Köln 2004 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 6: Theory II
HK 6.9: Vortrag
Montag, 8. März 2004, 18:15–18:30, E
Photons and the Triton at Very Low Energies — •Harald W. Griesshammer — Institut für Theoretische Physik (T39), TU München, Germany
Recently, the Effective Field Theory of the three-nucleon system in which pions are integrated out as heavy was systematised to all orders in the low-energy expansion [1]. In this consistent and model-independent approach, calculations involving external electro-weak currents can be performed straightforwardly, and the theoretical error can be estimated systematically. They are relevant e.g. for big-bang nucleo-synthesis and the extraction of neutron properties from experiments on light nuclei. Often, three-body forces are irrelevant, but in the doublet-S-wave (triton/3He) channel, three-body forces are stronger than naïvely expected. Using the requirement that physical low-energy observables are insensitive to details of the short distance treatment, two simple observables like the triton binding energy and scattering length suffice to determine the three-body forces for wave functions accurate to ∼ 1%. We present a calculation of the triton and 3He form factors and an investigation into charge symmetry breaking in the triton/3He-system. Our result for triton photo-disintegration resolves a 15% discrepancy between potential-model calculations and the measured total cross section at thermal neutron energies [2].
Work supported in part by DFG and BMBF.
[1.] Bedaque, Grießhammer, Hammer and Rupak:
Nucl. Phys.A714
[1.] (2003), 589 [nucl-th/0207034].
[2.] Bedaque, Grießhammer, Hammer and Rupak: in preparation.