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Ruling out four-neutrino oscillation interpretations of the LSND anomaly?

M. Maltoni, T. Schwetz, M. A. Tortola, J. W. F. Valle

TL;DR

This paper re-evaluates four-neutrino mass schemes (2+2 and 3+1) in light of updated solar (including SNO NC) and atmospheric data, plus short-baseline results, to test their compatibility with the LSND anomaly. Employing a parameterization with Δm^2_sol, Δm^2_atm, Δm^2_lsnd and sterile admixture parameters η_s, η_e, d_μ, the authors apply parameter-consistency and parameter-goodness-of-fit tests to quantify cross-dataset tensions. They find that (2+2) schemes are ruled out by solar and atmospheric data at multi-sigma levels (gof ~1.3×10^{-6}), while (3+1) schemes are strongly disfavoured by SBL disappearance constraints, with LSND data yielding only marginal compatibility (best PG around 0.56% for global LSND and much smaller for DAR). The overall conclusion is that all four-neutrino descriptions of the LSND anomaly are highly disfavoured, reinforcing the need for alternative explanations or new data (e.g., MiniBooNE) to resolve the LSND signal.

Abstract

Prompted by recent solar and atmospheric data, we re-analyze the four-neutrino description of current global neutrino oscillation data, including the LSND evidence for oscillations. The higher degree of rejection for non-active solar and atmospheric oscillation solutions implied by the SNO neutral current result as well as by the latest 1489-day Super-K atmospheric neutrino data allows us to rule out (2+2) oscillation schemes proposed to reconcile LSND with the rest of current neutrino oscillation data. Using an improved goodness of fit (gof) method especially sensitive to the combination of data sets we obtain a gof of only 1.6 times 10^{-6} for (2+2) schemes. Further, we re-evaluate the status of (3+1) oscillations using two different analyses of the LSND data sample. We find that also (3+1) schemes are strongly disfavoured by the data. Depending on the LSND analysis we obtain a gof of 5.6 times 10^{-3} or 7.6 times 10^{-5}. This leads to the conclusion that all four-neutrino descriptions of the LSND anomaly, both in (2+2) as well as (3+1) realizations, are highly disfavoured. Our analysis brings the LSND hint to a more puzzling status.

Ruling out four-neutrino oscillation interpretations of the LSND anomaly?

TL;DR

This paper re-evaluates four-neutrino mass schemes (2+2 and 3+1) in light of updated solar (including SNO NC) and atmospheric data, plus short-baseline results, to test their compatibility with the LSND anomaly. Employing a parameterization with Δm^2_sol, Δm^2_atm, Δm^2_lsnd and sterile admixture parameters η_s, η_e, d_μ, the authors apply parameter-consistency and parameter-goodness-of-fit tests to quantify cross-dataset tensions. They find that (2+2) schemes are ruled out by solar and atmospheric data at multi-sigma levels (gof ~1.3×10^{-6}), while (3+1) schemes are strongly disfavoured by SBL disappearance constraints, with LSND data yielding only marginal compatibility (best PG around 0.56% for global LSND and much smaller for DAR). The overall conclusion is that all four-neutrino descriptions of the LSND anomaly are highly disfavoured, reinforcing the need for alternative explanations or new data (e.g., MiniBooNE) to resolve the LSND signal.

Abstract

Prompted by recent solar and atmospheric data, we re-analyze the four-neutrino description of current global neutrino oscillation data, including the LSND evidence for oscillations. The higher degree of rejection for non-active solar and atmospheric oscillation solutions implied by the SNO neutral current result as well as by the latest 1489-day Super-K atmospheric neutrino data allows us to rule out (2+2) oscillation schemes proposed to reconcile LSND with the rest of current neutrino oscillation data. Using an improved goodness of fit (gof) method especially sensitive to the combination of data sets we obtain a gof of only 1.6 times 10^{-6} for (2+2) schemes. Further, we re-evaluate the status of (3+1) oscillations using two different analyses of the LSND data sample. We find that also (3+1) schemes are strongly disfavoured by the data. Depending on the LSND analysis we obtain a gof of 5.6 times 10^{-3} or 7.6 times 10^{-5}. This leads to the conclusion that all four-neutrino descriptions of the LSND anomaly, both in (2+2) as well as (3+1) realizations, are highly disfavoured. Our analysis brings the LSND hint to a more puzzling status.

Paper Structure

This paper contains 12 sections, 12 equations, 7 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Four-neutrino oscillations
  3. Solar neutrinos
  4. Atmospheric neutrinos
  5. Reactor and accelerator data
  6. (2+2) oscillations: ruled out by solar and atmospheric data
  7. (3+1) oscillations: strongly disfavoured by SBL data
  8. Comparing (3+1), (2+2) and (3+0) hypotheses
  9. Conclusions
  10. Statistical compatibility of different data sets
  11. Parameter consistency test (PC)
  12. Parameter goodness of fit (PG)

Figures (7)

  • Figure 1: The six types of four-neutrino mass spectra. The spacings in the vertical axes correspond to the different scales of mass-squared differences required in solar, atmospheric and short baseline neutrino oscillations.
  • Figure 2: Parameter dependence of the different data sets in our parameterization.
  • Figure 3: $\Delta \chi^2_\mathsc{sol}$ for the favoured LMA solution, before and after SNO NC data sno02, displayed as a function of $\eta_s$.
  • Figure 4: $\Delta\chi^2_\mathsc{atm}$ displayed as a function of $\eta_s$ for (3+1) and (2+2) schemes, before and after the most recent Super-K up-date skatm.
  • Figure 5: Comparison of the 99% C.L. regions of the global LSND analysis LSND2001 (shaded region) and of the analysis performed in Ref. Church:2002tc (solid line) using mainly the decay-at-rest (DAR) data sample.
  • ...and 2 more figures