Solar neutrino detectors

1
Nufact03 school, May 2003 T.Kajita (ICRR, U.of
Tokyo)
Low energy neutrino detectors - water, heavy
water and scintillator -

• Solar neutrino detectors
• water Cherenkov detector
  (Super-Kamiokande)
• heavy water detector (SNO)
• Detectors for reactor experiments (KamLAND)
• Water Cherenkov atmospheric neutrino detector
• (Super-Kamiokande)
• Summary

2
Solar neutrino detectors
3
Solar neutrino flux and solar neutrino experiments
Radio chemical experiments detect 37Ar, 71Ge ..
Cherenkov detectors detect (mainly) electrons
http//www.sns.ias.edu/jnb/
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Water Cherenkov detector (Super-Kamiokande)
Ee
E?
Ee
E?
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Detecting Cherenkov photons
electron
Photomultiplier tube (PMT)
50cm f (Super-K)
?
20cm f (SNO)
n1.34 in water ?42deg. for ß1
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Super-Kamiokande
11,146(50cm f PMT) Inner detector
40 photo-cathode coverage
Number of observed Ch photons 6 /MeV
(excluding scattered or reflected photons)
1,885(20cm f PMT) Outer detector
50,000 ton water Cherenkov detector (Fid. Mass is
22,500 tons)
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Super-Kamiokande detector under construction
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Super-Kamioakande detector
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Detecting Cherenkov photons and event
reconstruction
Time vertex position
direction Pulse height energy
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Detector calibration by an electron LINAC
Precise calibration of absolute energy scale,
energy resolution, and angular resolution using
electron LINAC.
ENDCAP
0.1mm thick Ti window

• Beam energy 5 16 MeV/c
• Beam energy spread lt 0.5

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Absolute energy calibration by LINAC
Systematic error in the absolute energy scale
0.64 .
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16N calibration
106 n /pulse 1 of n creates 16N 16N decay is
precisely known. 66.2 6.129MeVg
4.29MeVb, 28.0 10.419 MeV b, and etc. Data
taken at various positions in the
detector. Uniform direction complementary to
LINAC calibration.
DT generator
DT?Hen
n16O?p16N
(14.2 MeV)
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16N calibration data
Direction dependence of the energy scale
Energy spectrum
Azimuthal angle
0.5
(MC-DATA) / DATA
Zenith angle
0.5
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Solar neutrino data from Super-K
?e??e 22,400 events above 5MeV
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Remark on background
Old SK data
Background mainly Rn (214Bi ß decay) (Need a
very clean water)
Background above 6MeV mainly events produced by
cosmic ray muon interactions (µ16O ? µ X,
X?Yß?) (Need to cut events by time and space
correlation with µ (or go deeper).)
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SK energy spectrum data
SK collab. Phys. Lett. B 539 179 (2002) M.Smy,
talk at Neutrino2002
Energy spectrum (data/SSM)
?2(flat)20.2/20
5 10
15 Ee(MeV)
Consistent with flat.
17
SK day-night data
SK collab. Phys. Lett. B 539 179 (2002) M.Smy,
talk at Neutrino2002
Day-night flux difference
No evidence for d-n asym.
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Allowed region from the SK data
G.L.Fogli et al., hep-ph/0206162 SK collab.,
Phys. Lett. B539, 179 (2002)
SMA solution excluded Both LMA and LOW/Quasi-VAC
are allowed.
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SNO (1kton D2O solar neutrino detector)
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n Reactions in SNO
ES
-
-

Þ

e
?
e
?
x
x

• Both SK, SNO
• Strong directional sensitivity
• Mainly sensitive to ne,, less to n? and n?

Þ

n
-
CC
e
p
p
d
e

• Good measurement of ne energy spectrum
• Weak directional sensitivity ? 1-1/3cos(q)

- ne ONLY
NC
n
n


Þ

n
p
d
x
x

• Measure total 8B n flux from the sun.

- Equal cross section for all n types
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Three ways to measure the NC events

• Neutron Detection Method
• Capture on D
• Capture on Cl
• Capture on 3He
• Event by event separation of CC and NC events

• Pure D2O
• Good CC sensitivity
• Added Salt in D2O
• Enhanced NC sensitivity
• Neutral Current Detectors
• 3He proportional counters in the D2O

Nov. 1999- May 2001
n ? d ? t ? g ? e? (Eg 6.3 MeV)
n ? 35Cl ? 36Cl ? ?g ? e? (E?g 8.6 MeV)
Since June 2001
n ? 3He ? p ? t
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Sudbury Neutrino Observatory
1000 tonnes D2O
Support Structure for 9500 PMTs, 60 coverage
12 m Diameter Acrylic Vessel
1700 tonnes Inner Shielding H2O
5300 tonnes Outer Shield H2O
Urylon Liner and Radon Seal
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SNO detector under construction
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SNO Energy Calibration
6.13 MeV
19.8 MeV
CC solar ?(MC)
252Cf neutrons
bs from 8Li gs from 16N and t(p,g)4He
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Measuring U/Th Content

• Ex-situ
• Ion exchange (224Ra, 226Ra)
• Membrane Degassing (222Rn)
• count daughter product decays

• In-situ
• Low energy data analysis
• Separate 208Tl 214Bi
• Using Event isotropy

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Signal extraction Monte Carlo Simulation
Energy
Radial Response
Direction from the Sun
n ? d ? t ? g ? e? (Eg 6.25 MeV)
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SNO Results
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Main SNO result
Evidence for solar neutrino oscillation
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Allowed parameter region from SNO only
G.L.Fogli et al., hep-ph/0206162 SNO collab.,
PRL. 89, 011302 (2002)
SMA solution excluded Both LMA and LOW are
allowed. ?m2 is also constrained.
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Allowed parameter region from all solar neutrino
data
G.L.Fogli et al., hep-ph/0206162
SMA solution excluded at gt 3s LOW is disfavored
at 99. LMA solution favored.
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(No Transcript)
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KamLAND (1kton scintillatior detector)
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Anti-electron-neutrino production in reactors
Fission reaction U n ? X1 X2 .
Neutron rich
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Detecting reactor neutrinos in Liq. scintillators
210 ms
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Reactor neutrino interaction signal
Flux s
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KamLAND detector overview
electronics hut
KamLAND
SK
control room
N2 generator
water purification
KamLAND
liquid scintillator purification
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KamLAND detector (1000 ton Liq. Sci. detector)
Light output 320p.e./MeV
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inner view of spherical vessel
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(No Transcript)
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Reactors arround KamLAND
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Energy calibration
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Impurities in KamLAND
238U (3.50.5)x10-18 g/g inside fiducial volume
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KamLAND results
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Atmospheric neutrino experiments
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Atmospheric neutrinos
Cosmic Ray
p, K
Atmosphere
µ
e
nm
nm
ne
nm
ne
Neutrinos from the other side of the Earth.
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Atmospheric neutrino experiments
Soudan-2
Super-Kamiokande
MACRO
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Spectrum
E?(GeV)
E?(GeV)
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Various types of atmospheric neutrino events
FC (fully contained)
Both CC ?e and ?µ (NC) Need particle
identification to separate ?e and ?µ
?
12000 events (Super-K) 360 events (Soudan2)
PC (partially contained)
CC ?µ
900 events (Super-K) 40 events (Soudan2)
?
CC ?µ
Upward going muon
1900 events (through, SK) 420 events (stopping,
SK) 1200 events (through, MACRO) 400 events
(stopPC, MACRO)
?
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Particle identification
Outer detector (no signal)
Single Cherenkov ring electron-like event
Single Cherenkov ring muon-like event
Color timing Size pulse height
Particle ID
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Particle ID results
e from µ decay
Cosmic ray µ
e99
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Super-Kamiokande data
1489day FCPC data 1678day upward going muon
data

• Whole SK-1 data have been analyzed.

1-ring e-like 1-ring µ-like multi-ring
µ-like up-going µ
stopping
lt 1.3GeV
No osc.
Through going
Osc.
gt 1.3GeV
Up-going Down-going
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?µ??t oscillation results
Kamiokande
Soudan-2
Super-K
sin22?gt 0.92 ?m2(1.6
3.9)10-3eV2
MACRO
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Other detectors
Borexino
LSND
Kamiokande
Mini-BOONE
IMB
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Summary

• Large volume (heavy) water Cherenkov and liq.
  scintillator detectors with PMTs at the surfaces
  are very important technique to detect low energy
  neutrinos.
• The technique can be further used, for example,
  in future long base line neutrino oscillations
  with E?lt1GeV.

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End
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Introduction
?e ?? ?t
?3
?m23 ?23
2
?m13 ?13
2
small
Atmospheric neutrinos Long baseline exp.
? mass
Reactor exp. Long baseline
?m12 ?12
2
small
?2
Solar neutrinos Reactor exp.
?1
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Trigger threshold
6.5MeV
6.5MeV
LE analysis (May 96))
5.5MeV
SLE analysis (May 97)
SLE trigger (4.7MeV_at_50)
5.0MeV
SLE-V2 analysis
SLE-V2 trigger (4.2MeV_at_50) (550Hz)
LE trigger (5.7MeV_at_50) (10Hz)
Ee (MeV)
Since July 2000, further lowered by 12
(SLE-version 3). (100
eff. for gt4.5 MeV, 3.7MeV_at_50)
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Atmospheric neutrinos
Calculated zenith angle distribution
Atmosphere
?
?
Earth
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The accident in Super-Kamiokande and the status
Before.
The accident on Nov.12, 2001
Nov.2001
Mar.2002
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Status of SK (re-building the detector)
(Aug.2002)
New PMT container
Re-build the detector with ?the remaining 5200
PMTs (Inner detector) and ?1900 PMTs
(Outer detector).
Target date (start filling water) Oct.2002 Full
rebuilding We hope before 2007..
Floating floor