3,093 research outputs found
Theoretical developments on Quartic Gauge Boson Couplings at LEP
The search for quartic anomalous gauge couplings (QAGC) at LEP requires
appropriate predictions for the radiative processes e+ e- \to \nu\bar\nu
\gamma\gamma, e+ e- \to q\bar{q}\gamma\gamma and e+ e- \to 4 fermions+\gamma.
The current knowledge on dimension-six operators giving rise to QAGC is briefly
reviewed, together with their implementation in event generators. The accuracy
of calculations based on real approximations (used up to now for the LEP
experimental analysis) is examined by comparing them with the available exact
matrix element calculations.Comment: LaTeX, JHEP style, 5 pag. Talk presented at EPS HEP2001, Budapest,
Hungary, 12 - 18 July, 200
MCSTHAR++, a Monte Carlo code for the microcanonical hadronization
MCSTHAR++ is a new Monte Carlo code implementing the Statistical
Hadronization Model. This model assumes that hadronization proceeds through the
microcanonical decay of massive extended clusters. Unlike other hadronization
models, in this approach very few free parameters are needed, as has been
demonstrated in previous studies. The tuning of the model and the comparison
with the data is ongoing.Comment: 3 pages; To appear in the proceedings of the conference IFAE 2010,
Roma, Italy, 7-9 April 201
Next-to-Leading Photonic Corrections to Small-Angle Bhabha Scattering in the Structure Function Formalism
A general method for computing and higher-order
next-to-leading photonic corrections is presented and applied to the precision
calculation of the small-angle Bhabha scattering cross section in the
phase-space region of interest for the luminosity measurement at LEP. The
formulation is based on a proper matching of exact results
with higher-order corrections in the Structure Function formalism. The results
of the approach are analytically compared with theoretical calculations, both
for - and -channel processes, available for simple Event Selections.
Numerical predictions for realistic Event Selections are also provided and
critically compared with the ones existing in the literature.Comment: 16 pages, gzip'ed uuencoded tar fil
H -> gamma gamma: a Comment on the Indeterminacy of Non-Gauge-Invariant Integrals
We reanalyze the recent computation of the amplitude of the Higgs boson decay
into two photons presented by Gastmans et al.. The reasons for which this
result cannot be the correct one have been discussed in some recent papers. We
address here the general issue of the indeterminacy of integrals with
four-dimensional gauge-breaking regulators and to which extent it might
eventually be solved by imposing physical constraints. Imposing gauge
invariance as the last step upon R_xi gauge calculations with four-dimensional
gauge-breaking regulators, allows indeed to recover the well known H -> gamma
gamma result. However we show that in the particular case of the unitary gauge,
the indeterminacy cannot be tackled in this same way. The combination of
unitary gauge with a cutoff regularization scheme turns out to be
non-predictive.Comment: 17 pages, 6 figure
A Mechanism for Hadron Molecule Production in p pbar(p) Collisions
We propose a mechanism allowing the formation of loosely bound molecules of
charmed mesons in high energy proton-(anti)proton collisions.Comment: 4 pages, 3 figure
Six-fermion production and Higgs boson physics at future colliders
The six-fermion production processes ,
with all the lepton flavours and , relevant to the study of the
intermediate-mass Higgs boson at future linear colliders, are
analysed. A Monte Carlo program, taking into account the whole set of
tree-level scattering amplitudes and the relevant radiative effects, is
developed to provide integrated cross sections and generation of unweighted
events. The complete calculation is compared with the available results of real
Higgs production, and the opportunities of precision studies with event
generation are discussed, demonstrating the relevance of a full six-fermion
calculation. Numerical results for integrated cross sections with various
kinematical cuts and including radiative effects are given and commented. In
the analysis of event samples, several distributions are studied and found to
be sensitive to the presence and to the properties of the Higgs boson.Comment: LaTeX, 27 pages, 13 figures included. Minor changes, final version to
appear in Eur. Phys. J.
Six-Fermion Calculation of Intermediate-mass Higgs Boson Production at Future Colliders
The production of an intermediate-mass Higgs boson in processes of the kind
fermions at the energies of future linear colliders is studied.
The recently developed and fully automatic algorithm/code ALPHA is used to
compute the tree-level scattering amplitudes for the reactions . The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV,
properly adapted to 6-fermion production, in order to provide realistic
results, both in the form of cross sections and event samples at the partonic
level. Phenomenological results, that incorporate the effects of initial-state
radiation and beamstrahlung, are shown and commented, emphasizing the
potentials of full six-fermion calculations for precise background evaluation
as well as for detailed studies of the fundamental properties of the Higgs
particle.Comment: 31 pages, LaTeX, 15 eps low-resolution figures include
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