Abstract:
The pseudorapidity distribution of charged hadrons in pp collisions at root s = 13 TeV is measured using a data sample obtained with the CMS detector, operated at zero magnetic field, at the CERN LHC. The yield of primary charged long-lived hadrons produced in inelastic pp collisions is determined in the central region of the CMS pixel detector (vertical bar eta vertical bar < 2) using both hit pairs and reconstructed tracks. For central pseudorapidities (vertical bar eta vertical bar < 0.5), the charged-hadron multiplicity density is dN(ch)/d eta vertical bar(vertical bar eta vertical bar) < 0.5= 5.49 +/- 0.01 (stat) +/- 0.17 (syst), a value obtained by combining the two methods. The result is compared to predictions from Monte Carlo event generators and to similar measurements made at lower collision energies.
