Solar neutrino measurement at Super Kamiokande ICHEP'04 ICRR K.Ishihara for SK collaboration Super...
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![Page 1: Solar neutrino measurement at Super Kamiokande ICHEP'04 ICRR K.Ishihara for SK collaboration Super Kamiokande detector Result from SK-I Status of SK-II.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649eab5503460f94bb0ab8/html5/thumbnails/1.jpg)
Solar neutrino measurement at Super Kamiokande
ICHEP'04ICRRK.Ishiharafor SK collaboration
Super Kamiokande detectorResult from SK-IStatus of SK-IIFuture plan
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Super Kamiokande detector
50 k ton water Cherenkov Detector located at 1000 m underground.
41.4
m
39.3m
E e 9.87 MeV
cos sun 0.915
Feature of solar neutrino observation
8B neutrino measurement by + e- → + e- Strong directionalityReal time measurement.Sensitive to ee-
=~0.15×ee- High statistics ~15ev./day with Ee > 5MeV Studies on energy spectrum.
Precise energy calibration by LINAC and 16N.
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Solar neutrino observation at SK I
B8e flux 2.35 0.02 0.08 106 cm2 s
0.406 0.004 0.0140.013
SSM BP2004
Sun sun
e
May/31/96 – Jul/13/01 22400 events (14.5 ev/day)
Event/
day/k
ton/
bin
Direction to the Sun
Solar neutrino events
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SK-I day/night difference
Cos
Flu
x in
10^
6/cm
^3
SK-I (1496 days) 5.0-20. MeV 22.5 kton
day nightADNDay Night
Day Night 20.021 0.020 0.012
0.013
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Z
mantle
core
SK Day
z
Un-bined day/night analysisEnergy and zenith angle dependence of event rate variatoin.
(Δm2 = 6.3×10-5 eV2, tan2θ = 0.55)
L e iBi S
i 1
N bin
1
ni
Bi U i c mi S p c , E z c , E
#B.G. in eachenergy bin
#SignalEvents
Event“Time"
BackgroundShape
Solar signalshape
ADN 0.018 0.016 0.0120.013
cf. old method 0.02 0.021 0.0120.013
j j
i
MC
MC
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Energy spectrum of SK-I
m2=6.3x10-5eV2, tan2=0.55
m2=7.2x10-5eV2, tan2=0.38
Best fit 8B flux: 4.84 x 106 /cm2/sec
Energy correlated systematic error
Best fit 8B flux: 5.21 x 106 /cm2/sec
SK only (BP 2000 flux)
No distortion
Our data is consistent with no distortionOur data is consistent with no distortion..Consistent with LMA within 1 Consistent with LMA within 1 ..
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SSMSSM8
22osc
SSMSSM8
22osc8
B
tan, ,
B
tan,B
ii
ii
ii
ii hep
mheph
hep
mb
i
iii
ii
i
f
hb
hep
,
B
Datad
SSMSSM8i
timevar2
2
2
2
2
2
12
22 log2 L
R
R
S
S
B
BN
i i
iibin d
Oscillation analysis
Spectrum
RR
iSS
iB
iRSi ffff ,,
Energy correlated systematic error
Time variation
Function for energy correlated systematic errors
8B spec. shape
energy scale
energy resolution
![Page 8: Solar neutrino measurement at Super Kamiokande ICHEP'04 ICRR K.Ishihara for SK collaboration Super Kamiokande detector Result from SK-I Status of SK-II.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649eab5503460f94bb0ab8/html5/thumbnails/8.jpg)
Michael Smy, UC Irvine
SK only (95% C.L.)SK only (95% C.L.)SSM SSM Flux IndependentFlux Independent
SK onlySK only(68% C.L.)(68% C.L.)
SSM SSM FluxFluxIndependentIndependent
SK only (68% C.L.)SK only (68% C.L.)SSM SSM 88B B Flux (BP2004)Flux (BP2004)
SK only (95% C.L.)SK only (95% C.L.)SSM SSM 88B B Flux(BP2004)Flux(BP2004)
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Michael Smy, UC Irvine
SK only (95% C.L.)SK only (95% C.L.)SSM SSM Flux IndependentFlux Independent
SK onlySK only(68% C.L.)(68% C.L.)
SSM SSM FluxFluxIndependentIndependent
SK only (68% C.L.)SK only (68% C.L.)88B B Flux ConstrainedFlux Constrainedto BP2004 & SNO NCto BP2004 & SNO NC
SK only (95% C.L.)SK only (95% C.L.)88B B Flux ConstrainedFlux Constrainedto BP2004 & SNO NCto BP2004 & SNO NC
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Michael Smy, UC Irvine
KamLAND
SK/SNO
KamLAND from hep-ph/0406035(KamLAND Collaboration)
sin2 is determined by SK/SNO
Result form SK/SNO is consistent withResult form SK/SNO is consistent with that from KamLAND!that from KamLAND!
Dose this difference indicate new physics ?Dose this difference indicate new physics ?
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Status of SK-II
Period '96-'01 accident '03-'05#PMTs 11,146 5,182Photo Coverage 40 % 19 %Light yield ~6 p.e./MeV ~2.8 p.e/MeV Energy threshold 5.0 MeV 8.0 MeV
SK-I SK-II
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SK-II 325 days (22.5 kton)8.0-20.0 MeVSignal =
SK-II preliminary result
Flux = 2.38±0.09(stat.) × 106/cm2/scf. SK-I 2.35±0.02(stat.) ± 0.08(sys.)
Event rate at SK-II is consistent with SK-I!Event rate at SK-II is consistent with SK-I!
Solar neutrino events
Dec.24,2002 – March 25, 2004
Direction to the Sun
Systematic error is under study
82802161
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Day
Night
Day NightDay Night 2
0.025 0.075 stat.Average of SK-I
Day/Night Asymmetry and Energy Spectrum Day/Night Asymmetry and Energy Spectrum at SK-II are also consistent with SK-I!at SK-II are also consistent with SK-I!
SK-II works well !SK-II works well !
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Physics motivation in future
Find evidence of matter effect.(Find smoking gun of LMA.)
How to do ?
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Energy spectrum distortionRecoil electron
spectrum
reduce sys. error
reduce stat. error
Lower threshold
~10% upturn should be seen
tan2()0.550.380.380.380.28
m2 (eV2)6.3 x 10-5
4.8 x 10-5 7.2 x 10-5
10.0 x 10-5
7.2 x 10-5
Assumptions:Correlated systematic error: x 0.54.0-5.5MeV background: x 0.3(same BG as SK-I above 5.5MeV)
Significance of shectrum distortion
Sig
nifi
canc
e ()
Live time (year)
3σ
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Reject Background(~50% Radon, ~50% Gamma)
➢ Acrylic cover prevents radon from emitting from PMTs.
➢ Improve vertex fitter to reduce contamination of gamma events.Dependent on CPU power !
Reduce systematic ErrorWater transparency measurement with 7 laser calibrations.
SK tankLasers for w.t. measurements
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Analysis of lower energy region in SK-I
629 +128 -126(sta.) signals68016+-262 bg events
4.5 – 5.0 MeV dataFlux: 3.13±0.63(sta.)±0.16(sys.) /cm2/sec
Direction to the sun
1496 days
466 days
Solar neutrino energy spectrum
4.5-5.0 MeV data is consistent with data with E>5.0 MeV.
We've already successed to lower EWe've already successed to lower Ethth to 4.5 MeV ! to 4.5 MeV !
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summary
Day/night asymmetry is obtainedby un-binned methodADN= -1.8±1.6 +1.3/-1.2 %.
Preliminary results from SK-II are consistent with SK-I.
Hope to see definite energy spectrum distortion in SK-III, if it should be there.If not, it indicates new physics
13, CPT violation ...