We present the results of our recent study (arXiv:1510.08850) of the theoretical uncertainties that affect the predictions for the Higgs-boson transverse-momentum in gluon fusion when fixed- and all-order results are matched. Our investigation consists of a twofold analysis: first we present a detailed comparison of two recently introduced prescriptions for the determination of the matching scale (arXiv:1409.0531, arXiv:1505.00735), then we apply the results of these methods to three widely used matching frameworks, namely the aMC@NLO and POWHEG Monte Carlo approaches and analytic resummation. The results of our study are applied to the production of the SM Higgs boson and of the neutral Higgs bosons of the Two-Higgs-Doublet Model in a variety of scenarios.
Recent results on the Higgs plus jet production is reviewed. We have computed the two-loop amplitudes for $ gg \to Hg $, $ q\bar{q} \to Hg $ and $ qg \to Hq $ at the large Higgs transverse momentum. It was long-missing part of NLO corrections to the Higgs plus jet production above the top mass threshold. This results are combined with the real corrections to produce the Higgs boson transverse momentum distribution at NLO.
We compute the two-loop QCD corrections to amplitudes for processes $g g \to H g, q g \to H q$ and $q \bar{q} \to H g$ in the limit when the Higgs transverse momentum is larger than the top quark mass, $p_\perp \gg m_t$. These amplitudes are important ingredients for understanding higher-order QCD effects on Higgs transverse momentum distribution at large $p_\perp$.
We perform a detailed study of NLO parton shower matching uncertainties in Higgs boson pair production through gluon fusion at the LHC based on a generic and process independent implementation of NLO subtraction and parton shower matching schemes for loop-induced processes in the Sherpa event generator. We take into account the full top-quark mass dependence in the two-loop virtual corrections and compare the results to an effective theory approximation. In the full calculation, our findings suggest large parton shower matching uncertainties that are absent in the effective theory approximatio…
In this paper we explore composite Higgs scenarios through the effects of light top-partners in Higgs+Jet production at the LHC. The pseudo-Goldstone boson nature of the Higgs field means that single-Higgs production via gluon fusion is insensitive to the mass spectrum of the top-partners. However in associated production this is not the case, and new physics scales may be probed. In the course of the work we consider scenarios with both one and two light top-partner multiplets in the spectrum of composite states. We study corrections to the Higgs couplings and the effects that the light top-p…
Anatomy of the Higgs fits: a first guide to statistical treatments of the theoretical uncertainties
基于最近和即将到来的大型强子对撞机数据的希格斯玻色子耦合的研究打开了一个新的窗口，物理学超越了标准模型。在本文中，我们提出了一个统计指南的一致性治疗的理论不确定性进入希格斯速率拟合。贝叶斯和频率论的方法进行了系统的分析，在一个统一的形式主义。我们提出的边际似然分析表达式，同时实施的实验和理论的不确定性。我们回顾了理论误差的各种来源（QCD，EFT，PDF，生产模式污染.）。所有这些单独的不确定性都在基于矩的考虑的帮助下被彻底地结合起来。希格斯探测通道之间的理论相关性似乎会影响希格斯耦合空间中最佳拟合区域的位置和大小。我们讨论了个别理论误差的先验分布的形状的经常性问题，并发现一个近高斯先验产生的错误组合。我们还开发了偏见的方法，这是一种替代边缘化提供更保守的结果。介绍了应用偏倚原理的统计框架，并提出了偏倚的两种实现方式。最后，根据统计处理，标准模型预测的希格斯信号强度被发现位于$68\%$或$95\%$置信水平区域内，这些置信水平区域是从$7$和$8$ TeV LHC数据集的最新分析中获得的。
The ambiguity in the choice of a renormalization scheme and scale for the top-quark mass leads to an additional source of theoretical uncertainty in the calculation of the Higgs boson production cross section via gluon fusion. These uncertainties were found to be dominant in the case of off-shell Higgs production at next-to-leading order in QCD for large values of the Higgs virtuality $m_H^*$. In this work, we study the uncertainties related to the top-quark mass definition up to next-to-next-to-leading order (NNLO) in QCD. We include the full top-quark mass dependence up to three loops in the…
The transverse momentum ($p_T$) distribution of Higgs bosons at hadron colliders enables a detailed probe of its production dynamics and is a key ingredient to precision studies of Higgs boson properties, but receives very large QCD corrections. We obtain a precision prediction for the $p_T$ spectrum by matching second-order (NNLO) QCD corrections at large $p_T$ with resummation of third-order logarithmic (N$^3$LL) corrections at small $p_T$. We achieve significantly improved results for $p_T< 35\,{\rm GeV}$ with perturbative uncertainties $\lesssim \pm 6\%$, and thus a convergent perturbative…
We consider the extension of the transverse-momentum ($q_T$) subtraction method at next-to-next-to-next-to-leading order (N$^3$LO) in perturbative QCD. While all the $q_T$-subtraction ingredients at $q_T \neq 0$ are known in analytical form, the third-order collinear functions and helicity-flip functions, which contribute only at $q_T=0$, are approximated using a prescription which uses the known result for the total Higgs boson cross section at this order. As a first application of the third-order $q_T$-subtraction method, we present the N$^3$LO rapidity distribution of the Higgs boson at the…
Resummation ambiguities in the Higgs transverse-momentum spectrum in the Standard Model and beyond
本文研究了胶子熔合中Higgs横动量分布的预言，着重讨论了固定阶和全阶微扰结果的匹配问题。通过双重比较的方式，在这个分布上的匹配模糊的主要来源进行了研究。一方面，我们提出了一个详细的定性和定量比较最近推出的两种算法，用于确定匹配的规模。另一方面，我们将这两种方法的结果应用到三种广泛使用的方法中，用于在小横动量下对增强的贡献进行重新计算：MC@NLO和POWHEG Monte Carlo方法，以及解析重新计算。虽然这三组结果在低pT区域基本上是相容的，但在大pT时它们表现出相当大的差异。我们表明，这些差异可以显着减少适当的修改正式subleading条款的Monte Carlo实现。我们将我们的研究应用到标准模型希格斯玻色子和中性希格斯玻色子的双希格斯模型的参数空间的代表性方案，其中顶夸克和底夸克图进入截面在不同的强度。
We compute the next-to-leading order QCD corrections to the production of Higgs bosons with large transverse momentum $p_\perp \gg 2 m_t$ at the LHC. To accomplish this, we combine the two-loop amplitudes for processes $gg \to Hg$, $qg \to Hq$ and $q \bar q \to H g$, recently computed in the approximation of nearly massless top quarks, with the numerical calculation of the squared one-loop amplitudes for $gg \to Hgg$, $q g \to H q g$ and $q \bar q \to Hgg$ processes. The latter computation is performed with OpenLoops. We find that the QCD corrections to the Higgs transverse momentum distributi…
We quantify and examine the uncertainties in predictions of the lightest $CP$ even Higgs boson pole mass $M_h$ in the Minimal Supersymmetric Standard Model (MSSM), utilising current spectrum generators and including some three-loop corrections. There are two broadly different approximations being used: effective field theory (EFT) where an effective Standard Model (SM) is used below a supersymmetric mass scale, and a fixed order calculation, where the MSSM is matched to QCD$\times$QED at the electroweak scale. The uncertainties on the $M_h$ prediction in each approach are broken down into loga…
It was shown recently that standard resummation of logarithms of $Q/p_T$ can be supplemented with the resummation of logarithmic contributions at large $x=Q^2/s$ in the case of a colourless final state such as Higgs produced via gluon fusion or the production of a lepton pair via Drell--Yan mechanism. Such an improved transverse momentum resummation takes into account soft emissions that are emitted at very small angles. We report on recent phenomenological studies of a combined threshold-improved $p_T$ and threshold resummation formalism to the Higgs boson produced at the LHC where small-$p_T…
