Abstract
The pseudorapidity distributions of charged hadrons in proton-lead collisions at nucleon-nucleon center-of-mass energies sqrt{s_{mathrm{NN}}}=5.02 and 8.16 TeV are presented. The measurements are based on data samples collected by the CMS experiment at the LHC. The number of primary charged hadrons produced in non-single-diffractive proton-lead collisions is determined in the pseudorapidity range |ηlab| < 2.4. The charged-hadron multiplicity distributions are compared to the predictions from theoretical calculations and Monte Carlo event generators. In the center-of-mass pseudorapidity range |ηcm| < 0.5, the average charged-hadron multiplicity densities 〈dNch/dηcm〉|ηcm| < 0.5 are 17.31 ± 0.01 (stat) ± 0.59 (syst) and 20.10 ± 0.01 (stat) ± 0.85(syst) at sqrt{s_{mathrm{NN}}}=5.02 and 8.16 TeV, respectively. The particle densities per participant nucleon are compared to similar measurements in proton-proton, proton-nucleus, and nucleus-nucleus collisions.
Highlights
The CMS detectorThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter
The Hijing and Epos generators were tuned to data from RHIC and the LHC, respectively
The Hijing 1.3 calculation overpredicts the particle density because it has an older implementation of the gluon shadowing effects
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter. The silicon tracker measures charged particles within the range |ηlab| < 2.5 It consists of 1440 silicon pixel detector modules. The barrel region of the pixel detector consists of three layers, which are very close to the beam line They are located at average radii of 4.3, 7.2, and 11.0 cm, and provide excellent position resolution with their 150×100 μm pixels. The forward hadron (HF) calorimeter uses steel as an absorber and quartz fibers as the sensitive material. It consists of two halves, each located 11.2 m from the interaction region, and together they provide coverage in the range 3.0 < |ηlab| < 5.2. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. [28]
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