1,093 research outputs found
New physics in \epsilon' from chromomagnetic contributions and limits on Left-Right symmetry
New physics in the chromomagnetic flavor changing transition s->dg* can avoid
the strong GIM suppression of the Standard Model and lead to large
contributions to CP-violating observables, in particular to the epsilon'
parameter, that we address here. We discuss the case of the Left-Right
symmetric models, where this contribution implies bounds on the phases of the
right-handed quark mixing matrix, or in generic models with large phases a
strong bound on the Left-Right symmetry scale. To the leading order, a numeric
formula for epsilon' as a function of the short-distance coefficients for a
wide class of models of new physics is given.Comment: 12 pages, Eq. 12 and related numerics amende
What heavy quanta bounds could be inferred from a Higgs discovery?
The Higgs couplings can receive non-decoupling corrections due to heavy
quanta, and deviations from the SM can be used to test its presence. The
possible Higgs signal recently reported at LEP, with mh=115 GeV, severely
constrains the presence of heavy quanta, such as a heavy fourth family. At
Tevatron, the Higgs production by gluon fusion, followed by the decay h -> WW*,
can also be used to probe the existence of heavy colored particles, including
additional families, chiral sextet and octet quarks. Within the MSSM, we also
find that gluon fusion is a sensitive probe for the squark spectrum.Comment: 12 pages, 3 tables, 1 figure. Accepted in Mod. Phys. Lett. A (2001
Evidence for topological nonequilibrium in magnetic configurations
We use direct numerical simulations to study the evolution, or relaxation, of
magnetic configurations to an equilibrium state. We use the full single-fluid
equations of motion for a magnetized, non-resistive, but viscous fluid; and a
Lagrangian approach is used to obtain exact solutions for the magnetic field.
As a result, the topology of the magnetic field remains unchanged, which makes
it possible to study the case of topological nonequilibrium. We find two cases
for which such nonequilibrium appears, indicating that these configurations may
develop singular current sheets.Comment: 10 pages, 5 figure
Compressible hydromagnetic nonlinearities in the predecoupling plasma
The adiabatic inhomogeneities of the scalar curvature lead to a compressible
flow affecting the dynamics of the hydromagnetic nonlinearities. The influence
of the plasma on the evolution of a putative magnetic field is explored with
the aim of obtaining an effective description valid for sufficiently large
scales. The bulk velocity of the plasma, computed in the framework of the
LambdaCDM scenario, feeds back into the evolution of the magnetic power spectra
leading to a (nonlocal) master equation valid in Fourier space and similar to
the ones discussed in the context of wave turbulence. Conversely, in physical
space, the magnetic power spectra obey a Schroedinger-like equation whose
effective potential depends on the large-scale curvature perturbations.
Explicit solutions are presented both in physical space and in Fourier space.
It is argued that curvature inhomogeneities, compatible with the WMAP 7yr data,
shift to lower wavenumbers the magnetic diffusivity scale.Comment: 29 page
Central Charge Anomalies in 2D Sigma Models with Twisted Mass
We discuss the central charge in supersymmetric sigma models in
two dimensions. The target space is a symmetric K\"ahler manifold, CP is
an example. The U(1) isometries allow one to introduce twisted masses in the
model. At the classical level the central charge contains Noether charges of
the U(1) isometries and a topological charge which is an integral of a total
derivative of the Killing potentials. At the quantum level the topological part
of the central charge acquires anomalous terms. A bifermion term was found
previously, using supersymmetry which relates it to the superconformal anomaly.
We present a direct calculation of this term using a number of regularizations.
We derive, for the first time, the bosonic part in the central charge anomaly.
We construct the supermultiplet of all anomalies and present its superfield
description. We also discuss a related issue of BPS solitons in the CP(1) model
and present an explicit form for the curve of marginal stability.Comment: 30 pages, 1 figure, references adde
Matching factors for Delta S=1 four-quark operators in RI/SMOM schemes
The non-perturbative renormalization of four-quark operators plays a
significant role in lattice studies of flavor physics. For this purpose, we
define regularization-independent symmetric momentum-subtraction (RI/SMOM)
schemes for Delta S=1 flavor-changing four-quark operators and provide one-loop
matching factors to the MS-bar scheme in naive dimensional regularization. The
mixing of two-quark operators is discussed in terms of two different classes of
schemes. We provide a compact expression for the finite one-loop amplitudes
which allows for a straightforward definition of further RI/SMOM schemes.Comment: 22 pages, 5 figure
On the effective action of the vacuum photon splitting in Lorentz-violating QED
We consider one-loop radiative corrections from Lorentz- and CPT- violating
extended QED to address the specific problem of finding explicitly an effective
action describing amplitude of photon triple splitting. We show that it is not
possible to find a nonzero photon triple splitting effective action, at least
by using the derivative expansion method (at zero external momenta), up to
leading order in the Lorentz- and CPT- violating parameter.Comment: 4 pages, version to appear in EP
A Few Aspects of Heavy Quark Expansion
Two topics in heavy quark expansion are discussed. The heavy quark potential
in perturbation theory is reviewed in connection to the problem of the heavy
quark mass. The nontrivial reason behind the failure of the "potential
subtracted" mass in higher orders is elucidated. The heavy quark sum rules are
the second subject. The physics behind the new exact sum rules is described and
a simple quantum mechanical derivation is given. The question of saturation of
sum rules is discussed. A comment on the nonstandard possibility which would
affect analysis of BR_sl(B) vs. n_c is made.Comment: 21 pages, LaTeX, 7 eps figures. To appear in the Proceedings of the
UK Phenomenology Workshop on Heavy Flavour and CP Violation, Durham, UK,
17-22 September 200
Radiolysis of NaCl at high and low temperatures: development of size distribution of bubbles and colloids
New experimental results are presented on low temperature irradiation (18 °C) of rock-salt samples which had been exposed to initial doses up to 320 GRad at 100 °C. Differential scanning calorimetry (DSC) shows that the latent heat of melting (LHM) of sodium colloids decreases during subsequent low-temperature irradiation, whereas the stored energy (SE) increases slowly, indicating that the process of radiolysis continues. The decrease of the LHM is due to dissolution of large colloids, because the intensities of the melting peaks decrease during the second stage irradiation at low temperature. The model is formulated to describe the nucleation kinetics and the evolution of the size distribution of chlorine precipitates and sodium colloids in NaCl under high dose irradiation. It is shown that the mechanism of dissolution of large Na colloids during low temperature irradiation can be related to melting of sodium colloids.
Exact Results in Gauge Theories: Putting Supersymmetry to Work. The 1999 Sakurai Prize Lecture
Powerful methods based on supersymmetry allow one to find exact solutions to
certain problems in strong coupling gauge theories. The inception of some of
these methods (holomorphy in the gauge coupling and other chiral parameters, in
conjunction with instanton calculations) dates back to the 1980's. I describe
the early exact results -- the calculation of the beta function and the gluino
condensate -- and their impact on the subsequent developments. A brief
discussion of the recent breakthrough discoveries where these results play a
role is given.Comment: Based on the talk at the Centennial Meeting of The American Physical
Society, March 20-26, Atlanta, GA. LaTex (uses sprocl.sty), 36 pages, 5 eps
figures include
- …