Search results for "Compton wavelength"
showing 7 items of 7 documents
Polarizability contributions to the neutron-lepton amplitude at threshold
1973
Abstract Motivated by recent interest in the neutron-electron scattering amplitude at threshold, a detailed investigation of the two-photon exchange contribution, commonly known as the polarizability correction, to this amplitude is made, for general lepton mass. The contributions is related to the amplitude describing forward virtual Compton scattering on neutrons. To calculate it, we write dispersion relations for the Compton amplitudes and make use of the present knowledge of the neutron structure functions as well as the scaling hypothesis. The correction is much larger for muons than for electrons. Further, we discuss the region of validity of the extreme relativistic and the classical…
Finite-size Scaling of Meson Propagators
2001
Using quenched chiral perturbation theory we compute meson correlation functions at finite volume and fixed gauge field topology. We also present the corresponding analytical predictions for the unquenched theory at fixed gauge field topology. These results can be used to measure the low-energy parameters of the chiral Langrangian from lattice simulations in volumes much smaller than one pion Compton wavelength.
Compton scattering from the free and bound proton above π-threshold
2000
The differential cross sections for Compton scattering from the proton have been measured at MAMI with three different detector setups. There is a good agreement among all the results. The theoretical calculation based on dispersion relations shows that there is no drastic change necessary in the parameters of this approach.
Finite-size scaling of the left-current correlator with non-degenerate quark masses
2007
We study the volume dependence of the left-current correlator with non-degenerate quark masses to next-to-leading order in the chiral expansion. We consider three possible regimes: all quark masses are in the $\epsilon$-regime, all are in the $p$-regime and a mixed-regime where the lighest quark masses satisfy $m_v \Sigma V \leq 1$ while the heavier $m_s \Sigma V \gg 1$. These results can be used to match lattice QCD and the Chiral Effective Theory in a large but finite box in which the Compton wavelength of the lightest pions is of the order of the box size. We consider both the full and partially-quenched results.
Pion photoproduction and Compton scattering in quark models
2008
I review quark model studies for pion photoproduction and Compton scattering off nucleons. The important role of unitarity and electromagnetic gauge invariance is stressed.
Compton scattering off nucleons near threshold
2008
The energy dependence of the magnetic polarizability β has been evaluated by use of the delta resonance in the s- and u-channel of the Compton scattering amplitude. It was the idea to extract the influence of higher order terms (higher than ω2, ω = |k| being the photon energy) in the analysis of the polarizability. The static paramagnetic polarizability βPara(0) has been substituted by an energy dependent βδPara(k) and the result is compared with experimental data.
Finite-size scaling of vector and axial current correlators
2002
Using quenched chiral perturbation theory, we compute the long-distance behaviour of two-point functions of flavour non-singlet axial and vector currents in a finite volume, for small quark masses, and at a fixed gauge-field topology. We also present the corresponding predictions for the unquenched theory at fixed topology. These results can in principle be used to measure the low-energy constants of the chiral Lagrangian, from lattice simulations in volumes much smaller than one pion Compton wavelength. We show that quenching has a dramatic effect on the vector correlator, which is argued to vanish to all orders, while the axial correlator appears to be a robust observable only moderately …