77 research outputs found

    CP-violating Higgs boson production in association with three jets via gluon fusion

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    In these proceedings, we present results for Higgs production at the LHC via gluon fusion with triple real emission corrections and the validity range of the heavy-top effective theory approximation for this process. For a general CP-violating Higgs boson, we show that bottom-quark loop corrections in combination with large values of tanβ\tan \beta significantly distort differential distributions.Comment: 7 pages, 7 figures. To appear in the proceedings of Conference: C14-07-0

    Higgs boson production in association with three jets via gluon fusion at the LHC: Gluonic contributions

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    Higgs production in association with three jets via gluon fusion (GF) is an important channel for the measurement of the CP-properties of the Higgs particle at the LHC. In this letter, we go beyond the heavy top effective theory approximation and include at LO the full mass dependence of the top- and bottom-quark contributions. We consider the dominant sub-channel gg -> H ggg which involves the manipulation of massive rank-5 hexagon integrals. Furthermore, we present results for several differential distributions and show deviations from the effective theory as large as 100% at high pT for light Higgs masses.Comment: 5 pages, 4 figure

    ZZ production at high transverse momenta beyond NLO QCD

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    We study the production of the four-lepton final state l+ll+ll^+ l^- l^+ l^-, predominantly produced by a pair of electroweak Z bosons, ZZ. Using the LoopSim method, we merge NLO QCD results for ZZ and ZZ+jet and obtain approximate NNLO predictions for ZZ production. The exact gluon-fusion loop-squared contribution to the ZZ process is also included. On top of that, we add to our merged sample the gluon-fusion ZZ+jet contributions from the gluon-gluon channel, which is formally of N^3LO and provides approximate results at NLO for the gluon-fusion mechanism. The predictions are obtained with the VBFNLO package and include the leptonic decays of the Z bosons with all off-shell and spin-correlation effects, as well as virtual photon contributions. We compare our predictions with existing results for the total inclusive cross section at NNLO and find a very good agreement. Then, we present results for differential distributions for two experimental setups, one used in searches for anomalous triple gauge boson couplings, the other in Higgs analyses in the four charged-lepton final state channel. We find that the approximate NNLO corrections are large, reaching up to 20% at high transverse momentum of the Z boson or the leading lepton, and are not covered by the NLO scale uncertainties. Distributions of the four-lepton invariant mass are, however, stable with respect to QCD corrections at this order.Comment: 21 pages, 2 tables, 9 figure

    Precise predictions for (non-standard) W+photon+jet production

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    We report on a detailed investigation of the next-to-leading order (NLO) QCD corrections to WγW\gamma+jet production at the Tevatron and the LHC using a fully-flexible parton-level Monte Carlo program. We include the full leptonic decay of the WW, taking into account all off-shell and finite width effects, as well as non-standard WWγWW\gamma couplings. We find particularly sizable corrections for the currently allowed parameter range of anomalous couplings imposed by LEP data. In total the NLO differential distributions reveal a substantial phase space dependence of the corrections, leaving considerable sensitivity to anomalous couplings beyond scale uncertainty at large momentum transfers in the anomalous vertex.Comment: 22 pages, 14 figures, 2 tables, published versio

    High order perturbative corrections to the determination of |Vub| from the P+ spectrum in B -> Xu l nu

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    We investigate the behaviour of the perturbative relation between the photon energy spectrum in B -> Xs gamma and the hadronic P+ spectrum in semileptonic B -> Xu l nu decay at high orders in perturbation theory in the "large-beta_0" limit, in which only terms of order alpha_s^n beta_0^(n-1) are retained. The leading renormalon in the weight function W(Delta,P_gamma) relating the two spectra is confirmed to be at u=1/2, corresponding to nonperturbative corrections at O(Lambda_QCD/m_b). We show that the P_gamma dependent pieces of the weight function have no infrared renormalons in this limit, and so the factorial growth in perturbation theory arises solely from the constant terms. We find no numerical enhancement of leading logarithms, suggesting that fixed-order perturbation theory is more appropriate than a leading-log resummation for the extraction of |Vub|. The importance of various terms in the expansion of the weight function is studied using a model for the B -> Xs gamma photon spectrum. Our analysis suggests that higher order perturbative corrections do not introduce a significant uncertainty in the extraction of |Vub|.Comment: 20 pages, 2 figure

    ZA production in vector-boson scattering at next-to-leading order QCD

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    Cross sections and differential distributions for ZA production in association with two jets via vector boson fusion are presented at next-to-leading order in QCD. The leptonic decays of the Z boson with full off-shell effects and spin correlations are taken into account. The uncertainties due to different scale choices and pdf sets are studied. Furthermore, we analyze the effect of including anomalous quartic gauge couplings at NLO QCD.Comment: 10 pages, 11 figure

    Fit to the Bjorken, Ellis-Jaffe and Gross-Llewellyn-Smith sum rules in a renormalon based approach

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    We study the large order behaviour in perturbation theory of the Bjorken, Ellis-Jaffe and Gross-Llewellyn-Smith sum rules. In particular, we consider their first infrared renormalons, for which we obtain their analytic structure with logarithmic accuracy and also an approximate determination of their normalization constant. Estimates of higher order terms of the perturbative series are given. The Renormalon subtracted scheme is worked out for these observables and compared with experimental data. Overall, good agreement with experiment is found. This allows us to obtain {\hat a}_0 and some higher-twist non-perturbative constants from experiment: {\hat a}_0=0.141\pm 0.089; f_{3,RS}(1 GeV)=-0.124^{+0.137}_{-0.142} GeV^2.Comment: 23 pages, 18 figures, one reference added, journal versio

    WZ production in association with two jets at NLO in QCD

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    We report on the calculation of W±ZjjW^\pm Zjj production with leptonic decays at hadron-hadron colliders at next-to-leading order in QCD. These processes are important both to test the quartic gauge couplings of the Standard Model and because they constitute relevant backgrounds to beyond standard model physics searches. Our results show that the next-to-leading order corrections reduce significantly the scale uncertainties and have a non-trivial phase space dependence.Comment: 4 pages, 5 figure
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