227 research outputs found
A quantum phase gate implementation for trapped ions in thermal motion
We propose a novel scheme to implement a quantum controlled phase gate for
trapped ions in thermal motion with one standing wave laser pulse. Instead of
applying the rotating wave approximation this scheme makes use of the
counter-rotating terms of operators. We also demonstrate that the same scheme
can be used to generate maximally entangled states of trapped ions by a
single laser pulse
High-p_T Higgs Boson Production at Hadron Colliders to Order(alpha_s G_Fermi^3)
We study high-- Higgs boson production at hadron colliders to
order( ) in hadron collisions. In particular, we investigate
the process g+q/\bar{q}\ra q/\bar{q}+H, where or , for the
LHC (a 14~TeV, proton--proton collider). Our results are compared to
the order( ) calculation. The associated production of a
high-- Higgs boson with a --quark or anti--quark is comparable to the
order( ) calculation because of the large top quark mass and
the additional contribution of electroweak gauge and Goldstone bosons. The
associated production of light quarks, however, is not significant. We also
comment on new physics effects in the framework of the electroweak chiral
Lagrangian.Comment: Latex file,16 pages, 2 figures, uses psfig.sty, postscript file
available at ftp://cithe502.cithep.caltech.edu/pub/mrenna/cp0.ps or at
http://www.cithep.caltech.edu/~mrenn
Gluino Pair Production at Linear e^+e^- Colliders
We study the potential of high-energy linear colliders for the
production of gluino pairs within the Minimal Supersymmetric Standard Model
(MSSM). In this model, the process is mediated by
quark/squark loops, dominantly of the third generation, where the mixing of
left- and right-handed states can become large. Taking into account realistic
beam polarization effects, photon and -boson exchange, and current mass
exclusion limits, we scan the MSSM parameter space for various
center-of-mass energies to determine the regions, where gluino production
should be visible.Comment: 22 pages, 9 figure
Z' Decays into Four Fermions
If a new is discovered with a mass at LHC/SSC, its (rare)
decays into two charged leptons plus missing transverse energy will probe the
coupling to the lepton doublet and to , allowing
further discrimination among extended electroweak models.Comment: 9 pages plus 1 figure (not included but available), UG-FT-22/9
CP asymmetry in the Higgs decay into the top pair due to the stop mixing
We investigate a potentially large CP violating asymmetry in the decay of a
neutral scalar or pseudoscalar Higgs boson into the top-anti-top pair. The
source of the CP nonconservation is the complex mixing in the (left-right) stop
sector. One of the interesting consequence is the different rates of the Higgs
boson decays into CP conjugate polarized states.Comment: 14 pages, 8 figures include
Supersymmetry and the positron excess in cosmic rays
Recently the HEAT balloon experiment has confirmed an excess of high-energy
positrons in cosmic rays. They could come from annihilation of dark matter in
the galactic halo. We discuss expectations for the positron signal in cosmic
rays from the lightest superpartner. The simplest interpretations are
incompatible with the size and shape of the excess if the relic LSPs evolved
from thermal equilbrium. Non-thermal histories can describe a sufficient
positron rate. Reproducing the energy spectrum is more challenging, but perhaps
possible. The resulting light superpartner spectrum is compatible with collider
physics, the muon anomalous magnetic moment, Z-pole electroweak data, and other
dark matter searches.Comment: 4 pages, 2 figures, references added, minor wording change
Regge description of two pseudoscalar meson production in antiproton-proton annihilation
A Regge-inspired model is used to discuss the hard exclusive two-body
hadronic reactions (pbar p ----> pi+ pi-, pi0 pi0, K+ K-, Kbar0 K0) for the
FAIR facility project at GSI with the Panda detector. The comparison between
the differential cross sections predictions and the available data is shown to
determine the values of the few parameters of the model.Comment: 9 pages, 13 figure
Charged Higgs production from SUSY particle cascade decays at the LHC
We analyze the cascade decays of the scalar quarks and gluinos of the Minimal
Supersymmetric extension of the Standard Model, which are abundantly produced
at the Large Hadron Collider, into heavier charginos and neutralinos which then
decay into the lighter ones and charged Higgs particles, and show that they can
have substantial branching fractions. The production rates of these Higgs
bosons can be much larger than those from the direct production mechanisms, in
particular for intermediate values of the parameter , and could
therefore allow for the detection of these particles. We also discuss charged
Higgs boson production from direct two-body top and bottom squark decays as
well as from two- and three-body gluino decays.Comment: 30 pages with 10 figures, latex. Uses axodraw.sty and epsfig.st
Phenomenology of a Fluxed MSSM
We analyze the phenomenology of a set of minimal supersymmetric standard
model (MSSM) soft terms inspired by flux-induced supersymmetry (SUSY)-breaking
in Type IIB string orientifolds. The scheme is extremely constrained with
essentially only two free mass parameters: a parameter M, which sets the scale
of soft terms, and the mu parameter. After imposing consistent radiative
electro-weak symmetry breaking (EWSB) the model depends upon one mass parameter
(say, M). In spite of being so constrained one finds consistency with EWSB
conditions. We demonstrate that those conditions have two solutions for mu<0,
and none for mu>0. The parameter tan beta results as a prediction and is
approximately 3-5 for one solution, and 25-40 for the other, depending upon M
and the top mass. We examine further constraints on the model coming from b->s
gamma, the muon g-2, Higgs mass limits and WMAP constraints on dark matter. The
MSSM spectrum is predicted in terms of the single free parameter M. The low tan
beta branch is consistent with a relatively light spectrum although it is
compatible with standard cosmology only if the lightest neutralino is unstable.
The high tan beta branch is compatible with all phenomenological constraints,
but has quite a heavy spectrum. We argue that the fine-tuning associated to
this heavy spectrum would be substantially ameliorated if an additional
relationship mu=-2M were present in the underlying theory.Comment: 18 pages, minor revision
CP--odd Correlation in the Decay of Neutral Higgs Boson into , , or
We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
pair, a pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.Comment: 16 pages, plus 8 postscript graphs not posted befor
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