München 2006 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 11: Theorie
HK 11.3: Vortrag
Montag, 20. März 2006, 17:00–17:15, B
Triton Radiative Capture at Thermal Energies in Effective Field Theory — •Harald W. Grießhammer — Institut für Theoretische Physik (T39), TU München, Germany — Centre for Nuclear Studies, The George Washington University, Washington DC, USA
The cross section of radiative neutron capture by the deuteron at thermal neutron energies, nd→ tγ, is calculated in “pion-less” Effective Field Theory, the unique, model-independent and systematic low-energy version of QCD for processes involving momenta below the pion-mass. Nuclear models give a spread of [0.49…0.66] mb, depending on the 2-nucleon potential, and how the Δ(1232) as first nucleonic excitation is included. On the other hand, a process at 0.0253 eV incident neutron energy and less than 7 MeV photon energy should be insensitive to details of the deuteron wave-function and of a resonance with an excitation energy of 300 MeV. No new 3-nucleon forces are needed up to next-to-next-to-leading order for cut-off independent results, besides those fixed by the triton binding energy and nd scattering length in the triton channel. Our cross-section is completely determined by these, and by simple 2-body observables, as σtot=[ 0.485(LO)+0.011(NLO)+0.007(NNLO) ] mb= [0.503±0.003] mb [1]. It thus converges order by order in the low-energy expansion and compares well with the measured value, [0.509±0.015] mb.
[1] H. Sadeghi, S. Bayegan and H.W. Grießhammer, in preparation.