We present new results on the NNNLO top-antitop production cross section near threshold from potential and ultrasoft gluon corrections. The new non-logarithmic third-order terms are in the 10% range and lead to a significant reduction in the theoretical error.
I discuss single top quark production at the Tevatron and the LHC. The cross section, including soft-gluon threshold corrections through NNNLO, is presented for each partonic channel. The higher-order corrections provide significant contributions to the single top cross sections at both colliders.
We determine the NNLO electroweak correction to the $e^+ e^-\to b\bar{b}W^+W^- X$ production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider.
I present high-order calculations for single-top production in the Standard Model and in models with anomalous top-quark couplings. Theoretical results are presented for total cross sections and top-quark transverse momentum and rapidity distributions for the $t$ and $s$ single-top channels as well as for the associated production of a top quark with a $W$ boson in the Standard Model. Corrections from soft-gluon emission though NNNLO are included. I also show results for the associated production of a top quark with a $Z$ boson in processes involving anomalous top-quark couplings.
Top-Quark Decay at Next-to-Next-to-Next-to-Leading Order in QCD
School of Physics, Shandong University(山东大学物理学院);School of Physics, Peking University(北京大学物理学院);Center for High Energy Physics, Peking University(北京大学高能物理中心)
We present a calculation of the NLO QCD corrections to the loop-induced production of a photon pair through gluon fusion, including massive top quarks at two loops, where the two-loop integrals are calculated numerically. Matching the fixed-order NLO results to a threshold expansion, we obtain accurate results around the top quark pair production threshold. We analyse how the top quark threshold corrections affect distributions of the photon pair invariant mass and comment on the possibility of determining the top quark mass from precision measurements of the diphoton invariant mass spectrum.
The threshold scan at future lepton colliders is the most precise known method to determine the top quark mass (well below 100 MeV), a fundamental parameter of the Standard Model that co-determines the stability properties of the electroweak vacuum. We present a new method to match the continuum next-to-leading order QCD corrections with the next-to-leading logarithmic resummation of the Coulomb singularities of the quasi-toponium bound state at threshold where fixed-order perturbation theory is invalid. This matching is performed at the level of the fully exclusive $W^+bW^-\bar{b}$ final stat…
P-wave contribution to third-order top-quark pair production near threshold
次领先阶(NLO)P波库仑格林函数在阈值附近对e+ e碰撞中的顶对产生有三阶贡献。在本文中,我们计算的非线性光学P波格林函数的尺寸正则化,要求与非共振生产的W+ W- b \bar{b}的最终状态的一致组合,并提出了一个唯象分析的P波的贡献。我们进一步简要地讨论夸克生产阈值附近和顶部对生产的伽马-伽马碰撞,没有S波的贡献是本,P-波,从而构成了主导生产过程。
We review exclusive top pair production including decays at a future high-energy lepton collider, both in the threshold region and for higher energies. For the continuum process, we take complete QCD next-to-leading order matrix elements for the $2\to 6$ process with leptonic W decays into account. At threshold, we match the fixed-order relativistic QCD-NLO cross section to a nonrelativistic cross section with next-to-leading logarithmic (NLL) threshold resummation implemented via a form factor.
We compute the top quark threshold contributions to the $γγ$ production at the LHC. They appear when the invariant mass of the photon pair, $M_{γγ}$ just exceeds two times the mass of the top quark and induce some feature in the $M_{γγ}$ distribution. We determine the magnitude of this threshold effect and characterize this feature with a simple empirical fitting function to show that it is possible to observe this effect at the LHC in future. We also explore some possible improvements that may enhance its significance.