Practical improvements and merging of POWHEG simulations for vector boson production
Simone Alioli, Keith Hamilton, Emanuele Re
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41 pages, 19 figures. Figures updated from v1.5 to 1.6 of external Rivet program, reference line in figs. 4,5,11 corrected. Citations added, text unchanged
In this article we generalise POWHEG next-to-leading order parton shower (NLOPS) simulations of vector boson production and vector boson production in association with a single jet, to give matrix element corrected MENLOPS simulations. In so doing we extend and provide, for the first time, an exact and faithful implementation of the MENLOPS formalism in hadronic collisions. We also consider merging the resulting event samples according to a phase space partition defined in terms of an effective jet clustering scale. The merging scale is restricted such that the component generated by the associated production simulation does not impact on the NLO accuracy of inclusive vector boson production observables. The dependence of the predictions on the unphysical merging scale is demonstrated. Comparisons with Tevatron and LHC data are presented.
我们提出了一个实施的下一个领先的顺序强子生产的W玻色子与一对大质量的底夸克的框架中的POWHEG，一种方法，一贯接口NLO QCD计算与淋浴蒙特卡罗发电机。这个过程已经实现了使用POWHEG BOX，一个自动化的计算机代码，系统地适用于POWHEG方法的非线性光学QCD计算。在W玻色子衰变成轻子的自旋关联已被考虑使用标准的近似技术。我们目前的唯象结果为W b bbar-> l nu b bbar生产，在Tevatron和LHC，通过淋浴的POWHEG结果与PYTHIA和HERWIG，我们讨论了两个不同的淋浴蒙特卡罗程序的输出。
We use the POWHEG method to perform parton-shower matching for Drell-Yan production of W and Z bosons at the LHC at NLO QCD and NLO electroweak accuracy. In particular, we investigate an improved treatment of the vector-boson resonances within the POWHEG method. We employ an independent implementation of the POWHEG method and compare to earlier results within the POWHEGBOX. On the technical side, we provide the FKS formalism for photon-radiation off fermions within mass regularization.
We discuss the Standard Model Effective Field Theory (SM-EFT) contributions to neutral- and charge-current Drell-Yan production, associated production of the Higgs and a vector boson, and Higgs boson production via vector boson fusion. We consider all the dimension-six SM-EFT operators that contribute to these processes at leading order, include next-to-leading order QCD corrections, and interface them with parton showering and hadronization in Pythia8 according to the POWHEG method. We discuss existing constraints on the coefficients of dimension-six operators and identify differential and an…
We present a new Monte Carlo event generator for the production of a top-quark pair in association with a $W^\pm$ boson at hadron colliders in the POWHEG-BOX framework. We consider the next-to-leading-order QCD corrections to the $pp\to t\bar{t} W^\pm$ cross section, corresponding to the $\mathcal{O}(α_s^3α)$ and $\mathcal{O}(α_sα^3)$ terms in the perturbative expansion of the parton-level cross section, and model the decays of $W$ and top quarks at leading order retaining spin correlations. The fixed-order QCD calculation is further interfaced with the Pythia8 parton-shower event generator vi…
We extend and improve upon our previous calculation of electroweak top-quark pair hadroproduction in extensions of the Standard Model with extra heavy neutral and charged spin-1 resonances. In particular, we allow for flavour-non-diagonal $Z'$ couplings and take into account non-resonant production in the SM and beyond including the contributions with $t$-channel $W$ and $W'$ bosons. All amplitudes are generated using the Recola2 package. As in our previous work, we include NLO QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interfe…
We present results for Higgs boson pair production with variations of the trilinear Higgs boson self-coupling at next-to-leading order (NLO) in QCD including the full top quark mass dependence. Differential results at 14 TeV are presented, and we discuss the implications of anomalous trilinear couplings as well as differences between the PYTHIA 8.2 and HERWIG 7.1 parton showers in combination with POWHEG. The implementation of the NLO QCD calculation with variable Higgs boson self-coupling is made publicly available in the POWHEG-BOX-V2 Monte Carlo framework. A simple method for using the new …
Gluon fusion and $b\bar{b}$ corrections to $H W^+ W^- / H Z Z$ production in the POWHEG-BOX
对希格斯玻色子性质的研究是未来几年在大型强子对撞机（LHC）和未来对撞机（如强子-强子模式下的未来圆形对撞机（FCC-hh），LHC机器的潜在100 TeV后续）中要完成的最重要任务之一。在这种观点下，希格斯玻色子与弱规范玻色子的耦合的精确研究是至关重要的，需要尽可能多的信息。在POWHEG-BOX框架下，我们计算了一个标准模型Higgs玻色子与一对弱玻色子的产生截面和微分分布的次领先阶QCD修正，并与部分子簇射相匹配，给出了对过程$p p \to H W^+_{} W^-_{} (H Z Z)$的胶子融合修正$g g\to H W^+_{} W^-_{} ( H Z Z)$.这种校正可以是相当大的，相当于LHC（FCC-hh）的$H W^+_{} W^-_{}$过程中的$+3\,\%$（$+10\,\%$）和$H Z Z$过程中的$+18\,\%$（$+18\,\%$）。我们还首次研究了底夸克引发的通道$b\bar{b}\to H W^+_{} W^-_{} / H Z Z$的影响，发现它们在FCC-hh的$H W^+_{} W^-_{}$通道中引起了显著的$+18\,\%$校正。我们目前的结果在LHC和FCC-HH的总截面和分布。
A Positive-Weight Next-to-Leading-Order Monte Carlo Simulation of Deep Inelastic Scattering and Higgs Boson Production via Vector Boson Fusion in Herwig++
在Herwig++ Monte Carlo事件发生器中，将正权次序匹配方法（POWHEG）应用于深度非弹性散射（DIS）及相关的矢量-玻色子融合过程中的希格斯玻色子产生.该方案将部分子簇射模拟和次引导阶计算以一致的方式结合起来，只产生正权事件。模拟包含了一个完整的实施截断簇射所需的正确建模软排放的角度有序的部分子簇射。
We present an implementation of $t\bar t \ell^+\ell^-$ ($\ell=e,μ$) hadronic production at next-to-leading order in QCD matched to parton-shower event generators in the POWHEG BOX framework. The program we developed includes all leading-order contributions of order $α_s^2α^2$ for the specified final state, as well as the corresponding first-order QCD corrections. Decays of the top quarks have been simulated retaining spin-correlations in all tree-level matrix elements. We consider the case of the Large Hadron Collider at $\sqrt{s}=13$ TeV and compare results for $t\bar t \ell^+\ell^-$ producti…
We present numerical tests and predictions of the KrkNLO method for matching of NLO QCD corrections to hard processes with LO parton shower Monte Carlo generators (NLO+PS). This method was described in detail in our previous publications, where it was also compared with other NLO+PS matching approaches (MC@NLO and POWHEG) as well as fixed-order NLO and NNLO calculations. Here we concentrate on presenting some numerical results (cross sections and distributions) for $Z/γ^*$ (Drell-Yan) and Higgs-boson production processes at the LHC. The Drell--Yan process is used mainly to validate the KrkNLO …
A Positive-Weight Next-to-Leading Order Monte Carlo Simulation of Drell-Yan Vector Boson Production
在Herwig++ Monte Carlo事件发生器中，将正权重次领先阶（NLO）匹配方案（POWHEG）应用于Drell-Yan矢量玻色子产生.这种方法一致地结合了NLO计算和部分子簇射模拟，而不产生负权重事件。该模拟包括一个完整的实施截断簇射所需的正确描述软排放的角度有序的部分子簇射，第一次。结果进行了比较Tevatron W和Z的生产数据和预测的规范玻色子在LHC提出的横向动量谱。
We present the first combination of NLO QCD matrix elements for di-Higgs production, retaining the full top quark mass dependence, with a parton shower. Results are provided within both the POWHEG-BOX and MadGraph5_aMC@NLO Monte Carlo frameworks. We assess in detail the theoretical uncertainties and provide differential results. We find that, as expected, the shower effects are relatively large for observables like the transverse momentum of the Higgs boson pair, which are sensitive to extra radiation. However, these shower effects are still much smaller than the differences between the Born-i…
