D* meson production cross sections in e − p and e + p scattering processes at the HERA collider

The cause of the D* meson production cross sections in e ^? p and e ⁺ p deep inelastic scattering processes in the ZEUS experiment at the HERA collider that are anomalously different is determined.     

Inclusive one- and two-jet cross sections in γγ reactions at e+e− colliders

We have calculated inclusive one- and two jet production in photon-photon collisions superimposing direct, single-resolved and double-resolved cross sections for center of mass energies of the LEP1, LEP2 and NLC range. The direct and single-resolved cross sections are calculated up to next-to-leading order. The double-resolved two-jet cross section is calculated only in LO with a k factor estimated from the NLO one jet cross section. Various differential cross sections as functions of transverse momenta and rapidities of the jets are evaluated.     

Parton distributions in the virtual photon target up to NNLO in QCD

Parton distributions in the virtual photon target are investigated in perturbative QCD up to the next-to-next-to-leading order (NNLO). In the case Λ ²≪P ²≪Q ², where −Q ² (−P ²) is the mass squared of the probe (target) photon, parton distributions can be predicted completely up to the NNLO, but they are factorisation-scheme dependent. We analyse parton distributions in two different factorisation schemes, namely the and DIS _γ schemes, and we discuss their scheme dependence. We show that the factorisation-scheme dependence is characterised by the large-x behaviours of the quark distributions. The gluon distribution is predicted to be very small in absolute value except in the small-x region.     

NNLO QCD predictions of electron charge asymmetry for inclusive pp→W+X production in forward region at 13 and 14 TeV

This paper presents perturbative QCD predictions of the electron charge asymmetry for inclusive W~±X→e~±v+X production in proton-proton(pp) collisions.Perturbative QCD calculations are performed at nextto-next-to-leading order(NNLO) accuracy using different parton distribution function(PDF) models at 8,13,and 14 TeV center-of-mass energies of CERN LHC pp collisions.NNLO calculations are performed for electrons with transverse momenta above 20 GeV in the forward electron pseudorapidity region 2.0 ≤η_e≤4.25.NNLO predictions are first compared at 8 TeV with the measurements of the LHCb experiment at the LHC for the W~+/W~-cross section ratio and charge asymmetry distributions.The 8 TeV predictions using NNPDF3.1,CT14,and MMHT2014 PDF sets are reported to be in good agreement with the LHCb data for the entire η_e region,justifying the extension of the calculations to 13 and 14 TeV energies.The charge asymmetry predictions at NNLO accuracy are reported in the forward η_e bins at 13 and 14 TeV and compared among NNPDF3.1,CT14,and MMHT2014 PDF sets.Overall,the predicted W~± differential cross-section and charge asymmetry distributions based on different PDF sets are found to be consistent with each other for the entire η_e region.The charge asymmetry distributions are shown to be more sensitive to discriminate among different PDF models in terms of the 14 TeV predictions.     

W+W−γ production in e+e− annihilation in the TeV region

The reaction e⁺e⁻→γW⁺W⁻ has been studied at TeV energies as a possible background to Higgs production. Our results differ significantly from previous estimates and show that the ratio signal/background can be kept reasonably large.     

Electroweak corrections to Wγ and Zγ production at the LHC

We have calculated the electroweak corrections to the processes , , and at the LHC, with l=e,μ and . The virtual corrections are evaluated in leading-pole approximation, whereas the real corrections are taken into account exactly. These corrections are implemented into a Monte Carlo generator which includes both phase-space slicing and subtraction to deal with soft and collinear singularities. We present numerical results for total cross sections as well as for experimentally interesting distributions. Applying typical LHC cuts, the electroweak corrections are of the order of -5% for the total cross sections and exceed -20% for observables dominated by high center-of-mass energies of the partonic processes.     

Higher order perturbative QCD calculation of jet cross sections ine + e − annihilation

We present in detail the analytic calculation of the Sterman-Weinberg type 3-jet cross section to order α _s ² The fit to recent PLUTO data gives in the \({MS}\) scheme α _s which corresponds to Λ=0.24 GeV in the 1-loop approximation.     

Hadronic top-quark pair production in association with a hard jet at next-to-leading order QCD: phenomenological studies for the Tevatron and the LHC

We report on the calculation of the next-to-leading order QCD corrections to the production of top–antitop-quark pairs in association with a hard jet at the Tevatron and at the LHC. Results for integrated and differential cross sections are presented. We find a significant reduction of the scale dependence. In most cases the corrections are below 20% indicating that the perturbative expansion is well under control. Moreover, the forward–backward charge asymmetry of the top quark, which is analyzed at the Tevatron, is studied at next-to-leading order. We find large corrections, suggesting that the definition of the observable has to be refined.     

Large logarithm behaviour ofe + e − jet cross sections and event shape distributions inO(α s 2 )

We have calculated the leading and next-to-leading logarithm coefficients ofO(α _s ² )e ⁺ e ^? annihilation jet cross sections, thrust distribution and energy-energy correlation in the two-jet limit when the jet resolution and the event shape variables vanish. We have compared our results with expectations based on leading logarithm approximations used to resum the pertubative cross sections where this is possible. There is good agreement for the leading and next-to-leading coefficients of jet cross sections in the Durham scheme. Also for the thrust distribution and energy-energy correlation we find results which are consistent with the leading logarithm predictions.     

The production ofW + W − pairs in proton-antiproton colliders

We present the predictions of the Glashow-Weinberg-Salam [1] (GWS) model for the total cross-section and the angular and invariantmass differential cross sections for the reaction \(p\bar p \to W^ + W^ - X\) . We contrast these GWS predictions with those obtained by varying the anomalous magnetic moment of theW(κ), the analogue for theZWW coupling (κ _z ) and the relative strength of the γWW andZWW couplings (ω) from their GWS values. We find that changes in these parameters produce significant changes in both the total cross section and the angular and invariant mass differential cross sections. We also present the angular distribution of the decay leptons (W ⁺→/+v _l) and find in all cases it closely mirrors theW ⁺ angular distribution. We have given the intermediate results for the dominant quark subprocesses \((u\bar u \to W^ + W^ - ,d\bar d \to W^ + W^ - )\) .