131 research outputs found
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
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.
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
Success of cuckoo catfish brood parasitism reflects coevolutionary history and individual experience of their cichlid hosts
Obligate brood parasites manipulate other species into raising their offspring. Avian and insect brood parasitic systems demonstrate how interacting species engage in reciprocal coevolutionary arms races through behavioral and morphological adaptations and counteradaptations. Mouthbrooding cichlid fishes are renowned for their remarkable evolutionary radiations and complex behaviors. In Lake Tanganyika, mouthbrooding cichlids are exploited by the only obligate nonavian vertebrate brood parasite, the cuckoo catfish Synodontis multipunctatus. We show that coevolutionary history and individual learning both have a major impact on the success of cuckoo catfish parasitism between coevolved sympatric and evolutionarily naïve allopatric cichlid species. The rate of cuckoo catfish parasitism in coevolved Tanganyikan hosts was 3 to 11 times lower than in evolutionarily naïve cichlids. Moreover, using experimental infections, we demonstrate that parasite egg rejection in sympatric hosts was much higher, leading to seven times greater parasite survival in evolutionarily naïve than sympatric hosts. However, a high rejection frequency of parasitic catfish eggs by coevolved sympatric hosts came at a cost of increased rejection of their own eggs. A significant cost of catfish parasitism was universal, except for coevolved sympatric cichlid species with previous experience of catfish parasitism, demonstrating that learning and individual experience both contribute to a successful host response
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
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
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
GRB 160410A:The first chemical study of the interstellar medium of a short GRB
Short gamma-ray bursts (SGRBs) are produced by the coalescence of compact binary systems which are remnants of massive stars. GRB 160410A is classified as a short-duration GRB with extended emission and is currently the farthest SGRB with a redshift determined from an afterglow spectrum and also one of the brightest SGRBs to date. The fast reaction to the Neil Gehrels Swift Observatory alert allowed us to obtain a spectrum of the afterglow using the X-shooter spectrograph at the Very Large Telescope (VLT). The spectrum shows several absorption features at a redshift of z = 1.7177, in addition, we detect two intervening systems at z = 1.581 and z = 1.444. The spectrum shows Ly α in absorption with a column density of log (N(H I)/cm2) = 21.2 ± 0.2 which, together with Fe II, C II, Si II, Al II, and O I, allow us to perform the first study of chemical abundances in a SGRB host galaxy. We determine a metallicity of [X/H] = −2.3 ± 0.2 for Fe II and −2.5 ± 0.2 for Si II and no dust depletion. We also find no evidence for extinction in the afterglow spectral energy distribution modelling. The environment has a low degree of ionization and the C IV and Si IV lines are completely absent. We do not detect an underlying host galaxy down to deep limits. Additionally, we compare GRB 160410A to GRB 201221D, another high-z short GRB that shows absorption lines at z = 1.045 and an underlying massive host galaxy
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