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HK: Fachverband Hadronen und Kerne

HK 72: Nuclear Structure and Dynamics II

HK 72.1: Gruppenbericht

Donnerstag, 19. März 2009, 16:30–17:00, H-ZO 50

¹⁴C Dating Beta Decay with Chiral Effective Field Theory — •Jeremy Holt, Norbert Kaiser, and Wolfram Weise — Technische Universität München, München, Germany

The anomalously long beta-decay lifetime of ¹⁴C, which is essential for the science of radiocarbon dating, has long been a challenge for nuclear structure theory. Here we present a shell model calculation of this decay, treating the initial and final nuclear states as two p-holes in an ¹⁶O core. Employing the low-momentum nucleon-nucleon (NN) interaction V_low−k only, we find that the Gamow-Teller transition matrix element is too large to describe the known lifetime of ¹⁴C. As a novel approach to this problem, we invoke the chiral three-nucleon force (3NF) at leading order and derive from it a density-dependent in-medium NN interaction. After including these in-medium contributions, we find that the Gamow-Teller matrix element vanishes at a nuclear density close to that of saturated nuclear matter. The genuine short-range part of the 3NF is identified as the most important contribution leading to the observed suppression, and we find that although individual terms arising from the long- and medium-range parts of the chiral 3NF can be large, they significantly cancel. Work supported in part by BMBF, GSI, and by the DFG cluster of excellence: Origin and Structure of the Universe.