On cascade decays of squarks at the LHC in NLO QCD

In this paper we present an analysis at NLO QCD of the contribution from squark-squark production to the experimental signature $2j+l^{+}l^{-}+ \displaystyle{\not}E_T (+X)$ with opposite-sign same flavor leptons, taking into account decays and experimental cuts. We consider the case in which one squark decays directly into the lightest neutralino $\tilde{\chi}^{0} _{1}$ and the other one into the second lightest neutralino and subsequently into $l^{+}l^{-} \tilde{\chi}^{0} _{1}$ via an intermediate slepton. On the one hand we study the effects of the NLO corrections on invariant mass distributions which can be used for future parameter determination. On the other hand we analyze the impact on predictions for cut-and-count searches using the given experimental signature.     

Graviton plus vector boson production to NLO in QCD at the LHC

We present the next-to-leading order QCD corrections to the associated production of the vector gauge boson (Z/W^±$Z/W^{\pm }$) and the graviton in the large extra dimension model at the LHC. We estimate the impact of the QCD corrections on the total cross sections as well as the differential distributions of the gauge bosons and find that they are significant. We also study the dependence of the cross sections on the arbitrary factorization scale and show the reduction in the scale uncertainties at NLO level. Further, we discuss the ultraviolet sensitivity of the theoretical predictions.     

Strong QCD corrections to p-wave quarkonium decays

We have calculated one-loop QCD corrections to the annihilation widths of P-wave quarkonium states into hadrons and into two photons. Comparison with accurate experimental data may lead to a clear test of perturbative QCD if α_S turns out to be small enough for reasonable convergence.     

Single slepton production associated with a top quark at LHC in NLO QCD

Single slepton production in association with a top quark at the CERN Large Hadron Collider (LHC) is one of the important processes in probing the R-parity violation couplings. We calculate the QCD next-to-leading order (NLO) corrections to the $pp \to t\tilde{\ell}^{-}(\bar{t}\tilde{\ell}^{+})+X$ process at the LHC and discuss the impacts of the QCD corrections on kinematic distributions. We investigate the dependence of the leading order (LO) and the NLO QCD corrected integrated cross section on the factorization/renormalization energy scale, slepton, stop-quark and gluino masses. We find that the uncertainty of the LO cross section due to the energy scale is obviously improved by the NLO QCD corrections, and the exclusive jet event selection scheme keeps the convergence of the perturbative series better than the inclusive scheme. The results show that the polarization asymmetry of the top-quark will be reduced by the NLO QCD corrections, and the QCD corrections generally increase with the increment of the $\tilde{t}_{1}$ or $\tilde {g}$ mass value.     

NLO QCD corrections to Drell-Yan processes in the SANC framework

NLO QCD corrections to charged and neutral current Drell-Yan processes are computed with help of the computer system SANC. At the partonic level both quark-antiquark and quark-gluon scattering channels are taken into account. Subtraction of collinear singularities in the massive quark scheme is compared with the one in the $ \overline {MS} $ \overline {MS} scheme. Numerical results at the hadronic level are received for the LHC conditions with help of Monte-Carlo integrators and event generator programs based on the standard SANC modules. Comparison with analogous results of the MCFM package is shown.     

NLO QCD corrections to graviton induced deep inelastic scattering

We consider Next-to-Leading-Order QCD corrections to ADD graviton exchange relevant for Deep Inelastic Scattering experiments. We calculate the relevant NLO structure functions by calculating the virtual and real corrections for a set of graviton interaction diagrams, demonstrating the expected cancellation of the UV and IR divergences. We compare the NLO and LO results at the centre-of-mass energy relevant to HERA experiments as well as for the proposed higher energy lepton–proton collider, LHeC, which has a higher fundamental scale reach.     

SANCnews: Top decays in QCD and EW sectors

In this paper we present the results of the implementation of the decay t → bf ₁ $ \bar f $ \bar f ′₁ into the SANC system (f ₁ is a massless fermion). The new aspect of the work is the combination of QCD and EW corrections. All calculations are done at the one-loop level in the Standard Model. We give a detailed account of the new procedure — the forming of a class of J _{AW, WA} functions. These functions are related to the procedure of extraction of infrared and mass-shell singular divergences. The emphasis of this paper is on the presentation of numerical results for various approaches: complete one-loop calculations and different versions of pole approximations.     

Next-to-leading order QCD corrections to the production of two bottom-antibottom pairs at the LHC

We report the results of a computation of the full next-to-leading order QCD corrections to the production of two bb pairs at the LHC. This calculation at the parton level provides predictions for well separated b jets. The results show that the next-to-leading order corrections lead to an enhancement of the cross section for the central scale choice by roughly 50% with respect to the leading order result. The theoretical uncertainty estimated by variation of the renormalization and factorization scales is strongly reduced by the inclusion of next-to-leading order corrections.     

NLO QCD corrections to B_c(B_c~*) production around the Z pole at an e~+e~- collider

The production of B_c and B_c~* mesons at a Z-factory(an e~+e~- collider operating at energies around the Z pole) is calculated up to the next-to-leading order(NLO) QCD accuracy. The results show that the dependence of the total cross sections on the renormalization scale μ is suppressed by the corrections, and the NLO corrections enhance the total cross sections of B_c by 52%and of B_c~* by 33% when the renormalization scale is taken at μ = 2 mb. To observe the various behaviors of the production of the mesons B_c and B_c~*, such as the differential cross section vs. the out-going angle, the forward-backward asymmetry, and the distribution vs. the energy fraction z up to NLO QCD accuracy as well as the relevant K-factor(NLO to LO) for the production,are calculated, and it is pointed out that some of the observables obtained in the present work may be used as a specific precision test of the standard model.     

Note on the QED corrections to leptonic decays of the neutral vector boson

An exact calculation of the lowest-order QED corrections to leptonic decay rates of the neutral vector boson is presented and the origin of a discrepancy between two recent results is explained.