Charged jet cross section and fragmentation in proton-proton collisions at $\sqrt{s}$ = 7 TeV

TL;DR

This paper measures charged jet cross sections and fragmentation in proton-proton collisions at 7 TeV, comparing results with theoretical models and simulations to test their accuracy.

Contribution

First measurement of charged jet cross sections and fragmentation distributions at 7 TeV, with detailed comparison to PYTHIA and NLO pQCD calculations.

Findings

POWHEG accurately describes the jet cross section across the measured range.

PYTHIA6 reproduces fragmentation distributions within 15%.

Discrepancies observed with PYTHIA8 in fragmentation modeling.

Abstract

We report the differential charged jet cross section and jet fragmentation distributions measured with the ALICE detector in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 7 TeV. Jets with pseudo-rapidity $\left| \eta \right| < {\rm 0.5}$ are reconstructed from charged particles using the anti-$k_{\rm T}$ jet finding algorithm with a resolution parameter $R$ = 0.4. The jet cross section is measured in the transverse momentum interval 5 $\leq p_{\rm T}^{\rm ch \; jet} <$ 100 GeV/$c$. Jet fragmentation is studied measuring the scaled transverse momentum spectra of the charged constituents of jets in four intervals of jet transverse momentum between 5 GeV/$c$ and 30 GeV/$c$. The measurements are compared to calculations from the PYTHIA model as well as next-to-leading order perturbative QCD calculations with POWHEG + PYTHIA8. The charged jet cross section is described by POWHEG for the entire measured range of $p_{\rm T}^{\rm ch \; jet}$. For $p_{\rm T}^{\rm ch \; jet}$ $>$ 40 GeV/$c$, the PYTHIA calculations also agree with the measured charged jet cross section. PYTHIA6 simulations describe the fragmentation distributions to 15%. Larger discrepancies are observed for PYTHIA8.