822 research outputs found
Decay
Motivated by the experimental measurement of the decay rate, , and
the longitudinal polarization, , in the Cabibbo favored decay , we have studied theoretical prediction within the context of
factorization approximation invoking several form factors models. We were able
to obtain agreement with experiment for both and by using
experimentally measured values of the form factors ,
and in the semi-leptonic decay . We have also included in our calculation the effect of the
final state interaction () by working with the partial waves amplitudes
, and . Numerical calculation shows that the decay amplitude is
dominated by wave, and that the polarization is sensitive to the
interference between and waves. The range of the phase difference
accommodated by experimental error in
is large.Comment: 7 pages, LaTe
Radiative Leptonic Decays of Heavy Mesons
We compute the photon spectrum and the rate for the decays These photonic modes constitute a potentially large background
for the purely leptonic decays which are used to extract the heavy meson decay
constants. While the rate for D\to l\n\g is small, the radiative decay in the
meson case could be of comparable magnitude or even larger than B\to\m\n.
This would affect the determination of if the channel cannot be
identified. We obtain theoretical estimates for the photonic rates and disscuss
their possible experimental implications.Comment: 12 pages, RevTex, 3 uuencoded figures include
Resonant Two-body D Decays
The contribution of a resonance to is
calculated by applying the soft pion theorem to , and is
found to be about 30% of the measured amplitude and to be larger than the
component of this amplitude. We estimate a 70% contribution to
the total amplitude from a higher resonance. This implies large
deviations from factorization in D decay amplitudes, a lifetime difference
between D^0 and D^+, and an enhancement of mixing due to SU(3)
breaking.Comment: To be published in Physical Review Letters, some corrections,
references update
Critical Analysis of Theoretical Estimates for to Light Meson Form Factors and the Data
We point out that current estimates of form factors fail to explain the
non-leptonic decays and that the combination of data
on the semi-leptonic decays and on the non-leptonic
decays (in particular recent po\-la\-ri\-za\-tion
data) severely constrain the form (normalization and dependence) of the
heavy-to-light meson form factors, if we assume the factorization hypothesis
for the latter. From a simultaneous fit to \bpsi and \dk data we find that
strict heavy quark limit scaling laws do not hold when going from to
and must have large corrections that make softer the dependence on the masses.
We find that should increase slower with \qq than .
We propose a simple parametrization of these corrections based on a quark
model or on an extension of the \hhs laws to the \hl case, complemented with an
approximately constant . We analyze in the light of these data and
theoretical input various theoretical approaches (lattice calculations, QCD sum
rules, quark models) and point out the origin of the difficulties encountered
by most of these schemes. In particular we check the compatibility of several
quark models with the heavy quark scaling relations.Comment: 48 pages, DAPNIA/SPP/94-24, LPTHE-Orsay 94/1
Observation of the Dynamic Beta Effect at CESR with CLEO
Using the silicon strip detector of the CLEO experiment operating at the
Cornell Electron-positron Storage Ring (CESR), we have observed that the
horizontal size of the luminous region decreases in the presence of the
beam-beam interaction from what is expected without the beam-beam interaction.
The dependence on the bunch current agrees with the prediction of the dynamic
beta effect. This is the first direct observation of the effect.Comment: 9 page uuencoded postscript file, postscritp file also available
through http://w4.lns.cornell.edu/public/CLNS, submitted to Phys. Rev.
Radiogenic and Muon-Induced Backgrounds in the LUX Dark Matter Detector
The Large Underground Xenon (LUX) dark matter experiment aims to detect rare
low-energy interactions from Weakly Interacting Massive Particles (WIMPs). The
radiogenic backgrounds in the LUX detector have been measured and compared with
Monte Carlo simulation. Measurements of LUX high-energy data have provided
direct constraints on all background sources contributing to the background
model. The expected background rate from the background model for the 85.3 day
WIMP search run is
~events~keV~kg~day
in a 118~kg fiducial volume. The observed background rate is
~events~keV~kg~day,
consistent with model projections. The expectation for the radiogenic
background in a subsequent one-year run is presented.Comment: 18 pages, 12 figures / 17 images, submitted to Astropart. Phy
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