Neutrinoless double-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>decay in SU(2)×U(1) theories

Abstract

It is shown that gauge theories give contributions to neutrinoless double-$\ensuremath{\beta}$ decay [${(\ensuremath{\beta}\ensuremath{\beta})}_{0\ensuremath{\nu}}$] which are not covered by the standard parametrizations. While probably small, their existence raises the question of whether the observation of ${(\ensuremath{\beta}\ensuremath{\beta})}_{0\ensuremath{\nu}}$ implies the existence of a Majorana mass term for the neutrino. For a "natural" gauge theory we argue that this is indeed the case.