134 research outputs found
Spin-dependent neutrino-induced nucleon knockout
We study neutrino-induced nucleon knockout off atomic nuclei and examine the
polarization properties of the ejectile. A detailed study of the spin
dependence of the outgoing nucleon is presented. The numerical results are
derived within a non-relativistic plane-wave impulse-approximation approach.
Our calculations reveal large polarization asymmetries, and clear
dissimilarities between neutrino- and antineutrino-induced reactions. They
reflect the fact that neutrino-induced nucleon knockout is dominated by the
transverse axial current and gains its major contributions from forward nucleon
emission and backward lepton scattering.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.
Solar neutrino interactions: Using charged currents at SNO to tell neutral currents at Super-Kamiokande
In the presence of flavor oscillations, muon and tau neutrinos can contribute
to the Super-Kamiokande (SK) solar neutrino signal through the neutral current
process \nu_{\mu,\tau} e^{-}\to \nu_{\mu,\tau} e^{-}. We show how to separate
the \nu_e and \nu_{\mu,\tau} event rates in SK in a model independent way, by
using the rate of the charged current process \nu_e d \to p p e^{-} from the
Sudbury Neutrino Observatory (SNO) experiment, with an appropriate choice of
the SK and SNO energy thresholds. Under the additional hypothesis of no
oscillations into sterile states, we also show how to determine the absolute
^{8}B neutrino flux from the same data set, independently of the \nu_e survival
probability.Comment: 14 pages (RevTeX), incl. 3 figures (epsf), submitted to Phys. ReV.
Neutrino Oscillations and Moments of Electron Spectra
We show that the effects of neutrino oscillations on 8B solar neutrinos are
described well by the first two moments (the average and the variance) of the
energy distribution of scattered or recoil electrons. For the SuperKamiokande
and the Sudbury Neutrino Observatory experiments, the differences between the
moments calculated with oscillations and the standard, no-oscillation moments
are greater than 3 standard deviations for a significant fraction of the
neutrino mass-mixing (Delta m^2, sin^2 2 theta) parameter space.Comment: 16 pages, Latex, text+figures. To be published in Physical Review C,
January 199
What about a beta-beam facility for low energy neutrinos?
A novel method to produce neutrino beams has recently been proposed : the
beta-beams. This method consists in using the beta-decay of boosted radioactive
nuclei to obtain an intense, collimated and pure neutrino beam. Here we propose
to exploit the beta-beam concept to produce neutrino beams of low energy. We
discuss the applications of such a facility as well as its importance for
different domains of physics. We focus, in particular, on neutrino-nucleus
interaction studies of interest for various open issues in astrophysics,
nuclear and particle physics. We suggest possible sites for a low energy
beta-beam facility.Comment: 4 pages, 1 figur
Luminescence and formation of alkali-halide ionic excimers in solid Ne and Ar
Transitions from ionic states A²⁺X– of alkalihalides CsF, CsCl and RbF isolated in solid Ne and Ar films recorded under pulsed e-beam excitation are studied. The B(²∑₁/₂)-X(²∑₁/₂) and C(²П₃/₂)-A(²П₃/₂) luminescence bands of Cs2+F– (196.5 nm, 227 nm), Cs²⁺Cl– (220.1 nm, 249.2 nm) and Rb²⁺F– (136 nm) in Ne, and a weakerB–X emission of Cs²⁺F– (211.2 nm) in Ar are identified. For CsF the depopulation of the A²⁺X– state is dominated by the radiative decay. A ratio of the recorded exciplex emission intensities of I(CsF)/I(CsCl)/I(RbF) = 20/5/1 reflects the luminescence efficiency and for RbF and CsCl a competitive emission channel due to predissociation in the A²⁺X⁻(B²∑₁/₂) state is observed. For these molecules an efficient formation of the state X*₂ is confirmed through recording the molecular D`(³П₂g)-A`(³П₂u) transition. A strong dependence of the luminescence intensities on the alkalihalide content reveals quenching at concentrations higher than 0.7%
In-medium meson properties and field transformations
Since the existing calculations of the effective meson mass in nuclear medium
involve approximations, it is important to examine whether they satisfy the
general requirement of the equivalence theorem that the physical observables
should be independent of the choice of field variables. We study here
consequences of nucleon field transformations. As an illustrative case we
consider the in-medium effective pion mass calculated for the s-wave
pion-nucleon interaction in the linear density approximation. We demonstrate
that it is necessary to include the Born term explicitly in order that the
effective pion mass should obey the equivalence theorem.Comment: 10 pages, using RevTeX4. More detailed discussion, references added.
To be published in Phys. Rev.
Sensitivities of Low Energy Reactor Neutrino Experiments
The low energy part of the reactor neutrino spectra has not been
experimentally measured. Its uncertainties limit the sensitivities in certain
reactor neutrino experiments. The origin of these uncertainties are discussed,
and the effects on measurements of neutrino interactions with electrons and
nuclei are studied. Comparisons are made with existing results. In particular,
the discrepancies between previous measurements with Standard Model
expectations can be explained by an under-estimation of the low energy reactor
neutrino spectra. To optimize the experimental sensitivities, measurements for
\nuebar-e cross-sections should focus on events with large (1.5 MeV)
recoil energy while those for neutrino magnetic moment searches should be based
on events 100 keV. The merits and attainable accuracies for
neutrino-electron scattering experiments using artificial neutrino sources are
discussed.Comment: 25 pages, 9 figure
Tests of electron flavor conservation with the Sudbury Neutrino Observatory
We analyze tests of electron flavor conservation that can be performed at the
Sudbury Neutrino Observatory (SNO). These tests, which utilize B solar
neutrinos interacting with deuterium, measure: 1) the shape of the recoil
electron spectrum in charged-current (CC) interactions (the CC spectrum shape);
and 2) the ratio of the number of charged current to neutral current (NC)
events (the CC/NC ratio). We determine standard model predictions for the CC
spectral shape and for the CC/NC ratio, together with realistic estimates of
their errors and the correlations between errors. We consider systematic
uncertainties in the standard neutrino spectrum and in the charged-current and
neutral current cross-sections, the SNO energy resolution and absolute energy
scale, and the SNO detection efficiencies. Assuming that either matter-enhanced
or vacuum neutrino oscillations solve the solar neutrino problems, we calculate
the confidence levels with which electron flavor non-conservation can be
detected using either the CC spectrum shape or the CC/NC ratio, or both. If the
SNO detector works as expected, the neutrino oscillation solutions that
best-fit the results of the four operating solar neutrino experiments can be
distinguished unambiguously from the standard predictions of electron flavor
conservation.Comment: 31 pages (RevTeX) + 10 figures (postscript). Requires epsfig.sty.
Gzipped figures also available at ftp://ftp.sns.ias.edu/pub/lisi/snopaper .
To appear in Phys. Rev.
Supernova neutrinos in the light of FCNC
We study the effect of including flavor changing neutral currents (FCNC) in
the analysis of the neutrino signal of a supernova burst. When we include the
effect of the FCNC which are beyond the standard model (SM) in the study of the
MSW resonant conversion, we obtain dramatic changes in the \Delta
m^2-sin^2(2\theta) probability contours for neutrino detection.Comment: 8 pages in ReVTeX,3 figures. Revised manuscript submitted to Phys.
Rev.
Solar neutrino results and Violation of the Equivalence Principle: An analysis of the existing data and predictions for SNO
Violation of the Equivalence Principle (VEP) can lead to neutrino oscillation
through the non-diagonal coupling of neutrino flavor eigenstates with the
gravitational field. The neutrino energy dependence of this oscillation
probability is different from that of the usual mass-mixing neutrino
oscillations. In this work we explore, in detail, the viability of the VEP
hypothesis as a solution to the solar neutrino problem in a two generation
scenario with both the active and sterile neutrino alternatives, choosing these
states to be massless. To obtain the best-fit values of the oscillation
parameters we perform a chi square analysis for the total rates of solar
neutrinos seen at the Chlorine (Homestake), Gallium (Gallex and SAGE),
Kamiokande, and SuperKamiokande (SK) experiments. We find that the goodness of
these fits is never satisfactory. It markedly improves, especially for VEP
transformation to sterile neutrinos, if the Chlorine result is excluded from
the analysis. The 1117-day SK data for recoil electron spectrum are also
examined for signals of VEP oscillations. For these fits, we consider
variations of the Standard Solar Model by allowing the absolute normalizations
of the 8B and hep neutrinos to vary. Here the fits are quite good but the best
fit values of the parameters are rather different from those from the total
rates fits. A combined fit to the total rates and recoil electron spectrum data
is also performed. We present the 90% confidence limit contours for all the
three analyses mentioned above. The best-fit parameters obtained from the
recoil electron spectrum and the combined analysis of rate and spectrum are
used to predict the charge current and scattering electron spectrum at SNO.Comment: Latex, minor changes in text and in fig.4 and fig.5, to be published
in Phys. Rev.
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