Short-baseline electron neutrino disappearance, tritium beta decay, and neutrinoless double-beta decay

Abstract

We consider the interpretation of the MiniBooNE low-energy anomaly and the gallium radioactive source experiments anomaly in terms of short-baseline electron neutrino disappearance in the framework of 3 + 1 four-neutrino mixing schemes. The separate fits of MiniBooNE and gallium data are highly compatible, with close best-fit values of the effective oscillation parameters Delta m(2) and sin(2)upsilon. The combined fit gives Delta m(2) greater than or similar to 0.1 eV(2) and 0.11 less than or similar to sin(2)2 upsilon less than or similar to 0.48 at 2 sigma. We consider also the data of the Bugey and Chooz reactor antineutrino oscillation experiments and the limits on the effective electron antineutrino mass in beta decay obtained in the Mainz and Troitsk tritium experiments. The fit of the data of these experiments limits the value of sin(2)2 upsilon below 0.10 at 2 sigma. Considering the tension between the neutrino MiniBooNE and gallium data and the antineutrino reactor and tritium data as a statistical fluctuation, we perform a combined fit which gives Delta m(2) similar or equal to 2 eV and 0.01 less than or similar to sin(2)2 upsilon less than or similar to 0.13 at 2 sigma. Assuming a hierarchy of masses m1, m2, m3 << m4, the predicted contributions of m4 to the effective neutrino masses in beta decay and neutrinoless double-beta decay are, respectively, between about 0.06 and 0.49 and between about 0.003 and 0.07 eV at 2 sigma. We also consider the possibility of reconciling the tension between the neutrino MiniBooNE and gallium data and the antineutrino reactor and tritium data with different mixings in the neutrino and antineutrino sectors. We find a 2.6 sigma indication of a mixing angle asymmetry

Bulk neutrinos as an alternative cause of the gallium and reactor anti-neutrino anomalies

“…We have verified that taking into account these different contributions in the calculation of R as in Ref. [12] does not affect our final result, so for the purpose of this paper it is enough to use Eq. (10).…”

“…The mean value of the ratios of the measured over predicted rates is 0:86 AE 0:05, which is smaller than unity by about 2:7 [12]. This can also be explained by oscillation into sterile neutrinos with the similar mass squared difference, which explains the LSND/MiniBooNE anomaly.…”

“…An analysis of these results in terms of oscillation of e into sterile neutrinos was performed in Refs. [12,33].…”

Short-baselineν¯μ→ν¯eoscillations

“…e transitions. Therefore, it is possible that the effective parameters which govern neutrino and antineutrino oscillations are different, maybe because of a violation of the CPT symmetry [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. From a phenomenological point of view, it is interesting to consider the neutrino and antineutrino sectors independently, especially in view of possible experimental checks of the short-baseline "…”

Sterile neutrinos, coherent scattering, and oscillometry measurements with low-temperature bolometers

“…The most likely beyond the Standard Model explanation given to the observations made at LSND and MiniBooNE and, more recently, from reanalysis of reactor data is the existence of at least one sterile neutrino with a mass scale of 1 eV [8]. Ongoing short-baseline measurements, as well as other complimentary approaches [9], should be able to determine if the data continues to diverge from Standard Model predictions.…”