Speaker
Description
For over three decades, the gallium anomaly, a persistent discrepancy exceeding 5σ between measured and predicted neutrino capture rates on gallium-71 in the GALLEX, SAGE, and BEST experiments, has challenged the particle physics community. While frequently interpreted as evidence for short-baseline sterile neutrino oscillations, this scenario is increasingly in tension with recent bounds from reactor, solar, and accelerator experiments, including KATRIN and MicroBooNE. In this contribution, we revisit the theoretical evaluation of the cross-section for neutrino capture on gallium-71. We move beyond the standard detailed-balance framework by abandoning both the conventional leading-order approximation and the strict factorization of leptonic wave functions from the nuclear matrix element. Instead, we calculate exact Dirac-Hartree-Fock-Slater wave functions for bound and continuum electron states and integrate them directly with phenomenologically constrained Gamow-Teller transition densities. By ensuring these densities accurately reproduce the precisely measured germanium-71 half-life, we are able to evaluate the full, non-factorized transition amplitude. We demonstrate that this approach yields a substantial reduction of approximately 20% in the predicted charge-current neutrino capture cross-section. Ultimately, this reduction offers a viable solution to the gallium anomaly, effectively eliminating the need to invoke physics beyond the Standard Model.