular distance to the closest approach if the ions were undeflected.…”