Plant Science Innovation, Center for


Date of this Version



Journal of Research of the National Institute of Standards and Technology (July-August 2005) 110(4): 411-414.


U.S. government work.


In summary, we have computed the photon energy spectrum and photon polarization in neutron radiative β-decay in an effective field theory approach, utilizing HBCHPT and the SSE, including all terms in O(1/M). The leading contribution to the photon energy spectrum has been calculated previously [4]; we agree with the expression in Ref. [4] for Σspins |M|2, though we disagree with their numerical results for the photon energy spectrum. Moreover, we find that the O(1/M) terms are numerically quite small, generating contributions no larger than O(0.5 %), so that radiative neutron β-decay is quite insensitive to nucleon structure effects beyond those encoded in gV and gA . We have found that nucleon structure effects have a similarly negligible role in the determination of the photon polarization, so that a precise measurement of the photon polarization may well offer a crisp diagnostic of non-SM effects.