Relativistic corrections to polarized-tritium <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> decay

Forthcoming experiments like Project8 and Ptolemy aim at investigating with high precision the end-point of tritium $\beta$-decay spectrum sensitive to neutrino mass. In light this, using standard parametrization in terms nuclear polar form factors, we analyze complete relativistic expression for $\beta$-electron emitted by a nucleus. Given small parameters problem, systematically discuss approximations that can be made, present first two corrections lowest order formula. We particularly case an initially polarized target, consequences on as function show that, while it induces angular anisotropy measured future experiments, such cannot used additional handle constrain