12,764 research outputs found
Parity-Violating Electron Scattering from the Pion-Correlated Relativistic Fermi Gas
Parity-violating quasielastic electron scattering is studied within the
context of the relativistic Fermi gas and its extensions to include the effects
of pionic correlations and meson-exchange currents. The work builds on previous
studies using the same model; here the part of the parity-violating asymmetry
that contains axial-vector hadronic currents is developed in detail using those
previous studies and a link is provided to the transverse vector-isovector
response. Various integrated observables are constructed from the differential
asymmetry. These include an asymmetry averaged over the quasielastic peak, as
well as the difference of the asymmetry integrated to the left and right of the
peak -- the latter is shown to be optimal for bringing out the nature of the
pionic correlations. Special weighted integrals involving the differential
asymmetry and electromagnetic cross section, based on the concepts of y-scaling
and sum rules, are constructed and shown to be suited to studies of the
single-nucleon form factor content in the problem, in particular, to
determinations of the isovector/axial-vector and electric strangeness form
factors. Comparisons are also made with recent predictions made on the basis of
relativistic mean-field theory.Comment: 28 pages, LATeX, 13 figures (tar-compressed postscript files,
available from the authors), MIT preprint CTP#222
Parity-violating longitudinal response
The longitudinal quasielastic parity-violating electron scattering response
is explored within the context of a model that builds antisymmetrized RPA-HF
correlations on a relativistic Fermi gas basis. The large sensitivity to
nuclear dynamics of this observable, found in previous studies where only
pionic correlations were included, is shown to survive in the present model
where the effects from pion, rho, sigma and omega exchange in a version of the
Bonn potential are incorporated. Through an intricate diagrammatic
cancellation/filtration mechanism the longitudinal parity-violating response
turns out to be close to the one obtained in first-order perturbation theory
with the pion alone. Finally, in accord with our previous work, the
parity-violating response is seen to display appreciable sensitivity to the
electric strangeness content of the nucleon, especially at high momentum
transfer.Comment: 13 pages, uses REVTeX and epsfig, 10 postscript figures; a postscript
version of the paper is available by anonymous ftp at
ftp://carmen.to.infn.it/pub/barbaro/papers/951
Influence of nucleonic motion in Relativistic Fermi Gas inclusive responses
Impulsive hadronic descriptions of electroweak processes in nuclei involve
two distinctly different elements: one stems from the nuclear many-body physics
--- the medium --- which is rather similar for the various inclusive response
functions, and the other embodies the responses of the hadrons themselves to
the electroweak probe and varies with the channel selected. In this letter we
investigate within the context of the relativistic Fermi gas in both the
quasi-elastic and regimes the interplay between these two
elements. Specifically, we focus on expansions in the one small parameter in
the problem, namely, the momentum of a nucleon in the initial wave function
compared with the hadronic scale, the nucleon mass. Both parity-conserving and
-violating inclusive responses are studied and the interplay between
longitudinal () and transverse ( and ) contributions is highlighted.Comment: 11 pages, 1 figur
Nuclear response functions for the N-N*(1440) transition
Parity-conserving and -violating response functions are computed for the
inclusive electroexcitation of the N*(1440)(Roper) resonance in nuclear matter
modeled as a relativistic Fermi gas. Using various empirical parameterizations
and theoretical models of the N-N*(1440) transition form factors, the
sensitivity of the response functions to details of the structure of the Roper
resonance is investigated. The possibility of disentangling this resonance from
the contribution of Delta electroproduction in nuclei is addressed. Finally,
the contributions of the Roper resonance to the longitudinal scaling function
and to the Coulomb sum rule are also explored.Comment: 25 pages, 10 figures. Minor changes in the Introduction. Accepted in
NP
Parity violation in quasielastic electron-nucleus scattering within the relativistic impulse approximation
We study parity violation in quasielastic (QE) electron-nucleus scattering
using the relativistic impulse approximation. Different fully relativistic
approaches have been considered to estimate the effects associated with the
final-state interactions. We have computed the parity-violating quasielastic
(PVQE) asymmetry and have analyzed its sensitivity to the different ingredients
that enter in the description of the reaction mechanism: final-state
interactions, nucleon off-shellness effects, current gauge ambiguities.
Particular attention has been paid to the description of the weak neutral
current form factors. The PVQE asymmetry is proven to be an excellent
observable when the goal is to get precise information on the axial-vector
sector of the weak neutral current. Specifically, from measurements of the
asymmetry at backward scattering angles good knowledge of the radiative
corrections entering in the isovector axial-vector sector can be gained.
Finally, scaling properties shown by the interference nuclear
responses are also analyzed.Comment: 15 pages, 11 figure
Time-Series Analysis of Super-Kamiokande Measurements of the Solar Neutrino Flux
The Super-Kamiokande Consortium has recently released data suitable for
time-series analysis. The binning is highly regular: the power spectrum of the
acquisition times has a huge peak (power S > 120) at the frequency (in cycles
per year) 35.98 (period 10.15 days), where power measurements are such that the
probability of obtaining a peak of strength S or more by chance at a specified
frequency is exp(-S). This inevitably leads to severe aliasing of the power
spectrum. The strongest peak in the range 0 - 100 in a power spectrum formed by
a likelihood procedure is at 26.57 (period 13.75 days) with S = 11.26. For the
range 0 - 40, the second-strongest peak is at 9.42 (period 38.82 days) with S =
7.3. Since 26.57 + 9.42 = 35.99, we conclude that the weaker peak at 9.42 is an
alias of the stronger peak at 26.57. We note that 26.57 falls in the band 26.36
- 27.66, formed from twice the range of synodic rotation frequencies of an
equatorial section of the Sun for normalized radius larger than 0.1.
Oscillations at twice the rotation frequency, attributable to "m = 2"
structures, are not uncommon in solar data. We find from the shuffle test that
the probability of obtaining a peak of S = 11.26 or more by chance in this band
is 0.1 %. This new result therefore supports at the 99.9% confidence level
previous evidence, found in Homestake and GALLEX-GNO data, for rotational
modulation of the solar neutrino flux. The frequency 25.57 points to a source
of modulation at or near the tachocline.Comment: 15 pages, 8 figure
Decomposition of entanglement entropy in lattice gauge theory
We consider entanglement entropy between regions of space in lattice gauge
theory. The Hilbert space corresponding to a region of space includes edge
states that transform nontrivially under gauge transformations. By decomposing
the edge states in irreducible representations of the gauge group, the entropy
of an arbitrary state is expressed as the sum of three positive terms: a term
associated with the classical Shannon entropy of the distribution of boundary
representations, a term that appears only for non-Abelian gauge theories and
depends on the dimension of the boundary representations, and a term
representing nonlocal correlations. The first two terms are the entropy of the
edge states, and depend only on observables measurable at the boundary. These
results are applied to several examples of lattice gauge theory states,
including the ground state in the strong coupling expansion of Kogut and
Susskind. In all these examples we find that the entropy of the edge states is
the dominant contribution to the entanglement entropy.Comment: 8 pages. v2: added references, expanded derivation, matches PRD
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