1,294 research outputs found

    Higgs Production in Charged Current Six Fermion Processes at Future e+ee^+e^- Colliders

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    We study higgs physics at future e+ee^+e^- colliders taking into account the full set of Feynman diagrams for six fermion final states, which are produced for higgs masses near or above the two WW's threshold. In particular we examine events where one isolated lepton or two isolated leptons of different flavours signal the presence of two W\rm W^*'s. For these charged current processes, a detailed analysis of the relevance of irreducible and QCD background shows that appropriate cuts are generally sufficient to deal with it in the case of reconstructed or missing higgs mass distributions. These latter are however affected by a non negligible distortion and shift of the maximum.Comment: Latex, 16 pages, 8 Ps figures included. Revised version. One fig. added, qcd curve in fig.5 corrected, various changes in the tex

    Boson Fusion and Higgs production at the LHC in six fermion final states with one charged lepton pair

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    Boson boson scattering and Higgs production in boson boson fusion will be actively investigated at the LHC. We have performed a parton level study of all processes of the type q1q2q3q4q5q6l+lq_1 q_2 \to q_3 q_4 q_5 q_6 l^+l^- using for the first time a full fledged six fermion Monte Carlo event generator which employs exact matrix elements at \O(\alpha_{em}^6). We have examined Higgs production in vector boson fusion followed by the decay chain HZZl+ljjH\to ZZ\to l^+l^-jj, including exactly all electroweak irreducible backgrounds. In the high mass region we have compared the case of a relatively light Higgs with the no-Higgs case. The integrated cross section for the latter case is more than twice that in the former for a minimum invariant mass of the ZVZV pair of about 800 \GeV. We find, in a preliminary anlysis at parton level that, summing up the muon and the electron channels, about 30 events are expected in the light Higgs case for L=100 fb1fb^{-1}.Comment: Final version published in Phys.Rev.

    Interference Effects in Higgs production through Vector Boson Fusion in the Standard Model and its Singlet Extension

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    Interference effects play an important role in Electroweak Physics. They are responsible for the restoration of unitarity al large energies. When, as is often the case, higher order corrections are only available for some particular subamplitude, interferences need to be carefully computed in order to obtain the best theoretical prediction. In the new proposal to estimate the total Higgs width from the off shell cross section, the interference between the Higgs signal and the background is essential. It has been recently pointed out in gluon fusion that whenever more than one neutral, CP even, scalars are present in the spectrum large cancellations can occur. We extend these studies to Vector Boson Scattering, examining interference effects in the Higgs sector in the Standard Model and its one Higgs Singlet extension

    Hard Photon Pair Production at LEP

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    The production of photon pairs in e+effˉγγe^+e^-\rightarrow f \bar f \gamma\gamma processes is studied using exact helicity amplitudes at tree level. Total cross sections, including initial state radiation effects, are given. They are presented in the case of quarks as a function of ycuty_{\rm cut} in the JADE algorithm. In the case of leptons we use cuts similar to the ones employed in a recent L3 analysis. Masses of the final state fermions are taken into account when appropriate. The cross section e+eτ+τγγe^+e^-\rightarrow \tau^+ \tau^- \gamma\gamma is about 10\% larger when the τ\tau mass is neglected. We obtain, with a different method, results which are in good agreement with L3 Montecarlo simulation.Comment: 7 Pages (4 Figs available from the authors in Postscript or via Fax ), LaTex, DFTT 4/9

    Four quark processes at LEP 200

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    In this paper I investigate the production of four quarks at LEP 200 energies. Effects due to initial state QED corrections and background diagrams, including QCD contributions, are studied and examples of results obtained with an event generator presented.Comment: 9 pages, INLO-PUB-8/9

    PHASE - An event generator for six fermion physics at the LHC

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    PHASE is a Monte Carlo event generator, under construction, for all Standard Model processes with six fermions in the final state at the LHC. It employs the full set of tree level Feynman diagrams, taking into account fermion masses for b quarks. The program can generate unweighted events for any subset of all six fermion final states in a single run, by making use of dedicated pre-samples. An interface to hadronization is provided.Comment: 4 pages, Latex, 1 figure. Talk given by E. Accomando at the IX International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT03), KEK, Tsukuba, December 1-5, 200