80 research outputs found
Dyons as a source of CP and time invariance violation: electric dipole moments and K-meson decays
We consider a mechanism by which dyons (electrically charged magnetic
monopoles) can produce both a T- and P-odd (i.e. time reversal invariance and
parity violating) mixed polarizability beta [defined by Delta E = -beta E.B,
where Delta E is the energy change when electric (E) and magnetic (B) fields
are applied to a system] and a T- and P-odd interaction between two particles:
psi_1-bar gamma_5 psi_1 psi_2-bar psi_2, where the psi_i are electron and quark
spinors. The latter can create atomic and neutron electric dipole moments
(EDMs). From experimental bounds on these we find limits on the properties of
dyons. Our best limit, using the experimental limit for the EDM of the Tl atom,
is M |Q g (Q^2 - g^2)|^(-1/4) > 6 GeV, where M is the dyon mass and Q is the
electric and g the magnetic charge of the dyons. The contribution of dyons to
CP violation in K-meson decays is also estimated.Comment: 22 pages, 5 figures, RevTe
CP violation in
We study CP violation in decay.
This decay provides a good place to look for CP violation. Some observables are
very sensitive to the electric dipole moment and
therefore can be used to improve the experimental upper bound on .
CP violations in the lepton pair decays of and are also
discussed.Comment: 8 pages, RevTex, UM-P-92/113, OZ-92/3
Dynamical CP Violation in Composite Higgs Models
The dynamical origin of the CP violation in electroweak theory is
investigated in composite Higgs models. The mechanism of the spontaneous CP
violation proposed in other context by Dashen is adopted to construct simple
models of the dynamical CP violation.
Within the models the size of the neutron electric dipole moment is estimated
and the constraint on the -parameter in K-meson decays is
discussed.Comment: 20 pages, 2 figures not included, uses LaTeX, HUPD-922
A luminosity monitor for the A4 parity violation experiment at MAMI
A water Cherenkov luminosity monitor system with associated electronics has
been developed for the A4 parity violation experiment at MAMI. The detector
system measures the luminosity of the hydrogen target hit by the MAMI electron
beam and monitors the stability of the liquid hydrogen target. Both is required
for the precise study of the count rate asymmetries in the scattering of
longitudinally polarized electrons on unpolarized protons. Any helicity
correlated fluctuation of the target density leads to false asymmetries. The
performance of the luminosity monitor, investigated in about 2000 hours with
electron beam, and the results of its application in the A4 experiment are
presented.Comment: 22 pages, 12 figures, submitted to NIM
Constraints on Axion Models from
We explore a new class of axion models in which some, but not all, of the
left-handed quarks have a Peccei-Quinn symmetry. These models are potentially
afflicted by flavour changing neutral currents. We derive the bounds on the
Peccei-Quinn symmetry-breaking scale from bounds on the
branching ratio, showing that in some cases they are even stronger than the
astrophysical ones, but still not strong enough to kill off the models.Comment: 15pp RevTeX, 1 eps fig, uses graphics style. Expanded discussion on
massive scalars and pseudoscalars, typos. To appear in Physical Review
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
We report on a measurement of the asymmetry in the scattering of transversely
polarized electrons off unpolarized protons, A, at two Q values of
\qsquaredaveragedlow (GeV/c) and \qsquaredaveragedhighII (GeV/c) and a
scattering angle of . The measured transverse
asymmetries are A(Q = \qsquaredaveragedlow (GeV/c)) =
(\experimentalasymmetry alulowcorr \statisticalerrorlow
\combinedsyspolerrorlowalucor) 10 and
A(Q = \qsquaredaveragedhighII (GeV/c)) = (\experimentalasymme
tryaluhighcorr \statisticalerrorhigh
\combinedsyspolerrorhighalucor) 10. The first
errors denotes the statistical error and the second the systematic
uncertainties. A arises from the imaginary part of the two-photon
exchange amplitude and is zero in the one-photon exchange approximation. From
comparison with theoretical estimates of A we conclude that
N-intermediate states give a substantial contribution to the imaginary
part of the two-photon amplitude. The contribution from the ground state proton
to the imaginary part of the two-photon exchange can be neglected. There is no
obvious reason why this should be different for the real part of the two-photon
amplitude, which enters into the radiative corrections for the Rosenbluth
separation measurements of the electric form factor of the proton.Comment: 4 figures, submitted to PRL on Oct.
Nucleon Edm from Atomic Systems and Constraints on Supersymmetry Parameters
The nucleon EDM is shown to be directly related to the EDM of atomic systems.
From the observed EDM values of the atomic Hg system, the neutron EDM can be
extracted, which gives a very stringent constraint on the supersymmetry
parameters. It is also shown that the measurement of Nitrogen and Thallium
atomic systems should provide important information on the flavor dependence of
the quark EDM. We perform numerical analyses on the EDM of neutron, proton and
electron in the minimal supersymmetric standard model with CP-violating phases.
We demonstrate that the new limit on the neutron EDM extracted from atomic
systems excludes a wide parameter region of supersymmetry breaking masses above
1 TeV, while the old limit excludes only a small mass region below 1 TeV.Comment: 10 pages, 7 figure file
Effective Lagrangians and Parity-Conserving Time-Reversal Violation at Low Energies
Using effective Lagrangians, we argue that any time-reversal-violating but
parity-conserving effects are too small to be observed in flavor-conserving
nuclear processes without dramatic improvement in experimental accuracy. In the
process we discuss other arguments that have appeared in the literature.Comment: Revised manuscript, 11 pages, RevTex, epsf.st
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at = 0.108 (GeV/c)
We report on a measurement of the parity violating asymmetry in the elastic
scattering of polarized electrons off unpolarized protons with the A4 apparatus
at MAMI in Mainz at a four momentum transfer value of = \Qsquare
(GeV/c) and at a forward electron scattering angle of 30. The measured asymmetry is = (\Aphys
\Deltastat \Deltasyst) 10. The
expectation from the Standard Model assuming no strangeness contribution to the
vector current is A = (\Azero \DeltaAzero) 10. We
have improved the statistical accuracy by a factor of 3 as compared to our
previous measurements at a higher . We have extracted the strangeness
contribution to the electromagnetic form factors from our data to be +
\FakGMs = \GEsGMs \DeltaGEsGMs at = \Qsquare (GeV/c).
As in our previous measurement at higher momentum transfer for + 0.230
, we again find the value for + \FakGMs to be positive,
this time at an improved significance level of 2 .Comment: 4 pages, 3 figure
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