95 research outputs found
An alternative heavy Higgs mass limit
After commenting on the present value of the Higgs particle mass from
radiative corrections, we explore the phenomenological implications of an
alternative, non-perturbative renormalization of the scalar sector where the
mass of the Higgs particle does not represent a measure of observable
interactions at the Higgs mass scale. In this approach the Higgs particle could
be very heavy, even heavier than 1 TeV, and remain nevertheless a relatively
narrow resonance.Comment: 17 pages. Version accepted for publication in Journal of Physics
Electroweak parameters of the Z° resonance and the standard model
The four LEP experiments have each performed precision measurements of Z ° parameters. A method is described for combin- ing the results of the four experiments, which takes into account the experimental and theoretical systematic errors and their correlations. We apply this method to the 1989 and 1990 LEP data, corresponding to approximately 650 000 Z ° decays into hadrons and charged leptons, to obtain precision values for the Z ° parameters. We use these results to test the standard model and to constrain its parameters.Facultad de Ciencias Exacta
Electroweak parameters of the Z° resonance and the standard model
The four LEP experiments have each performed precision measurements of Z ° parameters. A method is described for combin- ing the results of the four experiments, which takes into account the experimental and theoretical systematic errors and their correlations. We apply this method to the 1989 and 1990 LEP data, corresponding to approximately 650 000 Z ° decays into hadrons and charged leptons, to obtain precision values for the Z ° parameters. We use these results to test the standard model and to constrain its parameters.Facultad de Ciencias Exacta
Associated single photons and doubly charged scalar at linear e-e- colliders
Doubly charged scalars, predicted in many models having exotic Higgs
representations, can in general have lepton-number violating (LFV) couplings.
We show that by using an associated monoenergetic final state photon seen at a
future linear e-e- collider, we can have a clear and distinct signature for a
doubly-charged resonance. The strength of the Delta L=2 coupling can also be
probed quite effectively as a function of the recoil mass of the doubly-charged
scalar.Comment: Reference adde
Hadronic Contributions to the Photon Vacuum Polarization and their Role in Precision Physics
I review recent evaluations of the hadronic contribution to the shift in the
fine structure constant and to the anomalous magnetic moment of the muon.
Substantial progress in a precise determination of these important observables
is a consequence of substantially improved total cross section measurement by
the CMD-2 and BES II collaborations and an improved theoretical understanding.
Prospects for further possible progress is discussed.Comment: 17 pages 7 figures 2 tables, update: incl. CMD-2 data, reference
Phenomenological Constraints on Extended Quark Sectors
We study the flavor physics in two extensions of the quark sector of the
Standard Model (SM): a four generation model and a model with a single
vector--like down--type quark (VDQ). In our analysis we take into account the
experimental constraints from tree--level charged current processes, rare Kaon
decay processes, rare B decay processes, the decay, ,
and mass differences, and the CP violating parameters \frac
\epsilon^\prime}{\epsilon}, and . All the constraints
are taken at two sigma. We find bounds on parameters which can be used to
represent the New Physics contributions in these models (, and in the
four--generation model, and , and in the VDQ model)
due to all the above constraints. In both models the predicted ranges for
(the CP asymmetry in semi-leptonic decays), ,
, and can be significantly higher than the predictions of the
SM, while the allowed ranges for and for are
consistent with the SM prediction.Comment: 22 pages, 5 figures (v3: added a reference, updated a reference,
added missing units
SUSY Magnetic Moments Sum Rules and Supersymmetry Breaking
It was recently shown that unbroken N=1 Susy relates, in a model independent
way, the magnetic transitions between states of different spin within a given
charged massive supermultiplet. We verify explicitly these sum rules for a
vector multiplet in the case of massless and massive fermions. The purpose of
this analysis is to provide the ground for the broken susy case. We study the
modifications of these results when an explicit soft Susy breaking realized
through a universal mass for all scalars is present. As a by-product we provide
a computation of the of the boson in the standard model which
corrects previous evaluations in the literature.Comment: 16+5 pages, Latex,(feynman.tex to print the figures), DFPD 94/TH/2
Direct Higgs production and jet veto at the Tevatron and the LHC in NNLO QCD
We consider Higgs boson production through gluon--gluon fusion in hadron
collisions, when a veto is applied on the transverse momenta of the
accompanying hard jets. We compute the QCD radiative corrections to this
process at NLO and NNLO. The NLO calculation is complete. The NNLO calculation
uses the recently evaluated NNLO soft and virtual QCD contributions to the
inclusive cross section. We find that the jet veto reduces the impact of the
NLO and NNLO contributions, the reduction being more sizeable at the LHC than
at the Tevatron.Comment: 22 pages, 12 postscript figure
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