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arXiv 1012.0767hep-ex
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STAR的最新结果和在RHIC极化$\vec{p}+\vec{p}$碰撞中$W^{-(+)}$玻色子产生的前景

Recent STAR results and prospects of $W^{-(+)}$ boson production in polarized $\vec{p}+\vec{p}$ collisions at RHIC

Joseph Seele

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5 pages, 4 figures, Proceedings of SPIN2010 international symposium, Julich, Germany, September 27 - October 2, 2010
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摘要：

2009年，RHIC自旋物理计划完成了$\sqrt{s} = 500$ GeV的极化$\vec{p}+\vec{p}$碰撞的第一个数据采集周期，积累了~12 pb的$^{-1}$和~39%的束极化。这为基于$W^{-(+)}$玻色子的产生研究质子的自旋-味道结构开辟了一个新纪元。$W^{-(+)}$玻色子是在$\bar{u}+d (\bar{d}+u)$碰撞中产生的，并且可以通过它们的轻子衰变$e^-+\bar{ν_e}(e^++ν_e)$来检测，其中只有相应的带电轻子被测量。区分$\bar{u}+d$和$\bar{d}+u$夸克组合需要区分高$p_T$电子和正电子的电荷符号，这又需要精确的跟踪信息。在中等速度时，STAR依靠时间投射室。在前向快速性方面，前向GEM跟踪器将提供新的跟踪能力，该跟踪器由正在建造的六个三重GEM探测器组成。利用高度分段的STAR电磁量热计，通过施加隔离准则抑制喷流事件，并根据测量的远侧能量否决双喷流事件，实现了对W玻色子信号事件的QCD背景抑制几个数量级。STAR的横截面和单自旋不对称性的极化$\vec{p}+\vec{p}$碰撞中的$W^{-(+)}$玻色子生产的第一次测量结果的状态将与涉及STAR前向GEM跟踪器的前景的讨论一起提出。

英文摘要：

In 2009, the RHIC spin physics program completed the first data taking period of polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s} = 500$ GeV, accumulating ~12 pb$^{-1}$ with ~39% beam polarization. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. $W^{-(+)}$ bosons are produced in $\bar{u}+d (\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^-+\bar{ν_e}(e^++ν_e)$, where only the respective charged lepton is measured. The discrimination of $\bar{u}+d$ and $\bar{d}+u$ quark combinations requires distinguishing the charge sign of high $p_T$ electrons and positrons, which in turn requires precise tracking information. At mid-rapidity, STAR relies on the Time Projection Chamber. At forward rapidity, new tracking capabilities will be provided by the Forward GEM Tracker, consisting of six triple-GEM detectors which are under construction. The suppression of QCD background over W boson signal events by several orders of magnitude is accomplished by using the highly segmented STAR Electromagnetic Calorimeters to impose isolation criteria suppressing jet events, and vetoing dijet events based on the measured away side energy. The status of the STAR results on the first measurements of the cross section and single spin asymmetry for $W^{-(+)}$ boson production in polarized $\vec{p}+\vec{p}$ collisions will be presented along with a discussion of prospects involving the STAR Forward GEM Tracker.

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