hiroyuki sekiya ichep2014 jul. 4 2014 @valencia, spain solar neutrinos in super-kamiokande ichep2014...
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Solar Neutrinos inSuper-Kamiokande
ICHEP2014 @Valencia July 4 2014
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Hiroyuki SekiyaICRR, University of Tokyo
for the Super-K Collaboration
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
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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WIMPs
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain 3
neSolar neutrinos observation
Super-K
n + e- n + e-
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
The results: Solar global fit This SK update and other latest results are combined.
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~2σ tension in Δm221
between solar and KamLAND
Solar
KamLAND
Solar+KamLAND
Reactor
preliminary
Non-zero q13 at 2 s from solar+KamLANDGood agreement with Daya Bay, RENO & DC (Neutrino2014)
Without reactor θ13 constraintCombined solar fit with KamLAND
sin2θ13=0.0242±0.0026
KamLANDSolar+KamLAND
Solar
sin2θ13=0.0221±0.0012
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Motivation
Vacuum oscillation dominant
Matter oscillation dominant
up-turn!
Search for the direct signals of the MSW effect
Neutrino survival probability
Solar matter effect
Energy spectrum distortionEarth matter effect
Flux day-night asymmetry
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Solar+KamLANDsin2θ12=0.308Δm2
21=7.50x10-5eV2
sin2θ12=0.311Δm2
21=4.85x10-5eV2
Solar
Regenerate ne by earth matter effectJHEP 0311:004(2003)
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Improvements in SK-IV Reduced 222Rn BG
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SK-III SK-IV
Achieved 3.5 MeV(kin.) energy threshold 8.6s signal is observed with MSG
Reduced systematic error 1.7% for flux cf. SK-I: 3.2% SK-III: 2.1%
4.0-4.5 MeV bin
New analysis in low energy bins Remaining BG-electrons from 214Bi should have more multiple-scatterings than signal-electrons have: MSG
3.5-4.0MeV
4.0-4.5MeV
MSG < 0.35 0.35<MSG<0.45 0.45<MSG
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
8B solar n in SK-I+II+III+IV8B n signals
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~70k solar neutrino events
8B n could be the BG for DM searchthrough NC coherent scattering.
FSK(8B) =2.344±0.034 x 106 cm-1s-1
preliminary
FSK+SNO(8B) =5.30 x 106 cm-1s-1+0.17
-0.11
preliminary
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Recoil electron spectra
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Dat
a/M
C(u
nosc
illat
ed)
preliminary
Kinetic energy (MeV)
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
SK-I+II+III+IV spectrum
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N.B. All SK phase are combined without regard to energy resolution or systematics in this figure
Neutrino energy spectrum is convoluted in the electron recoil spectrum. For de-convolution, generic functions are used as a survival probability;
Solar+KamLANDsin2θ12=0.308 Δm2
21=7.50x10-5eV2
Solarsin2θ12=0.311 Δm2
21=4.85x10-5eV2
SK recoil electron spectrum constrain the fit parameters (ci,ei) of the function and the allowed Pee(En) is derived using the allowed (ci,ei).
f8B=5.25 x 106/(cm2∙sec)
fhep=7.88 x 103/(cm2∙sec)
(total # of bins of SKI - IV is 83) χ2
Solar+KamLAND 70.13
Solar 68.14
quadratic fit 67.67
exponential fit 66.54
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Allowed Pee(En) for SK
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SK
Solar+KamLAND
Solar
✓MSW (solar+KamLAND) is consistent at ~1.6σ✓MSW (solar) fits better (at ~0.7σ)
sin2θ12=0.308Δm2
21=7.50x10-5eV2
sin2θ12=0.311Δm2
21=4.85x10-5eV2
preliminary
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Allowed Pee(En) for SK+SNO
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SK+SNOSNO
SK
Solar+KamLAND
Solar
✓SK and SNO are complementary for the shape constraint✓MSW is consistent at 1σ
sin2θ12=0.308Δm2
21=7.50x10-5eV2
sin2θ12=0.311Δm2
21=4.85x10-5eV2
preliminary
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Global view of Pee(En)
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SK+SNO
Borexino (8B)
all solar (pp) Borexino (pep)
Borexino (7Be)
Homestake+SK+SNO
(CNO)
preliminary
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain 13
Earth
θz
Solar best fit
Solar+KamLAND
preliminary
SK-I - IV combined (Eth=4.5 MeV for SK-I,III,IV 6.5 MeV for SK-II)
sin2θ12=0.308Δm2
21=7.50x10-5eV2
sin2θ12=0.311Δm2
21=4.85x10-5eV2
Sun
Flux zenith angle distribution
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Day/Night asymmetry amplitude
Fitted asymmetry amplitude
Δm221=4.84x10-5 eV2 Δm2
21=7.50x10-5 eV2
SK-I -2.0±1.8±1.0% -1.9±1.7±1.0%
SK-II -4.4±3.8±1.0% -4.4±3.6±1.0%
SK-III -4.2±2.7±0.7% -3.8±2.6±0.7%
SK-IV -3.6±1.6±0.6% -3.3±1.5±0.6%
combined -3.3±1.0±0.5% -3.1±1.0±0.5%non-zero
significance 3.0σ 2.8σ
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Rat
e/R
ate a
vera
ge
expected
preliminary
Δm221=4.84x10-5 eV2
sin2θ12=0.311 sin2θ13=0.025
Energy-dependence of the variation
First observation of day/night asymmetry at 3s significance level
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Δm221 dependence
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sin2θ12=0.311, sin2θ13=0.025
1σ KamLAND1σ Solar
SK-I,II,III,IV best fit
expected2.8σ2.9σ3.0σ
Solar regiondiffer from zero by 2.9~3.0σagree with expect by 1.0σ
differ from zero by more than 2.8σagree with expect by 1.3σ
KamLAND region
preliminary
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Summary
SK has observed ~70000 solar n interactions, by far the largest sample of solar neutrino events in the world.
SK data provide the first indication (at 2.8~3.0 s) of terrestrial matter effects on 8B solar n oscillation.
SK gives the world’s strongest constraints on the shape of the survival probability Pee(Eν) in the transition region between vacuum oscillations and MSW resonance.◦ SK spectrum results are consistent with MSW up-turn prediction
within ~1s. SK measurements strongly constrain neutrino oscillation parameters:
◦ SK gives world’s best constraint on Δm212 using neutrinos.
◦ There is a 2s tension between SK’s neutrino and KamLAND’s anti-neutrino measurement of Δm21
2. Last month SK started taking data at ~2.5 MeV at ~100% trigger
efficiency. Stay tuned for very low energy SK neutrino.
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Extra slides
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Full summary
SK has observed ~70000 solar neutrino interactions in ~4500days (1.5 solar cycles), by far the largest sample of solar neutrino events in the world.
SK data provide the first indication (at 2.8~3.0 sigma) of terrestrial matter effects on 8B solar neutrino oscillation. This is the first observation using a single detector and identical neutrino beams that matter affects neutrino oscillations.
SK has successfully lowered the analysis threshold to ~3.5 MeV kinetic recoil electron energy. SK gives the world’s strongest constraints on the shape of the survival probability Pee(Eν) in the
transition region between vacuum oscillations and MSW resonance. SK spectrum results slightly disfavor the MSW resonance curves, but are consistent with MSW
prediction within 1-1.7 sigma. SK measurements strongly constrain neutrino oscillation parameters: SK uniquely selects the Large Mixing Angle MSW region by >3sigma, gives world’s best constraint on solar Δm2 using neutrinos, and significantly contributes to the measurement of the solar angle. There is a 2 sigma tension between SK’s neutrino and KamLAND’s anti-neutrino measurement of
the solar Δm2. Last month SK started taking data at ~2.5 MeV at ~100% trigger efficiency. Stay tuned for very
low energy SK solar neutrino
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Wide-band Intelligent Trigger Reconstruction and Reduction just after Front-end
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Just started
100% trigger efficiency above 2.5MeV(kin.)
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Oscillation parameter
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain 21
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Improvements in SK-IV Reduced BG
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SK-III SK-IV
achieved 3.5 MeV(kin.) energy threshold
7.5s level signal is observed at 3.5MeV bin
Event rate becomes low and stable in SK-IV
Reduced systematic error 1.7% for flux cf. SK-I: 3.2% SK-III: 2.1%
4.0-4.5 MeV bin
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
significance of the signal
The MSG non-zero signal significance is 8.6 sigma (2.4129/0.2811)
3.5- 4.0 MeV Data/SSM=0.4596+0.0546-0.0535 Flux=2.4129+0.2866-0.2811
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
SK+SNO 8B total flux For each oscillation parameter set there is a minimum chi2 and a 8B error
term describing the parabolic increase of the chi2 with deviations from the best chi2. The reduced chi2 vs. 8B flux is below. The jump is due to the relatively coarse grid in theta12.
5.30+0.17-0.11x10^6/(cm2 sec), which is a (+3%,-2%) error on the total 8B for SK+SNO compared to the 1.5% error of SK's ES flux by itself.
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Systematic errors
Total 1.7 %
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Source SK-IV flux(3.5-19.5MeV)
SK-III flux(4.5-19.5MeV)
energy scale +1.14, -1.16% ±1.4%
energy resolution +0.14, -0.08% ±0.2%
B8 spectrum +0.33, -0.37% ±0.2%
trigger efficiency ±0.1% ±0.5%
angular resolution +0.32, -0.25% ±0.67%
vertex shift ±0.18% ±0.54%
BG event cut ±0.36% ±0.4%
hit pattern cut ±0.27% ±0.25%
another vertex cut removed ±0.45%
spallation cut ±0.2% ±0.2%
gamma cut ±0.26% ±0.25%
cluster hit cut +0.45, -0.44% ±0.5%
BG shape ±0.1% ±0.1%
signal extraction ±0.7% ±0.7%
cross section ±0.5% ±0.5%
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
8B solar n in SK-I+II+III+IV8B n signals
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Data set for global solar analysis
SK:◦ SK-I 1496 days, spectrum 4.5-19.5 MeV(kin.)+D/N:Ekin>4.5 MeV ◦ SK-II 791 days, spectrum 6.5-19.5 MeV(kin.)+D/N: Ekin>7.0 MeV◦ SK-III 548 days, spectrum 4.0-19.5 MeV(kin.)+D/N: Ekin>4.5 MeV◦ SK-IV 1669 days, spectrum 3.5-19.5 MeV(kin.)+D/N: Ekin>4.5 MeV
SNO:◦ Parameterized analysis (c0, c1, c2, a0, a1) of all SNO phased. (PRC88, 025501 (2013))
◦ Same method is applied to both SK and SNO with a0 and a1 to LMA expectation Radiochemical: Cl, Ga
◦ Ga rate: 66.1±3.1 SNU (All Ga global) (PRC80, 015807 (2009))◦ Cl rate: 2.56±0.23 SNU(Astrophys. J.496, 505 (1998) )
Borexino: Latest 7Be flux (PRL 107, 141302 (2011)) KamLAND reactor : Latest (3-flavor) analysis (PRD88, 3, 033001 (2013)) 8B spectrum: Winter 2006 (PRC73, 73, 025503 (2006)) 8B and hep flux
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The most up-to-date data are used
f8B=5.25 x 106/(cm2∙sec)
fhep=7.88 x 103/(cm2∙sec)
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Day/Night
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Amplitude fitStraight calc.(D-N)/((D+N)/2)Δm2
21=4.84x10-5 eV2 Δm221=7.50x10-5 eV2
SK-I -2.0±1.8±1.0% -1.9±1.7±1.0% -2.1±2.0±1.3%
SK-II -4.4±3.8±1.0% -4.4±3.6±1.0% -5.5±4.2±3.7%
SK-III -4.2±2.7±0.7% -3.8±2.6±0.7% -5.9±3.2±1.3%
SK-IV -3.6±1.6±0.6% -3.3±1.5±0.6% -4.9±1.8±1.4%
combined -3.3±1.0±0.5% -3.1±1.0±0.5% -4.1±1.2±0.8%non-zero
significance 3.0σ 2.8σ 2.8σexpected time variation as a function of cosθz
preliminary
(sin2θ12=0.311, sin2θ13=0.025)R
ate/
Rat
e ave
rage
α : day-night asym. scaling factor
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
exponential parameterization
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preliminary
✓SK spectrum, red : exponential, green : quadratic
Solar+KamLAND
Solar
sin2θ12=0.308Δm2
21=7.50x10-5eV2
sin2θ12=0.311Δm2
21=4.85x10-5eV2
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
SK-I+II+III+IV spectrum
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(total # of bins of SKI - IV is 83) χ2
Solar+KamLAND 70.13
Solar 68.14
quadratic fit 67.67
N.B. All SK phase are combined without regard to energy resolution or systematics in this figure
Neutrino energy spectrum is convoluted in the electron recoil spectrum. For de-convolution, a generic quadratic function is used as a survival probability;
Solar+KamLANDsin2θ12=0.308 Δm2
21=7.50x10-5eV2
Solarsin2θ12=0.311 Δm2
21=4.85x10-5eV2
SK recoil electron spectrum constrain the fit parameters (ci) of the function and the allowed Pee(En) is derived using the allowed (ci).
f8B=5.25 x 106/(cm2∙sec)
fhep=7.88 x 103/(cm2∙sec)
Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
Multiple scattering goodness
Induced multiple scattering goodness(MSG) in SK-IV analysis.
Although the 214Bi decay-electrons (majority of low energy BG) fluctuate up above 5.0MeV, they truly have energy less than 3.3MeV and should have more multiple scattering than true 5.0MeV electrons.
3.5-4.0MeV
4.0-4.5MeV
MSG < 0.35
MSG < 0.35
MSG > 0.45
MSG > 0.45
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
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 ICHEP2014 Jul. 4 2014 @Valencia, Spain
Comparison with others
BOREXINO
SNO KamLAND
Super-K
Super-K spectrum is the most precise!
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Hiroyuki Sekiya ICHEP2014 Jul. 4 2014 @Valencia, Spain
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 ICHEP2014 Jul. 4 2014 @Valencia, Spain
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 ICHEP2014 Jul. 4 2014 @Valencia, Spain
Convection suppression in SK
Very 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