72 research outputs found
Search for B0s oscillations using inclusive lepton events
A search for B0s oscillations is performed using a sample of semileptonic
b-hadron decays collected by the ALEPH experiment during 1991-1995. Compared to
previous inclusive lepton analyses, the proper time resolution and b-flavour
mistag rate are significantly improved. Additional sensitivity to B0s mixing is
obtained by identifying subsamples of events having a B0s purity which is
higher than the average for the whole data sample. Unbinned maximum likelihood
amplitude fits are performed to derive a lower limit of Deltam_s>9.5ps^-1 at
95% CL. Combining with the ALEPH D-s based analyses yields Deltam_s>9.6ps^-1 at
95% CL.Comment: 23 pages, 10 figure
Electroweak Physics at LHC
The prospects for electroweak physics at the LHC are reviewed focusing mainly on precision studies. This includes projections for measurements of the effective Z pole weak mixing angle, of top quark, W boson, and Higgs scalar properties, and new physics searches
Unitarity constraints on the stabilized Randall-Sundrum scenario
Recently proposed stabilization mechanism of the Randall-Sundrum metric gives
rise to a scalar radion, which couples universally to matter with a weak
interaction ( TeV) scale. Demanding that gauge boson scattering as
described by the effective low enerrgy theory be unitary upto a given scale
leads to significant constraints on the mass of such a radion.Comment: 10 page Latex 2e file including 4 postscript figures. Accepted in
Journal of Physics
Event shapes in e+e- annihilation and deep inelastic scattering
This article reviews the status of event-shape studies in e+e- annihilation
and DIS. It includes discussions of perturbative calculations, of various
approaches to modelling hadronisation and of comparisons to data.Comment: Invited topical review for J.Phys.G; 40 pages; revised version
corrects some nomenclatur
Phenomenological Aspects of Gauge Mediation with Sequestered Supersymmetry Breaking in light of Dark Matter Detection
In a recent work, a model of gauge mediation with sequestered supersymmetry
(SUSY) breaking was proposed. In this model, the mass of the gravitino is
O(100) GeV without causing the flavor-changing neutral-current problem. In
contrast to traditional gauge mediation, the gravitino is not the lightest SUSY
particle and the neutralino is the candidate of the dark matter. In this paper,
we investigate phenomenological aspects of this model and discuss the
possibility of the direct detection of the dark matter. In particular, we focus
on the light neutralino case and find that the light-Higgsino scenario such as
the focus point is interesting, taking account of the recent CDMS result.Comment: 17 pages, 8 figures; v2:references added, some corrections;
v3:version accepted for publication in JHE
Direct Detection of Dark Matter in Supersymmetric Models
We evaluate neutralino-nucleon scattering rates in several well-motivated
supersymmetric models, and compare against constraints on the neutralino relic
density, BF( b\to s\gamma ) as well as the muon anomalous magnetic moment a_\mu
. In the mSUGRA model, the indirect constraints favor the hyperbolic
branch/focus point (HB/FP) region of parameter space, and in fact this region
is just where neutralino-nucleon scattering rates are high enough to be
detected in direct dark matter search experiments! In Yukawa unified SUSY
SO(10) models with scalar mass non-universality, the relic density of
neutralinos is almost always above experimental bounds, while the corresponding
direct detection rates are below experimental levels. Conversely, in five
dimensional SO(10) models where gauge symmetry breaking is the result of
compactification of the extra dimension, and supersymmetry breaking is
communicated via gaugino mediation, the relic density is quite low, while
direct detection rates can be substantial.Comment: 25 page latex file including 18 EPS figures; revised version with
references added and cross sections rescaled; figures changed. A copy of the
paper with better resolution figures can be found at
http://www.hep.fsu.edu/~belyaev/projects/directz1
Precision Electroweak Tests of the Standard Model
The present status of precision electroweak data is reviewed. These data
include measurements of e+e- -> f+fbar, taken at the Z resonance at LEP, which
are used to determine the mass and width of the Z boson. In addition,
measurements have also been made of the forward-backward asymmetries for
leptons and heavy quarks, and also the final state polarisation of the
tau-lepton. At SLAC, where the electron beam was polarised, measurements were
made of the left-right polarised asymmetry, A_LR, and the left-right
forward-backward asymmetries for b and c quarks.
The mass, MW, and width, GW, of the W boson have been measured at the
Tevatron and at LEP, and the mass of the top quark, Mt, has been measured at
the Tevatron. These data, plus other electroweak data, are used in global
electroweak fits in which various Standard Model parameters are determined. A
comparison is made between the results of the direct measurements of MW and Mt
with the indirect results coming from electroweak radiative corrections. Using
all precision electroweak data fits are also made to determine limits on the
mass of the Higgs boson. The influence on these limits of specific
measurements, particularly those which are somewhat inconsistent with the
Standard Model, is explored. The data are also analysed in terms of the quasi
model-independent epsilon variables.
Finally, the impact on the electroweak fits of the improvements in the
determination of the W-boson and top-quark masses, expected from the Tevatron
Run 2, is examined.Comment: 80 pages, 36 Figures, Late
Singlet-doublet Higgs mixing and its implications on the Higgs mass in the PQ-NMSSM
We examine the implications of singlet-doublet Higgs mixing on the properties
of a Standard Model (SM)-like Higgs boson within the Peccei-Quinn invariant
extension of the NMSSM (PQ-NMSSM). The SM singlet added to the Higgs sector
connects the PQ and visible sectors through a PQ-invariant non-renormalizable
K\"ahler potential term, making the model free from the tadpole and domain-wall
problems. For the case that the lightest Higgs boson is dominated by the
singlet scalar, the Higgs mixing increases the mass of a SM-like Higgs boson
while reducing its signal rate at collider experiments compared to the SM case.
The Higgs mixing is important also in the region of parameter space where the
NMSSM contribution to the Higgs mass is small, but its size is limited by the
experimental constraints on the singlet-like Higgs boson and on the lightest
neutralino constituted mainly by the singlino whose Majorana mass term is
forbidden by the PQ symmetry. Nonetheless the Higgs mixing can increase the
SM-like Higgs boson mass by a few GeV or more even when the Higgs signal rate
is close to the SM prediction, and thus may be crucial for achieving a 125 GeV
Higgs mass, as hinted by the recent ATLAS and CMS data. Such an effect can
reduce the role of stop mixing.Comment: 26 pages, 3 figures; published in JHE
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