837 research outputs found
Modification of the Unitarity Relation for sin2beta-Vub in Supersymmetric Models
Recently, a more than 2sigma discrepancy has been observed between the well
measured inclusive value of Vub and the predicted value of Vub from the
unitarity triangle fit using the world average value of sin2beta. We attempt to
resolve this tension in the context of grand unified SO(10) and SU(5) models
where the neutrino mixing matrix is responsible for flavor changing neutral
current at the weak scale and the models with non-proportional A-terms (can be
realized simply in the context of intersecting D-brane models) and investigate
the interplay between the constraints arising from B_{s,d}-\bar B_{s,d}
mixings, epsilon_K, Br(tau -> mu gamma), Br(mu -> e gamma) and a fit of this
new discrepancy. We also show that the ongoing measurement of the phase of Bs
mixing will be able to identify the grand unified model. The measurement of
Br(tau -> e gamma) will also be able to test these scenarios, especially the
models with non-proportional A-terms.Comment: 20 pages, 4 figures. Minor corrections, references adde
Correlation between direct dark matter detection and Br(B_s -> mu mu) with a large phase of B_s - anti-B_s mixing
We combine the analyses for flavor changing neutral current processes and
dark matter solutions in minimal-type supersymmetric grand unified theory (GUT)
models, SO(10) and SU(5), with a large B_s - anti-B_s mixing phase and large
tan beta. For large tan beta, the double penguin diagram dominates the SUSY
contribution to the B_s - anti-B_s mixing amplitude. Also, the Br(B_s -> mu mu)
constraint becomes important as it grows as tan^6 beta, although it can still
be suppressed by large pseudoscalar Higgs mass m_A. We investigate the
correlation between B_s -> mu mu and the dark matter direct detection
cross-section through their dependence on m_A. In the minimal-type of SU(5)
with type I seesaw, the large mixing in neutrino Dirac couplings results in
large lepton flavor violating decay process tau to mu gamma, which in turn sets
upper bound on m_A. In the SO(10) case, the large mixing can be chosen to be in
the Majorana couplings instead, and the constraint from Br(tau -> mu gamma) can
be avoided. The heavy Higgs funnel region turns out to be an interesting
possibility in both cases and the direct dark matter detection should be
possible in the near future in these scenarios.Comment: 19 pages, 8 figure
Neutrino Mixing Predictions of a Minimal SO(10) Model with Suppressed Proton Decay
During the past year, a minimal renormalizable supersymmetric SO(10) model
has been proposed with the following properties: it predicts a naturally stable
dark matter and neutrino mixing angles theta_atm and theta_13 while at the same
time accommodating CKM CP violation among quarks with no SUSY CP problem.
Suppression of proton decay for all allowed values of tan beta strongly
restricts the flavor structure of the model making it predictive for other
processes as well. We discuss the following predictions of the model in this
paper, e.g. down-type quark masses, and neutrino oscillation parameters, U_e3,
delta_MNSP, which will be tested by long baseline experiments such as T2K and
subsequent experiments using the neutrino beam from JPARC. We also calculate
lepton flavor violation and the lepton asymmetry of the Universe in this model.Comment: 22 pages, 11 figure
Experimental and Atomistic Theoretical Study of Degree of Polarization from Multi-layer InAs/GaAs Quantum Dots
Recent experimental measurements, without any theoretical guidance, showed
that isotropic polarization response can be achieved by increasing the number
of QD layers in a QD stack. Here we analyse the polarization response of
multi-layer quantum dot stacks containing up to nine quantum dot layers by
linearly polarized PL measurements and by carrying out a systematic set of
multi-million atom simulations. The atomistic modeling and simulations allow us
to include correct symmetry properties in the calculations of the optical
spectra: a factor critical to explain the experimental evidence. The values of
the degree of polarization (DOP) calculated from our model follows the trends
of the experimental data. We also present detailed physical insight by
examining strain profiles, band edges diagrams and wave function plots.
Multi-directional PL measurements and calculations of the DOP reveal a unique
property of InAs quantum dot stacks that the TE response is anisotropic in the
plane of the stacks. Therefore a single value of the DOP is not sufficient to
fully characterize the polarization response. We explain this anisotropy of the
TE-modes by orientation of hole wave functions along the [-110] direction. Our
results provide a new insight that isotropic polarization response measured in
the experimental PL spectra is due to two factors: (i) TM[001]-mode
contributions increase due to enhanced intermixing of HH and LH bands, and (ii)
TE[110]-mode contributions reduce significantly due to hole wave function
alignment along the [-110] direction. We also present optical spectra for
various geometry configurations of quantum dot stacks to provide a guide to
experimentalists for the design of multi-layer QD stacks for optical devices.
Our results predict that the QD stacks with identical layers will exhibit lower
values of the DOP than the stacks with non-identical layers.Comment: 10 pages, 7 figures, and 1 tabl
Suppressing Proton Decay in the Minimal SO(10) Model
We show that in a class of minimal supersymmetric SO(10) models which have
been found to be quite successful in predicting neutrino mixings, all proton
decay modes can be suppressed by a particular choice of Yukawa textures. This
suppression works for contributions from both left and right operators for
nucleon decay and for arbitrary \tan\beta. The required texture not only fits
all lepton and quark masses as well as CKM parameters but it also predicts
neutrino mixing parameter U_e3 and Dirac CP phase \sin|\delta_MNS| to be
0.07-0.09 and 0.3-0.7 respectively. We also discuss the relation between the
GUT symmetry breaking parameters for the origin of these textures.Comment: 7 pages, 2 figure
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