A solution to the puzzle of quenched beta-decays.

For over 50 years, a central puzzle has been that observed β-decay rates are systematically smaller than theoretical predictions. This was attributed to an apparent quenching of the fundamental coupling constant gA in the nucleus by a factor of about 0.75 compared to the β-decay of a free neutron. The origin of this quenching is controversial and has so far eluded a first-principles theoretical understanding. This talk presents a solution to this puzzle, and shows that this quenching can be explained from two-body currents and many-body correlations. Using interactions and currents from chiral effective field theory that describe Gamow-Teller strength in light nuclei well, I will present first principles computations of Gamow-Teller strength in selected medium mass and the heavy nucleus 100Sn. Our results are consistent with experimental data, including the pioneering measurement for 100Sn [1,2]. These theoretical advances have been enabled by systematic effective field theories of the strong and weak interactions combined with powerful quantum many-body techniques and ever increasing computational power.

[1] Hinke, C. B. et al., Nature 486, 341-345 (2012).

[2] Batist, L. et al. Eur. Phys. J. A 46, 45-53 (2010).