Dr. Jeremy Holt (TUM): "Carbon-14 Dating Beta Decay and Chiral Effective Field Theory"

Monday 20 Apr 2009, 14:15 → 15:45 Europe/Berlin

3344 - Physics Department TUM Garching

The anomalously long beta-decay lifetime of $^{14}$C, 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 $^{16}$O 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 $^{14}$C. 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.

document Holt_200409.pdf