Study of azimuthal anisotropy of $\Upsilon$(1S) mesons in pPb collisions at $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV

TL;DR

This study measures the azimuthal anisotropy of $$(1S) mesons in high-multiplicity pPb collisions at 8.16 TeV, revealing smaller anisotropy than charmonia but similar to lead-lead results, using a two-particle correlation method.

Contribution

It provides the first measurement of $$(1S) azimuthal anisotropy in pPb collisions at this energy, employing a novel background subtraction technique.

Findings

Azimuthal anisotropy of $$(1S) is smaller than charmonia in pPb collisions.

Results are consistent with $$(1S) anisotropy in PbPb collisions at 5.02 TeV.

Method effectively suppresses nonflow effects in anisotropy measurement.

Abstract

The azimuthal anisotropy of $\Upsilon$(1S) mesons in high-multiplicity proton-lead collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 8.16 TeV. The $\Upsilon$(1S) mesons are reconstructed using their dimuon decay channel. The anisotropy is characterized by the second Fourier harmonic coefficients, found using a two-particle correlation technique, in which the $\Upsilon$(1S) mesons are correlated with charged hadrons. A large pseudorapidity gap is used to suppress short-range correlations. Nonflow contamination from the dijet background is removed using a low-multiplicity subtraction method, and the results are presented as a function of $\Upsilon$(1S) transverse momentum. The azimuthal anisotropies are smaller than those found for charmonia in proton-lead collisions at the same collision energy, but are consistent with values found for $\Upsilon$(1S) mesons in lead-lead interactions at a nucleon-nucleon center-of-mass energy of 5.02 TeV.