0000000000377205
AUTHOR
Ingo Sick
Measurement of the Recoil Polarization in thep(e→,e′p→)π0Reaction at theΔ(1232)Resonance
The recoil proton polarization has been measured in the $p(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}\stackrel{\ensuremath{\rightarrow}}{p}){\ensuremath{\pi}}^{0}$ reaction in parallel kinematics around $W\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1232\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$, ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.121\phantom{\rule{0ex}{0ex}}(\mathrm{GeV}/c{)}^{2}$, and $\ensuremath{\epsilon}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.718$ using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, ${P}_{x}/{P}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-…
Precise measurements of the neutron magnetic form factor
Abstract The neutron magnetic form factor Gmn has been determined via a measurement of the ratio of cross sections D(e,e′n) and D(e,e′p). The absolute detection efficiency of the neutron detector was measured with high accuracy using tagged neutrons produced from H(n,p)n elastic scattering by means of a high intensity neutron beam. This approach minimizes the model dependence and improves upon the weakest points of previous experiments. Data in the range q2=0.2–0.8 (GeV/c)2 with uncertainties of
The horizontal drift chambers for the focal plane proton-polarimeter of the 3-spectrometer setup at MAMI
Abstract Large-area horizontal drift chambers have been built for use in a proton polarimeter. A gas mixture of 20% argon and 80% ethane is used. The left–right assignment is achieved by measuring the difference of the signals induced on neighboring potential wires. A spatial resolution of 300 μm is achieved.
Measurement of GEp/GMp via polarization transfer at Q2 = 0.4 GeV /c2
The polarization transfer from longitudinally polarized electrons to protons in the elastic scattering p( e, e' p) has been measured around Q2 = 0.4 (GeV/c)2 with the three-spectrometer facility at the Mainz microtron MAMI. From this polarization transfer the ratio G Ep/(G Mp/μp) has been determined. The ratio is found to be slightly less than unity in agreement with recent results from other laboratories and from the Rosenbluth separation of cross-sections measured with unpolarized electrons.
Electromagnetic structure of few-nucleon ground states
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled $\chi$EFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled…
Charge radii and ground state structure of lithium isotopes: Experiment and theory reexamined
Changes in the nuclear charge radii of lithium isotopes were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. We discuss the choice of the reference isotope for absolute charge radii determinations in the lithium isotopic chain and report a new value for the charge radius of ${}^{6}$Li, based on the analysis of the world scattering data. A summary of the lithium nuclear charge radii obtained in this way is presented. Additionally, new calculations in fermionic molecular dynamics for the lithium isotopes were performed. We summarize the status of the lithium nuclear charge radii, magnetic dipole and electric quadrupole moment…
Polarization transfer in the 4HeH reaction
Abstract Polarization transfer in the 4He ( e → ,e′ p → ) 3 H reaction at a Q2 of 0.4 (GeV/c)2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark–meson coupling model.
Final State Interaction Effects in 3He(e ,e'p)
Abstract Asymmetries in quasi-elastic 3 He ( e → , e ′ p ) have been measured at a momentum transfer of 0.67 (GeV/ c ) 2 and are compared to a calculation which takes into account relativistic kinematics in the final state and a relativistic one-body current operator. With an exact solution of the Faddeev equation for the 3 He -ground state and an approximate treatment of final state interactions in the continuum good agreement is found with the experimental data.
Large recoil momenta in the D(e,e′p)n reaction
Abstract The D(e,e′p)n reaction cross section has been measured for recoil momenta ranging from 17 MeV/c up to 950 MeV/c at momentum transfers between 600 MeV/c and 700 MeV/c. At recoil momenta above 400 MeV/c, the gross features of the cross section are only reproduced if virtual nucleon excitations are included in the calculations.
Measurement of the Neutron Electric to Magnetic Form Factor Ratio atQ2=1.58 GeV2Using the ReactionHe→3(e→,e′n)pp
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…