3,659 research outputs found
Lorentz violation in neutron and allowed nuclear beta decay
We explore the possibility that the weak interaction violates Lorentz, and in
particular rotational, invariance in neutron and allowed nuclear beta decay. A
broad class of Lorentz-violating effects is considered, in which the standard
propagator of the W-boson acquires an additional Lorentz-violating tensor. The
general decay rate for allowed beta decay that incorporates such a modified
propagator is derived. The resulting Lorentz-violating signals are discussed
for the different types of beta-decay transitions, Fermi, Gamow-Teller, and
mixed. We study the implications of our formalism for dedicated beta-decay
experiments. We give a short overview of the few relevant experiments that have
been performed or are ongoing.Comment: 23 pages; added reference
Limits on Lorentz violation in neutral-Kaon decay
The KLOE collaboration recently reported bounds on the directional dependence
of the lifetime of the short-lived neutral kaon K_S with respect to the cosmic
microwave background dipole anisotropy. We interpret their results in a general
framework developed to probe Lorentz violation in the weak interaction. In this
approach a Lorentz-violating tensor \chi_{\mu\nu} is added to the standard
propagator of the W boson. We derive the K_S decay rate in a naive tree-level
model and calculate the asymmetry for the lifetime. By using the KLOE data the
real vector part of \chi_{\mu\nu} is found to be smaller than 10^-2. We briefly
discuss the theoretical challenges concerning nonleptonic decays.Comment: Presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 2013
Testing Lorentz invariance in orbital electron capture
Searches for Lorentz violation were recently extended to the weak sector, in
particular neutron and nuclear decay [1]. From experiments on forbidden
-decay transitions strong limits in the range of -
were obtained on Lorentz-violating components of the -boson propagator [2].
In order to improve on these limits strong sources have to be considered. In
this Brief Report we study isotopes that undergo orbital electron capture and
allow experiments at high decay rates and low dose. We derive the expressions
for the Lorentz-violating differential decay rate and discuss the options for
competitive experiments and their required precision.Comment: accepted for publication as a Brief Report in Physical Review
Nuclear beta decay with Lorentz violation
We consider the possibility of Lorentz-invariance violation in weak-decay
processes. We present a general approach that entails modifying the W-boson
propagator by adding a Lorentz-violating tensor to it. We describe the effects
of Lorentz violation on nuclear beta decay in this scenario. In particular we
show the expression for a first-forbidden transition with a spin change of two.
Using data from an old experiment on the rotational invariance of yttrium-90,
we derive several bounds on the Lorentz-violating parameters of the order of
10^(-6)-10^(-8).Comment: 4 pages; presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 2013; Added reference
Symmetry violations in nuclear and neutron decay
The role of decay as a low-energy probe of physics beyond the
Standard Model is reviewed. Traditional searches for deviations from the
Standard Model structure of the weak interaction in decay are discussed
in the light of constraints from the LHC and the neutrino mass. Limits on the
violation of time-reversal symmetry in decay are compared to the strong
constraints from electric dipole moments. Novel searches for Lorentz symmetry
breaking in the weak interaction in decay are also included, where we
discuss the unique sensitivity of decay to test Lorentz invariance. We
end with a roadmap for future -decay experiments.Comment: Accepted for publication in Rev. Mod. Phys. 86 pages, 13 figure
The Status of the Pion-Nucleon Coupling Constant
A review is given of the various determinations of the different piNN
coupling constants in analyses of the low-energy pp, np, pbarp, and pi-p
scattering data. The most accurate determinations are in the energy-dependent
partial-wave analyses of the NN data. The recommended value is f^2 = 0.075 . A
recent determination of f^2 by the Uppsala group from backward np cross
sections is shown to be model dependent and inaccurate, and therefore
completely uninteresting. We also argue that an accurate determination of f^2
using pp forward dispersion relations is not a realistic option.Comment: 19 pages, latex2e with a4wide.sty, more information is available at
http://NN-OnLine.sci.kun.nl . Invited talk at FBXV, Groningen, The
Netherlands, July 22-26, 1997. Invited talk at MENU97, Vancouver, B.C.,
Canada, July 28 - August 1, 199
Partial-Wave Analyses of all Proton-Proton and Neutron-Proton Data Below 500 MeV
In 1993 the Nijmegen group published the results of energy-dependent
partial-wave analyses (PWAs) of the nucleon-nucleon (NN) scattering data for
laboratory kinetic energies below Tlab=350 MeV (PWA93). In this talk some
general aspects, but also the newest developments on the Nijmegen NN PWAs are
reported. We have almost finished a new energy-dependent PWA and will discuss
some typical aspects of this new PWA; where it differs from PWA93, but also
what future developments might be, or should be.Comment: Presentation at the 19th European Conference on Few-Body Problems in
Physics, Groningen, The Netherlands, 23-27 August 2004. 4 pages REVTeX4, no
figure
Deuteron Magnetic Quadrupole Moment From Chiral Effective Field Theory
We calculate the magnetic quadrupole moment (MQM) of the deuteron at leading
order in the systematic expansion provided by chiral effective field theory. We
take into account parity and time-reversal violation which, at the quark-gluon
level, results from the QCD vacuum angle and dimension-six operators that
originate from physics beyond the Standard Model. We show that the deuteron MQM
can be expressed in terms of five low-energy constants that appear in the
parity- and time-reversal-violating nuclear potential and electromagnetic
current, four of which also contribute to the electric dipole moments of light
nuclei. We conclude that the deuteron MQM has an enhanced sensitivity to the
QCD vacuum angle and that its measurement would be complementary to the
proposed measurements of light-nuclear EDMs
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