23,252 research outputs found

### Is there New Physics in B Decays ?

Rare decays of the $B$ meson are sensitive to new physics effects. Several
experimental results on these decays have been difficult to understand within
the standard model (SM) though more precise measurements and a better
understanding of SM theory predictions are needed before any firm conclusions
can be drawn. In this talk we try to understand the present data assuming the
presence of new physics. We find that the data points to new physics of an
extended Higgs sector and we present a two higgs doublet model with a 2-3
flavor symmetry in the down type quark sector that can explain the deviations
from standard model reported in several rare B decays.Comment: 8 pages, Talk presented at Theory Canada II, Perimeter Institute,
Waterloo, Canada. New references added and update

### On the Observability of "Invisible" / "Nearly Invisible" Charginos

It is shown that if the charginos decay into very soft leptons or hadrons +
$\not{E}$ due to degeneracy/ near- degeneracy with the LSP or the sneutrino,
the observability of the recently proposed signal via the single photon (+ soft
particles) + $\not{E}$ channel crucially depends on the magnitude of the \SNU
mass due to destructive interferences in the matrix element squared. If the
\SNU's and, consequently, left-sleptons are relatively light, the size of the
signal, previously computed in the limit \MSNU \to \infty only, is
drastically reduced. We present the formula for the signal cross section in a
model independent way and discuss the observability of the signal at LEP 192
and NLC energies.Comment: 27 pages, Late

### Extracting alpha from B0(d) --> K0 anti-K0 Decays

We propose a new method for obtaining the CP phase alpha, based on
measurements of B0(d) --> K0 anti-K0, along with theoretical input. Due to the
similarities of QCD factorization (QCDf) and perturbative QCD (pQCD), this
input is basically the same for each of these models. Although the theoretical
error is large at present, many of the contributing quantities will be better
known in the future, leading to a smaller error. One outstanding question is
the extent to which the precision on quark masses, especially m_c/m_b, can be
improved. If one assumes that new physics is not present, the method can be
used to predict the values of CP asymmetries in B0(d) --> K0 anti-K0: 0.02 <=
A_{dir}^2 + A_{mix}^2 <= 0.125. A result outside this range would signal the
existence of long-distance effects beyond those included in models of
nonleptonic decays based on factorization (such as QCDf and pQCD), or the
presence of new physics.Comment: 5 pages, To appear in PR

### Thermoelectric properties of Bi2Te3 atomic quintuple thin films

Motivated by recent experimental realizations of quintuple atomic layer films
of Bi2Te3,the thermoelectric figure of merit, ZT, of the quintuple layer is
calculated and found to increase by a factor of 10 (ZT = 7.2) compared to that
of the bulk at room temperature. The large enhancement in ZT results from the
change in the distribution of the valence band density of modes brought about
by the quantum confinement in the thin film. The theoretical model uses ab
initio electronic structure calculations (VASP) with full quantum-mechanical
structure relaxation combined with a Landauer formalism for the linear-response
transport coefficients.Comment: 4 figures, submitted to AP

### Quantum discord between relatively accelerated observers

We calculate the quantum discord between two free modes of a scalar field
which start in a maximally entangled state and then undergo a relative,
constant acceleration. In a regime where there is no distillable entanglement
due to the Unruh effect, we show that there is a finite amount of quantum
discord, which is a measure of purely quantum correlations in a state, over and
above quantum entanglement. Even in the limit of infinite acceleration of the
observer detecting one of the modes, we provide evidence for a non-zero amount
of purely quantum correlations, which might be exploited to gain non-trivial
quantum advantages.Comment: 4 pages, 2 figure

### Drainage in a model stratified porous medium

We show that when a non-wetting fluid drains a stratified porous medium at
sufficiently small capillary numbers Ca, it flows only through the coarsest
stratum of the medium; by contrast, above a threshold Ca, the non-wetting fluid
is also forced laterally, into part of the adjacent, finer strata. The spatial
extent of this partial invasion increases with Ca. We quantitatively understand
this behavior by balancing the stratum-scale viscous pressure driving the flow
with the capillary pressure required to invade individual pores. Because
geological formations are frequently stratified, we anticipate that our results
will be relevant to a number of important applications, including understanding
oil migration, preventing groundwater contamination, and sub-surface CO$_{2}$
storage

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