arXiv 1208.42922012-08-21hep-ex

夸克偶素产生中的极化

Polarization in Quarkonium Production

James S. Russ

备注：: 6 pages, 10 figures, submission to FPCP2012

摘要：

强子碰撞中夸克偶素态的产生机制仍然很难理解。J/ $ψ$或$Υ(nS)$态到$μ^+ μ^-$最终态的衰变角分布对产生过程中的矩阵元素敏感，并提供了评估不同模型的独特工具。本次演讲将集中在新的结果自旋排列的$Υ(nS)$状态产生的$p\bar{p}$碰撞在$\sqrt{s}$ = 1.96 TeV使用CDF II探测器在费米实验室Tevatron。数据样本对应于6.7 fb $^{-1}$的积分亮度。的角分布分析作为两个柯林斯-Soper和s-通道螺旋度框架使用一个独特的数据驱动的背景确定方法的dimuon最终状态的横向动量的函数。分析的一致性检查比较框架不变的量来自参数化的角度分布测量在每个选择的参考系。该分析首次量化了$Υ(1S), Υ(2S)$和$Υ(3S)$衰变的完整三维角分布。在所有的坐标系中，衰变几乎都是各向同性的，即使在产生大的横动量时也是如此。

英文摘要：

Production mechanisms for quarkonium states in hadronic collisions remain difficult to understand. The decay angular distributions of J/$ψ$ or $Υ(nS)$ states into $μ^+ μ^-$ final states are sensitive to the matrix elements in the production process and provide a unique tool to evaluate different models. This talk will focus on new results for the spin alignment of $Υ(nS)$ states produced in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV using the CDF II detector at the Fermilab Tevatron. The data sample corresponds to an integrated luminosity of 6.7 fb$^{-1}$. The angular distributions are analyzed as functions of the transverse momentum of the dimuon final state in both the Collins-Soper and the s-channel helicity frames using a unique data-driven background determination method. Consistency of the analysis is checked by comparing frame-invariant quantities derived from parametrizations of the angular distributions measured in each choice of reference frame. This analysis is the first to quantify the complete three-dimensional angular distribution of $Υ(1S), Υ(2S)$ and $Υ(3S)$ decays. The decays are nearly isotropic in all frames, even when produced with large transverse momentum.

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