ϒ(nS) polarizations versus particle multiplicity in pp collisions at s=7 TeV


Khachatryan V., Sirunyan A., Tumasyan A., Adam W., Asilar E., Bergauer T., ...More

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol.761, pp.31-52, 2016 (SCI-Expanded) identifier

Abstract

The polarizations of the ϒ(1S), ϒ(2S), and ϒ(3S) mesons are measured as a function of the charged particle multiplicity in proton–proton collisions at s=7 TeV. The measurements are performed with a dimuon data sample collected in 2011 by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb−1. The results are extracted from the dimuon decay angular distributions, in two ranges of ϒ(nS) transverse momentum (10–15 and 15–35 GeV), and in the rapidity interval |y|>1.2. The results do not show significant changes from low- to high-multiplicity pp collisions, although large uncertainties preclude definite statements in the ϒ(2S) and ϒ(3S) cases.