Eur. Phys. J. A (2010) 46: 249-269
https://doi.org/10.1140/epja/i2010-11037-6

Regular Article - Theoretical Physics

Nucleon spin-polarisabilities from polarisation observables in low-energy deuteron Compton scattering

¹ Center for Nuclear Studies, Department of Physics, George Washington University, 20052, Washington, DC, USA
² Department of Physics and Astronomy, The University of North Carolina, Chapel Hill, NC, USA

^* e-mail: dshukla@physics.unc.edu

Received: 28 June 2010
Accepted: 7 September 2010
Published online: 24 October 2010

Abstract

We investigate the dependence of polarisation observables in elastic deuteron Compton scattering below the pion production threshold on the spin-independent and spin-dependent iso-scalar dipole polarisabilities of the nucleon. The calculation uses Chiral Effective Field Theory ( EFT) with dynamical (1232) degrees of freedom in the Small Scale Expansion (SSE) at next-to-leading order. Resummation of the NN intermediate rescattering states and including the induces sizeable effects. The analysis considers cross-sections and the analysing power of linearly polarised photons on an unpolarised target, and cross-section differences and asymmetries of linearly and circularly polarised beams on a vector-polarised deuteron. An intuitive argument helps one to identify kinematics in which one or several polarisabilities do not contribute. Some double-polarised observables are only sensitive to linear combinations of two of the spin-polarisabilities, simplifying a multipole analysis of the data. Spin-polarisabilities can be extracted at photon energies ≳ 100 MeV, after measurements at lower energies of 70 MeV provide high-accuracy determinations of the spin-independent ones. An interactive Mathematica 7.0 notebook of our findings is available from hgrie@gwu.edu.