The study of solar neutrinos and of non-standard neutrino interactions with Borexino

S Zavatarelli ,O Smirnov,D Semenov ,M Gromov,F Calaprice ,F Gabriele,A Jany,D Güffanti ,A Formozov ,S Marcocci,Xuefeng Ding ,S Rottenanger,A Di Giacinto,J Benziger ,L Papp,R B Vogelaar ,I Machulin ,A Goretti ,P Lombardi ,J Thurn,M Agostini ,I Drachnev ,K Altenmüller ,C Hagner ,Z Bagdasarian,M Gschwender,M Wójcik ,D Bravo,N Rossi,M Misiaszek,V Kobychev ,D Jeschke,M Redchuk,A Sotnikov,V Di Marcello,M Nieslony,G Testera,F Von Feilitzsch,S Kumaran ,M Giammarchi ,J Martýn ,F Ortica ,C Ghiano,K Choi ,Aldo Romani ,E Meroni,L Ludhová ,V Orekhov,S Schönert ,N Pilipenko,L Lukyanchenko,V Muratova ,M Meyer ,A Caminata,R Tartaglia,B Caccianiga,T Lachenmaier ,A Pocar,G Bonfini,V Atroshchenko,D D’angelo ,S Appel,G Lukyanchenko,M Laubenstein ,M Skorokhvatov ,D Franco,A Di Lüdovico ,G Korga,A Derbin ,L Pietrofaccia,G Bellini,A Chepurnov ,E Hungerford ,D Basilico,A Razeto,G Ranucci ,Ö Penek ,M Wurm ,L Di Noto,G Manuzio,S Davini,Aldo Ianni,Κ Zuber ,P Cavalcante,J Maricic,D Bick,F Cavanna,C Galbiati ,E Unzhakov ,I Lomskaya,Andrea Ianni,A Vishneva,A Re ,E Litvinovich,M T Ranalli ,Y Suvorov,L Miramonti ,L Cappelli ,O Zaimidoroga,M Pallavicini ,G Raikov,B Neumair,L Oberauer ,G Zuzel

doi:10.1088/1742-6596/1468/1/012192

S Zavatarelli , O Smirnov + Show 102 more

Open Access

https://doi.org/10.1088/1742-6596/1468/1/012192

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Abstract

The Borexino liquid scintillator neutrino observatory has a unique capability to perform high-precision solar neutrino observations thanks to its exceptional radiopurity and good energy resolution (5% at 1 MeV). A comprehensive study of the pp-chain neutrinos was presented that includes the direct measurements of 7Be, pp and pep neutrino fluxes with the highest precision ever achieved (down to 2.8% in the 7Be component), the 8B with the lowest energy threshold, the best limit on CNO neutrinos and the first Borexino limit on hep neutrinos. These results are important to validate the MSW-LMA oscillation paradigm across the full solar energy range and to exclude possible Non-Standard neutrino Interactions (NSIs). In particular the effects of neutrino-flavor-diagonal Neutral-Current (NC) interactions that modify the vee and vτe couplings while preserving their chiral and flavor structures, have been investigated. At detection, the shape of the electron-recoil spectrum is affected by changes in the vee and vτe couplings, quantified by the parameters and . New bounds to all four parameters were obtained, quite stringent compared to the global ones. In particular, the best constraint to-date on was achieved. A comprehensive summary of all the recent results on solar neutrinos from Borexino is reported in the present paper.

Highlights

Solar neutrinos are a unique probe of the Sun’s interior and at the same time they provide an intense natural beam for fundamental physics: they reach the Earth as a mixture of all neutrino flavours owing to the flavour-conversion mechanism enhanced by the MSW effect
Solar neutrino study and Borexino results For each of the events detected in Borexino, the total amount of the light and its time distribution among photomultipliers provide three important quantities: its deposited energy, from the total number of detected photoelectrons; its position within the detector, from the analysis of the photons arrival times at each photomultiplier; and its particle identification, from a pulseshape discrimination method that exploits the difference in time structure of liquid-scintillator light pulses induced by different particles [2]
The measured neutrino fluxes can be used either to probe our understanding of solar physics assuming the validity of the neutrino physics assumptions or, alternatively, to test the MSW-LMA paradigm assuming Standard Solar Model (SSM) flux predictions