Abstract

Inclusive jet production in pPb collisions at a nucleon–nucleon (NN) center-of-mass energy of sqrt{s_{_mathrm {NN}}} =5.02,mathrm{TeV} is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 30.1 nb^{-1} is analyzed. The jet transverse momentum spectra are studied in seven pseudorapidity intervals covering the range -2.0<eta _mathrm {CM}< 1.5 in the NN center-of-mass frame. The jet production yields at forward and backward pseudorapidity are compared and no significant asymmetry about eta _mathrm {CM} = 0 is observed in the measured kinematic range. The measurements in the pPb system are compared to reference jet spectra obtained by extrapolation from previous measurements in pp collisions at sqrt{s}=7,mathrm{TeV} . In all pseudorapidity ranges, nuclear modifications in inclusive jet production are found to be small, as predicted by next-to-leading order perturbative QCD calculations that incorporate nuclear effects in the parton distribution functions.

Highlights

  • The interpretation of the jet modification results in nucleus–nucleus collisions and the understanding of their relation to the properties of the quark gluon plasma (QGP) requires detailed knowledge of all nuclear effects that could influence the comparisons with the pp system

  • The uncertainties depend on the jet pT and pseudorapidity, and the table shows representative values in two jet pT and ηCM ranges

  • The remaining uncertainties are partially correlated in jet pT, with the unfolding uncertainty dominating at low jet pT and the jet energy scale (JES) uncertainty dominating at high jet pT

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Summary

Introduction

The interpretation of the jet modification results in nucleus–nucleus collisions and the understanding of their relation to the properties of the QGP requires detailed knowledge of all nuclear effects that could influence the comparisons with the pp system. Nuclear modifications may already be present at the initial state of the collisions, independently of QGP formation. Such modifications are collectively referred to as cold nuclear matter (CNM) effects and include parton energy loss and multiple scattering before the hard scattering, and modifications of the parton distribution functions in the nucleus (nPDFs) with respect to those of a free nucleon (PDFs). Some nPDF modifications have been previously deduced from measurements of lepton–nucleus deep inelastic scattering and Drell–Yan production of lepton pairs from qq annihilation in proton–nucleus collisions [17]. Measurements of π 0 production in deuteron–gold collisions at RHIC [18] are included in recent nPDF fits to better constrain the nuclear gluon distributions [19]. In the range 0.02 x 0.2, the nPDFs are enhanced (“antishadowing” [17]), and for x 0.2 a suppression has been seen (“EMC effect” [21])

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