385 research outputs found

    Exploiting the WH/ZH symmetry in the search for New Physics

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    We suggest to isolate the loop-induced gluon-initiated component (gg→ZHgg\to ZH) for associated ZHZH production by using the similarity of the Drell-Yan-like component for ZHZH production to the WHWH process. We argue that the cross-section ratio of the latter two processes can be predicted with high theoretical accuracy. Comparing it to the experimental ZH/WHZH/WH cross-section ratio should allow to probe for New Physics in the gg→ZHgg\to ZH component at the HL-LHC. We consider typical BSM scenarios in order to exemplify the effect they would have on the proposed observable.Comment: 22 pages, 10 figures. v2: Minor changes; matches published versio

    Effects of QCD radiation on inclusive variables for determining the scale of new physics at hadron colliders

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    We examine the effects of QCD initial-state radiation on a class of quantities, designed to probe the mass scale of new physics at hadron colliders, which involve longitudinal as well as transverse final-state momenta. In particular, we derive universal functions that relate the invariant mass and energy distribution of the visible part of the final state to that of the underlying hard subprocess. Knowledge of this relationship may assist in checking hypotheses about new processes, by providing additional information about their scales. We compare our results with those of Monte Carlo studies and find good general agreement

    Effects of invisible particle emission on global inclusive variables at hadron colliders

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    We examine the effects of invisible particle emission in conjunction with QCD initial state radiation (ISR) on quantities designed to probe the mass scale of new physics at hadron colliders, which involve longitudinal as well as transverse final-state momenta. This is an extension of our previous treatment, arXiv:0903.2013, of the effects of ISR on global inclusive variables. We present resummed results on the visible invariant mass distribution and compare them to parton-level Monte Carlo results for top quark and gluino pair-production at the LHC. There is good agreement as long as the visible pseudorapidity interval is large enough (eta ~ 3). The effect of invisible particle emission is small in the case of top pair production but substantial for gluino pair production. This is due mainly to the larger mass of the intermediate particles in gluino decay (squarks rather than W-bosons). We also show Monte Carlo modelling of the effects of hadronization and the underlying event. The effect of the underlying event is large but may be approximately universal.Comment: 22 pages, expanded sections and other minor modifications. Version published in JHE

    A study of multi-jet production in association with an electroweak vector boson

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    Abstract: We consider the production of a single Z or W boson in association with jets at the LHC. We compute the corresponding cross sections by matching NLO QCD predictions with the Herwig++ and Pythia8 parton showers, and by merging all of the underlying matrix elements with up to two light partons at the Born level. We compare our results with several 7-TeV measurements by the ATLAS and CMS collaborations, and overall we find a good agreement between theory and data
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