# (C) Other neutrino mixing results

The LSND collaboration reported in AGUILAR 2001 a signal which is consistent with ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ oscillations. In a three neutrino framework, this would be a measurement of $\theta _{12}$ and $\Delta \mathit m{}^{2}_{21}$. This does not appear to be consistent with most of the other neutrino data. The MiniBooNE experiment, reported in AGUILAR-AREVALO 2007 , does a two-neutrino analysis which, assuming $\mathit CP$ conservation, rules out AGUILAR 2001 . However, the MiniBooNE antineutrino data reported in AGUILAR-AREVALO 2013A are consistent with the signal reported in AGUILAR 2001 . The following listings include results which might be relevant towards understanding these observations. They include searches for ${{\mathit \nu}_{{\mu}}}$ $\rightarrow$ ${{\mathit \nu}_{{e}}}$ , ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ , sterile neutrino oscillations, and $\mathit CPT$ violation.

# $\Delta \boldsymbol m{}^{2}$ for sin$^2(2{}\theta )$ = 1 ( ${{\overline{\boldsymbol \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\boldsymbol \nu}}_{{e}}}$ ) INSPIRE search

VALUE (eV${}^{2}$) CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
$0.023\text{ to }0.060$ 90 1
 2013 A
MBNE MiniBooNE
$<0.16$ 90 2
 2012
MBNE MiniBooNE/SciBooNE
$\text{0.03 - 0.09}$ 90 3
 2010
MBNE E$_{{{\mathit \nu}}}>$ 475 MeV
$\text{0.03 - 0.07}$ 90 4
 2010
MBNE E$_{{{\mathit \nu}}}>$ 200 MeV
$<0.06$ 90
 2009 B
MBNE MiniBooNE
$<0.055$ 90 5
 2002
KAR2 Liquid Sci. calor.
$<2.6$ 90
 2002
NTEV NUTEV FNAL
$\text{0.03 - 0.05}$ 6
 2001
LSND LAMPF
$\text{0.05 - 0.08}$ 90 7
 1996
LSND LAMPF
$\text{0.048 - 0.090}$ 80 8
 1995
$<0.07$ 90 9
 1995
$<0.9$ 90
 1994 C
CHM2 CERN SPS
$<0.14$ 90 10
 1993
CNTR LAMPF
1  Based on ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ appearance of $78.4$ $\pm28.5$ events. The best fit values are $\Delta$m${}^{2}$ = 0.043 eV${}^{2}$ and sin$^22\theta$ = 0.88.
2  CHENG 2012 is a combined fit of MiniBooNE and SciBooNE antineutrino data.
3  This value is for a two neutrino oscillation analysis for excess antineutrino events with E$_{{{\mathit \nu}}}>$ 475 MeV. The best fit is at 0.07. The allowed region is consistent with LSND reported by AGUILAR 2001 . Supercedes AGUILAR-AREVALO 2009B.
4  This value is for a two neutrino oscillation analysis for excess antineutrino events with E$_{{{\mathit \nu}}}>$ 200 MeV with subtraction of the expected 12 events low energy excess seen in the neutrino component of the beam. The best fit value is 0.007 for $\Delta \mathit m{}^{2}$ = 4.4 eV${}^{2}$.
5  ARMBRUSTER 2002 is the final analysis of the KARMEN$~$2 data for $17.7~$m distance from the ISIS stopped pion and muon neutrino source. It is a search for ${{\overline{\mathit \nu}}_{{e}}}$, detected by the inverse $\beta$-decay reaction on protons and ${}^{12}\mathrm {C}$. 15 candidate events are observed, and $15.8$ $\pm0.5$ background events are expected, hence no oscillation signal is detected. The results exclude large regions of the parameter area favored by the LSND experiment.
6  AGUILAR 2001 is the final analysis of the LSND full data set. It is a search for ${{\overline{\mathit \nu}}_{{e}}}$ 30$~$m from LAMPF beam stop. Neutrinos originate mainly for ${{\mathit \pi}^{+}}$ decay at rest. ${{\overline{\mathit \nu}}_{{e}}}$ are detected through ${{\overline{\mathit \nu}}_{{e}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit n}}$ (20$<\mathit E_{{{\mathit e}^{+}}}<60$ MeV) in delayed coincidence with ${{\mathit n}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit d}}{{\mathit \gamma}}$ . Authors observe $87.9$ $\pm22.4$ $\pm6.0$ total excess events. The observation is attributed to ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ oscillations with the oscillation probability of $0.264$ $\pm0.067$ $\pm0.045\%$, consistent with the previously published result. Taking into account all constraints, the most favored allowed region of oscillation parameters is a band of $\Delta \mathit m{}^{2}$ from $0.2 - 2.0~$eV${}^{2}$. Supersedes ATHANASSOPOULOS 1995 , ATHANASSOPOULOS 1996 , and ATHANASSOPOULOS 1998 .
7  ATHANASSOPOULOS 1996 is a search for ${{\overline{\mathit \nu}}_{{e}}}$ 30$~$m from LAMPF beam stop. Neutrinos originate mainly from ${{\mathit \pi}^{+}}$ decay at rest. ${{\overline{\mathit \nu}}_{{e}}}$ could come from either ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ or ${{\mathit \nu}_{{e}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ ; our entry assumes the first interpretation. They are detected through ${{\overline{\mathit \nu}}_{{e}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit n}}$ (20$~$MeV $<\mathit E_{{{\mathit e}^{+}}}<$60 MeV) in delayed coincidence with ${{\mathit n}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit d}}{{\mathit \gamma}}$ . Authors observe $51$ $\pm20$ $\pm8$ total excess events over an estimated background $12.5$ $\pm2.9$. ATHANASSOPOULOS 1996B is a shorter version of this paper.
8  ATHANASSOPOULOS 1995 error corresponds to the $1.6\sigma$ band in the plot. The expected background is $2.7$ $\pm0.4$ events. Corresponds to an oscillation probability of ($0.34$ ${}^{+0.20}_{-0.18}$ $\pm0.07)\%$. For a different interpretation, see HILL 1995 . Replaced by ATHANASSOPOULOS 1996 .
9  HILL 1995 is a report by one member of the LSND Collaboration, reporting a different conclusion from the analysis of the data of this experiment (see ATHANASSOPOULOS 1995 ). Contrary to the rest of the LSND Collaboration, Hill finds no evidence for the neutrino oscillation ${{\overline{\mathit \nu}}_{{\mu}}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ and obtains only upper limits.
10  FREEDMAN 1993 is a search at LAMPF for ${{\overline{\mathit \nu}}_{{e}}}$ generated from any of the three neutrino types ${{\mathit \nu}_{{\mu}}}$, ${{\overline{\mathit \nu}}_{{\mu}}}$, and ${{\mathit \nu}_{{e}}}$ which come from the beam stop. The ${{\overline{\mathit \nu}}_{{e}}}$'s would be detected by the reaction ${{\overline{\mathit \nu}}_{{e}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit n}}$ . FREEDMAN 1993 replaces DURKIN 1988 .
References:
 AGUILAR-AREVALO 2013A
PRL 110 161801 Improved Search for ${{\overline{\mathit \nu}}_{{\mu}}}\leftrightarrow{{\overline{\mathit \nu}}_{{e}}}$ Oscillations in the MiniBooNE Experiment
 CHENG 2012
PR D86 052009 Dual Baseline Search for Muon Antineutrino Disappearance at 0.1 eV${}^{2}$ $<$ $\Delta$m${}^{2}$ $<$ 100 eV${}^{2}$
 AGUILAR-AREVALO 2010
PRL 105 181801 Event Excess in the MiniBooNE Search for ${{\overline{\mathit \nu}}_{{\mu}}}\leftrightarrow{{\overline{\mathit \nu}}_{{e}}}$ Oscillations
 AGUILAR-AREVALO 2009B
PRL 103 111801 A Search for Electron Antineutrino Appearance at the $\Delta \mathit m{}^{2}$ $\sim{}$ 1$~$eV${}^{2}$ Scale
 ARMBRUSTER 2002
PR D65 112001 Upper Limits for Neutrino Oscillations ${{\overline{\mathit \nu}}_{{\mu}}}-{{\overline{\mathit \nu}}_{{e}}}$ from Muon Decay at Rest
 AVVAKUMOV 2002
PRL 89 011804 A Search for ${{\mathit \nu}_{{\mu}}}-{{\mathit \nu}_{{e}}}$ and ${{\overline{\mathit \nu}}_{{\mu}}}-{{\overline{\mathit \nu}}_{{e}}}$ Oscillations at NUTeV
 AGUILAR 2001
PR D64 112007 Evidence for Neutrino Oscillations from the Observation of ${{\overline{\mathit \nu}}_{{e}}}$ Appearance in a ${{\overline{\mathit \nu}}_{{\mu}}}$ Beam
 ATHANASSOPOULOS 1996
PR C54 2685 Evidence for Neutrino Oscillations from Muon Decay at Rest
 ATHANASSOPOULOS 1995
PRL 75 2650 Candidate Events in a Search for ${{\overline{\mathit \nu}}_{{\mu}}}$ $\leftrightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$ Oscillations
 HILL 1995
PRL 75 2654 Alternative Analysis of the LSND Neutrino Oscillation Search Data on ${{\overline{\mathit \nu}}_{{\mu}}}$ $\leftrightarrow$ ${{\overline{\mathit \nu}}_{{e}}}$
 VILAIN 1994C
ZPHY C64 539 Search for Muon to Electron Neutrino Oscillations
 FREEDMAN 1993
PR D47 811 Limits on Neutrino Oscillations from ${{\overline{\mathit \nu}}_{{e}}}$ Appearance
 ATHANASSOPOULOS 1998
PRL 81 1774 Evidence for ${{\mathit \nu}_{{\mu}}}$ $\leftrightarrow$ ${{\mathit \nu}_{{e}}}$ Oscillations from the LSND