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arXiv 2004.03088hep-phhep-ex
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阈附近顶夸克对产生:单/双分布和质量测定

Top quark pair production near threshold: single/double distributions and mass determination

Wan-Li Ju, Guoxing Wang, Xing Wang, Xiaofeng Xu, Yongqi Xu, Li Lin Yang

摘要:

我们研究了在对不变质量$M_{t\bar{t}}$接近$2m_t$的阈值附近的顶夸克对的产生,这为提取顶夸克质量$m_t$提供了灵敏的观测量。利用有效场论方法,导出了运动学分布在阈极限下的次领先幂的因式分解和再分解公式,该公式将高阶库仑修正求和到强耦合常数下的所有阶次。我们的公式与文献中的公式相似,但在几个重要方面有所不同。我们将我们的公式应用于$M_{t\bar{t}}$分布,以及关于$M_{t\bar{t}}$的双微分截面和$t\bar{t}$对的快度。我们发现,再热效应显着增加的截面附近的阈值,并导致预测更好地与实验数据兼容比固定阶的。我们证明,将再膨胀效应的顶夸克质量测定可以移动提取值的$m_t$高达1.4 GeV。这种变化比以前实验研究中估计的不确定性要大得多,并导致顶夸克极质量的值与当前世界平均值更一致。

英文摘要:

We investigate top quark pair production near the threshold where the pair invariant mass $M_{t\bar{t}}$ approaches $2m_t$, which provides sensitive observables to extract the top quark mass $m_t$. Using the effective field theory methods, we derive a factorization and resummation formula for kinematic distributions in the threshold limit up to the next-to-leading power, which resums higher order Coulomb corrections to all orders in the strong coupling constant. Our formula is similar to those in the literature but differs in several important aspects. We apply our formula to the $M_{t\bar{t}}$ distribution, as well as to the double differential cross section with respect to $M_{t\bar{t}}$ and the rapidity of the $t\bar{t}$ pair. We find that the resummation effects significantly increase the cross sections near the threshold, and lead to predictions better compatible with experimental data than the fixed-order ones. We demonstrate that incorporating resummation effects in the top quark mass determination can shift the extracted value of $m_t$ by as large as 1.4 GeV. The shift is much larger than the estimated uncertainties in previous experimental studies, and leads to a value of the top quark pole mass more consistent with the current world average.

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