5,641 research outputs found
Asymptotic behavior of nucleon electromagnetic form factors in time-like region
We study the asymptotic behavior of the ratio of Pauli and Dirac
electromagnetic nucleon form factors, , in time-like region for
different parametrizations built for the space-like region. We investigate how
fast the ratio approaches the asymptotic limits according to the
Phragm\`en-Lindel\"of theorem. We show that the QCD-inspired logarithmic
behavior of this ratio results in very far asymptotics, experimentally
unachievable. This is also confirmed by the normal component of the nucleon
polarization, , in (in collisions of unpolarized
leptons), which is a very interesting observable, with respect to this theorem.
Finally we observe that the 1/Q parametrization of contradicts this
theorem.Comment: 9 pages, 1 figur
Polarization observables in lepton-deuteron elastic scattering including the lepton mass
Expressions for the unpolarized differential cross section and for various
polarization observables in the lepton-deuteron elastic scattering, , , , , have been obtained in one-photon-exchange
approximation, taking into account the lepton mass. Polarization effects have
been investigated for the case of a polarized lepton beam and polarized
deuteron target which can have vector or tensor polarization. Numerical
estimations of the lepton mass effects have been done for the unpolarized
differential cross section and for some polarization observables and applied to
the case of low energy muon deuteron elastic scattering.Comment: 29 pages, 6 figur
The fate of failed renal homografts retained after retransplantation
The fate of nonfunctioning or poorly functioning renal homografts which were left in situ at retransplantation was studied in 28 patients. In one recipient, lethal septicemia developed secondary to necrosis as well as infection of a retained intraabdominal graft. In three other patients, subsequent symptoms developed from retained extraperitoneal pelvic grafts, and these kidneys were removed without complication. It is suggested that grafts placed extraperitoneally can be left in place if retransplantation becomes necessary, provided that there is careful follow up study for signs of necrosis or infection. Removal of the kidney graft then may be performed electively at a later time, or this may never become necessary in a significant number of patients
Model independent study of massive lepton elastic scattering on the proton, beyond the Born approximation
Model independent expressions for all polarization observables in elastic scattering are obtained, taking into account the lepton mass and
including the two-photon exchange contribution. The spin structure of the
matrix element is parametrized in terms of six independent complex amplitudes,
functions of two independent kinematical variables. General statements about
the influence of the two--photon--exchange terms on the differential cross
section and on polarization observables are given. Polarization effects have
been investigated for the case of a longitudinally polarized lepton beam and
polarized nucleon in the final state.Comment: 28 pages, 3 figure
Quantum correction to tiny vacuum expectation value in two Higgs doublet model for Dirac neutrino mass
We study a Dirac neutrino mass model of Davidson and Logan. In the model, the
smallness of the neutrino mass is originated from the small vacuum expectation
value of the second Higgs of two Higgs doublets. We study the one loop
effective potential of the Higgs sector and examine how the small vacuum
expectation is stable under the radiative correction. By deriving formulae of
the radiative correction, we numerically study how large the one loop
correction is and show how it depends on the quadratic mass terms and quartic
couplings of the Higgs potential. The correction changes depending on the
various scenarios for extra Higgs mass spectrum.Comment: 27 pages,5 figures. The version corresponds to the revised one
accepted in PRD. In version 4, we have corrected errors of Fig.5 which
reflects the errata of PRD versio
Neutron electric form factor at large momentum transfer
Based on the recent, high precision data for elastic electron scattering from
protons and deuterons, at relatively large momentum transfer , we
determine the neutron electric form factor up to GeV. The values
obtained from the data (in the framework of the nonrelativistic impulse
approximation) are larger than commonly assumed and are in good agreement with
the Gari-Kr\"umpelmann parametrization of the nucleon electromagnetic form
factors.Comment: 11 pages 2 figure
Radiative corrections for electron proton elastic scattering taking into account high orders and hard photon emission
We investigate the effect of high order radiative corrections in unpolarized
electron proton elastic scattering and compare with the calculations at lowest
order, which are usually applied to experimental data. Particular attention is
devoted to the dependence of radiative corrections, which is
directly related to the electric proton form factor. We consider in particular
the effects of the interference terms for soft and hard photon emission. Both
quadratic amplitude describing the collinear emission along the scattered
electron as well as the interference with the amplitudes of emission from the
initial electron and the emission from protons are important in leading and
next to leading approximation and they may compensate in particular kinematical
conditions.Comment: 16 pages, 11 figures, 1 tabl
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