Effects of physics beyond the standard model on the neutrino charge radius: an effective Lagrangian approach

H. Novales--S\' anchez; A. Rosado; V. Santiago--Ol\' an; J. J. Toscano

doi:10.1103/PhysRevD.78.073014

paper

Effects of physics beyond the standard model on the neutrino charge radius: an effective Lagrangian approach

arXiv:0805.4177 · doi:10.1103/PhysRevD.78.073014

Abstract

In this work, we look for possible new physics effects on the electromagnetic charge and anapole form factors, $f_{Q} (q^{2})$ and $f_{A} (q^{2})$ , for a massless Dirac neutrino, when these quantities are calculated in the context of an effective electroweak Yang-Mills theory, which induces the most general $S U_{L} (2)$ --invariant Lorentz tensor structure of nonrenormalizable type for the $W W γ$ vertex. It is found that in this context, besides the standard model contribution, the additional contribution to $f_{Q} (q^{2})$ and $f_{A} (q^{2})$ ( $f_{Q}^{O_{W}} (q^{2})$ and $f_{A}^{O_{W}} (q^{2})$ , respectively) are gauge independent and finite functions of $q^{2}$ after adopting a renormalization scheme. These form factors, $f_{Q}^{O_{W}} (q^{2})$ and $f_{A}^{O_{W}} (q^{2})$ , get contribution at the one loop level only from the proper neutrino electromagnetic vertex. Besides, the relation $f_{Q}^{e f f} (q^{2}) = q^{2} f_{A}^{e f f} (q^{2})$ ( $f_{Q}^{e f f} (q^{2}) = f_{Q}^{S M} (q^{2}) + f_{Q}^{O_{W}} (q^{2})$ , $f_{A}^{e f f} (q^{2}) = f_{A}^{S M} (q^{2}) + f_{A}^{O_{W}} (q^{2})$ ) is still fulfilled and hence the relation $a_{ν}^{e f f} =< r_{ν}^{2} >^{e f f} /6$ ( $a_{ν}^{e f f} = a_{ν}^{S M} + a_{ν}^{O_{W}}$ , $< r_{ν}^{2} >^{e f f} =< r_{ν}^{2} >^{S M} + < r_{ν}^{2} >^{O_{W}}$ )is gotten, just as in the SM. Using the experimental constraint on the anomalous $W W γ$ vertex, a value for the additional contribution to the charge radius of $|< r^2_ν >^{O_W}| \lsim 10^{-34} cm^2$ is obtained, which is one order of magnitude lower than the SM value.

9 pages, 3 figures

Effects of physics beyond the standard model on the neutrino charge radius: an effective Lagrangian approach

Abstract

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