Probing non-standard neutrino interactions with neutrino factories

Abstract

We discuss the sensitivity reach of a neutrino factory measurement to non-standard neutrino interactions (NSI), which may exist as a low-energy manifestation of physics beyond the Standard Model. We use the muon appearance modes ν e → ν µ /ν e →ν µ and consider two detectors, one at L = 3000 km and the other at L = 7000 km; The latter is nearly at the magic baseline which is known to have a great sensitivity to matter density determination. Assuming the effects of NSI at the production and the detection are negligible, we discuss the sensitivities to NSI and the simultaneous determination of θ 13 and δ by examining the effects in the neutrino propagation of various systems in which two NSI parameters ε αβ are switched on. The sensitivities to offdiagonal ε's are found to be excellent up to small values of θ 13 . At sin 2 2θ 13 = 10 −4 , for example, |ε eτ | a few×10 −3 at 3σ CL for 2 degrees of freedom, whereas the ones for the diagonal ε's are also acceptable, |ε ee |(|ε τ τ |) 0.1(0.2) at the same CL. We demonstrate that the two-detector setting is powerful enough to resolve the θ 13 -NSI confusion problem, a notorious one which is thought to be an obstacle in determining θ 13 and δ. We believe that the results obtained in this paper open the door to the possibility of using neutrino factory as a discovery machine for NSI while keeping its primary function of performing precision measurements of the lepton mixing parameters.

Neutrino factory in stages: Low energy, high energy, off-axis

“…The benefit of the magic baseline option is qualitatively different physics, such as relevant for new physics searches in the presence of more than six oscillation parameters (see, e.g., Ref. [48]). We summarize the neutrino factory in stages for small sin 2 2θ 13 in Fig.…”

“…[23,[45][46][47], for non-standard physics, see, e.g., Refs. [24,48]. However, the largest increase in the discovery reaches will come from the energy upgrade.…”

Non-standard neutrino interactions at one loop

“…The typical bounds on production and detection NSIs are about ε µτ ∼ 10 −2 [20,21]. Higher sensitivities, of ε µτ ∼ < 10 −3 are within the reach of future neutrino experiments [22][23][24][25][26][27][28][29][30].…”

Constraining new physics with a positive or negative signal of neutrino-less double beta decay

“…Hence, it is necessary to think about how to deal with possible interference terms. Sometimes in the literature, such phases are ignored by assuming CP-invariance [63], which then results in relative signs only, which could be plus or minus [19], leading to minimal or maximal cancellation of the partial amplitudes. We will discuss this point in the following.…”