Measurement of dijet kT in p–Pb collisions at sNN

Abstract

A measurement of dijet correlations in p-Pb collisions at √ s NN = 5.02 TeV with the ALICE detector is presented. Jets are reconstructed from charged particles measured in the central tracking detectors and neutral energy deposited in the electromagnetic calorimeter. The transverse momentum of the full jet (clustered from charged and neutral constituents) and charged jet (clustered from charged particles only) is corrected event-by-event for the contribution of the underlying event, while corrections for underlying event fluctuations and finite detector resolution are applied on an inclusive basis. A projection of the dijet transverse momentum, k Ty = p ch+ne T,jet sin( ϕ dijet ) with ϕ dijet the azimuthal angle between a full and charged jet and p ch+ne T,jetthe transverse momentum of the full jet, is used to study nuclear matter effects in p-Pb collisions. This observable is sensitive to the acoplanarity of dijet production and its potential modification in p-Pb collisions with respect to pp collisions. Measurements of the dijet k Ty as a function of the transverse momentum of the full and recoil charged jet, and the event multiplicity are presented. No significant modification of k Ty due to nuclear matter effects in p-Pb collisions with respect to the event multiplicity or a PYTHIA8 reference is observed.

Experimental overview on small collision systems at the LHC

“…This conclusion is supported by a different approach, where events are ordered based on the zero-degree energy of slow neutrons produced in the collision on the Pb-going side, and an estimate of N coll from a data-driven approach inspired by the wounded nucleon model [121]. Furthermore, no significant nuclear modification has been seen in (charged) jet spectra [152], D-meson yields [148] nor dijet k T [153] at mid-rapidity either. While direct jet quenching [154] has not been observed, possible non-zero v 2 values of about 5% at p T up to 10 GeV/c albeit with rather large uncertainty have been reported [64].…”

Nuclear parton distributions from lepton-nucleus scattering and the impact of an electron-ion collider

“…In fact, until a few years ago, most nPDF analyses [17][18][19][20][21][22] were largely based on fixed-target DIS structure functions in lepton-nucleus scattering (with kinematic coverage restricted to x ∼ > 0.01) supplemented by some Drell-Yan cross-sections. A major improvement in this respect has been the recent availability of data on hard-scattering cross-sections from proton-lead collisions at the LHC, with processes ranging from jet [23][24][25][26][27] and electroweak boson production [28][29][30][31][32], to heavy quark production [33][34][35][36][37][38][39][40] among several others. Indeed, measurements of hard probes in p+Pb collisions provide useful information to constrain the nPDFs, as was demonstrated by a few recent studies [41,42].…”

Nonperturbative-transverse-momentum broadening in dihadron angular correlations in sNN=200GeV proton-nucleus collisions

“…Additional measurements that go beyond single inclusive hadrons may be able to shed further light on this phenomenon in p + A collisions. For example, dijet measurements in the kinematic regime of the Cronin effect have shown that the initial-state partonic transverse momentum is a function of the nucleus size [21], which was not observed at large jet transverse momentum [22].…”