# Elastic collisions with neutrinos

1: Do neutrinos undergo elastic collisions with fermions?

2: Would this imply a variable speed for neutrinos?

3: Can neutrinos transfer momenta in interactions?

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This question does not show any research effort – The Chaz 2.0 Sep 13 '11 at 5:24

1. Yes. Beam neutrino experiments regularly observe events in which a single hadron appears in the detector. Such events are attributable to $Z$ exchange reactions like $\nu + p \to \nu' + p' + \pi${*}, or $\nu + p \to \nu' + p'$ (where $p'$ is energetic enough to register in the detector). Reactions with leptonic products are not obvious because they could also arise from $W$ exchange reaction.
{*} This event may be elastic at the level where the neutrino interacts with a parton to form on on-shell pion from the nuclear sea. Such occurrences are called "quasi-elasitc scattering" by nuclear physicists. Alas some confusion arises because neutrino physicists reserve that phase for W exchange reaction likes $\nu_l + A \to l^- + A'$.