3,885 research outputs found
Light Gravitinos at Colliders and Implications for Cosmology
Light gravitinos, with mass in the eV to MeV range, are well-motivated in
particle physics, but their status as dark-matter candidates is muddled by
early-Universe uncertainties. We investigate how upcoming data from colliders
may clarify this picture. Light gravitinos are produced primarily in the decays
of the next-to-lightest supersymmetric particle, resulting in spectacular
signals, including di-photons, delayed and non-pointing photons, kinked charged
tracks, and heavy metastable charged particles. We find that the Tevatron with
20/fb and the 7 TeV LHC with 1/fb may both see evidence for hundreds of
light-gravitino events. Remarkably, this collider data is also well suited to
distinguish between currently viable light-gravitino scenarios, with striking
implications for structure formation, inflation, and other early-Universe
cosmology.Comment: 12 pages, 6 figures. To be submitted to Phys. Rev. D
Political Science in America: Oral Histories of a Discipline
Few academic disciplines have recorded their own origins and development in an organized way. The American Political Science Association, in cooperation with Pi Sigma Alpha, the political science honor society, and the University of Kentucky, have undertaken an extensive oral history project, the aim of which is to trace and record the growth of the discipline. The program has made it possible to amass hours of interviews with women and men who have influenced the study of political science.
Political Science in America contains interviews with fifteen major figures who speak frankly about the intellectual and institutional roots of political science and trace its evolution. Through their words, we learn what it was like to be a part of the earliest Ph.D. programs and to work with early leaders.
We discover how these leaders became interested in political science, what roles they played in building departments and research organizations, and what they learned from participation in government and politics. They discuss their own contributions and offer opinions on some of the major conflicts that have divided the discipline. Particularly enlightening are their varied perspectives on the growth of the behavioral movement in political science over the past fifty years. This book is of interest to all political scientists as a historical perspective on their discipline.
Michael A. Baer is professor of political science and provost of Northeastern University.
Malcolm E. Jewell is professor of political science at the University of Kentucky and director of the political science oral history program.
Lee Sigelman is professor of political science and dean of the faculty of social and behavioral sciences at the University of Arizona.https://uknowledge.uky.edu/upk_political_science_american_politics/1018/thumbnail.jp
Anomaly-Free Gauged R-Symmetry
We review the gauging of an R-symmetry in local and global susy. We then
construct the first anomaly-free models. We break the R-symmetry and susy at
the Planck scale and discuss the low-energy effects. We include a solution to
the mu-problem, and the prediction of observable effects at HERA. The models
also nicely allow for GUT-scale baryogenesis and R-parity violation without the
sphaleron interactions erasing the baryon-asymmetry.Comment: 6 pages, latex, no figures. Talk presented at SUSY-95. Work done in
collaboration with A. Chamseddin
Mixed Bino-Wino-Higgsino Dark Matter in Gauge Messenger Models
Almost degenerate bino and wino masses at the weak scale is one of unique
features of gauge messenger models. The lightest neutralino is a mixture of
bino, wino and higgsino and can produce the correct amount of the dark matter
density if it is the lightest supersymmetric particle. Furthermore, as a result
of squeezed spectrum of superpartners which is typical for gauge messenger
models, various co-annihilation and resonance regions overlap and very often
the correct amount of the neutralino relic density is generated as an interplay
of several processes. This feature makes the explanation of the observed amount
of the dark matter density much less sensitive to fundamental parameters. We
calculate the neutralino relic density assuming thermal history and present
both spin independent and spin dependent cross sections for the direct
detection. We also discuss phenomenological constraints from b to s gamma and
muon g-2 and compare results of gauge messenger models to well known results of
the mSUGRA scenario.Comment: 27 pages, 9 figures, references added, version to appear at JCA
LHC Signature of Mirage Mediation
We study LHC phenomenology of mirage mediation scenario in which anomaly and
modulus contributions to soft SUSY breaking terms are comparable to each other.
A Monte Carlo study of mirage mediation, with model parameters , GeV, , and , is presented. It is
shown that masses of supersymmetric particles can be measured in a model
independent way, providing information on SUSY breaking sector. In particular,
the mass ratio of gluino to the lightest neutralino for the benchmark scenario
is determined to be 1.9 \lesssim m_{\tildeg}/m_{\tilde\chi_1^0} \lesssim 3.1,
well reproducing theoretical input value of which is quite distinctive from the predictions of other SUSY scenarios in which gaugino
masses are unified at the GUT scale. The model parameters of mirage mediation
can be also determined from various kinematic distributions
Guest Artist Recital Series: Andrea Casarrubios, Cello; Cora Swenson Lee, Cello; Daniel Baer, Piano; November 2, 2023
Kemp Recital HallNovember 2, 2023Thursday Evening7:30 p.m
Convex cocompact subgroups of mapping class groups
We develop a theory of convex cocompact subgroups of the mapping class group
MCG of a closed, oriented surface S of genus at least 2, in terms of the action
on Teichmuller space. Given a subgroup G of MCG defining an extension L_G:
1--> pi_1(S) --> L_G --> G -->1 we prove that if L_G is a word hyperbolic
group then G is a convex cocompact subgroup of MCG. When G is free and convex
cocompact, called a "Schottky subgroup" of MCG, the converse is true as well; a
semidirect product of pi_1(S) by a free group G is therefore word hyperbolic if
and only if G is a Schottky subgroup of MCG. The special case when G=Z follows
from Thurston's hyperbolization theorem. Schottky subgroups exist in abundance:
sufficiently high powers of any independent set of pseudo-Anosov mapping
classes freely generate a Schottky subgroup.Comment: Published in Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol6/paper5.abs.htm
Edge channel confinement in a bilayer graphene -- quantum dot
We combine electrostatic and magnetic confinement to define a quantum dot in
bilayer graphene. The employed geometry couples -doped reservoirs to a
-doped dot. At magnetic field values around T, Coulomb blockade is
observed. This demonstrates that the coupling of the co-propagating modes at
the - interface is weak enough to form a tunnel barrier, facilitating
transport of single charge carriers onto the dot. This result may be of use for
quantum Hall interferometry experiments
Calculations of Neutralino-Stau Coannihilation Channels and the Cosmologically Relevant Region of MSSM Parameter Space
Assuming that the lightest supersymmetric particle (LSP) is the lightest
neutralino, we present a detailed exploration of neutralino-stau coannihilation
channels, including analytical expressions and numerical results. We also
include neutralino coannihilations with the selectron and smuon. We evaluate
the implications of coannihilations for the cosmological relic density of the
LSP, which is assumed to be stable, in the constrained minimal supersymmetric
extension of the Standard Model (CMSSM), in which the soft
supersymmetry-breaking parameters are universal at the supergravity GUT scale.
We evaluate the changes due to coannihilations in the region of the MSSM
parameter space that is consistent with the cosmological upper limit on the
relic LSP density. In particular, we find that the upper limit on the mass of
the neutralino is increased from about 200 GeV to about 600 GeV in the CMSSM,
and estimate a qualitatively similar increase for gauginos in the general MSSM.Comment: 38 pages in LaTeX, including 25 encapsulated postscript figures.
Added small clarification in the text, corrected some typos in the appendix.
Figures and conclusions unchange
An Alternative Yukawa Unified SUSY Scenario
Supersymmetric SO(10) Grand Unified Theories with Yukawa unification
represent an appealing possibility for physics beyond the Standard Model.
However Yukawa unification is made difficult by large threshold corrections to
the bottom mass. Generally one is led to consider models where the sfermion
masses are large in order to suppress these corrections. Here we present
another possibility, in which the top and bottom GUT scale Yukawa couplings are
equal to a component of the charged lepton Yukawa matrix at the GUT scale in a
basis where this matrix is not diagonal. Physically, this weak eigenstate
Yukawa unification scenario corresponds to the case where the charged leptons
that are in the 16 of SO(10) containing the top and bottom quarks mix with
their counterparts in another SO(10) multiplet. Diagonalizing the resulting
Yukawa matrix introduces mixings in the neutrino sector. Specifically we find
that for a large region of parameter space with relatively light sparticles,
and which has not been ruled out by current LHC or other data, the mixing
induced in the neutrino sector is such that , in
agreement with data. The phenomenological implications are analyzed in some
detail.Comment: 32 pages, 22 Figure
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