Measurement of W-boson production in p-Pb collisions at the LHC with ALICE

TL;DR

This paper reports on the measurement of W-boson production in proton-lead collisions at the LHC using the ALICE detector, providing insights into nuclear parton distribution functions and testing binary collision scaling.

Contribution

It presents the first measurement of W boson yields in p-Pb collisions at 5.02 TeV with ALICE, comparing results to pQCD calculations and exploring nuclear effects.

Findings

W boson yields are consistent with binary collision scaling.

Results support modifications of parton distribution functions in nuclei.

Data agree with next-to-leading order pQCD predictions.

Abstract

ALICE (A Large Ion Collider Experiment) is designed and optimized to study ultra-relativistic heavy-ion collisions, in which a hot and dense strongly-interacting medium is created. W bosons are produced in hard scattering processes occurring at the early stage of the collision and, since they are not affected by the strong interaction, they can be used as a benchmark for medium-induced effects. In proton-nucleus collisions the production of W bosons can be used to study the modification of parton distribution functions in the nucleus and to test the validity of binary collision scaling. The latter is studied by measuring the yield of W bosons in different intervals of event activity. In ALICE, the production of W bosons is measured via the contribution of their muonic decays to the inclusive $p_{\rm T}$-differential muon yield reconstructed with the muon spectro-meter at forward ($2.03 < \mathit{y}^{\mu}_{cms} < 3.53$) and backward rapidity ($-4.46< \mathit{y}^{\mu}_{cms} <-2.96$). The recent results from p--Pb collisions at a centre-of-mass energy of $\sqrt {s_{\rm NN}}$ = 5.02 TeV are presented and the measured cross sections are compared to perturbative Quantum Chromodynamics calculations at next-to-leading order.