m.nakahata kamioka observatory, icrr, ipmu, univ. of tokyo
DESCRIPTION
Kamiokande and Super- Kamiokande Results on Neutrino Astrophysics. M.Nakahata Kamioka observatory, ICRR, IPMU, Univ. of Tokyo. Professor Yoji Totsuka (1942-2008). Kamiokande spokesman: 1987 April ---- end. Super-Kamiokande spokesman: beginning ---- 2002. - PowerPoint PPT PresentationTRANSCRIPT
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M.NakahataKamioka observatory, ICRR,IPMU, Univ. of Tokyo
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Professor Yoji Totsuka(1942-2008)
Kamiokande spokesman: 1987 April ---- end
Super-Kamiokande spokesman: beginning ---- 2002
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Kamiokande detector (1983 – 1996)
16 m high, 15.6 m diameterInner counter: 948 20-inch PMTs
Anti-counter123 20-inch PMTs
neutrino
e
3000 ton water tank
Photo-sensitive: 2140 t
Fiducial volume: 680 t
(for solar neutrino)
Photocoverage: 20 %
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50000 t water tank (42m high, 40m diameter)
32000 t photo-sensitive volume
22000 t fiducial volume
11146 20-inch PMTs
Photocoverage: 40%
1000m underground in Kamioka mine
X 30 fiducial volume than Kamiokande
Super-Kamiokande detector (1996 – )
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History of Super-Kamiokande detector
11146 ID PMTs(40% coverage)
5182 ID PMTs(19% coverage)
11129 ID PMTs(40% coverage)
EnergyThreshold(total electron energy)
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
SK-I SK-II SK-III SK-IV
Acrylic (front)+ FRP (back)
ElectronicsUpgrade
SK-I SK-II SK-III SK-IV
5.0 MeV 7.0 MeV 4.5 MeVwork in progress
< 4.0 MeVtarget
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Original purpose of KamiokandeOriginal purpose of KamiokandeSearch for proton decay
p→e+0 Monte Carlo simulation
e+
0→
High resolution detector for measuring the branching ratio of proton decay.
It should be useful to pin down the true GUT model.
3500
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Low energy neutrino detectionLow energy neutrino detectionIt was found that the large photo-collection efficiency is useful also for detecting low energy neutrino.
Reconstructed energy = 19.8 MeV
An event at Kamiokande
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Advantage of Kamiokande as a “Advantage of Kamiokande as a “telescopetelescope””
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DirectionalityImaging Cherenkov detector has excellent directionality.
Energy informationThe number of observed Cherenkov photon is proportional to energy of particle.
Real time detectionReal time counter experiment.
neutrino
electron
+ e + e
Advantage of Kamiokande as a “Advantage of Kamiokande as a “telescopetelescope””
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Another advantage of Kamiokande: Particle identification(PID)
electron
muon
Mis-identification is less than 1%.
Evis=540 - 1200 MeV
Evis=270 - 540 MeV
Evis=130 - 270 MeV
Evis=80 - 130 MeV
Evis=30 - 80 MeV
PID was very important for the atmospheric neutrino analysis.
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First solar neutrino plot at Kamiokande
Jan,1987 --- May, 1988 (450 days)
Observed number of solar neutrino events was ~50.
Confirmed the “solar neutrino problem”.
Solar model prediction
K.S.Hirata et al., Phys. Rev. Lett. 63(1989) 16
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Solar neutrinos ( Super-Kamiokande )May 31, 1996 – July 13, 2001 (1496 days )
e-
sun
COSsun
Ee = 5.0 - 20 MeV
22400 solar events
(14.5 events/day)
8B flux : 2.35 0.02 0.08 [x 106 /cm2/sec]
(BP2004: 5.79 x 106 /cm2/sec)= 0.406 +0.014-0.013
0.004
DataSSM(BP2004)
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Combined analysis of SK, SNO CC and NCCombined analysis of SK, SNO CC and NC
SK ESSNO ES
SNO NC
SNO CC
SSM prediction (1)
8B solar neutrino e flux and (+) flux
Evidence for neutrino oscillation
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Solar neutrino energy spectrumKamiokande II and III (2079 days )
Based on ~600 solar events
Super-Kamiokande (1496 days )
Based on ~22400 solar events
5
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Excluded region by energy spectrum and day/nightSuper-Kamiokande 1496 days
S.Fukuda et al., Phys. Lett. B 539 (2002) 179
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Solar Neutrino future prospects in SK
pp7Be
8B
Aim to reduce background in SK
P(
e
e)
Vacuum osc. dominant
Transition from vacuum to matter osc.Upturn is expected in 8B spectrum.
matter dominant
e survival probability(at best fit parameter)
~70% reduction below 5.5MeV and lower threshold to 4MeV
Expected spectrum distortion with 5 years low BG SK data
,IV
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Supernova at LMC (February 23, 1987)Supernova at LMC (February 23, 1987)
BeforeAfter
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TimeJT: 1987 Feb 23 16:35:35 (±1min)UT: 7:35:35
Background level
SN1987A signal by KamiokandeSN1987A signal by Kamiokande
sec
11 events in 13 sec.
It was when the Kamiokande detector was almost ready for solar neutrino detection.
Vis
ible
en
erg
y (M
eV
)
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SN1987A: supernova at LMC(50kpc)Kamiokande-II IMB-3 BAKSAN
Kam-II (11 evts.)IMB-3 (8 evts.)Baksan (5 evts.)
Tot
al B
indi
ng E
nerg
y
95 % CLContours
Spectral e Temperature__
TheoryTheory
from G.Raffelt
Feb.23, 1987 at 7:35UT
24 events total
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Super-K: Expected number of eventsSuper-K: Expected number of events
~7,300 e+p events~300 +e events~360 16O NC events ~100 16O CC events (with 5MeV thr.)
for 10 kpc supernova
Neutrino flux and energy spectrum from Livermore simulation (T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998))
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Super-K: Time variation measurement by e+pAssuming a supernova at 10kpc.
Time variation of event rate Time variation of mean energy
Enough statistics to discriminate models
ep e+n events give direct energy information (Ee = E – 1.3MeV).
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Simulation of a SN at 10kpc
e+p
e+p
e+p e+p
+e +e
+e +e
Super-K: Expected angular distributionSuper-K: Expected angular distribution
Spectrum of +e events can be statistically extracted using the angular distributions.
Direction of supernova can be determined with an accuracy of ~5 degree.
Neutrino flux and spectrum from Livermore simulation
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S.Ando, NNN05
Supernova Relic NeutrinosSupernova Relic NeutrinosS.Ando, Astrophys.J.607:20-31,2004.
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10-6
10-5
10-4
10-3
10-2
10-1
11010 210 310 410 510 610 7
0 10 20 30 40 50 60 70 80Neutrino Energy (MeV)
Neut
rino
Flux
(/cm
2 /s
ec /M
eV)
Supernova Relic NeutrinosSupernova Relic Neutrinos
Constant SN rate (Totani et al., 1996)Totani et al., 1997Hartmann, Woosley, 1997Malaney, 1997Kaplinghat et al., 2000 Ando et al., 2005Lunardini, 2006Fukugita, Kawasaki, 2003(dashed)
Solar 8B e
Solar hep e
Expected number SRN events0.8 -5.0 events/year/22.5kton(10-30MeV)
(0.3 -1.9 events/year/22.5kton for 18-30MeV)
Large target mass like SK and high background reduction are necessary.
Large target mass like SK and high background reduction are necessary.
SRN predictions(e fluxes)
Reactor e
Atmospheric e
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0
0.5
1
1.5
2
2.5
3
3.5
4
Constant SN rate
(Totani et al. 1996)
Totani et al. 1997
Malaney et al. 1997)
Hartmann et al. 1997)
Kaplinghat et al. 2004
Ando et al. 2005
Fukugita et al. 2003
Lunardini et al. 2006
SK-II limit = 3.68 /cm2/sec
SK-I limit = 1.25 /cm2/sec Combined limit = 1.08 /cm2/sec
preliminary(E>18MeV)
Super-K results so farFlux limit VS predicted flux
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Energy spectrum of SK-IEnergy spectrum of SK-I and SK-IIand SK-II (>18MeV)(>18MeV)
Atmospheric → invisible → decay e
Atmospheric e
90% CL limit of SRN Total
background
Energy (MeV)Atmospheric e
Atmospheric → invisible → decay e
Spallation background
SK-I (1496days) SK-II(791 days)
Eve
nts
/4M
eV
Observed spectrum is consistent with estimated background.Search is limited by the invisible muon background.
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e can be identified by delayed coincidence.
Neutron tagging in water Neutron tagging in water Cherenkov detectorCherenkov detector
e
e+
pn
Positron and gamma ray vertices are within ~50cm.
Gd
n+Gd →~8MeV T = ~30 sec
Neutron capture gamma
(J.Beacom and M.Vagins) Phys.Rev.Lett.93:171101,2004
Add 0.2% GdCl3 in water
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Possibility of SRN detectionRelic model: S.Ando, K.Sato, and T.Totani, Astropart.Phys.18, 307(2003) with flux revise in NNN05.
If invisible muon background can be reduced by neutron tagging
Assuming invisible muon B.G. can be reduced by a factor of 5 by neutron tagging.
By 10 yrs SK data,Signal: 33, B.G. 27(Evis =10-30 MeV)
SK10 years (=67%)
Assuming 67% detection efficiency.
0123456789
10
10 15 20 25 30 35 40 45 50
relic+B.G.(inv.mu 1/5)
B.G. inv.mu(1/5)
atmsph.–
e
Visible energy (MeV)
even
ts/1
0yea
rs/2
MeV
We are studying feasibility of introducing gadolinium. (effect on water transparency, corrosion, cable connectors and etc.)
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Atmospheric neutrino anomaly in KamiokandeAtmospheric neutrino anomaly in Kamiokande
Initial hint
→e decay ratio
Data from 1983 to1985Small →e decay ratio
e
Momentum of single ring events
Paper in 1988
-like/e-like ratio is 60% of expectation.
EXPERIMENTAL STUDY OF THE ATMOSPHERIC NEUTRINO FLUX.KAMIOKANDE-II Collaboration (K.S. Hirata et al.), Phys.Lett.B205:416,1988
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Atomospheric anomaly in KamiokandeAtomospheric anomaly in KamiokandeZenith angle distribution of multi-GeV events (1994)
Y.Fukuda et al., Phys. Lett. B 335 (1994) 237.
downwardupward
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Zenith Angle distribution of SK
SK-I dataMonte Carlo (no oscillations)Monte Carlo (best fit oscillations)
\\
cos θzenith cos θzenith
cos θzenith
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Zenith Angle Analysis: SK-I + SK-II
Best fit:Δm2 = 2.1 x 10-3 eV2
sin2 2θ = 1.02χ2 = 830.1 / 745 d.o.f.
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L/E Analysis: SK-I + SK-II
χ2 fit to 43 bins of log10(L/E) with 29 systematic error terms
DatasetsSK-I FC/PC μ-like: 1489 daysSK-II FC/PC μ-like: 799 days
Use only event categories with good L/E resolution:
Partially-contained muons Fully-contained muons
Compare against:Neutrino decoherence (5.0σ)Neutrino decay (4.1σ)
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3 flavor analysis: SK-I + SK-IINormal Hierarchy Inverted Hierarchy
preliminary
Note: one mass scale dominance method(m212 is set to 0)
Full 3-flavor analysis is being prepared.
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SK-IV electronics: New front-end electronics, QBEE
QTC TDC FPGA
Network Interface Card
PMTsignal
Ethernet Readout
60MHz ClockTDC Trigger
QTC-Based Electronics with Ethernet(QBEE)
24 channel input QTC (custom ASIC)
3 gain stages Wide dynamic range(>2000pC) factor 5 larger than old electronics
Pipe line processing multi-hit TDC (AMT3) FPGA
Ethernet Readout 60MHz common system clock Internal calibration pulser Low power consumption ( <
1W/ch )
Calibration Pulser
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Difference in readout system
FormerElectronics
(ATM)
Readout (backplane, SCH, SMP)
Trigger (1.3sec x 3kHz)
HITSUMTrigger
logic
NewElectronics
(QBEE)
Readout (Ethernet)
Periodic trigger(17sec x 60kHz)
Clock
Hardware Triggerusing number of hit
(HITSUM)
1.3secevent window
Variableevent window
by software trigger
No hardware trigger. All hits are readout. Apply software trigger.No hardware trigger. All hits are readout. Apply software trigger.
12PMTsignals
permodule
24PMTsignals
permodule
Collect ALL hits every 17sec time window. The 60kHz clock synchronize time of hit information.
Former readout system
New readout system
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Performance of new electronics for supernova burst
Distance to SN vs. number of events
Dead time free in the new system
Performance for high rate
100% efficiency up to 130kHz for each channel.
It corresponds to ~1000 x supernova at galactic center.(100 times better than previous system.)
# of
hits
burst hit rate (kHz) 130kHz
input
output
Dead time free even for a supernova as close as 0.3kpc
Previous system
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Conclusion• Neutrino astronomy was born in Kamiokande. And it was evolved in
Super-Kamiokande.– KAM observed deficit of solar neutrinos, and SK contributed to the evidence for the
solar neutrino oscillation and parameter determination.– Neutrinos from SN1987A by KAM, and a large statistical observation of galactic
supernova is expected in SK.– Atmospheric neutrino anomaly in KAM, and evidence for atmospheric neutrino
oscillation in SK. Detailed analysis is going on in SK.– The flux upper limit of supernova relic neutrinos is close to the theoretical expectation.
SK is studying possibility of neutron tagging by gadolinium.
• New electronics and online system was installed in September 2008 at SK, and SK-IV is running.
• T2K will start soon (from April 2009).
• More physics outputs are expected at SK.