119 research outputs found
Determination of the Higgs-boson couplings and H-A mixing in the generalized SM-like Two Higgs Doublet Model
The feasibility of measuring the Higgs-boson properties at the Photon
Collider at TESLA has been studied in detail for masses between 200 and 350
GeV, using realistic luminosity spectra and detector simulation. We consider
the Two Higgs Doublet Model (II) with SM-like Yukawa couplings for h,
parametrized by only one parameter (tan(beta)). The combined measurement of the
invariant-mass distributions in the ZZ and W+W- decay-channels is sensitive to
both the two-photon width Gamma_{gamma gamma} and phase Phi_{gamma gamma}. From
the analysis including systematic uncertainties we found out that after one
year of Photon Collider running with nominal luminosity the expected precision
in the measurement of tan(beta) is of the order of 10%, for both light (h) and
heavy (H) scalar Higgs bosons. The H-A mixing angle Phi_{HA}, characterizing a
weak CP violation in the model with two Higgs doublets, can be determined to
about 100 mrad, for low tan(beta).Comment: 17 pages, 9 figures; published versio
Precision Mass Determination of the Higgs Boson at Photon-Photon Colliders
We demonstrate a measurement of the Higgs boson mass by the method of energy
scanning at photon-photon colliders, using the high energy edge of the photon
spectrum. With an integrated luminosity of 50 it is possible to
measure the standard model Higgs mass to within 110 MeV in photon-photon
collisions for m_h=100 GeV. As for the total width of the Higgs boson, the
statistical error is expected for
m_h=100 GeV, if both and are
fixed at the predicted standard model value.Comment: 7 pages, 4 figures, Given at 3nd International Workshop on
Electron-Electron Interactions at TeV Energies, Dec 10-12, Santa Cruz,
California, 199
Study of the Higgs-boson decays into WW and ZZ at the Photon Collider
Production of the Standard Model Higgs-boson at the Photon Collider at TESLA
is studied for the Higgs-boson masses above 150 GeV. Simulation of signal and
background processes takes into account realistic luminosity spectra and
detector effects. In the considered mass range, large interference effects are
expected in the W+W- decay channel. By reconstructing W+W- and ZZ final states,
not only the h->gamma gamma partial width can be measured, but also the
relative phase of the scattering amplitude. This opens a new window for the
precise determination of the Higgs-boson couplings. Models with heavy,
fourth-generation fermions and with enlarged Higgs sector (2HDM (II)) are
considered.Comment: 19 pages, 18 figures; updated version with improved precision of
estimate
Discovery limits for Techni-Omega production in Collisions
In a strongly-interacting electroweak sector with an isosinglet vector state,
such as the techni-omega, , the direct coupling
implies that an can be produced by fusion in
collisions. This is a unique feature for high energy or
colliders operating in an mode. We consider the processes and , both of which proceed via
an intermediate . We find that at a 1.5 TeV linear collider
operating in an mode with an integrated luminosity of 200 fb,
we can discover an for a broad range of masses and widths.Comment: To appear in the Proceedings of the 29th International Conference on
High Energy Physics, Vancouver, July 1998, 5 pages, Latex, 7 postscript
figure
Partially composite two-Higgs doublet model
In the extra dimensional scenarios with gauge fields in the bulk, the
Kaluza-Klein (KK) gauge bosons can induce Nambu-Jona-Lasinio (NJL) type
attractive four-fermion interactions, which can break electroweak symmetry
dynamically with accompanying composite Higgs fields. We consider a possibility
that electroweak symmetry breaking (EWSB) is triggered by both a fundamental
Higgs and a composite Higgs arising in a dynamical symmetry breaking mechanism
induced by a new strong dynamics. The resulting Higgs sector is a partially
composite two-Higgs doublet model with specific boundary conditions on the
coupling and mass parameters originating at a compositeness scale .
The phenomenology of this model is discussed including the collider
phenomenology at LHC and ILC.Comment: 20 pages, 7 figure
Necessity of mixed kinetic term in the description of general system with identical fields
Most general renormalizable interaction in the system with a set of scalar
fields having identical quantum numbers generates naturally mixed kinetic terms
in the Lagrangian. Taking into account these terms leads to modification both
the renormalization group equations and the tree level analysis as compare with
many published results. We obtain conditions for non-appearance of such a
running mixing in some important cases.Comment: 12 pages, 3 figure
Large contribution of virtual Delbrueck scattering to the emission of photons by relativistic nuclei in nucleus-nucleus and electron-nucleus collisions
Delbrueck scattering is an elastic scattering of a photon in the Coulomb
field of a nucleus via a virtual electron loop. The contribution of this
virtual subprocess to the emission of a photon in the collision of
ultra-relativistic nuclei Z_1 Z_2 -> Z_1 Z_2 gamma is considered. We identify
the incoming virtual photon as being generated by one of the relativistic
nuclei involved in the binary collision and the scattered photon as being
emitted in the process. The energy and angular distributions of the photons are
calculated. The discussed process has no infrared divergence. The total cross
section obtained is 14 barn for Au-Au collisions at the RHIC collider and 50
barn for Pb-Pb collisions at the LHC collider. These cross sections are
considerably larger than those for ordinary tree-level nuclear bremsstrahlung
in the considered photon energy range m_e << E_\gamma << m_e gamma, where gamma
is the Lorentz factor of the nucleus. Finally, photon emission in
electron-nucleus collisions e Z -> e Z gamma is discussed in the context of the
eRHIC option.Comment: 10 pages; 7 figure
Inverse Neutrinoless Double Beta Decay Revisited
We critically reexamine the prospects for the observation of the
lepton-number-violating process \eeWW using the option of a
high-energy collider (NLC). We find that, except in the most contrived
scenarios, constraints from neutrinoless double beta decay render the process
unobservable at an NLC of TeV. Other processes such
as \ggllww, \egnllw, \eennll (), and \egeww, which use
various options of the NLC, require a of at least 4 TeV for
observability.Comment: paper in LATEX, 24 pages, 10 figures in separate uuencoded psfile.
Complete psfile available via anonymous ftp at
ftp://lapphp0.in2p3.fr/pub/preprints-theorie/doublebeta.uu or via www at
http://lapphp0.in2p3.fr/preplapp/psth/doublebeta.ps.g
Using Scalars to Probe Theories of Low Scale Quantum Gravity
Arkani-Hamed, Dimopoulos and Dvali have recently suggested that gravity may
become strong at energies near 1 TeV which would remove the hierarchy problem.
Such a scenario can be tested at present and future colliders since the
exchange of towers of Kaluza-Klein gravitons leads to a set of new dimension-8
operators that can play important phenomenological roles. In this paper we
examine how the production of pairs of scalars at , and
hadron colliders can be used to further probe the effects of graviton tower
exchange. In particular we examine the tree-level production of pairs of
identical Higgs fields which occurs only at the loop level in both the Standard
Model and its extension to the Minimal Supersymmetric Standard Model. Cross
sections for such processes are found to be potentially large at the LHC and
the next generation of linear colliders. For the case the role
of polarization in improving sensitivity to graviton exchange is emphasized.Comment: 32 pages, 12 figures, latex, remarks added to tex
and couplings in collision with polarized beams
The potential of e mode of linear collider to probe
and vertices is investigated through the Z boson
production from the procees . Considering the longitudinal and
transverse polarization states of the Z boson and incoming polarized beams we
find the 95% C.L. limits on the form factors , ,
and with integrated luminosity 500
and 0.5, 1, 1.5 TeV energies. It is shown that the polarization can
improve sensitivities by factors 2-3 depending on the energy.Comment: 12 pages, 8 EPS figure
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