Solar Neutrino Analysis of Super-Kamiokande ICRC2013 @Rio de Janeiro 8 July 2013 Hiroyuki Sekiya ICRR, University of Tokyo for the Super-K Collaboration Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 1 Super-Kamiokande 50kton pure water Cherenkov detector 1km (2.7km w.e) underground in Kamioka 11129 50cm PMTs in Inner Detector 1885 20cm PMTs in Outer Detector Physics targets of Super-Kamiokande Atmospheric ν ~3.5 MeV ~20 ~100 ~1 GeV TeV Low energy Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 2 nx + e→ nx + e- Solar neutrinos observation Hiroyuki Sekiya ne ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 3 Current motivation Check the direct signals of the MSW effect Solar matter effect Energy spectrum up-turn Earth matter effect Flux day-night asymmetry Neutrino survival probability Vacuum oscillation dominant Matter oscillation dominant Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 4 New SK-IV results Results from 1306.3 days of SK-IV data SK-IV Hardware improvement ◦ Better water quality control Lowered threshold (~3.5MeV (kin.)) Large statistics with lower backgrounds. ◦ New electronics Better timing determination Better MC model of trigger efficiency. SK-IV Analysis improvement ◦ Introduce multiple scattering goodness(MSG) Although the 214Bi decay-electrons (majority of low energy BG) fluctuate up above 5.0 MeV, they truly have energy <3.3 MeV and should have more multiple scattering than true 5.0 MeV electrons, and therefore a lower MSG ◦ Reduced systematic error 1.7% for flux Hiroyuki Sekiya cf. SK-I: 3.2% SK-III: 2.1% ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 5 Lowered background Solar angular distribution 3.5~4.0MeV(kin.) event/day/kton Event rates 4.0-4.5MeV(kin.) SK-III SK-III SK-IV Stable low background level SK-IV Clear Solar peak ~7.5σ level 3.5MeV threshold is achieved! Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 6 Solar angle distributions with MSG in low energy 3.5-4.0MeV 0.45<MSG MSG < 0.35 0.35<MSG<0.45 4.0-4.5MeV Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 7 SK-IV energy spectrum Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 8 SK-I,II,III,IV Statistically combined spectrum Distortion due to E dependence of 1)Oscillation survival probability, 2) dsm/dse ,3) Systematic uncertainties sin2θ13=0.025 sin2θ12=0.304 , Δm2=7.45∙10-5eV2 Solar global+ KamLAND best value sin2θ12=0.314 , Δm2=4.84∙10-5eV2 Solar global best fit value Exponential fit for testing “upturn” Flat probability fit f8B=5.25×106/(cm2∙sec) fhep=7.88×103/(cm2∙sec) “upturn” shape is favored ~1s, “flat” is disfavored ~1s Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 9 Comparison with others SNO KamLAND Super-K BOREXINO Super-K spectrum is the most precise! Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 10 SK-I+II+III+IV Day/Night Flux Zenith angle distribution sin2θ12=0.314 , Δm2=4.8∙10-5eV2 Solar global best fit value sin2θ12=0.304 , Δm2=7.41∙10-5eV2 Solar global+ KamLAND best value qz cosqz = 1 L～15㎞ cosqz= -1, L～13000㎞ Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 11 Day-Night Asymmetry SK-I+II+III+IV energy distribution Asymmetry SK-I -2.0±1.7±1.0 % SK-II -4.3±3.8±1.0 % SK-III -4.3±2.7±0.7 % SK-IV -3.4±1.8±0.6 % Comb -3.2±1.1±0.5 % ined (2.7 σ from zero) sin2θ12=0.314 Δm212=4.84x10-5eV2 First indication of Earth matter effect! Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 12 Dependence of Asymmetry on Dm221 KamLAND Solar global Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 13 ne nt nm Neutrino oscillation analysis Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 14 Allowed oscillation parameter region from only SK Dm212 ,q12 Blue: day/night only 2s region Green: day/night +spectrum 2s region Red: Solar global+KamLAND SK provides most precise Dm212 among solar measurements Hiroyuki Sekiya f8B free fit ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 15 (Dm212 ,q12) from all solar data Green: Solar global dashed only SK+SNO Blue: KamLAND Red: Solar global+KamLAND Combined Solar Data Hiroyuki Sekiya KamLAND f8B=(5.25±0.20) x 106/(cm2∙sec) ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 16 q13 Analysis w/ Solar+KamLAND Solar+KamLAND Best fit +0.017 sin2θ13=0.031 -0.015 non-zero significance 2s 3σ Combined KamLAND Solar 2σ Data 1σ Consistent with reactor experiments (0.0242±0.0026) Daya Bay/Reno Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 17 Conclusion Solar neutrino measurement in Super-K keeps improving. ◦ lower threshold, lower BG, smaller errors, and larger statistics “1 s significance” spectrum distortion. Asymmetry in day/night flux! @2.7σ, ◦ Confirmation of Earth matter effect on Solar neutrino! Neutrino oscillation parameters are updated from solar + KamLAND global fit; ◦ Δm212=7.45x10-5eV2, sin2θ12=0.304+0.013-0.013, sin2θ13=0.031+0.017-0.015 Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 18 Extra slides Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 19 Solar neutrinos observation Neutrino-electron elastic scattering n + e- → n + e- • Solar direction sensitive • Realtime measurements •Energy spectrum •day/night flux differences •Seasonal variation ne Nuclear fusion reaction deep inside the Sun 4p➔2He+2e++2νe Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 20 Solar Neutrinos Pee p+p➝d+e++νe (99.77%) p+e-+p➝d+νe (0.23%) all solar BOREXINO pp d+p➝3He+γ BOREXINO pep MSW (solar&KL) MSW (solar) SK & SNO 3Ηe+α➝7Be+γ 15.08% 3Ηe+3Ηe➝α+2p 84.92% 3He+p➝α+e++ν e 7Be+e-➝7Li+ν 99.9% e 7Be+p➝8B+γ 0.1% Cl 8B 7Be BOREXINO Hep 8B+➝8Be*+e++ν e 7Li+p➝α+α; 8Be*➝α+α Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 10 -3 10 -5 10 -6 10 -7 15 2 -5 -4 Dm in 10 eV 10 2 2s 2 Dm in eV 2 contour (flux free) 10 -8 10 -9 10 DN (flux free) DN+Spec Solar+KamLAN D 5 0.0 10 0.1 0.2 0.3 0.4 sin -4 10 -3 2 0.5 (q ) 12 10 -2 10 -1 1 10 10 2 tan (q ) 12 Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 2 MSG Hiroyuki Sekiya For each PMT hit pair, the vectors to the Chrenkov ring cross points are the direction candidates MSG = vector sum of the candidates/ scalar sum of the candidates MSG of multiple scattering events should be small ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 23 Super-K water transparency @ Cherenkov light wavelength Measured by decay e-e+ from cosmic m-m+ SK-III SK-IV Started automatic temperature control anti-correlated with Supply water temperature Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 24 Convection suppression in SK Very precisely temperature-controlled (±0.01oC) water is supplied to the bottom. Return to Water system 3.5MeV-4.5MeV Event distribution Temperature gradation in Z The difference is only 0.2 oC Purified Water supply r2 Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 25 Current SK situation Stagnation and top-bottom asymmetry. Bacteria in low flow rate region OD top ID,OD top OD bottom ID bottom 12t/h 36t/h 60t/h Ver.14May 2012 Hiroyuki Sekiya Emanated (from PMT/ FRP) and accumulated Radon 12t/h ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
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