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arXiv 1302.0960hep-phhep-ex
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在LHC与底或顶夸克对有关产生的喷注之间的方位角相关

Azimuthal correlation among jets produced in association with a bottom or top quark pair at the LHC

Kaoru Hagiwara, Satyanarayan Mukhopadhyay

备注：
15 pages, 5 figures; v2: minor additions to text, references added, version as published in JHEP
发表信息：
JHEP05(2013)019
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摘要：

喷流与大质量标量、矢量或张量玻色子的角关联对于确定它们的自旋和CP性质是至关重要的。在LHC中，当采用适当的运动学选择切割（矢量玻色子融合切割）时，其横截面由虚胶子融合子过程控制，我们研究了具有高质量底夸克对或顶夸克对和两个喷流的事件中喷流角关联.在中间胶子与初始部分子共线的极限下，我们计算了qq，qg和gg碰撞引发的子过程的螺旋度振幅。我们首先用全矩阵元实胶子近似下的gg到t t棒或b b棒螺旋度振幅，得到了双喷注与t t棒或b b棒之间的方位角关联的一般表达式，并在两个运动学极限下，即在阈值附近产生重夸克对，在相对论极限下，重夸克对的不变质量远大于夸克质量。对于b b-酒吧+ 2喷流，我们发现强烈的方位角的相关性，这是不同的CP-偶或奇标量玻色子，可能会衰减到一个b-酒吧对事件的预期。对于t t-bar + 2喷注，在阈值M_（tt-bar）~ 2 m_t附近，角关联类似于CP奇标量+2喷注的角关联，而在相对论极限下，角关联类似于b b-bar + 2喷注的角关联。标准QCD过程中的这些关联将有助于建立实验技术来测量在LHC中通过胶子聚变产生的新粒子的自旋和CP性质。

英文摘要：

Angular correlation of jets produced in association with a massive scalar, vector or tensor boson is crucial in the determination of their spin and CP properties. We study jet angular correlations in events with a high mass bottom quark pair or a top quark pair and two jets at the LHC, whose cross-section is dominated by the virtual gluon fusion sub-processes when appropriate kinematic selection cuts (vector-boson fusion cuts) are applied. We evaluate helicity amplitudes for sub-processes initiated by qq, qg and gg collisions in the limit where the intermediate gluons are collinear to the initial partons. We first obtain a general expression for the azimuthal angle correlations among the dijets and t t-bar or b b-bar, in terms of the gg to t t-bar or b b-bar helicity amplitudes in the real gluon approximation of the full matrix elements, and find simple analytic expressions in the two kinematic limits, the production of a heavy quark pair near the threshold, and in the relativistic limit where the invariant mass of the heavy quark pair is much larger than the quark mass. For b b-bar + 2 jets we find strong azimuthal angle correlations which are distinct from those expected for events with a CP-even or odd scalar boson which may decay into a b b-bar pair. For t t-bar + 2 jets we find that the angular correlations are similar to that of a CP-odd scalar+2 jets near the threshold M_(t t-bar) ~ 2 m_t, while in the relativistic limit they resemble the distribution for b b-bar + 2 jets. These correlations in the standard QCD processes will help establish the experimental technique to measure the spin and CP properties of new particles produced via gluon fusion at the LHC.

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