72,054 research outputs found
-Particle Spectrum in the Reaction p+B
Using a simple phenomenological parametrization of the reaction amplitude we
calculated -particle spectrum in the reaction p+B at the resonance proton energy 675 KeV. The parametrization
includes Breit-Wigner factor with an energy dependent width for intermediate
state and the Coulomb and the centrifugal factors in -particle
emission vertexes. The shape of the spectrum consists of a well defined peak
corresponding to emission of the primary and a flat shoulder going
down to very low energy. We found that below 1.5 MeV there are 17.5% of
's and below 1 MeV there are 11% of them.Comment: 6 pages, 3 figure
Block-block entanglement and quantum phase transitions in one-dimensional extended Hubbard model
In this paper, we study block-block entanglement in the ground state of
one-dimensional extended Hubbard model. Our results show that the phase diagram
derived from the block-block entanglement manifests richer structure than that
of the local (single site) entanglement because it comprises nonlocal
correlation. Besides phases characterized by the charge-density-wave, the
spin-density-wave, and phase-separation, which can be sketched out by the local
entanglement, singlet superconductivity phase could be identified on the
contour map of the block-block entanglement. Scaling analysis shows that behavior of the block-block entanglement may exist in both
non-critical and the critical regions, while some local extremum are induced by
the finite-size effect. We also study the block-block entanglement defined in
the momentum space and discuss its relation to the phase transition from
singlet superconducting state to the charge-density-wave state.Comment: 8 pages, 9 figure
Tau Neutrino Astronomy in GeV Energies
We point out the opportunity of the tau neutrino astronomy for the neutrino
energy E ranging between 10 GeV and 10^3 GeV. In this energy range, the
intrinsic tau neutrino production is suppressed relative to the intrinsic muon
neutrino production. Any sizable tau neutrino flux may thus arise because of
the \nu_{\mu}\to \nu_{\tau} neutrino oscillations only. It is demonstrated
that, in the presence of the neutrino oscillations, consideration of the
neutrino flavor dependence in the background atmospheric neutrino flux leads to
the drastically different prospects between the observation of the
astrophysical muon neutrinos and that of the astrophysical tau neutrinos.
Taking the galactic-plane neutrino flux as the targeted astrophysical source,
we have found that the galactic-plane tau neutrino flux dominates over the
atmospheric tau neutrino flux for E > 10 GeV. Hence, the galactic-plane can at
least in principle be seen through the tau neutrinos with energies just greater
than 10 GeV. In a sharp contrast, the galactic-plane muon neutrino flux is
overwhelmed by its atmospheric background until E > 10^6 GeV.Comment: major revision of text and two new figures, to appear in PR
Muon Pair Production by Electron-Photon Scatterings
The cross section for muon pair productions by electrons scattering over
photons, , is calculated analytically in the leading order. It is
pointed out that for the center-of-mass energy range, ,
the cross section for is less than b. The differential
energy spectrum for either of the resulting muons is given for the purpose of
high-energy neutrino astronomy. An implication of our result for a recent
suggestion concerning the high-energy cosmic neutrino generation through this
muon pair is discussed.Comment: a comment added, to appear in Phys. Rev. D, Rapid Communicatio
Entanglement and quantum phase transition in the extended Hubbard model
We study quantum entanglement in one-dimensional correlated fermionic system.
Our results show, for the first time, that entanglement can be used to identify
quantum phase transitions in fermionic systems.Comment: 5 pages, 4 figure
Production and Decay of the Ge73-m Metastable State in a Low-Background Germanium Detector
The metastable states decay with a very characteristic signature
which allow them to be tagged event-by-event. Studies were performed using data
taken with a high-purity germanium detector in a low-background laboratory near
a nuclear power reactor core where \nuebar-flux was . The measured average and equilibrium production rates of
were and ,
respectively. The production channels were studied and identified. By studying
the difference in the production of between the reactor ON and OFF
spectra, the limiting sensitivities at the range of for the cross-sections of neutrino-induced nuclear
transitions were derived. The dominant background are due to -decays of
cosmic-ray induced Ga. The prospects of enhancing the sensitivities at
underground locations are discussed.Comment: 16 pages, 10 figure
Configuration-Space Location of the Entanglement between Two Subsystems
In this paper we address the question: where in configuration space is the
entanglement between two particles located? We present a thought-experiment,
equally applicable to discrete or continuous-variable systems, in which one or
both parties makes a preliminary measurement of the state with only enough
resolution to determine whether or not the particle resides in a chosen region,
before attempting to make use of the entanglement. We argue that this provides
an operational answer to the question of how much entanglement was originally
located within the chosen region. We illustrate the approach in a spin system,
and also in a pair of coupled harmonic oscillators. Our approach is
particularly simple to implement for pure states, since in this case the
sub-ensemble in which the system is definitely located in the restricted region
after the measurement is also pure, and hence its entanglement can be simply
characterised by the entropy of the reduced density operators. For our spin
example we present results showing how the entanglement varies as a function of
the parameters of the initial state; for the continuous case, we find also how
it depends on the location and size of the chosen regions. Hence we show that
the distribution of entanglement is very different from the distribution of the
classical correlations.Comment: RevTex, 12 pages, 9 figures (28 files). Modifications in response to
journal referee
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