1202.5239 (Susan Gardner et al.)

A T-odd Momentum Correlation in Radiative β-Decay    [PDF]

Susan Gardner, Daheng He

We consider neutron radiative \beta-decay, n\to p e^- \bar{\nu}_e\gamma, and
compute the T-odd momentum correlation in the decay rate characterized by the
kinematical variable \xi = {\bf l}_\nu \cdot ({\bf l}_e\times{\bf k}) arising
from electromagnetic final-state interactions in the Standard Model. Our
expression for the corresponding T-odd asymmetry A_\xi^{SM} is exact in
O(\alpha) up to terms of recoil order, and we evaluate it numerically under
various kinematic conditions. Noting the universality of the V-A law in the
absence of recoil order terms, we retain the parametric dependence on masses
and coupling constants throughout, so that our results serve as a template for
the computation of A_\xi^{SM} in allowed nuclear radiative \beta-decays and
hyperon radiative \beta-decays as well. We consider the pattern of A_\xi^{SM}
which appears in nuclear decays and show that A_\xi^{SM} can be suppressed in
particular cases, facilitating searches for new sources of CP-violation in such
processes.

View original: http://arxiv.org/abs/1202.5239