No evidence for neutrino oscillations is seen in our experiment which observed neutrinos from muon-decays at rest. Upper limits on oscillation parameters are presented for neutrino mixing of the kind {nu}{sub e}{leftrightarrow}{nu}{sub {mu}} and also of the kind {nu}{sub e}{leftrightarrow}{nu}{sub i}, i{ne}{mu}

Burman, R.L.

Cochran, D.R.F.

Duclos, J.

Frank, J.S.

Hargrove, C.K.

Hughes, V.W.

Kaspar, H.

Moser, U.

Nemethy, P.

Redwine, R.P.

Willis, S.E.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleLIMITS ON NEUTRINO OSCILLATIONS FROM MUON-DECAY NEUTRINOSPermalinkhttps://escholarship.org/uc/item/73s927z3AuthorsNemethy, P.Burman, R.L.Cochran, D.R.F.et al.Publication Date1980-06-01eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaDISCLAIMER This document was prepared as an account of work sponsored by the United States Government While this document is believed to contain conect information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any wanamy, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Govemment or any agency thereof, or the Regents of the University of Califomia. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Govemment or any agency thereof or the Regents of the University of California. Limits on Neutrino Oscillations from Muon-decay Neutrinos P. Nemethy, R.L. Burman, D.R.F. Cochran, J. Duclos, J.S. Frank, C.K. Hargrove, V.W. Hughes, H. Kaspar, U. Moser, R.P. Redwine and S.E. Willis(a) Yale University, New Haven, CT 06530, Los Alamos Scientific Laboratory, Los Alamos, NM 87545, Lawrence Berkeley Laboratory,Berkeley, CA 94720, Massachusetts Institute of Technology, Cambridge, MA 02139, National Research Council, Ottawa, Ontario KlA OR6, Canada, Centre d'Etudes Nucleaires de Saclay, F~91190 Gif-sur-Yvette, France, Swiss Institute for Nuclear Research, CH-5234 Villigen, Switzerland and University of Berne, CH-3012 Berne, Switzerland. Abstract: No evidence for neutrino oscillations is seen in our experi-ment which observed neutrinos from muon-decays at rest. Upper limits on oscillation parameters are presented for neutrino mixing of the kind ve ~ V~ and also of the kind Ve ~ vi, i f ~· In a recent Letter1 , we pointed out that our neutrino experiment on the nature of muon conservation also provides an upper limit on neutrino oscillations. Here we present a more detailed analysis of this result. Neutrino oscillations, first proposed byB. Pontecorvo2 and by Z. Mako, et a13 , are of considerable interest in the light of gauge theories with broken lepton flavor symmetry. Experimental upper limits on neutrino oscillations have been reported by E. Bellotti et al., 4 and by J. Blietschau et al.5; F. Reines et al. have reported evidence for neutrino instability.6 In our analysis we make use of our previously published evidence1 that muon conservation is an additive law. We also make the simplifying assumption that oscillations occur between only two neutrino states. Neutrino mixing is then described by a 2 x 2 matrix and the oscillations depend on two parameters, the mixing angle e. and the mass difference ~ = (mi - m~) between neutrino mass eigenstates. The oscillation . (a) Present address: Fermilab , Batavia, IL 60510 probability for neutrinos of momentum p at a distance D from the source is given by (1) In the experiment we utilized a six-ton water Cerenkov counter to observe Ve and Ve from the decay chain TI+ + ~+ VV (at rest) and~++ e+ Ve VV (at rest) by the charged current reactions Vep + ne+ (in H20) and - - + Ved + ppe or Ved +nne (in DzO). The neutrino source was the Clinton P. Anderson Meson Physics Facility (LAMPF) beam stop at a mean distance of 9 m from the detector. For details, - + R "' v lv decay = e and R' + = v /~ decay = e see Ref. 0.00 ± 1.09 ± L 0.06 0.37 0.41 The 7 results are. (2) (3) where we have added (in quadrature) a ± 10% uncertainty in neutrino flux and a +25%/-10% uncertainty8 in the neutrino deuteron cross-section cal-culation of J.S. 0 1 Connell9 to our experimental error in R'. Our null result (2) for R is a direct upper limit on v ++ v os-e V cillations producing Ve from the V~ in the muon decay. To evaluate this limit we weight the muon-decay V~ spectrum by the E2 dependence of the cross section and by the oscillation probability (1) averaged over the finite detector size (1.8 m) to obtain a predicted spectrum shape and normalization for any combination of the oscillation parameters ~ and e. After folding in the experimental resolution we fit these spectra to our observed spectrum of H20 events (Ref. 1, Fig. 2) above our energy cutoff of 25 MeV, to obtain the 68% and 90% confidence level upper limits on ~. as a function of the mixing parameter, sin2 28, shown in Fig. 1. Our heavy water measurement (3) does not distinguish electron neutrinos and electron antineutrinos. Since two muon neutrinos are produced for every electron neutrino in the 1T-]1-e decay sequence, v~ ++ Ve oscillations would increaseR'. However, our water measurement (2), which yielded Fig, 1, is a far more sensitive test for oscillations of this kind and limits their contribution to R1 to a negligible level. In the absence of Ve ++ v~ oscillations, Ve can still disappear by oscillations of the kind Ve ++vi, i + ~. (e.g., ve ++ VT), thus de-creasing R1 • Therefore, our observation (3) of R' at full strength puts a limit, albeit much weaker because of the big error bars, on such os-cillations. For any combination of ~ and 8, we fit the expected spectrum of the original ve events,less those that have changed into Vi,toourob-served spectrum (Ref. 1, Fig. 1) of DzO events (above 25 MeV) with the folding procedure described above. We obtain the 68% and 90% confidence level upper limits on ~. as a function of sin2 28, shown in Fig, 2. We note that the curves of Fig. 1 and Fig. 2 are not asymptotic. The limits oscillate with ~ , dramatically in the case of ve ++ vi (i *~). Fig. 3 and Fig. 4 show the large~ behavior of the limits for both cases. We conclude that our experiment does not show evidence for neutrino oscillations at the levels of sensitivity indicated in the figures. This research was supported in part by the U.S. Department of Energy under Contracts No. EY-76-C-3075, No. W-7405-ENG-36 and No. W-7405-ENG-48. References 1. S.E. Willis, V.W. Hughes, P. Nemethy, R.L. Burman, D.R.F. Cochran, J.S. Frank, R.P. Redwine, J. Duclos, H. Kaspar, C.K.Hargrove and U. Moser, Phys. Rev. Lett. 44, 522 (1980). 2. B. Pontecorvo, Zh. Eksp. Teor. Phys. 12. 549 (1957) trans!. in Soviet Phys. JETP ~. 429 (1958); B. Pontecorvo, Zh. Eksp. Teor. Fiz. 1725 (1967) trans1. in Soviet Phys. JETP 26, 984 (1968). 3. Z. Mako al., Frog. Teor. Phys, 28, 247 (1962). 4. E. Bellotti et al., Nuovo Cimento Lett. ll• 533 (1976). 5. J. Blietschau et , Nucl. Phys. Bl33, 205 (1978). 6. F. Reines et Univ. of California at Irvine preprint (1980). 7. After correcting an error in the expected V p cross section in e Ref. 1. 8. J.S. O'Connell, private communication. 9. J.S. O'Connell, Los Alamos Scientific Laboratory Report No. LA~ 5175-MA (1973), unpublished. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Upper limit on Ve +-+ v11 from H20 data. Upper limit on Ve+-+Vi (i"tlJ) from n2o data. Large /::,. behavior of ve +-+ v11 limit. The allowed region is to the left of the curves. Large /::,. behavior of v e +-+ vi ( i :t: 1J ) limit. The allowed region is to the left of the curves. ~5~ 4@0 l ' ' .. ~ \ 0/o C@f_ ' 0 °/o C.~. \ ---' \\ \ - \ C\1 \ \ \ C\IC\1 .0 \ E \ I \ C\J~ \ E II 1.6 \ <J ' ' ' ' 1.2 ' ' ' ' ' ........ 0. 0 0 0. 2 0.4 0. 1.0 6-80 sin2 3854A 2 Fig, 1 6 02 208 -C\1 > 204 (I) -NE 200 II I . 6 <J I. 2 0 6- 80 0 0. \ \ \ \ \ \ \ \ \ ' ' --- 68 c.t --- 90°/o c.t 3854AI Fig. 2 0 I I "'lllll! ~ 5 I ' c.L \ c.~. \ ---\ I I - I N > I Q) - , NN 20 \ E I \ N~ J II 15 I <l I \ ' 10 ' ) 5 0 ~~~~~~~~~~~~ 0 1.0 9 - 8 0 Fig. 3 35 Zle <qj 1ll!ll< 30 ~ / ( -N > Q) -- 68 c.t NN 20 --- 90 '%, c.O. E I ~ N- / E \ II <l 15 ' ' """"--10 5 0 ~~~~~~~~~~~~~~ 0 0.8 1.0 9 - 80 385<A< Fig. 4 

LIMITS ON NEUTRINO OSCILLATIONS FROM MUON-DECAY NEUTRINOS

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