Solar Neutrino Experiments A Review The CAP'09 Congress Moncton, 7-10 June, 2009 Alain Bellerive On behalf of the SNO Collaboration Carleton University, Ottawa, Canada From Solving the Solar Neutrino Problem to Precision Physics

Outline Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010  Introduction  Solar Neutrino Flux (update)  First Generation of Solar Neutrino Experiments  Chlorine – Gallium – Kamiokande  Second Generation of Solar Neutrino Experiment  SuperK – Borexino – SNO  The new stuff for 2010 !!!  Constraints on Oscillation Parameters  Future Prospects

Evidence for Neutrino Mixing Solar Neutrinos low energies Atmospheric Neutrinos high energies Beamstop Neutrinos tunable energies First evidence of neutrino oscillation Today’s talk !!! Parallel Session Talk by Dr. Yoshihisa Obayashi Plenary Talk by Tsuyoshi Nakaya

h The First Piece Solar Neutrino Flux  The Sun produces  e in fusion nuclear reactions  Survival probability depends on the neutrino energy  Solar neutrino oscillation occurs inside the Sun

±1% ±6% BPS08 ±6% ±1.1% ±11% ±16% Borexino Neutrino Production in the Sun Light Element Fusion Reactions p + p  2 H + e + + e p + e - + p  2 H + e 3 He + p  4 He + e + + e 7 Be + e -  7 Li + e % 0.25 % 15 % ~10 -5 % 8 B  8 Be* + e + + e 0.02 % Neutrino Production Radius BPS08: (Bahcall) Pena ‐ Garay C. & Serenelli A arXiv:

6 Sudbury Neutrino Observatory FAAQ2006Alain Bellerive ee

7 Solar Neutrino Mixing Survival Probability 3 Parameters ! The state evolves with time or distance P ee ≡P(  e →  e ) P ee = cos 4 (  )[1-sin 2 (2   ) sin 2 (  )] P ee ≈ 1-sin 2 (2   ) sin 2 (  ) where  =1.27  m 2 L / E Main Solar Physics:  m 2 & sin(2  ) Experiment: Distance (L) & Energy (E)

The Second Piece: First Generation Experiments Chlorine – Gallium - Kamiokande

Solar Neutrino Problem (Pre SNO) ExperimentMediumThreshold (MeV) Measured/SSM HomestakeChlorine ±0.03 SAGE+GALLEX/GNO Gallium ±0.03 SuperKH2OH2O ±0.013 Neutrino reactions Source: arXiv:hep-ph/ νeνe ~10 8 km Measured Predicted P ee

Phys.Rev. D64 (2001) LMA Allowed Regions SMA LOW VAC JustSo 2  m 2 (eV 2 ) tan 2  Combination of the Chlorine, Gallium, SK, and CHOOZ restricted the mixing parameters Pre SNO (~2001) TODAY Mixing Parameters

Arranging the Pieces: Second Generation Experiments SuperK – SNO - Borexino

12 Super Kamiokande 8 B (and hep) neutrino(s) detection x  + e - → x  + e - Sensitive to e      ( ,  + e - )  0.15 ×  ( e + e - ) High statistics ~15 events/day Real time measurement allow studies on time variations Studies energy spectrum 50 ktons of pure water

Timeline of Super-Kamiokande ID PMTs (40% coverage) 5182 ID PMTs (19% coverage) ID PMTs (40% coverage) Energy Threshold Total energy Kinetic energy SK-ISK-IISK-IIISK-IV Acrylic (front) + FRP (back) Electronics Upgrade SK-ISK-IISK-IIISK-IV 5.0 MeV ~4.5 MeV 7.0 MeV ~6.5 MeV 5.0 MeV ~4.5 MeV Target < 4.0 MeV <~3.5 MeV Current ~4.5 MeV ~4.0 MeV 41.4 m

Solar neutrino data of SK (period I) May 31,1996 – July 13,2001 (1496 days) E e = MeV  226(stat) solar  events 8 B flux: 2.35  0.02(stat)  0.08(syst) [x 10 6 /cm 2 /sec] Data SSM ≈ 0.41 Phys. Rev. D 73, (2006)

Daily Variation of SK Rate (Period I)

Borexino 7 Be and 8 B neutrinos detection x  + e - → x  + e - Sensitive to e      ( ,  + e - )  0.2 ×  ( e + e - ) Challenge: Control of Low Energy Background Energy window: [0.16 – 2.0] MeV for 7 Be > 3.0 MeV for 8 B

Work on installation continues Needs to resolve “political situation” Borexino Detector 18m Scintillator detector with an active mass of 278 tons of pseudocumene PC buffer and water for shielding to rarioactivity Scintillation light is detected via 2212 inward looking PMTs Energy resolution 5% (at 1 MeV) and position resolution 10 ‐ 15 cm

7 Be Analysis Borexino (192 live ‐ days) Signature for the monoenergetic MeV 7 Be neutrinos is the Compton-like edge of the recoil electrons at 665 keV 85 KrCosmogenic 11 C 210 Bi + CNO neutrinos After statistical subtraction of 210 Po alphas

Result of Borexino’s 7 Be Analysis Rate( 7 Be) = 49 ± 3 (stat) ± 4 (syst) cpd/100tons Φ( 7 Be) = (5.18 ± 0.51) × 10 9 cm ‐ 2 s ‐ 1 P ee = 0.56 ± 0:10 at MeV Under the assumption of SSM flux Detail by Sandra Savatarelli in parallel session talk Solar neutrino and terrestrial antineutrino fluxes measured with Borexino at LNGS Phys. Rev. Letts. 101, (2008)

tonnes Inner Shield H 2 O 1000 tonnes D 2 O 5300 tonnes Outer Shield H 2 O 12 m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage Image courtesy National Geographic Sudbury Neutrino Observatory 6000 mwe overburden 17.8 m

Key signatures for mixing with SNO 21 Flavor change ? P ee (E  ) ≠ 1 ! CC ES NC

Timeline of SNO Commissioning D 2 O + Salt D2OD2O D 2 O + 3 He counters 3 He counters Install Commission D 2 O Phase IPhase IIPhase III 306days391days396days PRL 87, , 2001 PRL 89, , 2002 PRL 89, , 2002 PRC 75, , 2007 PRL 92, , 2004 PRC 72, , 2005 Total of ~1100 live-days PRL101, , 2008 PRC, , 2010 Upcoming… Phase I-II-III combined analysis Combined Phase I-II Low Energy Threshold Analysis Data Analysis

SNO NCD’s Phase III p t n Ni wall 3 He:CF 4 gas Cu wire keV573 keV764 keV PRL101, , 2008

SNO Phases I+II Major Improvements  Tune up the Monte Carlo on calibration data based on 5 years of operational experience - Reduction of systematic uncertainties  Improve optics (especially at large radii) with late light and new energy estimator (improve energy resolution by 6%) Energy Threshold D 2 O phase T eff = 5 → 3.5 MeV Salt phase T eff = 5.5 → 3.5 MeV Improve statistics CC by ~40% NC by ~70% Allow to fit the background wall Night Day P ee typical LMA E

No distortion, no D/N:  2 = 1.94 / 4 d.o.f. LMA-prediction:  2 = 3.90 / 4 d.o.f. DAY NIGHT A DN  ( 8 B) = in units of 10 6 cm −2 s −1 SNO Phases I+II Direct joint-phase fit of P ee PRC, , Previous global best-fit LMA point tan 2  12 =0.468  m 2 =7.59x10 -5 eV 2 12 Previous global best-fit LMA point tan 2  12 =0.468  m 2 =7.59x10 -5 eV 2 12 Previous global best-fit LMA point tan 2  12 =0.468  m 2 =7.59x10 -5 eV 2 12

Global View

Data Sets Solar Oscillation Analysis  Radiochemical : Cl, Ga –Ga rate: 66.1 ±3.1 SNU SAGE+GNO/GALLEX [PRC80, (2009)] –Cl rate: 2.56 ±0.23 [Astrophys. J. 496 (1998) 505]  SK –SK-I 1496 days, zenith spectrum E ≥ 5.0 MeV –SK-II 791 days, spectrum + D/N E ≥ 7.5 MeV  Borexino – 7 Be rate: 49 ± 5 cpd/100tons [PRL101, (2008)]  SNO –Phase I + II (PMT Low Energy threshold E ≥ 4.0 MeV) –Phase III (NCD and PMT E ≥ 6.5MeV)  KamLAND reactor experiment: 2008 [PRL100, (2008)]  8 B spectrum: W. T. Winter et al., PRC 73, (2006). Plenary Talk by Fabrice Piquemal

Oscillation Analyses: Global Solar Best-fit LMA point: tan 2  12 = ( )  m 2 = 5.89x10 -5 eV 2 ( )  ( 8 B) = in units of 10 6 cm −2 s − Δ  8B = % 12 2 model

Solar + KamLAND 2-flavor Overlay

Best-fit LMA point: tan 2  12 =  12 =34.06 deg  m 2 = 7.59 x10 -5 eV 2 Solar + KamLAND 2-flavor 2 model Δ  8B = %  ( 8 B) = in units of 10 6 cm −2 s −1 12

3 model Solar + KamLAND 3-flavor Best-fit: sin 2  13 = x10 -2 sin 2  13 < (95% C.L.) Best-fit LMA point: tan 2  12 =  m 2 = 7.59 x10 -5 eV Remark: SNO and SK global oscillation analyses consistent

32 Sudbury Neutrino Observatory FAAQ2006Alain Bellerive Newest stuff for summer 2010 !!!

Vertex distributions in SK-III Data sample before fiducial volume cut 33 Tight fiducial volume cut is applied in E total <5.5MeV to remove the background events. (Rn  -rays from detector wall) MeV (13.3kt) MeV (12.3kt)5.5-20MeV (22.5kt) Fiducial volume in SK-III Z R SK detector Neutrino 2010 Rate/bin See poster: Solar neutrino results from SuperK by Hiroyuki Sekiya

Systematic uncertainties on total flux (SK-III) SK-IIISK-I (PRD73,112001) Energy scale+/-1.4 +/-1.6 Energy resolution+/-0.2 8B spectrum shape+/ /-1.0 Trigger efficiency+/ /-0.3 Vertex shift+/-0.54+/-1.3 Reduction+/ /-1.6 Small cluster hits cut+/-0.5 Spallation cut+/-0.2 External event cut+/-0.25+/-0.5 Background shape+/-0.1 Angular resolution+/ /-1.2 Signal extraction method+/-0.7 Cross section+/-0.5 Live time calculation+/-0.1 Total+/ /-3.2% The systematic error on total flux of SK-III is reduced by precise calibrations and software improvements Neutrino 2010 Energy region: E total = MeV Preliminary

Neutrino 2010 Total live time: 548 days, E total ≥ 6.5 MeV 289 days, E total < 6.5 MeV Energy region: E total = MeV 8 B Flux: 2.32±0.04(stat.)±0.05(syst.) (x10 6 /cm 2 /s) SK-III solar neutrino results Preliminary

8 B Analysis Borexino (487.7 live-days) arXiv: v3 [astro ‐ ph] accepted by Rev. Phys. D Rate( 8 B) = 0.22 ± 0.04(stat) ± 0.01(syst) cpd/100tons Φ( 8 B) = (2.4 ± 0.4 ± 0.1) × 10 6 cm ‐ 2 s ‐ 1 (oscillated)

7 Be flux: 2.35  0.02(stat)  0.08(syst) [x 10 6 /cm 2 /sec] Impact of Borexino 7 Be & 8 B Analyses 7 Be 8 B (>5 MeV) 8 B (>3 MeV) P ee Δm 2 =7.69×10 −5 eV 2 and tan 2 θ=0.45 BX: Under the assumption of SSM flux SNO: Directly measure P ee

Preliminary 7 Be Day spectrum: days 7 Be Night spectrum: days Statistical error: 2.3 cpd/100t The 7 Be flux is obtained from separate full fits of day and night spectra PS: Mass varying neutrino models of P.C. de Holanda rejected at 3σ level 7 Be Day/Night Asymmetry Borexino

SNO hep neutrino sensitivity (3phase) SSM

SNO Improvement – NCD (3-phase) Pulse shape discrimination to separate neutron(signal) from alpha (background)  Distinguish neutron and alpha pulses  Neutron pulses are created with two particles (a proton and a triton), and alpha pulses are created by a single particle  Timing and Ionization tracks are fundamentally different  After discrimination perform a fit of energy spectrum Projected Uncertainty on the Number of NC Neutrons Without With ±56 Signal-to-Background ratio: 0.33 (before cut) → 11.7 (after cut) alpha neutron

All phases combined D2O+Salt+NCD 8 B P ee (E ) fit SNO Full 3-Phase Expected improvement Δχ 2 P ee day A DN

Conclusion & Future Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010  Great physics out of solar neutrino experiments From solving SNP to precision physics  Direct evidence of solar neutrino oscillation by SNO  Global solar solution favors LMA (Cl+Ga+SK+BX+SNO)  Upcoming new SK I+II+III publications (3-flavor analysis)  SK-IV is capable of a lower energy threshold  More precise 7 Be from Borexino with more live-days soon Δ  7Be 10%→5%  Expect further improvement with SNO 3-phase analysis The only model-independent fit of solar survival probability Δ  8B 4%→3.5%

Merci ! Thank you! Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010

Solar + KamLAND 3-flavor Overlay Best-fit: sin 2  13 = x10 -2 sin 2  13 < (95% C.L.) Best-fit LMA point: tan 2  12 =  m 2 = 7.59 x10 -5 eV

SNO Survival Probability DAY NIGHT

SNO Survival Probability DAY NIGHT

SNO Survival Probability DAY NIGHT

SNO Survival Probability DAY NIGHT

Fit to spike energy spectrum allowing energy scale to float: shift is 0±0.6% Test of PDF shapes (distributed Rn spike)

As in the quark sector one defines a neutrino mixing matrix which relates the mass and weak eigenstates Mixing Matrix solaratmospheric CP violation short-baseline Neutrino: Quark: yes ??? Neutrino Mixing

Active solar neutrino oscillation: 4 parameters θ 12 & θ 13 mixing strength between flavor & mass eigenstates Δm 2 and Δm 2 where Δm 2 = m 2 – m 2 Δm 2 ∼ Δm 2 θ 23 & CP phase irrelevant Mass hierarchy with  m 2 > 0 is assumed! Note the small  e component in  3 from atmospheric results P(   →   )!!! It implies neutrinos have masses which leads to physics beyond the Minimal Standard Model Neutrino Mass ji 32 ij

Solar Neutrinos

53 Matter-Enhanced Neutrino Oscillations Neutrinos produced in weak state e  High density of electrons in the Sun  Superposition of mass states 1, 2, 3 changes through the MSW resonance effect  Solar neutrino flux detected on Earth consists of e +  P ee

54 Phase I (D 2 O) Phase II ( Salt+D 2 O) Phase III ( 3 He+D 2 O) Nov May 01 July 01 - Sep. 03 Nov Nov. 06 γ γ γ 35 Cl 36 Cl 36 Cl* n γ 2H2H 3H3H 3 H* n n captures on Deuterium 2 H(n,γ) 3 H σ = b 6.25 MeV single γ PMT array readout 2 tons of NaCl added n captures on Chlorine 35 Cl(n,γ’s) 36 Cl σ = 44b 8.6 MeV multiple γs PMT array readout n captures on 3 He 3 He(n,p) 3 H σ = 5330b MeV(p, 3 H) NCD readout n + 3 He  p + 3 H p 3H3H 5 cm n 3 He Three methods to detect neutrons n ν x + d→ ν x + P + n