140 research outputs found
Proof of an entropy conjecture for Bloch coherent spin states and its generalizations
Wehrl used Glauber coherent states to define a map from quantum density
matrices to classical phase space densities and conjectured that for Glauber
coherent states the mininimum classical entropy would occur for density
matrices equal to projectors onto coherent states. This was proved by Lieb in
1978 who also extended the conjecture to Bloch SU(2) spin-coherent states for
every angular momentum . This conjecture is proved here. We also recall our
1991 extension of the Wehrl map to a quantum channel from to , with corresponding to the Wehrl map to classical densities.
For each and we show that the minimal output entropy for
these channels occurs for a coherent state. We also show that coherent
states both Glauber and Bloch minimize any concave functional, not just
entropy.Comment: Version 2 only minor change
Shell-model calculations of neutrino scattering from 12C
Neutrino reaction cross-sections, , ,
-capture and photoabsorption rates on C are computed within a
large-basis shell-model framework, which included excitations up to
. When ground-state correlations are included with an open
-shell the predictions of the calculations are in reasonable agreement with
most of the experimental results for these reactions. Woods-Saxon radial wave
functions are used, with their asymptotic forms matched to the experimental
separation energies for bound states, and matched to a binding energy of 0.01
MeV for unbound states. For comparison purposes, some results are given for
harmonic oscillator radial functions. Closest agreement between theory and
experiment is achieved with unrestricted shell-model configurations and
Woods-Saxon radial functions. We obtain for the neutrino-absorption inclusive
cross sections: cm for the
decay-in-flight flux in agreement with the LSND datum of
cm; and cm for the decay-at-rest flux, less than the
experimental result of cm.Comment: 19 pages. ReVTeX. No figure
Evidence for nu_mu -> nu_e Oscillations from Pion Decay in Flight Neutrinos
A search for nu_mu -> nu_e oscillations has been conducted at the Los Alamos
Meson Physics Facility using nu_mu from pi^+ decay in flight. An excess in the
number of beam-related events from the C(nu_e,e^-)X inclusive reaction is
observed. The excess is too large to be explained by normal nu_e contamination
in the beam at a confidence level greater than 99%. If interpreted as an
oscillation signal, the observed oscillation probability of (2.6 +- 1.0 +- 0.5)
x 10^{-3} is consistent with the previously reported nu_mu_bar -> nu_e_bar
oscillation evidence from LSND.Comment: 70 pages (LaTeX), 32 figures (PostScript), submitted to Phys. Rev. C.
Additional information at http://nu1.lampf.lanl.gov/~lsn
Measurements of Charged Current Reactions of on
Charged Current reactions of on have been studied using a
decay-at-rest beam at the Los Alamos Neutron Science Center.
The cross section for the exclusive reaction
was measured to be cm. The observed
energy dependence of the cross section and angular distribution of the outgoing
electron agree well with theoretical expectations. Measurements are also
presented for inclusive transitions to excited states,
and compared with theoretical expectations. The
measured cross section, cm, is somewhat
lower than previous measurements and than a continuum random phase
approximation calculation. It is in better agreement with a recent shell model
calculation.Comment: 34 pages, 18 figures, accepted to PRC, replaced with the accepted on
Evidence for Neutrino Oscillations from Muon Decay at Rest
A search for nu_bar_mu to nu_bar_e oscillations has been conducted at the Los
Alamos Meson Physics Facility using nu_bar_mu from mu+ decay at rest. The
nu_bar_e are detected via the reaction (nu_bar_e,p) -> (e+,n), correlated with
the 2.2 MeV gamma from (n,p) -> (d,gamma). The use of tight cuts to identify e+
events with correlated gamma rays yields 22 events with e+ energy between 36
and 60 MeV and only 4.6 (+/- 0.6) background events. The probability that this
excess is due entirely to a statistical fluctuation is 4.1E-08. A chi^2 fit to
the entire e+ sample results in a total excess of 51.8 (+18.7) (-16.9) (+/-
8.0) events with e+ energy between 20 and 60 MeV. If attributed to nu_bar_mu ->
nu_bar_e oscillations, this corresponds to an oscillation probability (averaged
over the experimental energy and spatial acceptance) of 0.0031 (+0.0011)
(-0.0010) (+/- 0.0005).Comment: 57 pages, 34 figures, revtex, additional information available at
http://nu1.lampf.lanl.gov/~lsnd
Microscopic theories of neutrino-^{12}C reactions
In view of the recent experiments on neutrino oscillations performed by the
LSND and KARMEN collaborations as well as of future experiments, we present new
theoretical results of the flux averaged and
cross sections. The approaches used are
charge-exchange RPA, charge-exchange RPA among quasi-particles (QRPA) and the
Shell Model. With a large-scale shell model calculation the exclusive cross
sections are in nice agreement with the experimental values for both reactions.
The inclusive cross section for coming from the decay-in-flight of
is to be compared to the experimental value
of , while the one due to
coming from the decay-at-rest of is which
agrees within experimental error bars with the measured values. The shell model
prediction for the decay-in-flight neutrino cross section is reduced compared
to the RPA one. This is mainly due to the different kind of correlations taken
into account in the calculation of the spin modes and partially due to the
shell-model configuration basis which is not large enough, as we show using
arguments based on sum-rules.Comment: 17 pages, latex, 5 figure
Measurement of event shapes in deep inelastic scattering at HERA
Inclusive event-shape variables have been measured in the current region of
the Breit frame for neutral current deep inelastic ep scattering using an
integrated luminosity of 45.0 pb^-1 collected with the ZEUS detector at HERA.
The variables studied included thrust, jet broadening and invariant jet mass.
The kinematic range covered was 10 < Q^2 < 20,480 GeV^2 and 6.10^-4 < x < 0.6,
where Q^2 is the virtuality of the exchanged boson and x is the Bjorken
variable. The Q dependence of the shape variables has been used in conjunction
with NLO perturbative calculations and the Dokshitzer-Webber non-perturbative
corrections (`power corrections') to investigate the validity of this approach.Comment: 7+25 pages, 6 figure
Evidence for Oscillations from the LSND Experiment at LAMPF
A search for oscillations has been conducted
at the Los Alamos Meson Physics Facility by using from
decay at rest. The are detected via the reaction , correlated with a from
(). The use of tight cuts to identify events with
correlated rays yields 22 events with energy between 36 and
and only background events. A fit to the
events between 20 and yields a total excess of
events. If attributed to oscillations, this corresponds to an oscillation
probability of ()\%.Comment: 4 pages, 3 figures, revtex, psfig. additional information available
at http://nu1.lampf.lanl.gov/~lsnd
Measurement of the open-charm contribution to the diffractive proton structure function
Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has
been measured with the ZEUS detector at HERA using an integrated luminosity of
82 pb^{-1}. Diffractive events were identified by the presence of a large
rapidity gap in the final state. Differential cross sections have been measured
in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035,
beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross
sections are compared to theoretical predictions. The results are presented in
terms of the open-charm contribution to the diffractive proton structure
function. The data demonstrate a strong sensitivity to the diffractive parton
densities.Comment: 35 pages, 11 figures, 6 table
Measurements of the reactions 12C + nu_e -> e- + 12N g.s. and 12C + nu_e -> e- + 12N
Charged current reactions of nu_e on 12C have been studied using a mu
decay-at-rest nu_e beam from the Los Alamos Meson Physics Facility. More than
500 events from the exclusive reaction 12C + nu_e -> e- + 12N g.s. were
measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed
energy dependence of the cross section and the angular distribution of the
outgoing electron agree well with theoretical expectations. Measurements are
also presented for inclusive transitions to 12N excited states, 12C + nu_e ->
e- + 12N and compared with theoretical expectations. Results are consistent
with a recent Continuum Random Phase Approximation (CRPA) calculation.Comment: Figures included with psfi
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