A search for nu(mu) - nu(e) oscillations has been conducted with the LSND apparatus using v(mu) from pi(+) decay in flight. Two analyses observe a total of 40 beam-on high-energy (60-200 MeV) electron events consistent with the nu(e) C --> e(-) X inclusive reaction. This number is significantly above the 21.9 +/- 2.1 events expected from the nu(e) contamination in the beam and the beam-off background. If interpreted as an oscillation signal, the observed oscillation probability of (2.6 +/- 1.0 +/- 0.5) x 10(-3) is consistent with the previously reported <(nu)over bar>(mu) --> <(nu)over bar>(e) oscillation evidence from LSND.

A search for ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}$ oscillations has been conducted at the Los Alamos Meson Physics Facility using ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ from ${\ensuremath{\pi}}^{+}$ decay in flight. An excess in the number of beam-related events from the ${\ensuremath{\nu}}_{e}\stackrel{\ensuremath{\rightarrow}}{C}{e}^{\ensuremath{-}}X$ inclusive reaction is observed. The excess is too large to be explained by normal ${\ensuremath{\nu}}_{e}$ contamination in the beam at a confidence level greater than 99%. If interpreted as an oscillation signal, the observed oscillation probability of $(2.6\ifmmode\pm\else\textpm\fi{}1.0\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ is consistent with the previously reported ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{e}$ oscillation evidence from LSND.

A search for {nu}{sub {mu}}{r_arrow}{nu}{sub e} oscillations has been conducted at the Los Alamos Meson Physics Facility using {nu}{sub {mu}} from {pi}{sup +} decay in flight. An excess in the number of beam-related events from the {nu}{sub e}C{r_arrow}e{sup {minus}}X inclusive reaction is observed. The excess is too large to be explained by normal {nu}{sub e} contamination in the beam at a confidence level greater than 99{percent}. If interpreted as an oscillation signal, the observed oscillation probability of (2.6{plus_minus}1.0{plus_minus}0.5){times}10{sup {minus}3} is consistent with the previously reported {bar {nu}}{sub {mu}}{r_arrow}{bar {nu}}{sub e} oscillation evidence from LSND. {copyright} {ital 1998} {ital The American Physical Society}

A search for {nu}{sub {mu}}{r_arrow}{nu}{sub e} oscillations has been conducted with the LSND apparatus using {nu}{sub {mu}} from {pi}{sup +} decay in flight. Two analyses observe a total of 40 beam-on high-energy (60{endash}200 MeV) electron events consistent with the {nu}{sub e}thinspC{r_arrow}e{sup {minus}} thinspX inclusive reaction. This number is significantly above the 21.9{plus_minus}2.1 events expected from the {nu}{sub e} contamination in the beam and the beam-off background. If interpreted as an oscillation signal, the observed oscillation probability of (2.6{plus_minus}1.0{plus_minus}0.5){times}10{sup {minus}3} is consistent with the previously reported {ovr {nu}}{sub {mu}}{r_arrow}{ovr {nu}}{sub e} oscillation evidence from LSND. {copyright} {ital 1998} {ital The American Physical Society}

A search for nu_mu -> nu_e oscillations has been conducted at the Los Alamos Meson Physics Facility using nu_mu from pi^+ decay in flight. An excess in the number of beam-related events from the C(nu_e,e^-)X inclusive reaction is observed. The excess is too large to be explained by normal nu_e contamination in the beam at a confidence level greater than 99%. If interpreted as an oscillation signal, the observed oscillation probability of (2.6 +- 1.0 +- 0.5) x 10^{-3} is consistent with the previously reported nu_mu_bar -> nu_e_bar oscillation evidence from LSND.

For the exclusive reaction to the N-12 ground state the expected cross section can be reliably calculated using form factors independently determined from other measurements. LSND has measured flux-averaged cross sections of (9.1 +/- 0.4 +/- 0.9) x 10(-42) cm(2) for C-12(nu(e), e(-))N-12(g.s.) and (6.6+/-1.0+/-1.0) x 10(-41)cm(2) for C-12(nu(mu), mu(-))N-12(g.s.) in good agreement with expectations.Inclusive cross sections can not be predicted with as reliable a procedure. LSND measured a flux-averaged cross section to excited states of N-12, C-12(nu(e), e(-))N-12*, Of (5.7 +/- 0.6 +/- 0.6) x 10(-42)cm(2) in good agreement with a CRPA calculation. For the inclusive process C-12(nu(mu), mu(-))N-12 LSND measured a flux-averaged cross section of (11.2 +/- 0.3 +/- 1.8) x 10(-40)cm(2). This is significantly below a recent CRPA calculation.

Charged current scattering of ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ on ${}^{12}\mathrm{C}$ has been studied using a ${\ensuremath{\pi}}^{+}$ decay-in-flight ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ beam at the Los Alamos Meson Physics Facility. A sample of 56.8 $\ifmmode\pm\else\textpm\fi{}9.6$ events satisfying criteria for the exclusive reaction ${}^{12}{\mathrm{C}(\mathrm{\ensuremath{\nu}}}_{\mathrm{\ensuremath{\mu}}}{,\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.}$ was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section $(6.6\ifmmode\pm\else\textpm\fi{}1.0\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}{\mathrm{cm}}^{2}$ agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible ${}^{12}\mathrm{N}$ states ${}^{12}\mathrm{C}({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}})X.$ This flux-averaged cross section is $(11.2\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}{\mathrm{cm}}^{2},$ which is approximately half of that given by a recent continuum random-phase approximation calculation.

Charged current reactions of {nu}{sub e} on {sup 12}C have been studied using a {mu}{sup +} decay-at-rest {nu}{sub e} beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction {sup 12}C({nu}{sub e},e{sup {minus}}){sup 12}N{sub g.s.} were measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to {sup 12}N excited states, {sup 12}C({nu}{sub e},e{sup {minus}}){sup 12}N{sup {asterisk}} and compared with theoretical expectations. Results are consistent with a recent continuum random phase approximation (CRPA) calculation. {copyright} {ital 1997} {ital The American Physical Society}

Charged current reactions of v(e) on C-12 have been studied using a mu(+) decay-at-rest v(e) beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction C-12(v(e),e(-))N-12(g.s.) were measured in a large Liquid Scintillator Neutrinro Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to N-12 excited states, C-12(v(e),e(-))N-12* and compared with theoretical expectations. Results are consistent with a recent continuum random phase approximation (CRPA) calculation.

A search for neutrino oscillations of the type νμ → νc has been conducted at the Los Alamos Meson Physics Facility using νμ from muon decay at rest. Evidence for this transition has been reported previously. This paper discusses in detail the experimental setup, detector operation and neutrino source, including aspects relevant to oscillation searches in the muon decay-at-rest and pion decay in flight channels.

Charged current scattering of nu(mu) on C-12 has been studied using a pi(+) decay-in-flight nu(mu) beam at the Los Alamos Meson Physics Facility. A sample of 56.8 +/- 9.6 events satisfying criteria for the exclusive reaction C-12(nu(mu),mu(-))N-12(g.s.) was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section (6.6 +/- 1.0 +/- 1.0) X 10(-41) cm(2) agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible N-12 states C-12( nu(mu),mu(-))X This flux-averaged cross section is (11.2 +/- 0.3 +/- 1.8) X 10(-40) cm(2), which is approximately half of that given by a recent continuum random-phase approximation calculation.

Charged current reactions of νe on 12C have been studied using a μ+ decay-at-rest νe beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction 12C(νe,e−)12Ng.s. were measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to 12N excited states, 12C(νe,e−)12N* and compared with theoretical expectations. Results are consistent with a recent continuum random phase approximation (CRPA) calculation.Received 9 September 1996DOI:https://doi.org/10.1103/PhysRevC.55.2078©1997 American Physical Society

Charged current scattering of nu_mu on 12C has been studied using a pi+ decay-in-flight nu_mu beam at the Los Alamos Meson Physics Facility. A sample of 56.8 +- 9.6 events satisfying criteria for the exclusive reaction 12C + nu_mu -> mu- + 12N_g.s. was obtained using the large Liquid Scintillator Neutrino Detector (LSND). The observed flux-averaged cross section, (6.6 +- 1.0 +- 1.0) x 10^-41 cm^2, agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible 12N states, 12C + nu_\mu -> mu- + X. This flux-averaged cross section is (11.2 +- 0.3 +- 1.8)x 10^-40 cm^2, which is approximately half of that given by a recent Continuum Random Phase Approximation (CRPA) calculation.

Charged current reactions of {nu}{sub e} on {sup 12}C have been studied using a {mu}{sup +} decay-at-rest {nu}{sub e} beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction {sup 12}C({nu}{sub e},e{sup {minus}}){sup 12}N{sub g.s.} were measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to {sup 12}N excited states, {sup 12}C({nu}{sub e},e{sup {minus}}){sup 12}N{sup {asterisk}} and compared with theoretical expectations. Results are consistent with a recent continuum random phase approximation (CRPA) calculation. {copyright} {ital 1997} {ital The American Physical Society}

A search for <(nu)over bar (mu)> --> <(nu)over bar (e)> oscillations has been conducted at the Los Alamos Meson Physics Facility by using <(nu)over bar (mu)> from mu(+) decay at rest. The <(nu)over bar (e)> are detected via the reaction <(nu)over bar (e)> p --> e(+)n, correlated with a gamma from np --> d gamma (2.2 MeV). The use of tight cuts to identify e(+) events with correlated gamma rays yields 22 events with e(+) energy between 36 and 60 MeV and only 4.6 +/- 0.6 background events. A fit to the e(+) events between 20 and 60 MeV yields a total excess of 51.0(-19.5)(+20.2) +/- 8.0 events. If attributed to <(nu)over bar (mu)> --> <(nu)over bar (e)> oscillations, this corresponds to an oscillation probability of (0.31 +/- 0.12 +/- 0.05)%.

A search for <(nu)over bar>(mu)--><(nu)over bar>(e) oscillations has been conducted at the Los Alamos Meson Physics Facility using <(nu)over bar>(mu) from mu(+) decay at rest. The <(nu)over bar>(e) are detected via the reaction <(nu)over bar>(e)p-->e(+)n, correlated with the 2.2 MeV gamma from np-->d gamma. The use of tight cuts to identify e(+) events with correlated gamma rays yields 22 events with e(+) energy between 36 and 60 MeV and only 4.6+/-0.6 background events. The probability that this excess is due entirely to a statistical fluctuation is 4.1X10(-8). A chi(2) fit to the entire e(+) sample results in a total excess of 51.0(-19.5)(+20.2)+/-8.0 events with e(+) energy between 20 and 60 MeV. If attributed to <(nu)over bar>(mu)--><(nu)over bar>(e) oscillations, this corresponds to an oscillation probability (averaged over the experimental energy and spatial acceptance) of (0.31+/-0.12+/-0.05)%.