534 research outputs found
`St\"uckelberg interferometry' with ultracold molecules
We report on the realization of a time-domain `St\"uckelberg interferometer',
which is based on the internal state structure of ultracold Feshbach molecules.
Two subsequent passages through a weak avoided crossing between two different
orbital angular momentum states in combination with a variable hold time lead
to high-contrast population oscillations. This allows for a precise
determination of the energy difference between the two molecular states. We
demonstrate a high degree of control over the interferometer dynamics. The
interferometric scheme provides new possibilities for precision measurements
with ultracold molecules.Comment: 4 pages, 5 figure
Shell-Model Effective Operators for Muon Capture in ^{20}Ne
It has been proposed that the discrepancy between the partially-conserved
axial-current prediction and the nuclear shell-model calculations of the ratio
in the muon-capture reactions can be solved in the case of ^{28}Si by
introducing effective transition operators. Recently there has been
experimental interest in measuring the needed angular correlations also in
^{20}Ne. Inspired by this, we have performed a shell-model analysis employing
effective transition operators in the shell-model formalism for the transition
. Comparison of
the calculated capture rates with existing data supports the use of effective
transition operators. Based on our calculations, as soon as the experimental
anisotropy data becomes available, the limits for the ratio can be
extracted.Comment: 9 pages, 3 figures include
A CP asymmetry in e^+e^- \to \chi^0_i\chi^0_j \to \chi^0_j \tau stau_k with tau polarization
We propose a CP-odd asymmetry in the supersymmetric process e^+e^- \to
\chi^0_i \chi^0_j \to \chi^0_j \tau stau_k by means of the transverse \tau
polarization. We calculate the asymmetry and cross sections at a future linear
collider in the 500 GeV c.m.s. energy range with longitudinal polarized beams
and high luminosity. We work in the Minimal Supersymmetric Standard Model with
complex parameters \mu, M_1 and A_\tau. The asymmetry can reach values up to 60
%. We also estimate the sensitivity for measuring the \tau polarization
necessary to probe the CP asymmetry.Comment: 12 pages, 7 figure
CP Violation and Dark Matter
A brief review is given of the effects of CP violation on the direct
detection of neutralinos in dark matter detectors. We first summarize the
current developments using the cancellation mechanism which allows for the
existence of large CP violating phases consistent with experimental limits on
the electron and on the neutron electric dipole moments in a broad class of
SUSY, string and D brane models. We then discuss their effects on the
scattering of neutralinos from quarks and on the event rates. It is found that
while CP effects on the event rates can be enormous such effects are reduced
significantly with the imposition of the EDM constraints. However, even with
the inclusion of the EDM constraints the effects are still very significant and
should be included in a precision prediction of event rates in any SUSY, string
or D brane model.Comment: Based on an invited talk at the conference "Sources and Detection of
Dark Matter in the Universe", at Marina del Rey, CA, Feb. 23-25, 2000; 12
pages, Latex including 2 figure
Field-theoretical approach to particle oscillations in absorbing matter
The oscillations in absorbing matter are considered. The standard model
based on optical potential does not describe the total transition
probability as well as the channel corresponding to absorption of the
-particle. We calculate directly the off-diagonal matrix element in the
framework of field-theoretical approach. Contrary to one-particle model, the
final state absorption does not tend to suppress the channels mentioned above
or, similarly, calculation with hermitian Hamiltonian leads to increase the
corresponding values. The model reproduces all the results on the particle
oscillations, however it is oriented to the description of the above-mentioned
channels. Also we touch on the problem of infrared singularities. The approach
under study is infrared-free.Comment: 27 pages, 8 figure
On the EDM Cancellations in D-brane models
We analyze the possibility of simultaneous electron, neutron, and mercury
electric dipole moment (EDM) cancellations in the mSUGRA and D--brane models.
We find that the mercury EDM constraint practically rules out the cancellation
scenario in D-brane models whereas in the context of mSUGRA it is still allowed
with some fine-tuning.Comment: 10 pages, to appear in Phys. Rev. Let
- …