Search results for "quantum electrodynamics"

Contributions of internal nucleon structure to the nuclear charge and current operators

1983

The relativistic pair current and contributions of nucleon isobars are evaluated in the constituent-quark model. Isovector charge and isoscalar current contributions change substantially compared to previous calculations. The magnetic form factor of the deuteron and the charge form factors of3He and3H are modifed significantly and the previously predicted large differences in the form factors of3He and3H are considerably reduced.

Three-Body Analysis of Incoherent Photoproduction of η Mesons on the Deuteron near Threshold

2003

The importance of three-body dynamics in the ηnp system in elastic and inelastic η-deuteron scattering as well as coherent and incoherent η photo-production on the deuteron in the energy region from threshold up to 30 MeV above has been investigated. It is shown that a restriction to first order rescattering with respect to the NN- and ηN-final state interactions, i.e., restriction to rescattering in the two-body subsystems, does not give a sufficiently accurate approximation to the s-wave reaction amplitude and that higher order terms, as described by the three-body dynamics give very substantial contributions.

E0 suppression in pion photoproduction on 13C

1990

Abstract Recently measured anomalously low cross sections for 13 C(γ, π − ) 13 N at low energy and θ π lab = 90° 0761 have been analyzed in a DWIA calculation. It has been found that the EO contribution alone is able to explain the data, so that the M1 cross section is expected to vanish. Using constraints from recent magnetic electron scattering, an explanation is possible by assuming a significantly lower reduced density matrix element for spin-flip isovector transitions with angular momentum L = 2 than predicted by Cohen and Kurath.

Exchange currents in electric transitions and the r�le of siegert's theorem: A case study in deuteron photodisintegration

1981

The size of exchange corrections to electric transitions is investigated for deuteron photodisintegration. Large contributions are found in El transitions, which become dominant above 40 MeV. Most of them are already included by using Siegert's theorem together with classical one-body operators. Higher multipoles are only little affected except for rather high energies. The Born approximation for the final states gives in general a poor description.

S11 RESONANCES IN A COUPLED-CHANNEL DYNAMICAL MODEL

2005

A self-consistent analysis of pion scattering and pion photoproduction within a coupled channels dynamical model is presented. The results indicate the existence of a third and a fourth S11 resonance with the masses 1846±47 and 2113±70 MeV . In the case of pion photoproduction, we found that background contributions to the imaginary part of the S-wave multipole become large and negative in the region of the S11(1535) resonance. Due to this fact, much larger resonance contributions are required in order to explain the results of the recent multipole analysis. For the first S11(1535) resonance we obtain a value of 72±2×10-3 GeV -1/2 for the electromagnetic helicity amplitude A1/2.

Disappearance of zero sound in asymmetric nuclear matter

1997

Abstract We investigate the thermal RPA response of asymmetric nuclear matter interacting through a Skyrme interaction. For every spin-isospin channel, the evolution of the zero sound as a function of both neutron excess and temperature is analyzed.

Model-dependence of the γZ-dispersion correction to the proton's weak charge

2013

We analyze the dispersion correction to elastic parity violating electron-proton scattering due to γZ exchange and theoretical uncertainties associated with this correction. The new Standard Model prediction for the weak charge of the proton in the kinematics of the Q-Weak experiment, QWp = (0.0767±0.0008±0.0020γZ), the latter error being dominated by the uncertainty in the isospin structure of the inclusive cross-section.

A Generic High-Dose-Rate 192Ir Source Model for Model-Based Dose Calculation Methods in Brachytherapy Beyond the TG-43 Formalism

2013

Towards a Thermodynamic Description of Supercontinuum Generation

2009

Based on the kinetic wave theory, we describe continuous-wave supercontinuum generation as a thermalization process, i.e., an irreversible evolution of the optical field towards a state of maximum nonequilibrium entropy.

Event-by-event fluctuations in a perturbative QCD plus saturation plus hydrodynamics model : Determining QCD matter shear viscosity in ultrarelativis…

2016

We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading-order perturbative QCD using a saturation conjecture to control soft-particle production and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries against the LHC and RHIC measurements. We compare also the computed event-by-event probability distribut…