Speaker
Berhan Demissie
(George Washington University, Washington)
Description
Compton scattering processes are ideal to study electric and magnetic dipole polarizability coeffcients of nucleons [1]. These fundamental quantities parametrize the response to a monochromatic photon probe. In this work, the inelastic channel γd → γnp is treated in χEFT, with a focus on the NQFP - neutron quasi-free peak - kinematic region. In this region, the momentum of the outgoing proton is small enough that it is considered to remain at rest. This provides access to the Compton scattering process γn → γn from which the neutron scalar polarizabilites α and β are extracted. Using χEFT, differential cross-sections, d^3σ/dE_ndΩγ Ωn, in the photon energy range of 200-400 MeV are computed. The biggest contribution comes from the impulse approximation, with small corrections stemming from final state interaction, meson exchange currents and rescattering. A new extraction of neutron polarizabilities from a two-parameter fit to the Kossert et al. [2] data taken at MAMI in 2002 is presented. Previously, the experiment was designed and the data analysed based on a theoretical model [3] that computed the NQFP differential cross-sections. The re-analysis of this data in a consistent, model independent framework - χEFT - provides reliable extraction of polarizabilies with controlled uncertainties.
This work is supported in part by the US Department of Energy under grant DE-FG02-
95ER-40907.
References
1. H. W. Grießhammer, J. A. McGovern, D. R. Phillips, G. Feldman, Prog. Part. Nucl. Phys. 67, 841 (2012).
2. K. Kossert et al., Phys. Rev. Lett. 88, 162301 (2002).
3. M. I. Levchuk, A. I. L’vov, and V. A. Petrun’kin, Few-Body Syst. 16, 101 (1994).
Primary author
Berhan Demissie
(George Washington University, Washington)
