Abstract:
The polarizations of the \(\Upsilon\)(1S), \(\Upsilon\)(2S), and \(\Upsilon\)(3S) mesons are measured as a function of the charged particle multiplicity in proton-proton collisions at\(\sqrt{s}\) = 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 \(\Upsilon\)(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 \(\Upsilon\)(2S) and \(\Upsilon\)(3S) cases.
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