The next-to-leading order analysis for the cross section for hadroproduction of top quark pairs close to threshold is presented. Within the framework of non-relativistic QCD a significant enhancement compared to fixed order perturbation theory is observed which originates from the characteristic remnant of the 1S peak below production threshold of top quark pairs. The analysis includes all color singlet and color octet configurations of top quark pairs in S-wave states and, for the dominant configurations, it employs all-order soft gluon resummation for the hard parton cross section. Numerical results for the Large Hadron Collider at $\sqrt{s} = 14 $TeV and $\sqrt{s} = 10 $TeV and also for the Tevatron are presented. The possibility of a top quark mass measurement from the invariant mass distribution of top quark pairs is discussed.
Threshold resummation for gluon fusion $ZH$ production at the LHC
RWTH Aachen University（亚琛工业大学）；Indian Institute of Technology Kanpur（坎普尔印度理工学院）；Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology Guwahati（古瓦哈提印度理工学院）；Durham University（杜伦大学）
Momentum-space threshold resummation in $tW$ production at the LHC
我们计算了$tW$产生对所有阶数的软胶子修正。软极限定义在对不变质量或包含一个粒子的运动学方案中。我们发现，在非线性光学中，软胶子效应的贡献在总截面和微分分布中占主导地位。利用重整化群方程对软胶子效应进行了全阶近似计算，发现NLO+NNLL的结果使非线性光学截面增加了$12\%\sim 17\%$，这与方案和对撞机能量有关.我们的结果与在8和13 TeV LHC上的测量结果一致。我们还提供了在14 TeV的LHC的总截面的预测。
Threshold Resummation of Drell-Yan type colorless processes at LHC
RWTH Aachen University（亚琛工业大学）；Indian Institute of Technology Kanpur（坎普尔印度理工学院）；Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology Guwahati（古瓦哈提印度理工学院）；Durham University（杜伦大学）
The exclusive $J/Ψ$ and $Υ$ photoproduction in fixed - target collisions at the LHC and $ep(A)$ collisions at the Electron ion collider in China (EicC) is investigated considering different models for the treatment of the vector meson production at low energies, close to the threshold. Results for the total cross sections and associated distributions are presented. We predict a large number of $J/Ψ$ events at the LHC in the rapidity range covered by the LHCb detector. For the EicC, our predictions point out that a detailed analysis of the near threshold $J/Ψ$ and $Υ$ photoproduction is feasibl…
Top-Antitop Production and Decay at Threshold at the LHC in QCD Perturbation Theory
INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）；Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano-Bicocca（米兰比可卡大学G. Occhialini物理系）
We show that the Pomeron exchanges play a unique role in vector charmonium scatterings. Such a mechanism can provide a natural explanation for the nontrivial structures in the di-$J/ψ$ spectrum observed by the LHCb Collaboration. The narrow structure $X(6900)$, as a dynamically generated resonance pole, can arise from the Pomeron exchanges and coupled-channel effects between the $J/ψ$-$J/ψ$, $J/ψ$-$ψ(2S)$ scatterings. A pole structure near the di-$J/ψ$ threshold is also found. Meanwhile, we predict that $X(6900)$ can produce significant threshold enhancement in the $J/ψ$-$ψ(2S)$ energy spectru…
We investigate threshold resummation of soft gluon corrections for the s-channel process of a single top quark production in association with a Higgs boson in the Standard Model. We choose to work in the three-particle invariant mass kinematics in direct QCD, i.e. in the space of Mellin moments. Our results take into account terms of up to next-to-leading logarithmic (NLL) precision, as well as $\mathcal{O} (α_s)$ non-logarithmic terms which do not vanish at threshold. After presenting analytical expressions we discuss the corresponding numerical results for the total cross section and the inv…
Probing the anomalous electromagnetic dipole moments of the top quark in $γp$ collision at the LHC, the HL-LHC and the HE-LHC
确定顶夸克的电磁偶极矩是对撞机实验中顶夸克物理计划的重要目标之一。为此，我们讨论了在大型强子对撞机（LHC）、高亮度大型强子对撞机（HL-LHC）和高能大型强子对撞机（HE-LHC）上通过过程$pp\rightarrow p γp \rightarrow p t \bar{t} X$产生顶夸克对来研究顶夸克电、磁偶极矩的敏感性。我们应用纯轻子和半轻子衰变研究末态顶夸克对的产生。此外，我们考虑了系统的不确定性的$0,3\%$和$5\%$。从过程$pp\rightarrow p γp \rightarrow p t \bar{t} X$获得的关于异常$a_{A}$和$a_{V}$偶联的最佳限度是$|a_{A}|=0.0200$和$a_{V}=[-0.9959; 0.0003]$。因此，我们的结果表明，$pp\rightarrow p γp \rightarrow p t \bar{t} X$过程是一个很好的前景探测顶夸克的电和磁偶极矩在HL-LHC和HE-LHC。
Contributions from dimension six strong flavor changing operators to top anti-top, top plus gauge boson, and top plus Higgs boson production at the LHC
Exclusive $pp \to pp π^{+}π^{-}$ reaction: from the threshold to LHC
我们评估差分分布的四体$p p \to p p π^+ π^-$反应构成了一个不可约的背景，三体过程$p p \to p p M$，其中$M$是一个广泛的共振在$π^+ π^-$通道，例如$M=σ, ρ^{0}, f_{0}(980), f_{2}(1275), f_{0}(1500)$。我们包括双衍射的贡献（包括坡密子和reggeon交换），以及π介子-π介子再散射的贡献。第一个过程占主导地位，在较高的能量和小的π-π不变质量，而第二个变得重要，在较低的能量和较高的π-π不变质量。在Regge方法中计算振幅。我们比较我们的结果与测量的截面的ISR实验在欧洲核子研究中心。我们预测未来的实验在PANDA，RHIC，Tevatron和LHC能源。给出了π介子有效质量、π介子快度和横动量的微分分布。$(y_{π^+}, y_{π^-})$中的二维分布特别有趣。入射能量越高，π介子在同一半球发射的优先性越高。所考虑的过程对核子-核子总截面和π介子包含的截面有相当大的贡献。
Motivated by the expectation that new physics may manifest itself in the form of very heavy new particles, most of the operation time of the LHC is devoted to $pp$ collisions at the highest achievable energies and collision rates. The large collision rates imply tight trigger requirements that include high thresholds on the final-state particles' transverse momenta $p_{T}$ and an intrinsic background in the form of particle pileup produced by different collisions occurring during the same bunch crossing. This strategy is potentially sub-optimal for several well-motivated new physics models whe…
Single top production associated with a neutral scalar at LHC in topcolor-assisted technicolor
顶色辅助的人工色（TC 2）模型预测了一些中性标量，如顶介子（$π^0_t$）和顶希格斯（$h^0_t$）。这些标量具有变味中性流（FCNC）顶夸克耦合，其中顶粲跃迁耦合可能相当大。在欧洲核子研究中心的大型强子对撞机（LHC）上，这种FCNC耦合通过部分子过程$cg \to t π_t^0$和$cg \to t h_t^0$诱导了与中性标量相关的单顶产生。在本文中，我们研究了这些生产，发现它们的生产率可以超过$3σ$的LHC的参数空间的大部分灵敏度。由于在标准模型和最小超对称模型中，这些稀有过程在LHC中的产生率小得不可观测，因此这些稀有过程将作为TC2模型的一个很好的探针。
