Measurement of the Jet Energy Scale in the CMS experiment ... - IIHE

CHAPTER 2: The CMS experiment at the LHC 25HCALThe hadronic calorimeter (HCAL) [51] is designed to measure the energy of hadrons.The hadronic barrel (HB) is located between the ECAL and the solenoid coil and iscomplemented by the outer part (HO) placed outside the magnet. The HO is designedto absorb the remnant of the hadronic shower which has not been fully absorbed inthe HB. The HB covering the pseudorapidity range up to |η| = 1.3, provides a granularityof ∆η × ∆φ = 0.087 × 0.087. The hadronic endcap (HE) covers the region1.3 < |η| < 3.0 with the same granularity as HB up to |η| = 1.6 and a decreasing granularityto ∆η × ∆φ = 0.17 × 0.17 for the rest of HE coverage. The forward hadroniccalorimeter (HF) provides an extended coverage of the pseudorapidity from |η| = 3.0up to |η| = 5.0. The HCAL sub-detector is a sampling calorimeter where layers ofabsorber, result in producing hadron showers, interleaving with layers of active material,which measure the energy of the showered particles. In the HB and HE, brassplates are used as absorber material while the plastic scintillators constitute the activematerial. The HF is constructed from steel as absorber and as active material, quartzfibers are used.The initial calibration of the HCAL is performed using test beam data and a genericparametrization as of the ECAL can be obtained for the HCAL energy resolution. Thecombined energy resolution of the HCAL and the ECAL in the barrel region of thedetector is parametrized as [52]σ(E)E = 84.7% √E/GeV⊕ 7.4%.Therefore, a reconstructed jet with an energy of 100 GeV can be measured by thecalorimeter system with a precision of about 11.2%.The final calibration of the HCAL is achieved with the use of physics events based onthe kinematical properties of the objects produced in the hard interaction which areexplained in more detail in the next chapter.A quarter of the longitudinal view of the ECAL and HCAL sub-detectors can befound in Figure 2.8 where the pseudorapidity boundaries are also overlaid.2.2.3 Muon SystemThe muon chambers [53], the outermost sub-detector of the CMS experiment, is aimedto identify muons and measure their momenta. Three types of detectors are used inthe muon system, being drift tubes (DT), cathode strip chambers (CSC) and resistiveplate chambers (RPC). While the first and second ones provide precise trajectorymeasurements, the last one is characterized for its fast signal processing. The DTs areused in the barrel part of the detector, while the CSCs are used in the endcaps. Thelayers of RPCs are installed in both the barrel and the endcaps.