9,060 research outputs found
GUT predictions for quark-lepton Yukawa coupling ratios with messenger masses from non-singlets
We propose new predictions from grand unified theories (GUTs) [applicable to both supersymmetric (SUSY) and non-SUSY models] for the ratios of quark and lepton Yukawa couplings. These new predictions arise from splitting the masses of the messenger fields for the GUT-scale Yukawa operators by Clebsch-Gordan factors from GUT symmetry breaking. This has the effect that these factors enter inversely in the predicted quark-lepton Yukawa coupling ratios, leading to new possible GUT predictions. We systematically construct the new predictions that can be realized in this way in SU(5) GUTs and Pati-Salam unified theories and discuss model building applications
Measuring x-ray polarization in the presence of systematic effects: Known background
The prospects for accomplishing x-ray polarization measurements of
astronomical sources have grown in recent years, after a hiatus of more than 37
years. Unfortunately, accompanying this long hiatus has been some confusion
over the statistical uncertainties associated with x-ray polarization
measurements of these sources. We have initiated a program to perform the
detailed calculations that will offer insights into the uncertainties
associated with x-ray polarization measurements. Here we describe a
mathematical formalism for determining the 1- and 2-parameter errors in the
magnitude and position angle of x-ray (linear) polarization in the presence of
a (polarized or unpolarized) background. We further review relevant
statistics-including clearly distinguishing between the Minimum Detectable
Polarization (MDP) and the accuracy of a polarization measurement.Comment: 12 pages, 4 figures, for SPIE conference proceeding
On understanding the figures of merit for detection and measurement of x-ray polarization
The prospects for accomplishing X-ray polarization measurements appear to
have grown in recent years after a more than 35-year hiatus. Unfortunately,
this long hiatus has brought with it some confusion over the statistical
uncertainties associated with polarization measurements of astronomical
sources. The heart of this confusion stems from a misunderstanding (or
potential misunderstanding) of a standard figure of merit-the minimum
detectable polarization (MDP)-that one of us introduced many years ago. We
review the relevant statistics, and quantify the differences between the MDP
and the uncertainty of an actual polarization measurement. We discuss the
implications for future missions.Comment: 5 pages, 2 figures, to be presented at SPIE conference 7732 (paper
13), corrected typo
Methods of optimizing X-ray optical prescriptions for wide-field applications
We are working on the development of a method for optimizing wide-field X-ray
telescope mirror prescriptions, including polynomial coefficients, mirror shell
relative displacements, and (assuming 4 focal plane detectors) detector
placement along the optical axis and detector tilt. With our methods, we hope
to reduce number of Monte-Carlo ray traces required to search the
multi-dimensional design parameter space, and to lessen the complexity of
finding the optimum design parameters in that space. Regarding higher order
polynomial terms as small perturbations of an underlying Wolter I optic design,
we begin by using the results of Monte-Carlo ray traces to devise trial
analytic functions, for an individual Wolter I mirror shell, that can be used
to represent the spatial resolution on an arbitrary focal surface. We then
introduce a notation and tools for Monte-Carlo ray tracing of a polynomial
mirror shell prescription which permits the polynomial coefficients to remain
symbolic. In principle, given a set of parameters defining the underlying
Wolter I optics, a single set of Monte-Carlo ray traces are then sufficient to
determine the polymonial coefficients through the solution of a large set of
linear equations in the symbolic coefficients. We describe the present status
of this development effort.Comment: 14 pages, to be presented at SPIE conference 7732 (paper 93
Implications of gauge-mediated supersymmetry breaking with vector-like quarks and a ~125 GeV Higgs boson
We investigate the implications of models that achieve a Standard Model-like
Higgs boson of mass near 125 GeV by introducing additional TeV-scale
supermultiplets in the vector-like 10+\bar{10} representation of SU(5), within
the context of gauge-mediated supersymmetry breaking. We study the resulting
mass spectrum of superpartners, comparing and contrasting to the usual
gauge-mediated and CMSSM scenarios, and discuss implications for LHC
supersymmetry searches. This approach implies that exotic vector-like fermions
t'_{1,2}, b',and \tau' should be within the reach of the LHC. We discuss the
masses, the couplings to electroweak bosons, and the decay branching ratios of
the exotic fermions, with and without various unification assumptions for the
mass and mixing parameters. We comment on LHC prospects for discovery of the
exotic fermion states, both for decays that are prompt and non-prompt on
detector-crossing time scales.Comment: 32 pages. v2: references added, figure caption 5.3 correcte
Refined gluino and squark pole masses beyond leading order
The physical pole and running masses of squarks and gluinos have recently
been related at two-loop order in a mass-independent renormalization scheme. I
propose a general method for improvement of such formulas, and argue that
better accuracy results. The improved version gives an imaginary part of the
pole mass that agrees exactly with the direct calculation of the physical width
at next-to-leading order. I also find the leading three-loop contributions to
the gluino pole mass in the case that squarks are heavier, using effective
field theory and renormalization group methods. The efficacy of these
improvements for the gluino and squarks is illustrated with numerical examples.
Some necessary three-loop results for gauge coupling and fermion mass beta
functions and pole masses in theories with more than one type of fermion
representation, which are not directly accessible from the published
literature, are presented in an Appendix.Comment: 14 pages. v2: typos in equations (A.11), (A.17), and (A.18) fixe
Radiative Inflation and Dark Energy
We propose a model based on radiative symmetry breaking that combines
inflation with Dark Energy and is consistent with the WMAP 7-year regions. The
radiative inflationary potential leads to the prediction of a spectral index
0.955 \lesssim n_S \lesssim 0.967 and a tensor to scalar ratio 0.142 \lesssim r
\lesssim 0.186, both consistent with current data but testable by the Planck
experiment. The radiative symmetry breaking close to the Planck scale gives
rise to a pseudo Nambu-Goldstone boson with a gravitationally suppressed mass
which can naturally play the role of a quintessence field responsible for Dark
Energy. Finally, we present a possible extra dimensional scenario in which our
model could be realised.Comment: 15 pages, 4 figures; v2: references added, appendix added, Section 5
slightly modified; content matches published versio
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