Combining NLO QCD and Electroweak Radiative Corrections to W boson Production at Hadron Colliders in the POWHEG Framework

The precision measurement of the mass of the $W$ boson is an important goal of the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). It requires accurate theoretical calculations which incorporate both higher-order QCD and electroweak corrections, and also provide an interface to parton-shower Monte Carlo programs which make it possible to realistically simulate experimental data. In this paper, we present a combination of the full ${cal O}(alpha)$ electroweak corrections of {tt WGRAD2}, and the next-to-leading order QCD radiative corrections to $Wtoell u$ production in hadronic collisions in a single event generator based on the {tt POWHEG} framework, which is able to interface with the parton-shower Monte Carlo programs {tt Pythia} and {tt Herwig}. Using this new combined QCD+EW Monte Carlo program for $W$ production we provide numerical results for total cross sections and kinematic distributions of relevance to the $W$ mass measurement at the Tevatron and the LHC for the processes $pp,pbar p to W^pm to mu^pm u_mu$. In particular, we discuss the impact of EW corrections in the presence of QCD effects when including detector resolution effects.

W- and Z-boson production with a massive bottom-quark pair at the Large Hadron Collider

We present total and differential cross sections for W b anti-b and Z b anti-b production at the CERN Large Hadron Collider with a center-of-mass energy of 14 TeV, including Next-to-Leading Order (NLO) QCD corrections and full bottom-quark mass effects. We also provide numerical results obtained with a center-of-mass energy of 10 TeV. We study the scale uncertainty of the total cross sections due to the residual renormalization- and factorization-scale dependence of the truncated perturbative series. While in the case of Z b anti-b production the scale uncertainty of the total cross section is reduced by NLO QCD corrections, the W b anti-b production process at NLO in QCD still suffers from large scale uncertainties, in particular in the inclusive case. We also perform a detailed comparison with a calculation that considers massless bottom quarks, as implemented in the Monte Carlo program MCFM. The effects of a non-zero bottom-quark mass (m_b) cannot be neglected in phase-space regions where the relevant kinematic observable, such as the transverse momentum of the bottom quarks or the invariant mass of the bottom-quark pair, are of the order of m_b. The effects on the total production cross sections are usually smaller than the residual scale uncertainty at NLO in QCD.

Top quark theory review for the Tevatron, LHC, and ILC

I will briefly review the status of higher-order calculations for top-quark observables, comment on the need for improvements, discuss some of the recent theoretical advances, and present a few examples to highlight the role of top-quark observables in searches for signals of physics beyond the Standard Model.

NLO QCD corrections to Z b anti-b production with massive bottom quarks at the Fermilab Tevatron

We calculate the Next-to-Leading Order (NLO) QCD corrections to Z b anti-b production in hadronic collisions including full bottom-quark mass effects. We present results for the total cross section and the invariant mass distribution of the bottom-quark jet pair at the Fermilab Tevatron p anti-p collider. We perform a detailed comparison with a calculation that considers massless bottom quarks, as implemented in the Monte Carlo program MCFM. We find that neglecting bottom-quark mass effects overestimates the total NLO QCD cross section for Z b anti-b production at the Tevatron by about 7%, independent of the choice of the renormalization and factorization scales. Moreover, bottom-quark mass effects can impact the shape of the bottom-quark pair invariant mass distribution, in particular in the low invariant mass region.