40 research outputs found
The vacuum structure in a supersymmetric gauged Nambu-Jona-Lasinio model
The dynamical breakdown of the symmetry triggered by a
top-antitop condensate is studied in a supersymmetric version of the gauged
Nambu-Jona-Lasinio model. An effective potential approach is used to
investigate the vacuum structure and the equivalence with the minimal
supersymmetric standard model. The role of the soft supersymmetry breaking
terms is analyzed in detail in a version of the model where the electroweak
gauge interactions are turned off.Comment: 32 pages (+2 figures not included), Latex, LPTHE 93/0
Cosmic Microwave Background Temperature and Polarization Anisotropy in Brans-Dicke Cosmology
We develop a formalism for calculating cosmic microwave background (CMB)
temperature and polarization anisotropies in cosmological models with
Brans-Dicke gravity. We then modify publicly available Boltzmann codes to
calculate numerically the temperature and polarization power spectra. Results
are illustrated with a few representative models. Comparing with the
general-relativistic model with the same cosmological parameters, both the
amplitude and the width of the acoustic peaks are different in the Brans-Dicke
models. We use a covariance-matrix calculation to investigate whether the
effects of Brans-Dicke gravity are degenerate with those of variation in other
cosmological parameters and to simultaneously determine whether forthcoming CMB
maps might be able to distinguish Brans-Dicke and general-relativistic
cosmology. Although the predicted power spectra for plausible Brans-Dicke
models differ from those in general relativity only slightly, we find that MAP
and/or the Planck Surveyor may in principle provide a test of Brans-Dicke
theory that is competitive to solar-system tests. For example, if all other
parameters except for the CMB normalization are fixed, a value of the
Brans-Dicke parameter omega as large as 500 could be identified with MAP, and
for Planck, values as large as omega \simeq3000 could be identified; these
sensitivities are decreased roughly by a factor of 3 if we marginalize over the
baryon density, Hubble constant, spectral index, and reionization optical
depth. In more general scalar-tensor theories, omega may evolve with time, and
in this case, the CMB probe would be complementary to that from solar-system
tests.Comment: 27 pages, 10 figures, typeset using RevTe
Phase Transition in Anyon Superconductivity at Finite Temperature
The magnetic response of the charged anyon fluid at temperatures larger than
the fermion energy gap is investigated in the self-consistent field
approximation. In this temperature region a new phase, characterized by an
inhomogeneous magnetic penetration, is found. The inhomogeneity is linked to
the existence of an imaginary magnetic mass which increases with the
temperature. The system stability in the new phase is proved by investigating
the electromagnetic field rest-energy spectrum.Comment: 18 pages, revte
Towards multi-scale dynamics on the baryonic branch of Klebanov-Strassler
We construct explicitly a new class of backgrounds in type-IIB supergravity
which generalize the baryonic branch of Klebanov-Strassler. We apply a
solution-generating technique that, starting from a large class of solutions of
the wrapped-D5 system, yields the new solutions, and then proceed to study in
detail their properties, both in the IR and in the UV. We propose a simple
intuitive field theory interpretation of the rotation procedure and of the
meaning of our new solutions within the Papadopoulos-Tseytlin ansatz, in
particular in relation to the duality cascade in the Klebanov-Strassler
solution. The presence in the field theory of different VEVs for operators of
dimensions 2, 3 and 6 suggests that this is an important step towards the
construction of the string dual of a genuinely multi-scale (strongly coupled)
dynamical model.Comment: 37 pages, 7 figures. References added, version to appear in JHE
What the Tevatron Found?
The CDF collaboration has reported a 4.1\sigma\ excess in their lepton,
missing energy, and dijets channel. This excess, which takes the form of an
approximately Gaussian peak centered at a dijet invariant mass of 147 GeV, has
provoked a great deal of experimental and theoretical interest. Although the
D\O\ collaboration has reported that they do not observe a signal consistent
with CDF, there is currently no widely accepted explanation for the discrepancy
between these two experiments. A resolution of this issue is of great
importance---not least because it may teach us lessons relevant for future
searches at the LHC---and it will clearly require additional information. In
this paper, we consider the ability of the Tevatron and LHC detectors to
observe evidence associated with the CDF excess in a variety of channels. We
also discuss the ability of selected kinematic distributions to distinguish
between Standard Model explanations of the observed excess and various new
physics scenarios.Comment: 14 pages, 4 figures, 2 tables. Accepted for publication by JHEP. v2:
minor changes to text and figure
Modified Gravity and Cosmology
In this review we present a thoroughly comprehensive survey of recent work on
modified theories of gravity and their cosmological consequences. Amongst other
things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, and
Bimetric theories, as well as TeVeS, f(R), general higher-order theories,
Horava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra
dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher
co-dimension braneworlds. We also review attempts to construct a Parameterised
Post-Friedmannian formalism, that can be used to constrain deviations from
General Relativity in cosmology, and that is suitable for comparison with data
on the largest scales. These subjects have been intensively studied over the
past decade, largely motivated by rapid progress in the field of observational
cosmology that now allows, for the first time, precision tests of fundamental
physics on the scale of the observable Universe. The purpose of this review is
to provide a reference tool for researchers and students in cosmology and
gravitational physics, as well as a self-contained, comprehensive and
up-to-date introduction to the subject as a whole.Comment: 312 pages, 15 figure
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30
Connecting String/M Theory to the Electroweak Scale and to LHC Data
The Standard Model of particle physics explains (almost) all observed
non-gravitational microscopic phenomena but has many open theoretical
questions. We are on the threshold of unraveling the mysteries of the Standard
Model and discovering its extension. This could be achieved in the near future
with the help of many experiments in particle physics and cosmology, the LHC in
particular. Assuming that data confirming the existence of new physics beyond
the Standard Model is obtained, one is left with the very important and
challenging task of solving the "Inverse Problem", \emph{viz.} "How can one
deduce the nature of the underlying (perhaps microscopic) theory from data?"
This thesis explores this question in detail, and also proposes an approach to
address the problem in a meaningful way which could prove crucial to the
possible solution to this problem in the future. The proposed approach has
three aspects - a) To systematically study classes of microscopic (string/
theory) constructions to the extent that they could be connected to low energy
physics (electroweak scale), b) To find patterns of experimental observables
which are sensitive to the properties of the underlying theoretical
constructions thereby allowing us to distinguish among different constructions,
and c) To try to get insights about the qualitative features of the theoretical
model from data in a bottom-up approach which complements the top-down approach
and strengthens it as well. This thesis studies all the above aspects in
detail. The methods used and results obtained in this thesis will hopefully be
of great importance in solving the Inverse Problem.Comment: PhD Thesis, 320 pages, 63 figures References Adde
Extended Theories of Gravity and their Cosmological and Astrophysical Applications
We review Extended Theories of Gravity in metric and Palatini formalism
pointing out their cosmological and astrophysical application. The aim is to
propose an alternative approach to solve the puzzles connected to dark
components.Comment: 44 pages, 11 figure