Transcript Kamiokande and Super-Kamiokande Results on Neutrino Astrophysics M.Nakahata Kamioka observatory, ICRR, IPMU, Univ. of Tokyo.

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
Kamiokande detector (1983 – 1996)
neutrino
Inner counter:
948 20-inch PMTs
16 m high, 15.6 m diameter
Anti-counter
123 20-inch PMTs
e
3000 ton water tank
Photo-sensitive: 2140 t
Fiducial volume: 680 t
(for solar neutrino)
Photocoverage: 20 %
Super-Kamiokande detector (1996 – )

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
History of Super-Kamiokande detector
1996
1997
1998
1999
2000
2001
2002
SK-I
SK-I
11146 ID PMTs
(40% coverage)
Energy
Threshold 5.0 MeV
(total electron energy)
2003
2004
2005
2006
SK-II
Acrylic (front)
+ FRP (back)
SK-II
5182 ID PMTs
(19% coverage)
7.0 MeV
2007
SK-III
SK-III
11129 ID PMTs
(40% coverage)
2008
2009
SK-IV
SK-IV
Electronics
Upgrade
4.5 MeV
< 4.0 MeV
work in progress
target
Original purpose of Kamiokande
Search for proton decay
3500
p0→gg
e+
p→e+p0 Monte Carlo simulation
High resolution detector for measuring
the branching ratio of proton decay.
It should be useful to pin down the true
GUT model.
Low energy neutrino detection
It was found that the large photo-collection efficiency is
useful also for detecting low energy neutrino.
An event at Kamiokande
Reconstructed energy = 19.8 MeV
Advantage of Kamiokande as a “telescope”
Advantage of Kamiokande as a “telescope”
Directionality
Imaging Cherenkov detector has excellent directionality.
neutrino
n+en+e
electron
Energy information
The number of observed Cherenkov photon is proportional
to energy of particle.
Real time detection
Real time counter experiment.
Another advantage of Kamiokande: Particle identification(PID)
electron
Evis=540 - 1200 MeV
Evis=270 - 540 MeV
Evis=130 - 270 MeV
muon
Evis=80 - 130 MeV
Evis=30 - 80 MeV
Mis-identification is less than 1%.
PID was very important for the atmospheric neutrino analysis.
First solar neutrino plot at Kamiokande
K.S.Hirata et al., Phys. Rev. Lett. 63(1989) 16
Jan,1987 --- May, 1988 (450 days)
Solar model prediction
Observed number of solar neutrino events was ~50.
Confirmed the “solar neutrino problem”.
Solar neutrinos (Ｓｕｐｅｒ－Ｋａｍｉｏｋａｎｄｅ)
May 31, 1996 – July 13, 2001 (1496 days )
Ee = 5.0 - 20 MeV
n
e-
qsun
22400 solar n events
(14.5 events/day)
COSqsun
flux : 2.35  0.02  0.08 [x 106 /cm2/sec]
Data
= 0.406 0.004 +0.014
(BP2004: 5.79 x 106 /cm2/sec)
-0.013
SSM(BP2004)
8B
Combined analysis of SK, SNO CC and NC
8B
solar neutrino ne flux and (nm+nt) flux
SSM prediction (1s)
SNO NC
SNO CC
SNO ES
SK ES
Evidence for neutrino oscillation
Solar neutrino energy spectrum
Kamiokande II and III
(2079 days )
Based on ~600 solar n events
Super-Kamiokande
(1496 days )
Based on ~22400 solar n events
5
Excluded region by energy spectrum and day/night
Super-Kamiokande 1496 days
S.Fukuda et al., Phys. Lett. B 539 (2002) 179
Solar Neutrino future prospects in SK
P(ne  ne)
ne survival probability
(at best fit parameter)
Transition from vacuum to matter osc.
Upturn is expected in 8B spectrum.
Aim to reduce background in SK
,IV
~70% reduction below 5.5MeV
and lower threshold to 4MeV
Vacuum
osc.
dominant
matter dominant
Expected spectrum
distortion with 5 years low
BG SK data
pp
7Be
8B
Supernova at LMC (February 23, 1987)
After
Before
SN1987A signal by Kamiokande
It was when the Kamiokande detector was almost ready
for solar neutrino detection.
Visible energy (MeV)
11 events in 13 sec.
Background level
sec
JT: 1987 Feb 23 16:35:35 (±1min)
UT:
7:35:35
Time
SN1987A: supernova at LMC(50kpc)
Feb.23, 1987 at 7:35UT
Kam-II (11 evts.)
IMB-3 (8 evts.)
Baksan (5 evts.)
24 events total
IMB-3
Total Binding Energy
Kamiokande-II
from G.Raffelt
BAKSAN
95 % CL
Contours
Theory
_
Spectral ne Temperature
Super-K: Expected number of events
Neutrino flux and energy spectrum from Livermore simulation
(T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216(1998))
~7,300 ne+p events
~300 n+e events
~360 16O NC g events
~100 16O CC events
(with 5MeV thr.)
for 10 kpc supernova
Super-K: Time variation measurement by ne+p
Assuming a supernova at 10kpc.
nep e+n events give direct energy information (Ee = En – 1.3MeV).
Time variation of event rate
Time variation of mean energy
Enough statistics to discriminate models
Super-K: Expected angular distribution
n+e
n+e
ne+p
ne+p
n+e
ne+p
n+e
ne+p
Simulation of
a SN at 10kpc
Direction of supernova can
be determined with an
accuracy of ~5 degree.
Spectrum of n+e events
can be statistically
extracted using the
angular distributions.
Neutrino flux and spectrum
from Livermore simulation
Supernova Relic Neutrinos
S.Ando, Astrophys.J.607:20-31,2004.
S.Ando, NNN05
Supernova Relic Neutrinos
Reactor n (ne)
Constant SN rate (Totani et al., 1996)
Totani et al., 1997
Woosley, 1997
Solar 8B (ne) Hartmann,
Malaney, 1997
Kaplinghat et al., 2000
Ando et al., 2005
Lunardini, 2006
Solar hep (ne) Fukugita, Kawasaki, 2003(dashed)
SRN predictions
(ne fluxes)
Atmospheric ne
Expected number SRN events
0.8 -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.
Super-K results so far
Flux limit VS predicted flux
Energy spectrum of SK-I and SK-II (>18MeV)
SK-I (1496days)
Total
background
Atmospheric nm →
invisible m → decay e
Atmospheric nm →
invisible m → decay e
Events/4MeV
90% CL limit
of SRN
SK-II(791 days)
Atmospheric ne
Atmospheric ne
Energy (MeV)
Spallation background
Observed spectrum is consistent with estimated background.
Search is limited by the invisible muon background.
Neutron tagging in water
Cherenkov detector
Neutron capture gamma
ne
n+Gd →~8MeV g
n
p
DT = ~30 msec
Add 0.2% GdCl3 in water
(J.Beacom and M.Vagins)
Phys.Rev.Lett.93:171101,2004
e+
Gd
g
Positron and gamma ray
vertices are within ~50cm.
ne can be identified by delayed coincidence.
Possibility of SRN detection
Relic 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
SK10 years (e=67%)
Assuming invisible muon B.G. can
be reduced by a factor of 5 by
neutron tagging.
Assuming 67% detection efficiency.
By 10 yrs SK data,
Signal: 33, B.G. 27
(Evis =10-30 MeV)
We are studying feasibility of
introducing gadolinium. (effect on
water transparency, corrosion,
cable connectors and etc.)
Atmospheric neutrino anomaly in Kamiokande
Paper in 1988
Initial hint
m→e decay ratio
EXPERIMENTAL STUDY OF THE ATMOSPHERIC NEUTRINO FLUX.
KAMIOKANDE-II Collaboration (K.S. Hirata et al.), Phys.Lett.B205:416,1988
Momentum of single ring events
e
m
Data from 1983 to1985
Small m→e decay ratio
m-like/e-like ratio is 60% of
expectation.
Atomospheric anomaly in Kamiokande
Zenith angle distribution of multi-GeV events (1994)
Y.Fukuda et al., Phys. Lett. B 335 (1994) 237.
upward
downward
Zenith Angle distribution of SK
cos θzenith
\
cos θzenith
cos θzenith
SK-I data
Monte Carlo (no oscillations)
Monte Carlo (best fit oscillations)
Zenith Angle Analysis: SK-I + SK-II
Best fit:
Δm2 = 2.1 x 10-3 eV2
sin2 2θ = 1.02
χ2 = 830.1 / 745 d.o.f.
L/E Analysis: SK-I + SK-II
Datasets
SK-I FC/PC μ-like: 1489 days
SK-II FC/PC μ-like: 799 days
Use only event categories with
good L/E resolution:
Partially-contained muons
Fully-contained muons
χ2 fit to 43 bins of log10(L/E)
with 29 systematic error terms
Compare against:
Neutrino decoherence (5.0σ)
Neutrino decay (4.1σ)
3 flavor analysis: SK-I + SK-II
Normal Hierarchy
preliminary
Inverted Hierarchy
Note: one mass scale dominance method(dm212 is set to 0)
Full 3-flavor analysis is being prepared.
SK-IV electronics: New front-end electronics, QBEE
Network Interface Card
QTC-Based Electronics with Ethernet
(QBEE)
Ethernet Readout
 24 channel input
 QTC (custom ASIC)
60MHz Clock  3 gain stages
TDC Trigger  Wide dynamic range(>2000pC)
PMT
signal
factor 5 larger than old electronics
 Pipe line processing


QTC
TDC
Calibration Pulser 



FPGA
multi-hit TDC (AMT3)
FPGA
Ethernet Readout
60MHz common system clock
Internal calibration pulser
Low power consumption
( < 1W/ch )
Difference in readout system
Former readout system
12PMT
signals
per
module
Former
Electronics
(ATM)
HITSUM
Trigger (1.3msec x 3kHz)
Trigger
logic
Readout (backplane, SCH, SMP)
Hardware Trigger
using number of hit
(HITSUM)
1.3msec
event window
New readout system
No hardware trigger. All hits are readout. Apply software trigger.
24PMT
signals
per
module
New
Electronics
(QBEE)
Periodic trigger
(17msec x 60kHz)
Clock
Readout (Ethernet)
Collect ALL hits every 17msec
time window. The 60kHz clock
synchronize time of hit
information.
Variable
event window
by software trigger
Performance of new electronics for supernova burst
# of hits
Performance for high rate
Distance to SN vs. number of events
input
output
burst hit rate (kHz)
Dead time free in the
new system
130kHz
 100% efficiency up to 130kHz
for each channel.
 It corresponds to ~1000 x
supernova at galactic
center.(100 times better than
previous system.)
Previous system
 Dead time free even for a
supernova as close as 0.3kpc
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.