Two-particle azimuthal correlations in γp interactions using pPb collisions at √s_NN=8.16TeV

Authors

A. Tumasyan, CMS Collaboration

Date of this Version

7-20-2023

Citation

PhysicsLettersB844(2023)137905. https://doi.org/10.1016/j.physletb.2023.137905

Comments

Open access.

Abstract

The first measurements of the Fourier coefficients (V_nΔ) of the azimuthal distributions of charged hadrons emitted from photon-proton (γp) interactions are presented. The data are extracted from 68.8nb⁻¹of ultra-peripheral proton-lead (pPb) collisions at √s_NN=8.16 TeVusing the CMS detector. The high energy lead ions produce a flux of photons that can interact with the oncoming proton. This γp system provides a set of unique initial conditions with multiplicity lower than in photon-lead collisions but comparable to recent electron-positron and electron-proton data. The V_nΔ coefficients are presented in ranges of event multiplicity and transverse momentum (p^T) and are compared to corresponding hadronic minimum bias pPb results. For a given multiplicity range, the mean p_T of charged particles is smaller in γp than in pPb collisions. For both the γp and pPb samples, V_1Δ is negative, V_2Δ is positive, and V_3Δ consistent with 0. For each multiplicity and p_T range, V_2Δ is larger for γp events. The γp data are consistent with model predictions that have no collective effects.