292 research outputs found
Supergauge interactions and electroweak baryogenesis
We present a complete treatment of the diffusion processes for supersymmetric
electroweak baryogenesis that characterizes transport dynamics ahead of the
phase transition bubble wall within the symmetric phase. In particular, we
generalize existing approaches to distinguish between chemical potentials of
particles and their superpartners. This allows us to test the assumption of
superequilibrium (equal chemical potentials for particles and sparticles) that
has usually been made in earlier studies. We show that in the Minimal
Supersymmetric Standard Model, superequilibrium is generically maintained --
even in the absence of fast supergauge interactions -- due to the presence of
Yukawa interactions. We provide both analytic arguments as well as illustrative
numerical examples. We also extend the latter to regions where analytical
approximations are not available since down-type Yukawa couplings or supergauge
interactions only incompletely equilibrate. We further comment on cases of
broken superequilibrium wherein a heavy superpartner decouples from the
electroweak plasma, causing a kinematic bottleneck in the chain of
equilibrating reactions. Such situations may be relevant for baryogenesis
within extensions of the MSSM. We also provide a compendium of inputs required
to characterize the symmetric phase transport dynamics.Comment: 49 pages, 9 figure
The Inert Doublet Model and Inelastic Dark Matter
The annual modulation observed by DAMA/NaI and DAMA/Libra may be interpreted
in terms of elastic or inelastic scattering of dark matter particles. In this
paper we confront these two scenarios within the framework of a very simple
extension of the Standard Model, the Inert Doublet Model (IDM). In this model
the dark matter candidate is a scalar, the lightest component of an extra Higgs
doublet. We first revisit the case for the elastic scattering of a light scalar
WIMP, M_DM~10 GeV, a scenario which requires that a fraction of events in DAMA
are channelled. Second we consider the possibility of inelastic Dark Matter
(iDM). This option is technically natural in the IDM, in the sense that the
mass splitting between the lightest and next-to-lightest neutral scalars may be
protected by a Peccei-Quinn (PQ) symmetry. We show that candidates with a mass
M_DM between ~535 GeV and ~50 TeV may reproduce the DAMA data and have a cosmic
abundance in agreement with WMAP. This range may be extended to candidates as
light as ~50 GeV if we exploit the possibility that the approximate PQ symmetry
is effectively conserved and that a primordial asymmetry in the dark sector may
survive until freeze-out.Comment: 16 pages, 7 figures. v2: minor changes and discussion on the
embedding in SO(10) added. v3: matches the published version in JCA
Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure
The combination of ultra-cold atomic clouds with the light fields of optical
cavities provides a powerful model system for the development of new types of
laser cooling and for studying cooperative phenomena. These experiments
critically depend on the precise tuning of an incident pump laser with respect
to a cavity resonance. Here, we present a simple and reliable experimental
tuning scheme based on a two-mode laser spectrometer. The scheme uses a first
laser for probing higher-order transversal modes of the cavity having an
intensity minimum near the cavity's optical axis, where the atoms are confined
by a magnetic trap. In this way the cavity resonance is observed without
exposing the atoms to unwanted radiation pressure. A second laser, which is
phase-locked to the first one and tuned close to a fundamental cavity mode
drives the coherent atom-field dynamics.Comment: 7 pages, 7 figure
CP violation in chargino decays in the MSSM
In the minimal supersymmetric standard model (MSSM) with complex parameters,
supersymmetric loop effects can lead to \emph{CP} violation. We calculate the
rate asymmetries of decays of charginos into the lightest neutralino and a
boson on the basis of the most important loop contributions in the third
generation squark sectors. It turns out that the \emph{CP} violating
asymmetries can be a few per cent in typical regions of the parameter space of
the MSSM. These processes would provide very promising channels for probing
\emph{CP} violation in the MSSM at future high-energy colliders.Comment: 15 pages, 5 figures, LaTeX2
Hadronic Total Cross-sections Through Soft Gluon Summation in Impact Parameter Space
The Bloch-Nordsieck model for the parton distribution of hadrons in impact
parameter space, constructed using soft gluon summation, is investigated in
detail.
Its dependence upon the infrared structure of the strong coupling constant
is discussed, both for finite as well as singular, but integrable,
. The formalism is applied to the prediction of total proton-proton
and proton-antiproton cross-sections, where screening, due to soft gluon
emission from the initial valence quarks, becomes evident.Comment: 20 pages, Latex2e, input FEYNMAN,12 postscipt figures. Submitted to
PR
Super duality and irreducible characters of ortho-symplectic Lie superalgebras
We formulate and establish a super duality which connects parabolic
categories between the ortho-symplectic Lie superalgebras and classical Lie
algebras of types. This provides a complete and conceptual solution of
the irreducible character problem for the ortho-symplectic Lie superalgebras in
a parabolic category , which includes all finite-dimensional irreducible
modules, in terms of classical Kazhdan-Lusztig polynomials.Comment: 30 pages, Section 5 rewritten and shortene
Black Hole Chromosphere at the LHC
If the scale of quantum gravity is near a TeV, black holes will be copiously
produced at the LHC. In this work we study the main properties of the light
descendants of these black holes. We show that the emitted partons are closely
spaced outside the horizon, and hence they do not fragment into hadrons in
vacuum but more likely into a kind of quark-gluon plasma. Consequently, the
thermal emission occurs far from the horizon, at a temperature characteristic
of the QCD scale. We analyze the energy spectrum of the particles emerging from
the "chromosphere", and find that the hard hadronic jets are almost entirely
suppressed. They are replaced by an isotropic distribution of soft photons and
hadrons, with hundreds of particles in the GeV range. This provides a new
distinctive signature for black hole events at LHC.Comment: Incorporates changes made for the version to be published in Phys.
Rev. D. Additional details provided on the effect of the chromosphere in
cosmic ray shower
Relic Neutralino Densities and Detection Rates with Nonuniversal Gaugino Masses
We extend previous analyses on the interplay between nonuniversalities in the
gaugino mass sector and the thermal relic densities of LSP neutralinos, in
particular to the case of moderate to large tan beta. We introduce a set of
parameters that generalizes the standard unified scenario to cover the complete
allowed parameter space in the gaugino mass sector. We discuss the physical
significance of the cosmologically preferred degree of degeneracy between
charginos and the LSP and study the effect this degree of degeneracy has on the
prospects for direct detection of relic neutralinos in the next round of dark
matter detection experiments. Lastly, we compare the fine tuning required to
achieve a satisfactory relic density with the case of universal gaugino masses,
as in minimal supergravity, and find it to be of a similar magnitude. The
sensitivity of quantifiable measures of fine-tuning on such factors as the
gluino mass and top and bottom masses is also examined.Comment: Uses RevTeX; 14 pages, 16 figure
Cosmological bounds on large extra dimensions from non-thermal production of Kaluza-Klein modes
The existing cosmological constraints on theories with large extra dimensions
rely on the thermal production of the Kaluza-Klein modes of gravitons and
radions in the early Universe. Successful inflation and reheating, as well as
baryogenesis, typically requires the existence of a TeV-scale field in the
bulk, most notably the inflaton. The non-thermal production of KK modes with
masses of order 100 GeV accompanying the inflaton decay sets the lower bounds
on the fundamental scale M_*. For a 1 TeV inflaton, the late decay of these
modes distort the successful predictions of Big Bang Nucleosynthesis unless
M_*> 35, 13, 7, 5 and 3 TeV for 2, 3, 4, 5 and 6 extra dimensions,
respectively. This improves the existing bounds from cosmology on M_* for 4, 5
and 6 extra dimensions. Even more stringent bounds are derived for a heavier
inflaton.Comment: 17 pages, latex, 4 figure
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