Abstract
A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range 200<Eγ<800 MeV. The experiment used a 4π detection system, a circularly polarized tagged photon beam and a frozen spin target which provided longitudinally polarized deuterons. These new results are a significant improvement on the existing data and allow a detailed comparison with state-of-the-art calculations.
Highlights
IntroductionExtensive experimental and theoretical research has been carried out on the study of the helicity dependence of photoinduced reactions on the proton and the deuteron above the pion production threshold (see, for instance, Ref. [1]).doi:10.1016/j.physletb.2009.01.061Thanks to the presence of interference terms among the different reaction amplitudes such data give more precise information on the elementary photon–nucleon interaction mechanisms than unpolarized data
In the past years, extensive experimental and theoretical research has been carried out on the study of the helicity dependence of photoinduced reactions on the proton and the deuteron above the pion production threshold.doi:10.1016/j.physletb.2009.01.061Thanks to the presence of interference terms among the different reaction amplitudes such data give more precise information on the elementary photon–nucleon interaction mechanisms than unpolarized data
We present in this Letter new data on the helicity dependent total inclusive photoabsorption cross section on deuterium from 200 to 800 MeV and helicity dependent semi-exclusive γ d → N Nπ data up to Eγ 430 MeV
Summary
Extensive experimental and theoretical research has been carried out on the study of the helicity dependence of photoinduced reactions on the proton and the deuteron above the pion production threshold (see, for instance, Ref. [1]).doi:10.1016/j.physletb.2009.01.061Thanks to the presence of interference terms among the different reaction amplitudes such data give more precise information on the elementary photon–nucleon interaction mechanisms than unpolarized data. The helicity dependent photonuclear observables provide an experimental test of the well-known Gerasimov–Drell–Hearn (GDH) sum rule [2,3] This sum rule links the anomalous magnetic moment κ of a particle of spin S and mass M to the integral over the weighted spin asymmetry of the total absorption cross section of circularly polarized photons on a longitudinally polarized target: ∞ σp − ν σa dν = e2 M2 S (1). GDH and A2 Collaborations / Physics Letters B 672 (2009) 328–332 where ν is the photon energy and σp (σa) denotes the total absorption cross section for parallel (antiparallel) orientation of photon and particle spins.
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