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Absence of a day-night asymmetry in the Be solar neutrino rate in Borexino |
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| Institution: | a APC, Laboratoire AstroParticule et Cosmologie, 75231 Paris cedex 13, France b Joint Institute for Nuclear Research, Dubna 141980, Russia c Dipartimento di Fisica, Universitá e INFN, Genova 16146, Italy d M. Smoluchowski Institute of Physics, Jagiellonian University, Krakow, 30059, Poland e INFN Laboratori Nazionali del Gran Sasso, Assergi 67010, Italy f Institute for Nuclear Research, Kiev 03680, Ukraine g NRC Kurchatov Institute, Moscow 123182, Russia h Dipartimento di Fisica, Universitá degli Studi e INFN, Milano 20133, Italy i Max-Plank-Institut für Kernphysik, Heidelberg 69029, Germany j Dipartimento di Chimica, Universitá e INFN, Perugia 06123, Italy k Chemical Engineering Department, Princeton University, Princeton, NJ 08544, USA l Physics Department, Princeton University, Princeton, NJ 08544, USA m St. Petersburg Nuclear Physics Institute, Gatchina 188350, Russia n Physik Department, Technische Universität München, Garching 85747, Germany o Instituto de Fi`sica Corpuscular, CSIC-UVEG, Valencia E-46071, Spain p Physics Department, University of Massachusetts, Amherst, MA 01003, USA q Physics Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA r Institut für Experimentalphysik, Universität Hamburg, Germany |
| Abstract: | We report the result of a search for a day-night asymmetry in the 7Be solar neutrino interaction rate in the Borexino detector at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The measured asymmetry is Adn=0.001±0.012 (stat)±0.007 (syst), in agreement with the prediction of MSW-LMA solution for neutrino oscillations. This result disfavors MSW oscillations with mixing parameters in the LOW region at more than 8.5 σ. This region is, for the first time, strongly disfavored without the use of reactor anti-neutrino data and therefore the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics. |
| Keywords: | Solar neutrinos Day-night effect CPT violation Neutrino oscillations |
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