Probing flavor changing neutrino interactions using neutrino beams from a muon storage ring

Abstract

We discuss the capabilities of a future neutrino factory based on intense neutrino beams from a muon storage ring to explore the non-standard neutrino matter interactions, which are assumed to be sub-leading effects in the standard mass induced neutrino oscillations. The conjunction of these two mechanisms will magnify fake CP violating effect in the presence of matter which is not coming from the CP phase in the neutrino mixing matrix. We show that such fake CP violation can be observed in neutrino factory experiments by measuring the difference between the neutrino and anti-neutrino probabilities. In order to perform such test, we consider three neutrino flavors, admitting the mixing parameters in the range consistent with the oscillation solution to the atmospheric and the solar neutrino problems, as well as with the constraints imposed by the reactor neutrino data. We show that with a 10 kt detector with 5 years of operation, a stored muon energy E µ ≥ 20 GeV, 2 × 10 20 muon decays per year, and a baseline L ∼ 732 km, such a neutrino facility can probe the non-standard flavor changing neutrino interactions down to the level of (10 −3 − 10 −2 ) G F , in both ν µ → ν τ /ν µ →ν τ and ν e → ν τ /ν e →ν τ modes.

CP-violation from non-unitary leptonic mixing

“…(3) is on purpose very similar to that used to study non-standard neutrino interactions from four-fermion operators in Refs. [11,12,13]. Some CP-odd effects have also been considered in these scenarios [12].…”

“…It is interesting, though, to understand qualitatively and in detail the role of matter effects and, whenever relevant, the dependence on small neutrino parameters, such as ∆ 21 L and sin 2θ 13 . For this purpose, we will consider below an expansion of the oscillation probabilities at higher order than that implied by Eq.…”

“…For instance, in Ref. [13] new matter effects stemming from the operator ∼ ν SM α γ µ P L ν SM β f γ µ f were studied. This kind of operators give rise to non-diagonal corrections to the effective potential for the evolution equation in matter (in the SM flavor basis).…”

“…Non-standard neutrino interactions are usually introduced through the addition of effective four-fermion operators to the SM Lagrangian [11,12,13], made out of the SM fields and invariant under the SM gauge group. They can affect the production or detection processes or modify the matter effects in the propagation, depending on the operator or combination of operators considered.…”

“…These are usually implemented through the addition of effective four-fermion operators to the SM Lagrangian [11,12,13]. These operators can affect the production and detection processes or modify the matter effects in the propagation.…”