Search results for " form factor"

Model independent determination of GEn from the reaction

1988

Abstract Electrodisintegration of vector polarized deuterium by longitudinally polarized electrons offers a possibility for measuring the neutron electric form factor G En . In principle, the electron asymmetry is essentially proportional to G En when quasi-free kinematics are employed. We investigate the model dependence of this result by employing several NN force models both with and without meson-exchange and isobar corrections. We find the asymmetry to be remarkably model independent near the neutron quasi-elastic peak.

Quasi-elastic electron-deuteron scattering and the electric form factor of the neutron

1978

Electromagnetic nucleon form factors in the spacelike region

1997

Abstract Form factors for elastic electron scattering parametrise the collective response of a struck object and provide information vital for the understanding of its ground state. The quality of existing data for the neutron is much behind that for the proton; it will now benefit from coincidence experiments at modern cw accelerators. For the electric form factor the scattering of high energy polarised electrons from polarised targets or the spin transfer to the recoiling neutron from unpolarised targets now exhibits its full potential in running experiments and delivers first results.

The E0 transition in pion photoproduction and radiative pion capture on 13C

1990

Abstract The E0 contribution of the reactions 13 C( γ , π − ) 13 N g.s. as well as 13 C( π + , γ ) 13 N g.s. has been calculated in an extended shell-model space using a nonlocal DWIA framework. A realistic shell-model wave function that includes configurations from the (2s, 1d) as well as the (2p, 1f) shells has been employed for the A = 13 system and leads to a significant suppression of the E0 transition. The large suppression can be understood in terms of the E0 radial integrals over the relevant single-particle densities. A variety of angular distributions demonstrates the good overall agreement with experimental data.

Measurement of the magnetic form factor of the neutron

1993

The [sup 2]H([ital e],[ital e][prime][ital n])[sup 1]H quasielastic cross section was measured at [ital Q][sup 2] values of 0.109, 0.176, and 0.255 (GeV/[ital c])[sup 2]. The neutron detection efficiency was determined by the associated particle technique with the [sup 2]H([gamma],[ital pn]) reaction for each of the three neutron kinetic energies. These [sup 2]H([ital e],[ital e][prime][ital n]) measurements of the coincidence cross sections are the first at low [ital Q][sup 2]. The cross sections are sensitive primarily to the neutron magnetic form factor [ital G][sub [ital M]][sup [ital n]] at these kinematics. The extracted [ital G][sub [ital M]][sup [ital n]] values have smaller uncerta…

Baryon transition form factors at the pole

2016

Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_M$, $G_E$, and $G_C$ form factors for the $\Delta(1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^2=5$ GeV$^2$. We also explore…

BLM scale for the pion transition form factor

2001

The NLO Brodsky-Lepage-Mackenzie (BLM) scale for the pion transition form factor has been determined. To achieve that, a consistent calculation up to nf-proportional NNLO contributions to both the hard-scattering amplitude and the perturbatively calculable part of the pion distribution amplitude has been performed. By combining and matching the results obtained for these two amplitudes, a proper cancellation of collinear singularities has been established and the gamma5 ambiguity problem (related to the use of the dimensional regularization method) has been resolved by using the naive-gamma5 as well as the 't Hooft-Veltman (HV) schemes. It has been demonstrated that the prediction for the p…

Polarization Effects in Photo- and Electrodisintegration of the Deuteron

1986

Polarization observables in deuteron photodisintegration like photon and target asymmetries and one- and two nucleon polarization of the final state are studied with respect to their sensitivity to subnuclear degrees of freedom. Furthermore it is shown that the electric form factor of the neutron has a sizeable influence on the polarization asymmetry in d(\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}}{e}\),e’n)p with polarized electrons. Uncertainties arising from potential model dependence are discussed.

Reply to "Comment on `Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution'"

2016

To comply with the critique of the Comment [J. Arrington, arXiv:1602.01461], we consider another modification of the proton electric form factor, which resolves the "proton-radius puzzle". The proposed modification satisfies all the consistency criteria put forward in the Comment, and yet has a similar impact on the puzzle as that of the original paper. Contrary to the concluding statement of the Comment, it is not difficult to find an ad hoc modification of the form factor at low $Q$ that resolves the discrepancy and is consistent with analyticity constraints. We emphasize once again that we do not consider such an ad hoc modification of the proton form factor to be a solution of the puzzl…

Light-cone quark model with spin force for the nucleon and Δ (1232)

1992

Abstract Electromagnetic structure functions for the nucleon, static observables for the nucleon and N → Δ (1232) transition form factors are calculated in a relativistic constituent quark model on the light cone. The model simulates the main effect of the spin force between quarks in terms of smaller (and lighter) scalar ud diquarks in the nucleon. The polarized proton structure function is found to agree with the EMC data.