Pseudorapidity distribution of charged hadrons in proton-proton collisions at sqrt(s) = 13 TeV

TL;DR

This paper measures the distribution of charged hadrons in proton-proton collisions at 13 TeV using the CMS detector, providing data that helps validate and improve theoretical models of particle production.

Contribution

It presents the first detailed measurement of charged hadron pseudorapidity distribution at 13 TeV with the CMS detector, using novel methods and comparing results to models and previous energies.

Findings

Charged-hadron multiplicity density at eta<0.5 is 5.49 +/- 0.01 (stat) +/- 0.17 (sys).

Results are consistent with some Monte Carlo predictions and extend previous measurements to higher energy.

Provides data for tuning particle production models at LHC energies.

Abstract

The pseudorapidity distribution of charged hadrons in pp collisions at sqrt(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 (abs(eta)<2) using both hit pairs and reconstructed tracks. For central pseudorapidities (abs(eta)<0.5), the charged-hadron multiplicity density is dN/d(eta)[charged,abs(eta) < 0.5] = 5.49 +/- 0.01 (stat) +/- 0.17 (sys), 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.