488 research outputs found
Exploration of 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 with respect to the
dipole anisotropy of the cosmic microwave background. We interpret their
results in an effective field theory framework developed to probe the violation
of Lorentz invariance in the weak interaction and previously applied to
semileptonic processes, in particular decay. In this approach a general
Lorentz-violating tensor is added to the standard propagator of
the boson. We perform an exploratory study of the prospects to search for
Lorentz violation in nonleptonic decays. For the kaon, we find that the
sensitivity to Lorentz violation is limited by the velocity of the kaons and by
the extent to which hadronic effects can be calculated. In a simple model we
derive the decay rate and calculate the asymmetry for the lifetime.
Using the KLOE data, limits on the values of are determined.Comment: accepted for publication in Physics Letters
On-line Excited-State Laser Spectroscopy of Trapped Short-Lived Ra Ions
As an important step towards an atomic parity violation experiment in one
single trapped Ra ion, laser spectroscopy experiments were performed with
on-line produced short-lived Ra ions. The isotope shift of
the 6\,^2D\,-\,7\,^2P and
6\,^2D\,-\,7\,^2P transitions and the hyperfine structure
constant of the 7\,^2S and 6\,^2D states in Ra
were measured. These values provide a benchmark for the required atomic theory.
A lower limit of ms for the lifetime of the metastable
6\,^2D state was measured by optical shelving.Comment: 4.2 pages, 6 figures, 2 tables
Emission patterns of neutral pions in 40 A MeV Ta+Au reactions
Differential cross sections of neutral pions emitted in 181Ta + 197Au
collisions at a beam energy of 39.5A MeV have been measured with the photon
spectrometer TAPS. The kinetic energy and transverse momentum spectra of
neutral pions cannot be properly described in the framework of the thermal
model, nor when the reabsorption of pions is accounted for in a
phenomenological model. However, high energy and high momentum tails of the
pion spectra can be well fitted through thermal distributions with unexpectedly
soft temperature parameters below 10 MeV.Comment: 16 pages (double-spaced), 5 figures; corrections after referee's
comments and suggestion
Neutron clock as a friction-meter
Fast-fission reactions in collisions of four heavy systems (well below the fusion extra-push energy threshold), for which Hinde and coworkers had measured the prescission neutron multiplicities, have been analysed in terms of the deterministic dynamic model of Feldmeier coupled to a time-dependent statistical cascade calculation. In order to reproduce the measured prescission multiplicities and the observed (nearly symmetric) mass divisions, the energy dissipation must be dramatically changed with regard to the standard one-body dissipation: In the entrance channel, in the process of forming a composite system, the energy dissipation must be reduced to at least half of the one-body dissipation strength (k(s)(in) less than or equal to 0.5), and in the exit channel (from a mononucleus shape to scission) it must be increased to about 10 times that value (k(s)(out) approximate to 10)
Selection of heavy ion reaction channels via particle K X-ray coincidences
To identify the residual nuclei in very asymmetric heavy-ion reactions heavy-ion K X-ray coincidences have been measured. The usefulness and limitations of this method are discussed, and its feasibility is demonstrated in a study of the 14N+197Au reaction at 140 MeV
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