Erlangen 2001 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 3: Theorie I
HK 3.1: Gruppenbericht
Montag, 19. März 2001, 16:30–17:00, B
Nucleon Polarisabilities from Deuteron Compton Scattering in Effective Field Theory — •Harald W. Grießhammer1, Gautam Rupak2,3, Jiunn-Wei Chen2, Martin J. Savage2, and Roxanne P. Springer2,4 — 1Technische Universität München — 2University of Washington, Seattle — 3TRIUMF, Vancouver — 4Duke University, Durham
The Effective Field Theory of low energy few nucleon systems in which pions are not dynamical degrees of freedom allows for simple, model independent, systematic and rigorous computations with an error estimate. An analytic calculation of the differential cross section for elastic Compton scattering on the deuteron at photon energies ω in the range of 25−50 MeV is presented to next-to-next-to-leading order, i.e. to an accuracy of about 3%. The iso-scalar, scalar electric and magnetic nucleon polarisabilities α0 and β0 enter as the only free parameters and can be determined with a theoretical uncertainty of about 20%. Using data at ωLab=49 MeV, we find α0=8.4± 3.0(exp)± 1.7(theor), β0=8.9± 3.9(exp)± 1.8(theor), each in units of 10−4 fm3. With the experimental constraint for the iso-scalar Baldin sum rule, α0=7.2± 2.1(exp)± 1.6(theor), β0=6.9∓ 2.1(exp)∓ 1.6(theor). A more accurate result requires: (i) better experimental data, and (ii) a higher order theoretical calculation including contributions from two so far undetermined four-nucleon-two-photon operators. Results of a next-to-leading order calculation in the theory with dynamical, perturbative pions are also shown to agree with experiment. [nucl-th/0012096]