Search results for "Magnetic form factor"

Parity Violating Electron Scattering at the MAMI Facility in Mainz

2005

We report here on a new measurement of the parity violating (PV) asymmetry in the scattering of polarized electrons on unpolarized protons performed with the setup of the A4-collaboration at the MAMI accelerator facility in Mainz. This experiment is the first to use counting techniques in a parity violation experiment. The kinematics of the experiment is complementary to the earlier measurements of the SAMPLE collaboration at the MIT Bates accelerator and the HAPPEX collaboration at Jefferson Lab. After discussing the experimental context of the experiments, the setup at MAMI and preliminary results are presented.

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…

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.

The neutron electric form factor and quasi-elastic electron-deuteron scattering

2008

Measurement of the Neutron Electric to Magnetic Form Factor Ratio atQ2=1.58  GeV2Using the ReactionHe→3(e→,e′n)pp

2013

A measurement of beam helicity asymmetries in the reaction $^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}(\stackrel{\ensuremath{\rightarrow}}{e},{e}^{\ensuremath{'}}n)pp$ is performed at the Mainz Microtron in quasielastic kinematics to determine the electric to magnetic form factor ratio of the neutron ${G}_{E}^{n}/{G}_{M}^{n}$ at a four-momentum transfer ${Q}^{2}=1.58\text{ }\text{ }{\mathrm{GeV}}^{2}$. Longitudinally polarized electrons are scattered on a highly polarized $^{3}\mathrm{He}$ gas target. The scattered electrons are detected with a high-resolution magnetic spectrometer, and the ejected neutrons are detected with a dedicated neutron detector composed of scintillator ba…

Measurement of the Charge-Averaged Elastic Lepton-Proton Scattering Cross Section by the OLYMPUS Experiment

2020

Physical review letters 126(16), 162501 (1-6) (2021). doi:10.1103/PhysRevLett.126.162501

Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII

2021

Physics letters / B 817, 136328 (2021). doi:10.1016/j.physletb.2021.136328

Electromagnetic form factors of the nucleon in a relativistic quark pair creation model

2001

We study the effects of the | qqq q\bar{q} > component of the hadronic wave function on the description of the electromagnetic structure of the nucleon. Starting with a qqq baryonic wave function which describes the baryonic and mesonic low energy spectrum, the extra q\bar{q} pair is generated through a relativistic version of the 3P_0 model. It is shown that this model leads to a renormalization of the quark mass that allows one to construct a conserved electromagnetic current. We conclude that these dynamical relativistic corrections play an important role in reproducing the Q2 dependence of the electromagnetic form factors at low Q^2.

Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering Determined by the OLYMPUS Experiment

2017

The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, $R_{2\gamma}$, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01~GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of $\approx 20\degree$ to $80\degree$. The relative luminosity between the two beam species was mo…