Neutrino damping in a fermion and scalar background. (arXiv:1812.05672v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Nieves_J/0/1/0/all/0/1">José F. Nieves</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Sahu_S/0/1/0/all/0/1">Sarira Sahu</a>
We consider the propagation of a neutrino in a background composed of a
scalar particle and a fermion using a simple model for the coupling of the form
$lambdabar f_Rnu_Lphi$. In the presence of these interactions there can be
damping terms in the neutrino effective potential and index of refraction. We
calculate the imaginary part of the neutrino self-energy in this case, from
which the damping terms are determined. The results are useful in the context
of Dark Matter-neutrino interaction models in which the scalar and/or fermion
constitute the dark-matter. The corresponding formulas for models in which the
scalar particle couples to two neutrinos via a coupling of the form
$lambda^{(nunuphi)}barnu^c_Rnu_Lphi$ are then obtained as a special
case, which can be important also in the context of neutrino collective
oscillations in a supernova and in the Early Universe hot plasma before
neutrino decoupling. A particular feature of our results is that the damping
term in a $nuphi$ background is independent of the antineutrino-neutrino
asymmetry in the background. Therefore, the relative importance of the damping
term may be more significant if the neutrino-antineutrino asymmetry in the
background is small, because the leading $Z$-exchange and $phi$-exchange
contributions to the effective potential, which are proportional to the
neutrino-antineutrino asymmetry, are suppressed in that case, while the damping
term is not.
We consider the propagation of a neutrino in a background composed of a
scalar particle and a fermion using a simple model for the coupling of the form
$lambdabar f_Rnu_Lphi$. In the presence of these interactions there can be
damping terms in the neutrino effective potential and index of refraction. We
calculate the imaginary part of the neutrino self-energy in this case, from
which the damping terms are determined. The results are useful in the context
of Dark Matter-neutrino interaction models in which the scalar and/or fermion
constitute the dark-matter. The corresponding formulas for models in which the
scalar particle couples to two neutrinos via a coupling of the form
$lambda^{(nunuphi)}barnu^c_Rnu_Lphi$ are then obtained as a special
case, which can be important also in the context of neutrino collective
oscillations in a supernova and in the Early Universe hot plasma before
neutrino decoupling. A particular feature of our results is that the damping
term in a $nuphi$ background is independent of the antineutrino-neutrino
asymmetry in the background. Therefore, the relative importance of the damping
term may be more significant if the neutrino-antineutrino asymmetry in the
background is small, because the leading $Z$-exchange and $phi$-exchange
contributions to the effective potential, which are proportional to the
neutrino-antineutrino asymmetry, are suppressed in that case, while the damping
term is not.
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