1,294 research outputs found

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

We study higgs physics at future $e^+e^-$ 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 $W$'s threshold. In particular we
examine events where one isolated lepton or two isolated leptons of different
flavours signal the presence of two $\rm W^*$'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

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 $q_1 q_2 \to q_3 q_4 q_5 q_6 l^+l^-$ 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 $H\to ZZ\to l^+l^-jj$,
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 $ZV$ 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 $fb^{-1}$.Comment: Final version published in Phys.Rev.

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

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

The production of photon pairs in $e^+e^-\rightarrow f \bar f \gamma\gamma$
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 $y_{\rm cut}$ 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 $e^+e^-\rightarrow \tau^+ \tau^-
\gamma\gamma$ is about 10\% larger when the $\tau$ 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

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

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

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