ϒ(nS) polarizations versus particle multiplicity in pp collisions at

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• 作者：The CMS Collaboration^⋆ ; V. Khachatryan ; A.M. Sirunyan ; A. Tumasyan
• 关键词：CMS ; Physics ; Quarkonium production ; Quarkonium polarization ; QCD medium effects
• 刊名：Physics Letters B
• 出版年：2016
• 出版时间：10 October 2016
• 年：2016
• 卷：761
• 期：Complete
• 页码：31-52
• 全文大小：911 K

文摘

The polarizations of the ϒ(1S)$\mathrm{\Upsilon }(\mathrm{1}\mathrm{S})$, ϒ(2S)$\mathrm{\Upsilon }(\mathrm{2}\mathrm{S})$, and 599153c9434f1288" title="Click to view the MathML source">ϒ(3S)$\mathrm{\Upsilon }(\mathrm{3}\mathrm{S})$ mesons are measured as a function of the charged particle multiplicity in proton–proton collisions at $\sqrt{s}=7\text{TeV}$. 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)$\mathrm{\Upsilon }(\mathrm{n}\mathrm{S})$ transverse momentum (10–15 and 15–35 GeV), and in the rapidity interval |y|<1.2$|y|<1.2$. The results do not show significant changes from low- to high-multiplicity pp collisions, although large uncertainties preclude definite statements in the ϒ(2S)$\mathrm{\Upsilon }(\mathrm{2}\mathrm{S})$ and 599153c9434f1288" title="Click to view the MathML source">ϒ(3S)$\mathrm{\Upsilon }(\mathrm{3}\mathrm{S})$ cases.