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Marco G. Giammarchi Istituto Nazionale di Fisica Nucleare

Results from Borexino 26th Rencontres de Blois - 2014. Marco G. Giammarchi Istituto Nazionale di Fisica Nucleare Via Celoria 16 – 20133 Milano ( Italy ) marco.giammarchi@mi.infn.it http://pcgiammarchi.mi.infn.it/giammarchi/. On behalf of the BOREXINO Collaboration

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Marco G. Giammarchi Istituto Nazionale di Fisica Nucleare

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  1. ResultsfromBorexino 26th Rencontres de Blois - 2014 Marco G. Giammarchi Istituto Nazionale di Fisica Nucleare Via Celoria 16 – 20133 Milano (Italy) marco.giammarchi@mi.infn.it http://pcgiammarchi.mi.infn.it/giammarchi/ On behalf of the BOREXINO Collaboration Reporting on the Solar Resultsonly 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future Rencontres de Blois - May 2014

  2. the Borexino Collaboration Virginia Tech Gran Sasso Hamburg Moscow München St. Petersburg Kurchatov Moscow Mainz JINR Dubna Houston TU Dresden Los Angeles Paris Perugia UMass Amherst Milano Jagiellonian Kraków Genova Heidelberg Princeton Napoli Rencontres de Blois - May 2014

  3. We believe we understand the Sun pp-cycle >99% energy production 5 ν species CNO-cycle <1% energy production 3 ν species Neutrinos are produced in severalreactions in bothcycles Rencontres de Blois - May 2014 3

  4. 1. BOREXINO 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future Borexinois a low background Neutrino Detector forsub-MeVsolar Neutrino (and other) studies Detecting Solar Neutrinos, Geo-neutrinos and other rare phenomena • Maindetectionreaction: elasticscattering in a scintillator • Low interactionrates: 0.1/1 event/day/ton of target mass • Low energy (mostly <10 MeV, betterif <2 MeV) • Low threshold and low background (radiopurity) • Underground location to shield from cosmicrays (106reduction of muonflux) Rencontres de Blois - May 2014

  5. Experimental site Laboratori Nazionali del Gran Sasso Assergi (AQ) Italy 1400m of rock shielding ~3800 m.w.e. Abruzzo, Italy 120 Km from Rome External Labs Borexino Detector and Plants Rencontres de Blois - May 2014

  6. The Borexino Detector Stainless Steel Sphere: • 2212 PMTs • ~ 1000 m3 buffer of pc+dmp (light queched) Neutrino electron scattering ne ->n e Scintillator: 270 t PC+PPO (1.4 g/l) Nylon vessels: (125 μm thick) Inner: 4.25 m Outer: 5.50 m (radon barrier) Water Tank: γ and n shield μ water Č detector 208 PMTs in water 2100 m3 Carbon Steel Plates 2020 legslegs Rencontres de Blois - May 2014

  7. Fillingphaseof the Borexino detector (2007, Laboratorio del Gran Sasso) 11 m Photomultipliers Scintillator Water Nylon Vessels Rencontres de Blois - May 2014 7

  8. Solar Neutrinos: the predictedspectrum ,Borexino Rencontres de Blois - May 2014 8

  9. StudyofSolarNeutrinos Solar Neutrino Problem  Neutrino Oscillations Rencontres de Blois - May 2014 9

  10. Neutrino Oscillation Solution (W. Hiroko’s talk atNeutel 2013) Large Mixing Angle + MSW mechanism in the Sun Global, 3-lepton flavoranalysis Rencontres de Blois - May 2014 10

  11. However: beforeBorexino, onlyradiochemicalexperimentscouldobserve solar neutrinosbelow 1 MeV. Real-time experimentsweresensiblemostly to > 5 MeV Open Issues Rencontres de Blois - May 2014 11

  12. 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future 2. Be-7 fluxmeasurement Eν = 862 keV (monoenergetic) ΦSSM = 4.8· 109 ν s-1 cm2 νe νx Electron recoil spectrum Cross Section  10-44 cm2 (@ 1MeV) Rencontres de Blois - May 2014

  13. LMA Rencontres de Blois - May 2014 13

  14. 3. B-8 measurement 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future • Analysiswith 3 MeVthreshold • Borexino rate : ≈ 0.2 cpd / (100 tons) • Backgrounds: • Muons, Neutrons • External background • Fast cosmogenics • C-10, Be-11 • Tl-208,Bi-214 Rencontres de Blois - May 2014

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  16. 4. pepdetection and CNO limit 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future p + e - + p d + e Pepreaction Monoenergetic 1.44 MeV neutrinos Rencontres de Blois - May 2014

  17. Rencontres de Blois - May 2014 17

  18. C-11 reductionstrategy: • Threefoldcoincidence (muon,neutron,C11) • Pulseshapediscrimination electron/gamma/positron (Ps formation) • Multivariate fit with alsoenergy and position First pepmeasurement and the best CNO limit Rencontres de Blois - May 2014 18

  19. Solar neutrino components measured by Borexino ,Borexino Rencontres de Blois - May 2014 19

  20. Neutrino OscillationspropertiesmeasuredbyBorexino Vacuum Regime Matter Regime Solar electron neutrino survivalprobabilityas a functionof neutrino energy LMA-MSW with standard neutrino interactions Rencontres de Blois - May 2014 20

  21. 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Future 6. Future (summary) • BorexinoPhase II (solar neutrinos): • ppdetection • CNO study • Cycles of Purification (Water Extraction) : • Reduce 85Kr and 210Bi affecting the pep and CNO analyses • Kr background reduced to a negligible rate • Bi-210 reduced (tens of counts/day 100 tons) and possiblystudied by means of the time evolution of Po-210 rate. Rencontres de Blois - May 2014

  22. CNO detection CNO reactions are responsible for lessthan 1% of the Sunenergy generation However, thiscycleshould be dominant for higher mass stars (highertemperatures) Giventheir small flux and lowenergy, neutrinos from CNO haveneverbeenmeasureddirectly. ppdetection Theymake up more than 90% of the totalflux and haveneverbeendirectlyobserved. Main source of background is C-14 and itspileupeffect. C-14 spectralshape and pileup Rencontres de Blois - May 2014

  23. Thankyouforyourattention (& selectedbibliography) • G. Alimontiet al., Nucl. Instr. & Methods A600 (2009) 568 Detector • C. Arpesellaet al., Phys. Lett. B 568 (2008) 101 • C. Arpesellaet al., Phys. Rev. Lett. 101 (2008) 091302 • G. Bellini et al., Phys. Rev. Lett. 107 (2011) 141302 • G. Bellini et al., Phys. Lett. B 707 (2012) 22 Be-7 • G. Bellini et al., Phys. Rev. D 82 (2010) 033006 B-8 • G. Bellini et al., Phys. Lett. B 687 (2010) 299 • G. Bellini et al., Phys. Lett. B 722 (2013) 295 Geoν • G. Bellini et al., Phys. Rev. Lett 108 (2012) 051302 pep Rencontres de Blois - May 2014 23

  24. Backup Slides Rencontres de Blois - May 2014

  25. 1. BOREXINO 2. Be-7 fluxmeasurement 3. B-8 measurement 4. pepdetection and CNO limit 5. Geoneutrinos 6. Future 5. Geoneutrinos AntiNeutrinosemitted in beta decays of naturallyoccurringradioactiveisotopes in the Earth’scrust and mantle Moderate NuclearReactorsbkgd at LNGS Detection by Inverse Beta Decay (1.8 MeVthr.) Unoscillated Geo-nu and nuclearreactor nu Unoscillated Geo-nu Positron-Gamma (2.2 MeV) delayedcoincidence Rencontres de Blois - May 2014

  26. Search for positron/neutron-capturedelayedcoincidences in the Borexino detector • Main background sources: • Li-9, He-8, untaggedmuons, accidentals……… • And of coursenuclearreactors • First observationpublished in 2010 New analysisbased on 1353 days of data Phys. Lett. B 722 (2013) 295 Reactorantineutrinosat LNGS Rencontres de Blois - May 2014 26

  27. 1353 days in Borexino: antineutrino geo analysis NuclearReactor component : Found : 21 eventsabove geo endpoint Expected : 22.0 +- 1.6 Geoneutrinos vs Reactorneutrinos: 68.27%, 95.45%, 99.73% Confidencelevelcontour plots for geo and reactorneutrinos Free parameters - Weight of Geo nu - WeightReactor nu Th/U = 3.9 fixed (condhriticvalue) Extreme expectations of BSE (Bulk Silicate Earth) model Reactorsignalexpectation (1 TNU = 1 Terrestrial Neutrino Unit = 1 event/year/1032protons) Rencontres de Blois - May 2014

  28. Best fitvalues: Geofluxes IfU,Thcontributions are left free: Rencontres de Blois - May 2014

  29. Going for pep and CNO: 11C tagging The main background for pep and CNO analysis is 11C, a long lived (τ=30min) cosmogenicβ+ emitter with ~1MeV end-point (shifted to 1-2MeV range) τ (n capture): ~250μs μ 11C Production Channels: [Galbiati et al., Phys. Rev. C71, 055805, 2005] • 95.5% with n: (X,X+n) • X = γ, n, p, π±, e±, μ. • 4.5% invisible : • (p,d); (π+,π0+p). n γ β τ (11C): ~30min 11C rate = (28.5 ±0.5) cpd exp. pep rate ~ 3cpd Rencontres de Blois - May 2014

  30. Going for pep and CNO: positronium Electron/Positrondiscrimination due toPsformation in positronevents (D. Franco, G. Consolati and D. Trezzi, Phys. Rev. C 83 (2011) 015504 Rencontres de Blois - May 2014

  31. The Cr-51 source, with an activity of ~10 Mci Obtained by irradiation of Cr-50 . 3-months experiment to be performed in 2015 B. A Ce-144 antineutrino source can be used. Due to the antineutrino tag, the activitycould be muchsmaller, in the 80 kCirange. C. The Ce-144 source positionedat the center of the detector Rencontres de Blois - May 2014

  32. Short distance neutrino Oscillations with BoreXino (SOX) Experimentalanomalieswhich are difficult to accomodate in a simple 3-flavor scenario Afourth (sterile) neutrino? («Gallium», «Reactor», «LSND-MiniBoone» anomalies) Borexino can be used to perform a short baseline experiment with neutrino source Exploration of parameters in the plane L/E of the order of eV2 Rencontres de Blois - May 2014

  33. Neutrino Oscillations PMNS neutrino mixing matrix, analogous to CKM matrix for quarks Solution of the Solar Neutrino Problem is neutrino oscillation with matter (MSW) effect at Large Mixing Angle (LMA) Rencontres de Blois - May 2014

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