Measurement of inclusive charged-particle b-jet production in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

TL;DR

This paper reports the measurement of inclusive b-jet production in proton-proton and proton-lead collisions at 5.02 TeV, showing that cold nuclear matter effects are negligible within current experimental uncertainties.

Contribution

It extends the lower transverse momentum limit of b-jet measurements at the LHC and provides data for testing QCD calculations involving b-jet production.

Findings

Nuclear modification factor $R_{pPb}^{b-jet}$ is consistent with unity.

b-jet production in p-Pb is unaffected by cold nuclear matter effects.

Measurements agree with NLO pQCD calculations using POWHEG and PYTHIA.

Abstract

A measurement of the inclusive b-jet production cross section is presented in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, using data collected with the ALICE detector at the LHC. The jets were reconstructed in the central rapidity region $|\eta|<0.5$ from charged particles using the anti-$k_{\rm T}$ algorithm with resolution parameter $R=0.4$. Identification of b jets exploits the long lifetime of b hadrons, using the properties of secondary vertices and impact parameter distributions. The $p_{\rm T}$-differential inclusive production cross section of b jets, as well as the corresponding inclusive b-jet fraction, are reported for pp and p-Pb collisions in the jet transverse momentum range $10 \le p_{\text{T, ch jet}} \le 100$ GeV/$c$, together with the nuclear modification factor, $R_{\rm pPb}^{\text{b-jet}}$. The analysis thus extends the lower $p_{\rm T}$ limit of b-jet measurements at the LHC. The nuclear modification factor is found to be consistent with unity, indicating that the production of b jets in p-Pb at $\sqrt{s_{\rm NN}} = 5.02$ TeV is not affected by cold nuclear matter effects within the current precision. The measurements are well reproduced by POWHEG NLO pQCD calculations with PYTHIA fragmentation.