hiroyuki sekiya icrc2013 jul. 8 2013 @rio de janeiro, brazil solar neutrino analysis of...
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Solar Neutrino Analysis ofSuper-Kamiokande
ICRC2013 @Rio de Janeiro 8 July 2013
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Hiroyuki SekiyaICRR, University of Tokyo
for the Super-K Collaboration
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
50kton pure water Cherenkov detector
1km (2.7km w.e) underground in Kamioka
11129 50cm PMTs in Inner Detector1885 20cm PMTs in Outer Detector
~3.5 ~20 ~1
Solar ν
MeV
Relic SN ν
GeV TeV
Atmospheric ν
~100
Physics targets of Super-Kamiokande
Proton decay
Super-Kamiokande
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Low energy
WIMPs
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 3
neSolar neutrinos observation
nx + e-
→ nx + e-
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Current motivation
Vacuum oscillation dominant
Matter oscillation dominant
up-turn!
Check the direct signals of the MSW effect
Neutrino survival probability
Solar matter effectEnergy spectrum up-turn
Earth matter effectFlux day-night asymmetry
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
New SK-IV results
◦ 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.
◦ 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 cf. SK-I: 3.2% SK-III: 2.1%
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SK-IV Hardware improvement
SK-IV Analysis improvement
Results from 1306.3 days of SK-IV data 237days
data added to
Neutrino2012 re
sults
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Lowered backgroundEvent rates4.0-4.5MeV(kin.)
Stable low background level
Solar angular distribution 3.5~4.0MeV(kin.)
Clear Solar peak ~7.5σ level3.5MeV threshold is achieved!
even
t/day
/kto
n
SK-IVSK-III SK-III
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SK-IV
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Solar angle distributionswith MSG in low energy
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3.5-4.0MeV
4.0-4.5MeV
MSG < 0.35 0.35<MSG<0.45
0.45<MSG
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
SK-IV energy spectrum
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Statistically combined spectrum
f8B=5.25×106/(cm2∙sec) fhep=7.88×103/(cm2∙sec)
sin2θ12=0.304 , Δm2=7.45∙10-5eV2Solar global+ KamLAND best value
sin2θ12=0.314 , Δm2=4.84∙10-5eV2Solar global best fit value
Flat probability fit
Exponential fit for testing “upturn”
sin2θ13=0.025
SK-I,II,III,IV
“upturn” shape is favored ~1s, “flat” is disfavored ~1s
Distortion due to E dependence of1)Oscillation survival probability, 2) dsm/dse ,3) Systematic uncertainties
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Comparison with others
BOREXINO
SNO KamLAND
Super-K
Super-K spectrum is the most precise!
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Day/Night FluxZenith angle distribution
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cosqz = 1 L ~ 15 ㎞qz
cosqz= -1, L ~ 13000 ㎞
SK-I+II+III+IV
sin2θ12=0.314 , Δm2=4.8∙10-5eV2Solar global best fit valuesin2θ12=0.304 , Δm2=7.41∙10-5eV2
Solar global+ KamLAND best value
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Day-Night Asymmetry
sin2θ12=0.314Δm212=4.84x10-5eV2
SK-I+II+III+IV energy distribution
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AsymmetrySK-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 %Combined
-3.2±1.1±0.5 % (2.7 σ from zero)
First indication of
Earth matter effect!
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Dependence of Asymmetry on Dm221
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Solar global
KamLAND
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Neutrino oscillation analysis
ne
nmnt
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Allowed oscillation parameter region from only SKDm21
2 ,q12
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Blue: day/night only 2s regionGreen: day/night +spectrum 2s region
Red: Solar global+KamLAND
SK provides most precise Dm21
2
among solarmeasurements
f8B free fit
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
(Dm212 ,q12) from all solar data
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f8B=(5.25±0.20) x 106/(cm2∙sec)
Green: Solar global dashed only SK+SNO Blue: KamLANDRed: Solar global+KamLAND
KamLANDSolarData
Combined
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
q13 Analysis w/ Solar+KamLAND
3σ
1σ
2σ
KamLAND
SolarDataCombined
Daya Bay/Reno
Consistent with reactor experiments (0.0242±0.0026)
Solar+KamLANDBest fitsin2θ13=0.031
+0.017
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non-zerosignificance2 s
-0.015
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
ConclusionSolar 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; ◦Δm2
12=7.45x10-5eV2, sin2θ12=0.304+0.013-0.013,
sin2θ13=0.031+0.017-0.015
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Extra slides
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Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil 20
ne
Solar neutrinos observation
• Solar direction sensitive• Realtime measurements
• Energy spectrum• day/night flux differences• Seasonal variation
Nuclear fusion reaction deep inside the Sun
4p➔2He+2e++2νe
Neutrino-electron elastic scatteringn + e- → n + e-
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Solar Neutrinos
SK & SNO
BORE-XINO
Cl
all solar BOREXINOBORE-XINO
8B
pp
Hep
pep
Pee
7Be
MSW (solar&KL)MSW (solar)
p+p d+e➝ ++νe(99.77%)p+e-+p d+➝ νe(0.23%)
3He+p α+e➝ ++νe
d+p➝3He+γ
3Ηe+α➝7Be+γ 15.08%
7Be+p➝8B+γ 0.1%
8B+➝8Be*+e++νe
3Ηe+3Ηe α+2p➝ 84.92%
7Li+p α+α;➝ 8Be* α+α➝
7Be+e-➝7Li+νe 99.9%
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
contour (flux free)
DN (flux free)DN+SpecSolar+KamLAND
2s
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
MSG
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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
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Super-K water transparency
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anti-correlated with Supply water temperature
@ Cherenkov light wavelengthMeasured by decay e-e+ from cosmic m-m+
SK-IVSK-III
Started automatic temperature control
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
Convection suppression in SKVery precisely temperature-controlled
(±0.01oC) water is supplied to the bottom.
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3.5MeV-4.5MeVEvent distributionReturn to
Water system
PurifiedWater supply
r2
Temperature gradation in Z
The difference is only 0.2 oC
Hiroyuki Sekiya ICRC2013 Jul. 8 2013 @Rio de Janeiro, Brazil
ID bottomOD bottom
OD topID,OD top 12t/h
12t/h
36t/h
60t/h
Ver.14May 2012
Current SK situationStagnation and top-bottom asymmetry.
Emanated (from PMT/FRP) and accumulated Radon
Bacteria in low flow rate region