Search results for "Momentum transfer"
showing 10 items of 134 documents
Virtual compton scattering under π0 threshold at Q2=0.33 GeV2. Preliminary results
1999
We have measured the absolute unpolarized cross sections for photon electro-production off the proton ep → epγ with the Three-Spectrometer-Setup at MAMI at a momentum transfer q=600 MeV/c and a virtual photon polarization ɛ=0.62. The momentum q ′ of the outgoing real photon range from 33 to 111 MeV/c. We extracted two combinations of the recently introduced generalized polarizabilities [1,2].
Study of the anomalous magnetic moment of the muon computed from the Adler function
2014
We compute the Adler function on the lattice from vacuum polarization data with twisted boundary conditions using numerical derivatives. The study is based on CLS ensembles with two flavours of $O(a)$ improved Wilson fermions. We extrapolate the lattice data for the Adler function to the continuum limit and to the physical pion mass and analyze its dependence on the momentum transfer. We discuss the application of this method to the extraction of the $u,d$ contribution to $a_\mu^{\mathrm{HLO}}$.
Measuring the surface thickness of the weak charge density of nuclei
2020
The present PREX-II and CREX experiments are measuring the rms radius of the weak charge density of $^{208}$Pb and $^{48}$Ca. We discuss the feasibility of a new parity violating electron scattering experiment to measure the surface thickness of the weak charge density of a heavy nucleus. Once PREX-II and CREX have constrained weak radii, an additional parity violating measurement at a momentum transfer near 0.76 fm$^{-1}$ for $^{208}$Pb or 1.28 fm$^{-1}$ for $^{48}$Ca can determine the surface thickness.
The Drell-Hearn-Gerasimov Sum Rule
1994
The Drell-Hearn-Gerasimov (DHG) sum rule relates the helicity structure of the photoabsorption cross section to the anomalous magnetic moment of the nucleon. It is based on Lorentz and gauge invariance, crossing symmetry, causality and unitarity. A generalized DHG sum rule my be derived for virtual photons. At low momentum transfer this generalized sum rule is saturated by the resonance region, at high momentum transfer it may be expressed by the parton spin distributions measured in deep inelastic scattering. The longitudinal-transverse interference determines the Cottingham sum rule, which is related to the electric and magnetic form factors over the whole range of momentum transfer.
Gerasimov-Drell-Hearn sum rule and related integrals
2001
The spin structure of the nucleon resonance region is analyzed on the basis of our phenomenological model MAID. Predictions are given for the Gerasimov-Drell-Hearn sum rule as well as generalized integrals over spin structure functions. The dependence of these integrals on momentum transfer is studied and rigorous relationships between various definitions of generalized Gerasimov-Drell-Hearn integrals and spin polarizabilities are derived. These results are compared to the predictions of chiral perturbation theory and phenomenological models.
Final State Interaction Effects in 3He(e ,e'p)
2003
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.
Multipole strength inC12from the (e,e’α) reaction for momentum transfers up to 0.61fm−1
1995
We have excited the giant resonance region in $^{12}\mathrm{C}$ via inelastic electron scattering, and have measured the first complete angular correlations for charged particle emission for this reaction for four values of momentum transfer ranging from 0.24 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ to 0.61 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. By analyzing the \ensuremath{\alpha}-emission channels via the Legendre and resonance formalisms, we unambiguously determined the multipole contributions to the total cross section for \ensuremath{\alpha} emission to the ground state of $^{8}\mathrm{Be}$, and have set limits on these contributions for \ensuremath{\alpha} emission to the first…
Meson exchange and isobar admixture contributions to elastic electron-deuteron scattering
1974
The deuteron structure functions for elastic electron scattering and the deuteron static properties have been calculated with the inclusion of isobar admixtures to the deuteron wave function and meson exchange currents. At higher momentum transfers the structure functions are increased significantly because of the strong enhancement of the deuteron magnetic dipole form factor. Roughly 15–35% of this enhancement depending on the momentum transfer arise from the meson exchange currents.
Polarizability effects in electronic and muonic atoms
1983
TheS state polarizability shifts are derived from the virtual forward Compton scattering in the unretarded dipole approximation. In the non-relativistic limit ω N /2m≪1, the shift is proportional to the photonuclear sum rule σ−3/2, while in the relativistic limit ω N /2m≫1 it is proportional to a logarithmically weighted σ−2 sum rule. In both cases, the characteristic momentum transfer is (2mω N )1/2. The non-locality from the intermediate lepton propagation removes the divergence typical of the static limit. Explicit formulas for the shifts are given for both the relativistic and non-relativistic limits.
The generalized Gerasimov–Drell–Hearn sum rule for deuteron electrodisintegration
2004
The generalized Gerasimov-Drell-Hearn sum rule $I^{GDH}_{\gamma^*d}(Q^2)$ for deuteron electrodisintegration $d(e,e')np$ as function of the squared four-momentum transfer $Q^2$ is evaluated by explicit integration. The calculation is based on a conventional nonrelativistic framework using a realistic $NN$-potential and including contributions from meson exchange currents, isobar configurations and leading order relativistic terms. Good convergence is achieved. The prominent feature is a deep negative minimum, $I_{\gamma^* d}^{GDH}=-9.5$ mb, at low $Q^2\approx 0.2$ fm$^{-2}$ which is almost exclusively driven by the nucleon isovector anomalous magnetic moment contribution to the magnetic dip…