Interpretation of angular distributions of Z-boson production at colliders

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• 作者：Jen-Chieh Peng^a ; ^{jcpeng@illinois.edu" class="auth_mail" title="E-mail the corresponding author} ; Wen-Chen Chang^b ; Randall Evan McClellan^a ; Oleg Teryaev^c
• 关键词：Drell&ndash ; Yan process ; Lam&ndash ; Tung relation ; QCD
• 刊名：Physics Letters B
• 出版年：2016
• 出版时间：10 July 2016
• 年：2016
• 卷：758
• 期：Complete
• 页码：384-388
• 全文大小：316 K

文摘

High precision data of dilepton angular distributions in γ^⁎/Z${\gamma }^{⁎}/Z$ production were reported recently by the CMS Collaboration covering a broad range of the dilepton transverse momentum, q_T$q_T$, up to ∼300 GeV$\sim 300\text{GeV}$. Pronounced q_T$q_T$ dependencies of the λ and ν   parameters, characterizing the cos²⁡θ${\cos }^2\theta$ and cos⁡2ϕ$\cos 2\varphi$ angular distributions, were found. Violation of the Lam–Tung relation was also clearly observed. We show that the q_T$q_T$ dependence of λ   allows a determination of the relative contributions of the $q\overline{q}$ annihilation versus the qG   Compton process. The violation of the Lam–Tung relation is attributed to the presence of a non-zero component of the $q-\overline{q}$ axis in the direction normal to the “hadron plane” formed by the colliding hadrons. The magnitude of the violation of the Lam–Tung relation is shown to reflect the amount of this ‘non-coplanarity”. The observed q_T$q_T$ dependencies of λ and ν from the CMS and the earlier CDF data can be well described using this approach.