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arXiv 1001.3422hep-phhep-ex
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LHC顶夸克对产生中的自旋关联效应

Spin Correlation Effects in Top Quark Pair Production at the LHC

Gregory Mahlon, Stephen J. Parke

备注：
27 pages, 11 postscript figures. A trivial error in Fig 11 was corrected which does not affect the conclusions
发表信息：
Phys.Rev.D81:074024,2010
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摘要：

在14 TeV的质子-质子对撞机，大型强子对撞机（LHC），我们表明，顶夸克对生产占主导地位，在低不变质量的两个类螺旋胶子的融合，产生顶夸克对在左-左或右-右螺旋配置。然而，在较高的不变质量下，产生主要是由非类螺旋胶子的融合，产生上下或上下非对角构型的顶夸克对，与通过夸克-反夸克湮灭产生顶夸克对相同。我们详细研究了低不变质量区，并表明，自旋关联可以很容易地观察到在这个区域中的顶部夸克的衰变产物的方位角，Δ φ，在实验室框架的差异的分布。由于大型强子对撞机产生顶夸克对的截面很大，即使切割要求顶夸克对的不变质量小于400 GeV，在应用探测器效率之前，大约的产量将是每fb^{-1} 10^4个双轻子（e，mu）事件。因此，即使在质量不变的限制下，也有足够的统计量来形成双轻子事件的Delta-phi分布。我们还讨论了在轻子加喷流通道中观察这些自旋相关的可能性。

英文摘要：

At a 14 TeV proton-proton collider, the Large Hadron Collider (LHC), we show that top quark pair production is dominated at low invariant mass by the fusion of two like-helicity gluons, producing top quark pairs in the left-left or right-right helicity configurations. Whereas, at higher invariant mass the production is dominated by the fusion of unlike-helicity gluons, producing top quark pairs in the up-down or down-up off-diagonal configurations, identical to top quark pair production via quark-antiquark annihilation. We study in detail the low invariant mass region, and show that the spin correlations can be easily observed in this region by looking at the distribution of the difference in the azimuthal angles, Delta-phi, of the dileptons decay products of the top quarks in the laboratory frame. Due to the large cross section for top pair production at the LHC, even with a cut requiring that the invariant mass of the top quark pair be less than 400 GeV, the approximate yield would be 10^4 di-lepton (e, mu) events per fb^{-1} before detector efficiencies are applied. Therefore, there is ample statistics to form the Delta-phi distribution of the dilepton events, even with the invariant mass restriction. We also discuss possibilities for observing these spin correlations in the lepton plus jets channel.

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