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, $F_2/F_1$, in time-like region for different parametrizations built for the space-like region. We investigate how fast the ratio $F_2/F_1$ 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, $P_y$, in $e^++e^-\to N+\bar{N}$ (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 $F_2/F_1$ 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, $\ell+D\to \ell+D$, $\ell=e$, $\mu$, $\tau$, 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 $\mu+p\to \mu+p$ 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 $Q^2$, we determine the neutron electric form factor up to $Q^2=3.5$ GeV$^2$. 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 $\epsilon$ 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