381 research outputs found
Looking for anomalous gamma-gamma-H and Z-gamma-H couplings at future linear collider
We consider the possibility of studying anomalous contributions to the
gamma-gamma-H and Z-gamma-H vertices through the process e-gamma--> e-H at
future e-gamma linear colliders, with Sqrt(S)=500-1500 GeV. We make a model
independent analysis based on SU(2)xU(1) invariant effective operators of dim=6
added to the standard model lagrangian. We consider a light Higgs boson (mostly
decaying in bar(b)-b pairs), and include all the relevant backgrounds. Initial
e-beam polarization effects are also analyzed. We find that the process
e-gamma--> e-H provides an excellent opportunity to strongly constrain both the
CP-even and the CP-odd anomalous contributions to the gamma-gamma-H and
Z-gamma-H vertices.Comment: LaTeX, 33 pages, 16 eps figures, extended section
Bounds on anomalous gamma-gamma-H and Z-gamma-H couplings at future e-gamma linear colliders
We study the bounds on the anomalous contributions to the gamma-gamma-H and
Z-gamma-H vertices that can be obtained via the process e-gamma-->e H. We
consider the representative case of an intermediate Higgs mass production of
MH=120 GeV and for a center of mass energy of Sqrt{S}=500 GeV and Sqrt{S}=1500
GeV. We use a model independent analysis based on SU(2)xU(1) invariant
operators of dimension 6 added to the Standard Model lagrangian. We find that
this process provides an excelent way to put strong constraints both in the
sector of CP-even and CP-odd anomalous couplings contribution to the
gamma-gamma-H and Z-gamma-H vertices.Comment: LaTeX, 6 pages, To appear in the proceedings of the International
Workshop on Linear Colliders, Sitges, Barcellona, Spain, April 28 - May 5,
(1999
Anomalous gamma-gamma-H and Z-gamma-H couplings in the process e,gamma->e,H
The bounds on the anomalous contributions to the ggh and zgh vertices that
can be obtained via the process eg->eh are discussed through a model
independent analysis based on SU(2) X U(1) invariant operators of dim=6. A
light Higgs boson with m_H ~ 120 GeV and center-of-mass energies of
\sqrt{S}=500 GeV and \sqrt{S}=1500 GeV are assumed. The process eg->eh is shown
to provide an excellent way to strongly constraint both the CP-even and CP-odd
anomalous contributions in the ggH and ZgH couplings.Comment: 8 pages. To appear in the DESY report on "Physics Studies for a
Future Linear Collider", DESY 123
Testing the vertex at future linear colliders for intermediate Higgs masses
Higgs production in collisions, through the one-loop reaction
at large , can provide a precise determination of the
vertex.Comment: 2 pages (standard LaTeX code); Contribution to the Proceedings of the
Int. Europhysics Conference on High Energy Physics (Jerusalem, 19-26 August
1997
Vertex Effects at Future Colliders
We show that the Higgs production in collisions, through the
one-loop reaction at large transverse momentum, can provide a
precise determination of the vertex. We concentrate on the analysis
of signal rates vs background looking for strategies to improve the ratio
. Possible bounds on anomalous contributions to the vertex are
derived.Comment: 5 pages (standard LaTeX code); Talk given at "Beyond the Standard
Model V" Conference, April 29 - May 4 1997, Balholm (Norway); to be published
in the Proceeding
Measuring Z-gamma-Higgs vertex effects at e-gamma linear colliders
The one-loop process e,gamma->e,h for intermediate Higgs masses is
considered. Exact cross sections for unpolarized and longitudinally polarized
beams are computed and found to be more than two orders of magnitude larger
than the rates for the crossed process e,e->gamma,h, in the energy range
\sqrt{s}=(0.5-2) TeV. We show that, apart from being competitive with the
gamma,gamma->H process for testing the one-loop gamma-gamma-H vertex, by
requiring a final electron tagged at large angle the channel e,gamma->e,h
provides an excellent way of testing the Z-gamma-H vertex.Comment: 11 pages, 8 figures. A gzipped complete postscript file is available
at ftp://hpteo.roma1.infn.it/pub/preprints/mele/Rome1-1178.ps.gz To appear in
the Report DESY 97-123
On the search for 50 GeV neutrinos
Using the computer code CompHEP we estimate the number of events and the
background, at LEP II and TESLA, for the reaction ,
where is a hypothetical Dirac neutrino with mass of the order of 50 GeV.Comment: Standard LaTeX, 9 pages, 2 tables, 3 figure
Precision measurements, extra generations and heavy neutrino
The existence of extra chiral generations with all fermions heavier than
is strongly disfavored by the precision electroweak data. The exclusion
of one additional generation of heavy fermions in SUSY extension of Standard
Model is less forbidden if chargino and neutralino have low degenerate masses
with GeV. However the data are fitted nicely even by a few
extra generations, if one allows neutral leptons to have masses close to 50
GeV. Such heavy neutrino can be searched in the reaction at LEP-200 with total final luminosity of .Comment: 5 pages, 6 figures, Proceedings ICHEP2000 Osaka conferenc
Mass of the higgs versus fourth generation masses
The predicted value of the higgs mass is analyzed assuming the
existence of the fourth generation of leptons () and quarks ().
The steep and flat directions are found in the five-dimensional parameter
space: , , , , . The LEPTOP fit of the precision
electroweak data is compatible (in particular) with GeV, GeV, GeV, GeV, and GeV. The quality of fits drastically improves when the data on b- and
c-quark asymmetries and new NuTeV data on deep inelastic scattering are
ignored.Comment: 8 pages, 4 figure
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