220 research outputs found
Flavor Changing Processes in Supersymmetric Models with Hybrid Gauge- and Gravity-Mediation
We consider supersymmetric models where gauge mediation provides the dominant
contributions to the soft supersymmetry breaking terms while gravity mediation
provides sub-dominant yet non-negligible contributions. We further assume that
the gravity-mediated contributions are subject to selection rules that follow
from a Froggatt-Nielsen symmetry. This class of models constitutes an example
of viable and natural non-minimally flavor violating models. The constraints
from mixing in the neutral K system imply that the modifications to the
Standard Model predictions for mixing in the neutral B_d and B_s systems are
generically at most at the percent level, but can be of order ten percent for
large . The modifications for the neutral D system mixing are
generically at most of order a few percent, but in a special subclass of models
they can be of order one. We point out processes relevant for
flavor violation in hybrid mediation.Comment: 30 pages, 3 figure
Constraining New Physics with the CDF Measurement of CP Violation in
Recently, the CDF collaboration has reported a measurement of the CP
asymmetry in the decay: . We
analyze the constraints that follow from this measurement on the size and the
phase of contributions from new physics to B-\barB mixing. Defining the
relative phase between the full amplitude and the Standard Model
contribution to be , we find a new bound: \sin2\theta_d\gsim-0.6
(-0.87) at one sigma (95% CL). Further implications for the CP asymmetry in
semileptonic B decays are discussed.Comment: 13 pages, harvmac, 3 figures; v2: a discussion of new physics effects
on tree level decays added; references added; accepted for publication in
Physical Review Letter
Generation of macroscopic quantum-superposition states by linear coupling to a bath
We demonstrate through an exactly solvable model that collective coupling to
any thermal bath induces effectively nonlinear couplings in a quantum many-body
(multi-spin) system. The resulting evolution can drive an uncorrelated
large-spin system with high probability into a macroscopic
quantum-superposition state. We discuss possible experimental realizations.Comment: 4 pages, 2 figures, Physical Review Letters (in press
Final State Interactions and New Physics in B -> pi K Decays
Within the Standard Model, and if one assumes that soft rescattering effects
are negligible, the CP asymmetry A^dir_CP (B^\pm -> \pi^\pm K) is predicted to
be very small and the ratio R = BR(B_d -> \pi^\mp K^\pm)/BR(B^\pm -> \pi^\pm K)
provides a bound on the angle \gamma of the unitarity triangle, sin^2 \gamma
\leq R. We estimate the corrections from soft rescattering effects using an
approach based on Regge phenomenology, and find effects of order 10% with large
uncertainties. In particular, we conclude that A^dir_CP \sim 0.2 and sin^2
\gamma \sim 1.2 R could not be taken unambiguously to signal New Physics. Using
SU(3) relations, we suggest experimental tests that could constrain the size of
the soft rescattering effects thus reducing the related uncertainty. Finally,
we study the effect of various models of New Physics on A^dir_CP and on R.Comment: 20 pages, RevTex, no figures; a few typos corrected, references
added, brief additional discussion of uncertanties is adde
Direct CP violation in charm and flavor mixing beyond the SM
We analyze possible interpretations of the recent LHCb evidence for CP
violation in D meson decays in terms of physics beyond the Standard Model. On
general grounds, models in which the primary source of flavor violation is
linked to the breaking of chiral symmetry (left-right flavor mixing) are
natural candidates to explain this effect, via enhanced chromomagnetic
operators. In the case of supersymmetric models, we identify two motivated
scenarios: disoriented A-terms and split families. These structures predict
other non-standard signals, such as nuclear EDMs close to their present bounds
and, possibly, tiny but visible deviations in K and B physics, or even sizable
flavor-violating processes involving the top quark or the stops. Some of these
connections, especially the one with nuclear EDMs, hold beyond supersymmetry,
as illustrated with the help of prototype non-supersymmetric models.Comment: 30 pages, 6 figure
Constraining Models of New Physics in Light of Recent Experimental Results on
We study extensions of the Standard Model where the charged current weak
interactions are governed by the CKM matrix and where all tree-level decays are
dominated by their Standard Model contribution. We constrain both analytically
and numerically the ratio and the phase difference between the New Physics and
the Standard Model contributions to the mixing amplitude of the neutral
system using the experimental results on , ,
and . We present new results concerning models with minimal
flavor violation and update the relevant parameter space. We also study the
left-right symmetric model with spontaneously broken CP, probing the viability
of this model in view of the recent results for and other
observables.Comment: 32 pages, including 9 figures, typos and error in fig. 1 corrected,
minor modificiation in the text, conclusions unchanged, to appear in PR
Non anomalous U(1)_H gauge model of flavor
A non anomalous horizontal gauge symmetry can be responsible for the
fermion mass hierarchies of the minimal supersymmetric standard model. Imposing
the consistency conditions for the absence of gauge anomalies yields the
following results: i) unification of leptons and down-type quarks Yukawa
couplings is allowed at most for two generations. ii) The term is
necessarily somewhat below the supersymmetry breaking scale. iii) The
determinant of the quark mass matrix vanishes, and there is no strong
problem. iv) The superpotential has accidental and symmetries. The
prediction allows for an unambiguous test of the model at low
energy.Comment: 5 pages, RevTex. Title changed, minor modifications. Final version to
appear in Phys. Rev.
Fermion Masses and Gauge Mediated Supersymmetry Breaking from a Single U(1)
We present a supersymmetric model of flavor. A single U(1) gauge group is
responsible for both generating the flavor spectrum and communicating
supersymmetry breaking to the visible sector. The problem of Flavor Changing
Neutral Currents is overcome, in part using an `Effective Supersymmetry'
spectrum among the squarks, with the first two generations very heavy. All
masses are generated dynamically and the theory is completely renormalizable.
The model contains a simple Froggatt-Nielsen sector and communicates
supersymmetry breaking via gauge mediation without requiring a separate
messenger sector. By forcing the theory to be consistent with SU(5) Grand
Unification, the model predicts a large tan beta and a massless up quark. While
respecting the experimental bounds on CP violation in the K-system, the model
leads to a large enhancement of CP violation in B-(B bar) mixing as well as in
B decay amplitudes.Comment: LaTeX, 25 pages, 8 figure
Signatures of multi-TeV scale particles in supersymmetric theories
Supersymmetric particles at the multi-TeV scale will escape direct detection
at planned future colliders. However, such particles induce non-decoupling
corrections in processes involving the accessible superparticles through
violations of the supersymmetric equivalence between gauge boson and gaugino
couplings. In a previous study, we parametrized these violations in terms of
super-oblique parameters and found significant deviations in well-motivated
models. Here, we systematically classify the possible experimental probes of
such deviations, and present detailed investigations of representative
observables available at a future linear collider. In some scenarios, the
option and adjustable beam energy are exploited to achieve high
precision. It is shown that precision measurements are possible for each of the
three coupling relations, leading to significant bounds on the masses and
properties of heavy superparticles and possible exotic sectors.Comment: 37 pages including 17 figures, REVTe
Markers of Inflammation and Fibrosis in Alcoholic Hepatitis and Viral Hepatitis C
High levels of profibrinogenic cytokine transforming factor beta (TGF-β), metalloprotease (MMP2), and tissue inhibitor of matrix metalloprotease 1 (TIMP1) contribute to fibrogenesis in hepatitis C virus (HCV) infection and in alcohol-induced liver disease (ALD). The aim of our study was to correlate noninvasive serum markers in ALD and HCV patients with various degrees of inflammation and fibrosis in their biopsies. Methods. Serum cytokines levels in HCV-infected individuals in the presence or absence of ALD were measured. Student's-t-test with Bonferroni correction determined the significance between the groups. Results. Both tumor-necrosis-factor- (TNF)-α and TGF-β levels increased significantly with the severity of inflammation and fibrosis. TGF-β levels increased significantly in ALD patients versus the HCV patients. Proinflammatory cytokines' responses to viral and/or toxic injury differed with the severity of liver inflammation. A combination of these markers was useful in predicting and diagnosing the stages of inflammation and fibrosis in HCV and ALD. Conclusion. Therapeutic monitoring of TGF-β and metalloproteases provides important insights into fibrosis
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