Can nonstandard interactions jeopardize the hierarchy sensitivity of DUNE?

Abstract

We study the effect of non-standard interactions (NSIs) on the propagation of neutrinos through the Earth matter and how it affects the hierarchy sensitivity of the DUNE experiment. We emphasize on the special case when the diagonal NSI parameter ǫee = −1, nullifying the standard matter effect. We show that, if in addition, CP violation is maximal then this gives rise to an exact intrinsic hierarchy degeneracy in the appearance channel, irrespective of the baseline and energy. Introduction of off-diagonal NSI parameter, ǫeτ , shifts the position of this degeneracy to a different ǫee. Moreover the unknown magnitude and phases of the off-diagonal NSI parameters can give rise to additional degeneracies. Overall, given the current model independent limits on NSI parameters, the hierarchy sensitivity of DUNE can get seriously impacted. However, a more precise knowledge on the NSI parameters, specially ǫee, can give rise to an improved sensitivity. Alternatively, if NSI exists in nature, and still DUNE shows hierarchy sensitivity, certain ranges of the NSI parameters can be excluded. Additionally, we briefly discussed the implications of ǫee = −1 (in the Earth) on MSW effect in the Sun. Although neutrino oscillation has been identified as the dominant phenomenon to explain the results of various experiments, the possibility of sub-leading effects originating from new physics beyond the Standard Model (SM) cannot be ignored. Among these, non-standard interactions have received a lot of attention lately specially

Can we probe intrinsic CP and T violations and nonunitarity at long baseline accelerator experiments?

“…Going beyond the recent studies revealing how potential new physics scenarios can hinder the clean determination of this important parameter [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], we address the issue of clean separation of the intrinsic leptonic CP phase from the extrinsic contribution arising due to SI as well as new physics 7 . We also show the impact of new physics on testing non-unitarity.…”

“…The large allowed range for θ 34 (< 25 o ) permits us to use such a large value for it. Although θ 34 has marginal effect on the ν µ → ν e channel, the ν e → ν τ channel depends quite significantly on θ 34 . This, in turn, produces the large wiggles for δ∆P CP eτ .…”

“…We also probe deviations due to new physics scenarios. We go beyond the SM in two respects -one in which we introduce subdominant effects due to a possible source of new physics dubbed as NSI [17][18][19][20][21][22][23][24][25][26] and another where the presence of extra sterile state can lead to non-unitarity in the 3×3 part even though the overall mixing matrix is still unitary [27][28][29][30][31][32][33][34] and examine consequences relevant to long baseline experiments (For other new physics scenarios such as non-unitarity, see [35][36][37][38][39]). We highlight the regions in L − E space where the effects due to CP and T violation are drastically modified due to new physics.…”

Exploring NSI degeneracies in long-baseline experiments

“…It has been found that, as in the nonunitary case, a degeneracy appears that could weaken the resolution in the phase, δ [43]. Due to this degeneracy, the sensitivity of DUNE to the standard CP phase in the presence of NSI has been under inquiry [44][45][46][47][48][49][50][51][52].…”

“…In this context, the sensitivity to NSI in the future DUNE experiment [6] has been extensively studied [38][39][40][41][42] in order to know the expectative constraints in the future. It has been found that, as in the nonunitary case, a degeneracy appears that could weaken the resolution in the phase, δ [43].…”