Precision theoretical analysis of neutron radiative beta decay to order O ( α 2 / π 2 )

In the Standard Model (SM) we calculate the decay rate of the neutron radiative β− decay to order O(α2/π2∼10−5), where α is the fine-structure constant, and radiative corrections to order O(α/π∼10−3). The obtained results together with the recent analysis of the neutron radiative β− decay to next-to-leading order in the large proton-mass expansion, performed by Ivanov et al. [Phys. Rev. D 95, 033007 (2017)], describe recent experimental data by the RDK II Collaboration [Bales et al., Phys. Rev. Lett. 116, 242501 (2016)] within 1.5 standard deviations. We argue a substantial influence of strong low-energy interactions of hadrons coupled to photons on the properties of the amplitude of the neutron radiative β− decay under gauge transformations of real and virtual photons.