Unexplained Excess of Electronlike Events from a 1-GeV Neutrino Beam

Abstract

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A. A. Aguilar-Arevalo,⁵ C. E. Anderson,¹⁸ A. O. Bazarko,¹⁵ S. J. Brice,⁷ B. C. Brown,⁷ L. Bugel,⁵ J. Cao,¹⁴ L. Coney,⁵ J. M. Conrad,^5,13 D. C. Cox,¹⁰ A. Curioni,¹⁸ Z. Djurcic,⁵ D. A. Finley,⁷ B. T. Fleming,¹⁸ R. Ford,⁷ F. G. Garcia,⁷ G. T. Garvey,¹¹ C. Green,^7,11 J. A. Green,^10,11 T. L. Hart,⁴ E. Hawker,^3,11 R. Imlay,¹² R. A. Johnson,³ G. Karagiorgi,^5,13 P. Kasper,⁷ T. Katori,¹⁰ T. Kobilarcik,⁷ I. Kourbanis,⁷ S. Koutsoliotas,² E. M. Laird,¹⁵ S. K. Linden,¹⁸ J. M. Link,¹⁷ Y. Liu,¹⁴ Y. Liu,¹ W. C. Louis,¹¹ K. B. M. Mahn,⁵ W. Marsh,⁷ G. McGregor,¹¹ W. Metcalf,¹² P. D. Meyers,¹⁵ F. Mills,⁷ G. B. Mills,¹¹ J. Monroe,^5,13 C. D. Moore,⁷ R. H. Nelson,⁴ V. T. Nguyen,^5,13 P. Nienaber,¹⁶ J. A. Nowak,¹² S. Ouedraogo,¹² R. B. Patterson,¹⁵ D. Perevalov,¹ C. C. Polly,^9,10 E. Prebys,⁷ J. L. Raaf,³ H. Ray,^8,11 B. P. Roe,¹⁴ A. D. Russell,⁷ V. Sandberg,¹¹ R. Schirato,¹¹ D. Schmitz,⁵ M. H. Shaevitz,⁵ F. C. Shoemaker,¹⁵ D. Smith,⁶ M. Sodeberg,¹⁸ M. Sorel,⁵ P. Spentzouris,⁷ I. Stancu,¹ R. J. Stefanski,⁷ M. Sung,¹² H. A. Tanaka,¹⁵ R. Tayloe,¹⁰ M. Tzanov,⁴ R. Van de Water,¹¹ M. O. Wascko,¹² D. H. White,¹¹ M. J. Wilking,⁴ H. J. Yang,¹⁴ G. P. Zeller,^5,11 and E. D. Zimmerman⁴

(MiniBooNE Collaboration)

¹University of Alabama, Tuscaloosa, Alabama 35487, USA
²Bucknell University, Lewisburg, Pennsylvania 17837, USA
³University of Cincinnati, Cincinnati, Ohio 45221, USA
⁴University of Colorado, Boulder, Colorado 80309, USA
⁵Columbia University, New York, New York 10027, USA
⁶Embry Riddle Aeronautical University, Prescott, Arizona 86301, USA
⁷Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
⁸University of Florida, Gainesville, Florida 32611, USA
⁹University of Illinois, Urbana, Illinois 61801, USA
¹⁰Indiana University, Bloomington, Indiana 47405, USA
¹¹Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
¹²Louisiana State University, Baton Rouge, Louisiana 70803, USA
¹³Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
¹⁴University of Michigan, Ann Arbor, Michigan 48109, USA
¹⁵Princeton University, Princeton, New Jersey 08544, USA
¹⁶Saint Mary's University of Minnesota, Winona, Minnesota 55987, USA
¹⁷Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
¹⁸Yale University, New Haven, Connecticut 06520, USA

Received 14 December 2008; published 11 March 2009

TheMiniBooNE Collaboration observes unexplained electronlike events in the reconstructed neutrinoenergy range from 200 to 475 MeV. With 6.46×10²⁰ protons ontarget, 544 electronlike events are observed in this energy range,compared to an expectation of 415.2±43.4 events, corresponding to anexcess of 128.8±20.4±38.3 events. The shape of the excess inseveral kinematic variables is consistent with being due to either_e and [overline nu ] _e charged-current scattering or _µ neutral-current scattering witha photon in the final state. No significant excess ofevents is observed in the reconstructed neutrino energy range from475 to 1250 MeV, where 408 events are observed compared toan expectation of 385.9±35.7 events.

URL:	http://link.aps.org/doi/10.1103/PhysRevLett.102.101802
DOI:	10.1103/PhysRevLett.102.101802
PACS:	14.60.Lm; 14.60.Pq; 14.60.St 14.60.Lm Ordinary neutrinos (ν_e, ν_μ, ν_τ) 14.60.Pq Neutrino mass and mixing 14.60.St Non-standard-model neutrinos, right-handed neutrinos, etc. YEAR: 2009