403 research outputs found
Normalization of the covariant three-body bound state vertex function
The normalization condition for the relativistic three nucleon Bethe-Salpeter
and Gross bound state vertex functions is derived, for the first time, directly
from the three body wave equations. It is also shown that the relativistic
normalization condition for the two body Gross bound state vertex function is
identical to the requirement that the bound state charge be conserved, proving
that charge is automatically conserved by this equation.Comment: 24 pages, 9 figures, published version, minor typos correcte
Neutrino-Oxygen CC0 scattering in the SuSAv2-MEC model
We present the predictions of the SuSAv2-MEC model for the double
differential charged-current muonic neutrino (antineutrino) cross section on
water for the T2K neutrino (antineutrino) beam. We validate our model by
comparing with the available inclusive electron scattering data on oxygen and
compare our predictions with the recent T2K -O data, finding
good agreement at all kinematics. We show that the results are very similar to
those obtained for C scattering, except at low energies, and we
comment on the origin of this difference. A factorized spectral function model
of O is also included for purposes of comparison.Comment: 28 pages, 10 figures, JLAB-THY-17-2586. Version 2 accepted for
publication in Journal of Physics G: Nucl. Part. Phy
Origin of Relativistic Effects in the Reaction D(e,e'p)n at GeV Energies
In a series of recent publications, a new approach to the non-relativistic
reduction of the electromagnetic current operator in calculations of
electro-nuclear reactions has been introduced. In one of these papers, the
conjecture that at energies of a few GeV, the bulk of the relativistic effects
comes from the current and not from the nuclear dynamics was made, based on the
large relativistic effects in the transverse-longitudinal response. Here, we
explicitly compare a fully relativistic, manifestly covariant calculation
performed with the Gross equation, with a calculation that uses a
non-relativistic wave function and a fully relativistic current operator. We
find very good agreement up to missing momenta of 400 MeV/c, thus confirming
the previous conjecture. We discuss slight deviations in cross sections for
higher missing momenta and their possible origin, namely p-wave contributions
and off-shell effects.Comment: 25 pages, 11 figure
Elastic e-d Scattering Data and the Deuteron Wave Function
What range of momentum components in the deuteron wave function are available
e d elastic scattering data sensitive to ? This question is addressed within
the context of a model calculation of the deuteron form factors, based on
realistic interactions and currents. It is shown that the data on the ,
, and observables at fm essentially probe
momentum components up to .Comment: 5 figure
Scaling of Dirac Fermions and the WKB approximation
We discuss a new method for obtaining the WKB approximation to the Dirac
equation with a scalar potential and a time-like vector potential. We use the
WKB solutions to investigate the scaling behavior of a confining model for
quark-hadron duality. In this model, a light quark is bound to a heavy di-quark
by a linear scalar potential. Absorption of virtual photons promotes the quark
to bound states. The analog of the parton model for this case is for a virtual
photon to eject the bound, ground-state quark directly into free continuum
states. We compare the scaling limits of the response functions for these two
transitions
Relativistic Effects in the Electromagnetic Current at GeV Energies
We employ a recent approach to the non-relativistic reduction of the
electromagnetic current operator in calculations of electronuclear reactions.
In contrast to the traditional scheme, where approximations are made for the
transferred momentum, transferred energy and initial momentum of the struck
nucleon in obtaining an on-shell inspired form for the current, we treat the
problem exactly for the transferred energy and transferred momentum. We
calculate response functions for the reaction at CEBAF (TJNAF)
energies and find large relativistic corrections. We also show that in Plane
Wave Impulse Approximation, it is always possible to use the full operator, and
we present a comparison of such a limiting case with the results incorporating
relativistic effects to the first order in the initial momentum of the struck
nucleon.Comment: 31 pages, 8 figures, Revte
Vocation, Belongingness, and Balance: A Qualitative Study of Veterinary Student Well-Being
An elevated risk for suicide among veterinarians has stimulated research into the mental health of the veterinary profession, and more recently attention has turned to the veterinary student population. This qualitative study sought to explore UK veterinary students' perceptions and experiences of university life, and to consider how these may affect well-being. Semi-structured interviews were conducted with 18 students from a single UK school who were purposively selected to include perspectives from male, female, graduate-entry, standard-entry (straight from high school), and widening participation students across all 5 years of the program. Three main themes were identified: a deep-rooted vocation, navigating belongingness, and finding balance. Participants described a long-standing goal of becoming a veterinarian, with a determination reflected by often circuitous routes to veterinary school and little or no consideration of alternatives. Although some had been motivated by a love of animals, others were intrinsically interested in the scientific and problem-solving challenges of veterinary medicine. Most expressed strong feelings of empathy with animal owners. The issue of belongingness was central to participants' experiences, with accounts reflecting their efforts to negotiate a sense of belongingness both in student and professional communities. Participants also frequently expressed a degree of acceptance of poor balance between work and relaxation, with indications of a belief that this imbalance could be rectified later. This study helps highlight future avenues for research and supports initiatives aiming to nurture a sense of collegiality among veterinary students as they progress through training and into the profession
Quark-hadron duality in a relativistic, confining model
Quark-hadron duality is an interesting and potentially very useful
phenomenon, as it relates the properly averaged hadronic data to a perturbative
QCD result in some kinematic regions. While duality is well established
experimentally, our current theoretical understanding is still incomplete. We
employ a simple model to qualitatively reproduce all the features of
Bloom-Gilman duality as seen in electron scattering. In particular, we address
the role of relativity, give an explicit analytic proof of the equality of the
hadronic and partonic scaling curves, and show how the transition from coherent
to incoherent scattering takes place.Comment: This paper is dedicated to the memory of our collaborator Nathan
Isgur. (34 pages, 13 figures
Exchange Current Corrections to Neutrino--Nucleus Scattering
Relativistic exchange current corrections to neutrino--nucleus cross sections
are presented assuming non--vanishing strange quark form factors for the
constituent nucleons. For charged current processes the exchange current
corrections can lower the impulse approximation results by 10\% while these
corrections are found to be sensitive to both the nuclear density and the
strange quark axial form factor of the nucleon for neutral current processes.
Implications on the LSND experiment to determine this form factor are
discussed.Comment: 11 pages, 2 figures, revtex 3.0, full postscript version of the file
and figures available at
http://www.nikhefk.nikhef.nl/projects/Theory/preprints/preprints.html To
appear in Phys. Rev. Lett
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