Xiao-Zhou Li

NLO QCD and electroweak corrections to WWW production at the LHC

In this paper we calculate the next-to-leading order (NLO) QCD [O(αsα)] and electroweak (EW) [O(α4)] corrections to the WWW production at the LHC and deal with the subsequent leptonic decays from W bosons by adopting an improved narrow-width approximation which takes into account the spin correlation and finite-width effects. The NLO QCD correction from the real jet radiation is discussed, which significantly enhances the production rate, particularly in the high-energy region. We also provide the integrated cross section for the WWW production and various kinematic distributions of final products at the QCD+EW NLO. We find that the convergence of the perturbative QCD description can be improved by applying a hard jet veto in the event selection, but this jet veto would introduce a new source of theoretical uncertainty. The pure NLO QCD relative correction to the integrated cross section for the WWW production at the 14 TeV LHC is on the order of 30% in the jet-veto event selection scheme with p cut T, jet = 50 GeV, while the genuine NLO EW relative correction can reach about 15% in the inclusive event selection scheme. Our numerical results show that both the NLO QCD and NLO EW corrections should be taken into consideration in precision predictions. PACS: 12.15.Lk, 12.38.Bx, 14.70.Fm

QCD and electroweak corrections to ZZ + jet production with Z-boson leptonic decays at the LHC

In this paper we present the full NLO QCD + NLO EW corrections to the Z-boson pair production in association with a hard jet at the LHC. The subsequent Z-boson leptonic decays are included by adopting both the naive NWA and MadSpin methods for comparison. Since the ZZ+jet production is an important background for single Higgs boson production and new physics search at hadron colliders, the theoretical predictions with high accuracy for the hadronic production of ZZ+jet are necessary. We present the numerical results of the integrated cross section and various kinematic distributions of final particles, and conclude that it is necessary to take into account the spin correlation and finite width effects from the Z-boson leptonic decays. We also find that the NLO EW correction is quantitatively nonnegligible in matching the experimental accuracy at the LHC, particularly is significant in high transverse momentum region. PACS: 12.15.Lk, 12.38.Bx, 14.70.Hp

Revisiting the large extra dimension effects on

In the framework of the large extra dimensions (LED) model, we investigate the effects induced by the Kaluza-Klein gravitons up to the QCD next-to-leading order (NLO) on the W -pair production followed by a subsequential W -decay at the CERN LHC. We depict the regions in the L −MS parameter space where the LED effect can and cannot be observed from the analyses of the pp → WW +X and pp → WW → Wl (−) ν +X processes. We find that the ability of probing the LED effects can be improved by taking the cutoffs for the invariant mass of the W -pair and the transverse momentum of the final lepton. Our results demonstrate that the NLO QCD corrections to observables are significant, and do not show any improvement for the renormalization/factorization scale uncertainty on the QCD NLO corrected cross section, because the leading-order result underestimates the scale dependence. PACS: 11.10.Kk, 12.38.Bx, 14.70.Fm

W

We investigate the double Higgs production and decay at the 14 TeV LHC and 33 TeV HE-LHC in both the standard model and Randall-Sundrum (RS) model. In our calculation we consider reasonably only the contribution of the lightest two Kaluza-Klein (KK) gravitons. We present the integrated cross sections and some kinematic distributions in both models. Our results show that the RS effect in the vicinities of MHH ∼ M1, M2 (the masses of the lightest two KK gravitons) or in the central Higgs rapidity region is quite significant, and can be extracted from the heavy SM background by imposing proper kinematic cuts on final particles. We also study the dependence of the cross section on the RS model parameters, the first KK graviton mass M1 and the effective coupling c0, and find that the RS effect is reduced obviously with the increment of M1 or decrement of c0. PACS: 11.10.Kk, 14.80.Cp, 12.38.Bx

-pair production at the LHC in next-to-leading order QCD

We present the complete next-to-leading order (NLO) QCD and NLO electroweak (EW) corrections to the W-boson pair production associated with a hard jet at the LHC including the spin correlated W-boson leptonic decays. The dependence of the leading order (LO) and NLO corrected cross sections on the jet transverse momentum cut is investigated. In dealing with the subsequent resonant W-boson decays, we adopt the MadSpin method where the spin correlation effect is included. We also provide the LO and NLO corrected distributions of the transverse momenta and rapidities of final products. The results show that the NLO EW correction is significant in high transverse momentum region due to the EW Sudakov effect.

Double Higgs boson production and decay in Randall-Sundrum model at hadron colliders

We investigate the possible large extra dimensions (LED) effects induced by the Kaluza–Klein (KK) gravitons up to the QCD next-to-leading order (NLO) on ZZW production at the large hadron collider (LHC). The integrated cross-sections and some kinematic distributions are presented in both the Standard Model (SM) and the LED model. The numerical results demonstrate that the NLO QCD corrections are sizeable and remarkably reduce the leading order (LO) LED effect depending strongly on the phase space. The NLO LED relative discrepancies of the total cross-section could become sizable for the ZZW production, if we apply proper event selection criteria. We find that the LO result overestimates the LED effect and is insufficient to provide a believable theoretical prediction.

NLO QCD and electroweak corrections to

The Georgi-Machacek (GM) model is a distinctive TeV-scale extension of the Standard Model (SM) due to the introduction of two (one real and one complex) scalar triplets to the Higgs sector. It predicts the existence of doubly charged Higgs bosons

WW+

H_5^{pmpm}

jet production with leptonic

and the vacuum expectation value of Higgs triplets

W

v_Delta