102 research outputs found

    Determination of transverse momentum dependent gluon density from HERA structure function measurements

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    The transverse momentum dependent gluon density obtained with CCFM evolution is determined from a fit to the latest combined HERA structure function measurements.Comment: Contribution to DIS201

    Higgs production via gluon fusion from kT-factorisation

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    Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass, an approximation which reduces the top quark loop to an effective vertex. We present a numerical analysis of the error thus introduced by performing a Monte Carlo calculation for gg->h in kT-factorisation, using the parton shower generator CASCADE. We proceed to compare CASCADE to the collinear Monte Carlos PYTHIA, MC@NLO and POWHEG. We study the dependence of parton radiation on the resummation of high-energy corrections taken into account by kT-factorisation, and its influence on predictions for the Higgs pT spectrum.Comment: Contribution to the Workshop Diffraction 2010, Otranto (Italy), September 201

    Matrix Elements with Vetoes in the CASCADE Monte Carlo Event Generator

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    We illustrate a study based on a veto technique to match parton showers and matrix elements in the Cascade Monte Carlo event generator, and present a numerical application to gluon matrix elements for jet production.Comment: Published in DIS 2012 proceeding

    Complementarity of Lepton-Charge and Forward-Backward Drell-Yan Asymmetries for Precision Electroweak Measurements and Quark Density Determinations

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    We address the impact of future measurements of charged and neutral current Drell-Yan (DY) asymmetries and their combination on Parton Distribution Functions (PDFs) uncertainties. We quantify the reduction of PDF uncertainties using the QCD tool xFitter. We examine the effects of such reduced PDF errors on both Standard Model (SM) and Beyond SM (BSM) observables.Comment: 5 pages, 4 figures, contribution to the Proceedings for the XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects, Stony Brook University, New York, USA, 12-16 April 202

    Photon-induced contributions to di-lepton production at the LHC Run II

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    We report on recent studies of photon-induced (PI) contributions to di-lepton production and their implications for Beyond Standard Model (BSM) Z′Z^\prime-bosons searches at the LHC.Comment: Proceedings of XXV International Workshop on Deep-Inelastic Scattering and Related Subjects, 3-7 April 2017, University of Birmingham, U

    Real and virtual photons effects in di-lepton production at the LHC

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    We show the SM prediction of di-lepton production at the LHC where to the usual Drell-Yan production we add the contribution from Photon-Initiated processes. We discuss the effects of the inclusion of photon interactions in the high invariant mass region (TeV region) and their consequences on BSM heavy Z'-boson searches.Comment: 7 pages, 6 figures, Proceeding of Les Rencontres de Physique de la Vall\'ee d'Aoste, La Thuile 201

    The effect of real and virtual photons in the di-lepton channel at the LHC

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    We present a study of di-lepton production at the CERN Large Hadron Collider with a particular focus on the contribution resulting from both real and virtual photons in the initial state. We discuss the region of phase space in which the invariant mass of the lepton pair is of the order of several TeV, where searches for new physics phenomena yielding a di-lepton signature are presently carried out. We study both the yield and associated uncertainties for all possible topologies in photon-induced di-lepton production and compare these with what is expected in the standard Drell-Yan channel, where quark-antiquark pairs are responsible for the production of lepton pairs. We analyse the impact of these QED contributions on the expected Standard Model background and on searches for new physics. In this latter case, we use the production of an extra heavy Z′Z^\prime-boson predicted by the Sequential Standard Model (SSM) as a benchmark process.Comment: 9 pages, 5 figure

    Emergence of resummation scales in the evolution of the QCD strong coupling and PDFs

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    The QCD strong coupling and the parton distribution functions (PDFs) of the proton are fundamental ingredients for phenomenology at high-energy facilities such as the Large Hadron Collider (LHC). It is therefore of crucial importance to estimate any theoretical uncertainties associated to them. Both the coupling and the PDFs obey their own renormalisation-group equations (RGEs) whose solution determines their scale evolution. Although the kernels that govern these RGEs have been computed to very high perturbative precision, they are not exactly known. In this contribution, we outline a procedure that allows us to assess the uncertainty on the evolution of the coupling and the PDFs due to our imperfect knowledge of their respective evolution kernels. Inspired by transverse-momentum and threshold resummation, we introduce additional scales, that we dub resummation scales, that can be varied to estimate the uncertainty on the evolution at any scale. As a test case, we consider the deep-inelastic-scattering structure function 2 in a region relevant for the extraction of PDFs. We study the effect of varying these resummation scales and compare it to the usual renormalisation and factorisation scale variations
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