85 research outputs found
Supersymmetric Grand Unified Theories and Global Fits to Low Energy Data
We present a self-consistent analysis of several supersymmetric
(SUSY) grand unified theories recently discussed in the literature. We obtain
global fits to low energy data, including gauge couplings, fermion masses and
mixing angles, gauge boson masses and . One of the
models studied provides an excellent fit to the low energy data with
for 3 degrees of freedom, in a large region of the
experimentally allowed SUSY parameter space. We also discuss the consequences
of our work for a general MSSM analysis at the scale.Comment: 6 pages, Latex, 2 figures include
Predictions for Higgs and SUSY spectra from SO(10) Yukawa Unification with mu > 0
We use Yukawa unification to constrain SUSY parameter space. We
find a narrow region survives for (suggested by \bsgam and the
anomalous magnetic moment of the muon) with , , \gev and \gev. Demanding Yukawa unification thus makes definite predictions for
Higgs and sparticle masses.Comment: 10 pages, 3 figures, revised version to be published in PR
Sparticle mass spectra from SU(5) SUSY GUT models with Yukawa coupling unification
Supersymmetric grand unified models based on the gauge group SU(5) often
require in addition to gauge coupling unification, the unification of b-quark
and -lepton Yukawa couplings. We examine SU(5) SUSY GUT parameter space
under the condition of Yukawa coupling unification using 2-loop MSSM
RGEs including full 1-loop threshold effects. The Yukawa-unified solutions
break down into two classes. Solutions with low tan\beta ~3-11 are
characterized by gluino mass ~1-4 TeV and squark mass ~1-5 TeV. Many of these
solutions would be beyond LHC reach, although they contain a light Higgs scalar
with mass <123 GeV and so may be excluded should the LHC Higgs hint persist.
The second class of solutions occurs at large tan\beta ~35-60, and are a subset
of unified solutions. Constraining only unification to ~5%
favors a rather light gluino with mass ~0.5-2 TeV, which should ultimately be
accessible to LHC searches. While our unified solutions can be
consistent with a picture of neutralino-only cold dark matter, invoking
additional moduli or Peccei-Quinn superfields can allow for all of our
Yukawa-unified solutions to be consistent with the measured dark matter
abundance.Comment: 19 pages, 5 figures, 1 table, PDFLate
SUSY GUTs under Siege : Proton Decay
SO(10) supersymmetric grand unified theories [SUSY GUTs] provide a beautiful
framework for physics beyond the standard model. Experimental measurements of
the three gauge couplings are consistent with unification at a scale GeV. In addition predictive models for fermion masses and
mixing angles have been found which fit the low energy data, including the
recent data for neutrino oscillations. SO(10) boundary conditions can be tested
via the spectrum of superparticles. The simplest models also predict neutron
and proton decay rates. In this paper we discuss nucleon decay rates and obtain
reasonable upper bounds. A clear picture of the allowed SUSY spectra as
constrained by nucleon decay is presented.Comment: 13 page
Neutrino Masses and Lepton-Flavor Violation in Supersymmetric Models with lopsided Froggatt-Nielsen charges
We analyze in detail lepton-flavor violation (LFV) in the charged-lepton
sector such as , , and the
conversion in nuclei, within the framework of supersymmetric models
with lopsided Froggatt--Nielsen charges, in which the large mixing in the
neutrino sector as well as small mixings in the quark sector can be naturally
accommodated. We show that the present experimental limits on the LFV processes
already exclude some of the models. The future proposed search for LFV,
especially in muon processes, can provide a significant probe to this
framework. We also stress the importance of the measurement of
in neutrino experiments, and the fact that the KamLAND experiment could play a
significant role to test a certain class of models.Comment: 33 pages, 20 figure
On the possible space-time fractality of the emitting source
Using simple space-time implementation of the random cascade model we
investigate numerically a conjecture made some time ago which was joining the
intermittent behaviour of spectra of emitted particles with the possible
fractal structure of the emitting source. We demonstrate that such details are
seen, as expected, in the Bose-Einstein correlations between identical
particles. \\Comment: Thoroughly rewritten and modify version, to be published in Phys.
Rev.
Particle Physics Approach to Dark Matter
We review the main proposals of particle physics for the composition of the
cold dark matter in the universe. Strong axion contribution to cold dark matter
is not favored if the Peccei-Quinn field emerges with non-zero value at the end
of inflation and the inflationary scale is superheavy since, under these
circumstances, it leads to unacceptably large isocurvature perturbations. The
lightest neutralino is the most popular candidate constituent of cold dark
matter. Its relic abundance in the constrained minimal supersymmetric standard
model can be reduced to acceptable values by pole annihilation of neutralinos
or neutralino-stau coannihilation. Axinos can also contribute to cold dark
matter provided that the reheat temperature is adequately low. Gravitinos can
constitute the cold dark matter only in limited regions of the parameter space.
We present a supersymmetric grand unified model leading to violation of Yukawa
unification and, thus, allowing an acceptable b-quark mass within the
constrained minimal supersymmetric standard model with mu>0. The model
possesses a wide range of parameters consistent with the data on the cold dark
matter abundance as well as other phenomenological constraints. Also, it leads
to a new version of shifted hybrid inflation.Comment: 32 pages including 6 figures, uses svmult.cls, some clarifications
added, lectures given at the Third Aegean Summer School "The Invisible
Universe: Dark Matter and Dark Energy", 26 September-1 October 2005, Karfas,
Island of Chios, Greece (to appear in the proceedings
Higgs-Mediated in Minimal Supersymmetry
In this letter we demonstrate a new source for large flavor-changing neutral
currents within the minimal supersymmetric standard model. At moderate to large
tan(beta), it is no longer possible to diagonalize the masses of the quarks in
the same basis as their Yukawa couplings. This generates large flavor-violating
couplings of the form and where H is any of
the three neutral, physical Higgs bosons. These new couplings lead to rare
processes in the B system such as decay and B-Bbar mixing.
We show that the latter is anomalously suppressed, while the former is in the
experimentally interesting range. Current limits on
already provide nontrivial constraints on models of moderate to large
tan(beta), with an observable signal possible at Run II of the Tevatron if m_A
< 400-600 GeV, extending to the TeV range if a proposed Run III of 30/fb were
to occur.Comment: 9 pages LaTeX, 1 figure. Small numerical improvement and comment on
b->X_s l+l- adde
More Model-Independent Analysis of b->s Processes
We study model-independently the implications of non-standard scalar and
pseudoscalar interactions for the decays b ->s gamma, b -> s g, b -> s l^+l^-
(l=e,mu) and B_s -> mu^+ mu^-. We find sizeable renormalization effects from
scalar and pseudoscalar four-quark operators in the radiative decays and at
O(alpha_s) in hadronic b decays. Constraints on the Wilson coefficients of an
extended operator basis are worked out. Further, the ratios R_H = BR(B -> H
mu^+ mu^-)/BR(B -> H e^+ e^-), for H=K^(*), X_s, and their correlations with
B_s -> mu^+ mu^- decay are investigated. We show that the Standard Model
prediction for these ratios defined with the same cut on the dilepton mass for
electron and muon modes, R_H= 1 + O(m^2_mu/m^2_b), has a much smaller
theoretical uncertainty (<1%) than the one for the individual branching
fractions. The present experimental limit R_K < 1.2 puts constraints on scalar
and pseudoscalar couplings, which are similar to the ones from current data on
BR(B_s -> mu^+ mu^-). We find that new physics corrections to R_{K*} and
R_{X_s} can reach 13% and 10%, respectively.Comment: 28 pages, 6 figures; Table 1 updated, two refs added (to appear in
PRD
Yukawa Unification as a Window into the Soft Supersymmetry Breaking Lagrangian
We study Yukawa unification, including the effects of a physical neutrino
mass consistent with the Superkamiokande observations, in a string/-brane
inspired Pati-Salam model which allows the most general non-universal scalar
and gaugino masses, including the usual -term contributions which arise in
SO(10). We investigate how the tight constraints from rare decays such as and can provide information about the
family dependent supersymmetry breaking soft Lagrangian, for example the
trilinears associated with the second and third family. Many of our results
also apply to SO(10) to which the model approximately reduces in a limiting
case. In both models we find that Yukawa unification is perfectly viable
providing the non-universal soft masses have particular patterns. In this sense
Yukawa unification acts as a window into the soft supersymmetry breaking
Lagrangian.Comment: References added. 82 pages, 57 figures, Late
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