Transcript Neutrino Physics and Astrophysics with SuperKamiokande Jordan A

Solar & Atmospheric
Oscillation Experiments
Greg Sullivan
University of Maryland
Aspen Winter Conference
January 21, 1999
n
??
e
 Past
 Neutrino Mass & Oscillations
 Present
 Atmospheric neutrinos
 Solar neutrinos
 Future
 Can we detect them?
 In 1934 Bethe & Peierls calculated the
cross section for neutrino interaction of
10-44 cm2.
 Nature (London) 133, 532(1934)
“It is therefore absolutely impossible to
observe processes of this kind with
neutrinos created in nuclear
transformations”
“… one can conclude that there is no
practically possible way of observing
the neutrino.”
“… and it is not necessary to assume
interaction in order to explain the
function of the neutrino nuclear
transformations ...”
 In fact, it was some 20 years before they
were detected using a nuclear reactor as
a source.
Solar Neutrino Spectrum
Solar Neutrinos detected
 R. Davis and his 37Cl detector
 same principle used to try and detect
antineutrinos from a nuclear reactor in
1955.
 measured the flux of neutrinos from the
sun almost continuously since about
1970!
Solar Neutrino Rate in Cl
Detector is 1/3-1/2 expected
Explanations?
 Astrophysics - Standard Solar Model
 Neutrinos from 7Be and 8B
 Very sensitive to Sun’s core temperature
 Particle Physics Solutions --- Neutrino
properties are not what we think!
 Electron Neutrinos don’t make it to earth
 Magnetic properties of n
 ne change flavor in transit - Neutrino
Oscillations!
 Non zero neutrino mass!
 Lepton flavor mixing!
Neutrino Mass & Neutrino
Oscillations?
 What is the mass of the neutrino?
 Is it identically zero?
 If not, Why is it so small?
see-saw mechanism
The most general mass Lagrangian for one neutrino flavor is:
Lm  mD nLnR  nRnL   mLnLcnL  mRnRcnR

h. c.
where m D , m L , m R represent the Dirac, left-handed Majorana
and right-handed Majorana masses. This can be written in
matrix form as:
Lm  S M S
where,
n
S  
n
L
R
 n
 n
 mL
M  
 mD
c
L
c
R



mD 

mR 
The physical mass eigenstates are found by diagonalizing the
mass matrix. If we assume m L = 0 we get:
m1, 2 
mR
2

1 


1
4 m D2
m R2




For a heavy right-handed scale m R >> m D , we get two mass
eigenstates
mH  mR
mn 
2
D
m
mR
( heavy n )
( light n )
50 MeV  500 mW
10  6  10' s eV
Neutrino Oscillations
 If n mass is not 0 and flavor is not absolutely
conserved then “mixing” may occur between
different type of neutrinos. Weak eigenstates
of the neutrino are mixtures of the neutrinos
with definite mass.
For two neutrino species ne and n we have:
n e  n 1 cos  n 2 sin
n   n 1 sin  n 2 cos
where n and n2 are the mass eigenstates.
In a weak decay one produces a definite weak eigenstate
n  t  0  n e
.
.
At a later time the probability of the final state will be:
n t   n 1 e  iE t cos  n 2 e  iE t sin
1
2
The survival probability is:
2


1
.
27

m
2
2
eV Lkm

P n e  n e ; L   1sin 2  sin 
EGeV

.
Solar Neutrino Experiments
 Homestake - Radiochemical
 Huge tank of Cleaning Fluid
ne + 37Cl
e- + 37Ar
 Mostly 8B neutrinos + some 7Be
 30 years at <0.5 ev/day
 1/3 SSM
 Sage/Gallex - Radiochemical
 “All” neutrinos
ne + 71Ga
e- + 71Ge
 4 years at ~0.75 ev /day
 ~2/3 SSM
 Kamiokande-II and -III
 8B neutrinos only
ne
Elastic Scattering
 10 years at 0.44 ev /day
 ~1/2 SSM
Summary of Results Before Super-K
 Four experiments measured versus
predicted from solar model
Experiment
SSM(BP92) DATA
GALLEX
(Ga)
132  7
SAGE
(Ga)
DATA/SSM
70  8
0.54
“
73  11
Homestake
(Cl)
8  1.1
2.55  .25
0.32
Kamioka
(H2O)
5.7  .8
2.80  .38
0.49
BP95
FROM Langacker -Allowed regions at 95% CL from individual
experiments and from the global fit. The Earth effect is included for both timeaveraged and day/night asymmetry data, full astrophysical and nuclear physics
uncertainties and their correlations are accounted for, and a joint statistical
analysis is carried out. The region excluded by the Kamiokande absence of the
day/night effect is also indicated.
Atmospheric Neutrinos
n n
ne ne

2
Ratio predicted to ~ 5%
Absolute Flux Predicted to ~20% :
• primary CR spectrum
• geomagnetic cutoff
• hadron production
modeled from
accelerator data
Atmospheric Neutrino
Anomaly
 The Observed Ratio of n/ne is too low
 Produced when pions generated in the
upper atmosphere by cosmic rays decay.
P  N   X



  n 



 e n  n e

 Predicted Ratio of n/ne ~ 2
 Observed Ratio is ~ 1
 Particle Physics Solutions --- Neutrino
properties are not what we think!
 Muon Neutrinos don’t make it to earth
n change flavor in transit - Neutrino
Oscillations!
 Non zero neutrino mass!
 Lepton flavor mixing!
Worldwide Results on “R”
Before Super-Kamiokande
Two Suggestions of Neutrino
Transformation
 Solar Neutrinos (~1-15 Mev ne)
 Davis experiment (Cl) saw ~30% of
expected flux of ne from 8B & 7Be
 Galium experiments showed less than
expected flux of ne from all processes
 Kamiokande saw ~40% ne from 8B
 These results can not be reconciled with
the standard solar model
 Atmospheric Neutrinos (~.1 - 3 GeV)
 IMB and Kamiokande saw less than
expected ratio of n/ ne
 One Proposed Explanation was:
Neutrino Oscillations
 Solar neutrinos might be ne
 Atmos. neutrinos might be n
n
nt
Super-Kamiokande
The Next generation
Underground Neutrino
Detector.
Super-Kamiokande is a 50,000 ton
water Cerenkov detector at a
depth of 1000 meters in the
Kamioka Mozumi mine in Japan.
 Detector Characteristics
 41 m h x 39 m dia.
 50,000 tonne total/22,000 tonne fiducial
 11,200 20” PMTs inner detector
 1,850 8” PMTs anti-detector
 40% photocathode coverage
 Trigger Threshold ~5 MeV
 Resolution
 Energy 16%/(E)1/2 at 10 MeV
 Position ~50 cm at 10 MeV
 Angular ~30 degrees at 10 MeV
SuperKamiokande
Collaboration
























Institute for Cosmic Ray Research, University of Tokyo
Gifu University
Institute for Nuclear Study, University of Tokyo
National Laboratory for High Energy Physics, KEK
Kobe University
Miyagi Education University
Niigata University
Osaka University
Tokai University
Tohoku University
Tokyo Institute of Technology
Boston University
Brookhaven National Laboratory
University of California, Irvine
California State University, Dominguez Hills
Cleveland State University
George Mason University
University of Hawaii
Los Alamos National Laboratory
Louisiana State University
University of Maryland
State University of New York, Stony Brook
University of Warsaw
University of Washington
The Super-K Detector
The Super-Kamiokande Tank
During Filling in 1996
Stopping Muon
Electron from decay of
stopping muon
Muon - Electron Identification
Sub-Gev
(535 days)
Evis < 1.33 GeV
Pe > 100 MeV/c
P > 200 MeV/c
Data
MC
e-like
1231
1049
-like
1158 1574
1 Ring
Multi-ring
 / eData
 / eMC
911
981
 0.63  .026 (stat )  .05 (syst )
Multi-Gev
(535 days)
Evis > 1.33 GeV
Fully Contained
Data
MC
-like
290
230
236
297
Multi-ring
533
560
1 Ring
e-like
Partially Contained
Total =
-like
 / eData
 / eMC

Data
MC
301
372
0.65  .05 ( stat )  .08 ( syst )
Worldwide Results on “R”
 Detectors continue to run
 MACRO upward going muons
 Soudan II
 Super-K muons
If the muon n‘s oscillate, what
it look like?
 Depletion of n relative to ne
 “double ratio” R

 / e data
R
 / e MC
 1
 L dependence of n flux
 Zenith angle dependence
Zenith Angle Dependence
Survival Probability vs. Distance
(1GeV,.003 eV^2)
1
Probability
0.75
0.5
0.25
0
10
100
1000
10000
Distance (km)
 1.27 m2 Lkm 

Pn   n  ;L   1  sin 2 sin 
EGeV


2
2
Zenith Angle Dependence
Zenith Angle Dependence
L/E Distribution of
Atmospheric Neutrinos
The dashed lines show the expected shape
for nnt at m2=2.2 x 10-3 eV2 and
sin2 2 = 1.
Atmospheric Results
East-West Effect
Zenith Angle Distribution
(736 Day Sample)
Zenith Angle Dependence
(736 day sample)
MACRO Detector
 Data collected ‘89 - Dec ‘97
 ~3 live-years with 6 full SM
 ~480 Upward Going Muon events
R(data/MC)= 0.74  .036sta.046sys.13theo
 Probability for no oscillations
P(null) = 14%
 Best fit mass assuming maximal mixing:
m2 ~ 2 x 10-3 eV2
MACRO upward-going muons
 Probabilities Number + Shape
 Probability of no oscillations
P(null)  0.1%
 Best fit oscillation parameters
sin22 = 1.0 , m2  2 x 10-3 eV2
P(best fit)  17%
A Picture of the Sun using
Neutrinos in Super-K
10 MeV Electron in Super-K
Super Low Energy (SLE) Data
Solar Neutrino Flux
(New 708 Day Sample)
Data
 0.471  0.008 ( stat )  0.013 ( syst )
SSM BP98
Day-Night Results
708 day Sample
DN
DN
  0.026  0.016 ( stat )  0.013 ( syst )
Energy Spectrum
708 day + 419 day SLE
Spectrum and Oscillations?
 Data favors Vacuum solution (red)
 small angle MSW (blue) starting to get
squeezed by flatness with SLE data
Hep Neutrinos ?
 Set limit on hep flux from data
 integral of events between Ethres & Eend
 Ethres= 17 MeV , Eend= 25MeV
Hep flux < 8 SSM at 90% C.L.
 Ethres= 19 MeV , Eend= 20 MeV
Hep flux < 20 SSM at 90% C.L.
Seasonal Variation
Energy Dependence of
Seasonal Variation for Just-so
solution
Seasonal Variation in High
Energy Data
Summary of Super-K Results
 Atmospheric Neutrinos
 Strong Evidence for n  nt ns)
Oscillations
 New results consistent
 Higher statistics may allow separation of
(nt ns)
 Solar Neutrinos
 No evidence for Day/Night Effect
 Squeezes Large Angle Solution
 Super Low E and more statistics
somewhat flattens energy spectrum
 Starting Squeeze Small Angle
Solution
 Vacuum (Just-So) solution is still alive
 Continue to Run
 Postponed the scheduled June ‘99
shutdown
Future ~2000
 Atmospheric Neutrinos
 Continued running of Super-Kamiokande
 Neutral Currents ?
 Distinguish n nt from n ns
 MACRO muons & neutrinos
 Soudan II
 KEK to Super-K (K2K)
 Solar Neutrinos
 Spectral Distortion at High Energy
 Instrumental Effect?
 Energy Scale & Resolution
LINAC limitations
 D-T Generator to make 16N as
calibration source (NSF)
 Hep Neutrinos?
 Need 20 times predicted flux
 Use Super-K data >18 MeV to set limit
on hep flux??
 Statistics?
 Seasonal Variation needs more data
Future 2000+
 Atmospheric Neutrinos
 Accelerator Experiments (FNAL, CERN,
KEK)
 Known Neutrino Direction
 Better Neutrino Energy Measurement
 Appearance Experiment ??
 Solar Neutrinos
 Continued Super-Kamiokande Running
 New Experiments Soon - should settle the
solar neutrino problem
 Sudbury Neutrino Observatory (SNO)
 Canada,US,UK 11 institutions
 Fill Apr, 98 -- Feb, 99 ?
 6 mo. Debug & Calibration
 1 Yr. pure D2O
 Borexino
 ICARUS
SNO Detector
-1000 tonnes of D2O
-6800 feet
Underground
-10,000 pmts
 Detector Performance
 Threshold 5MeV - 8B neutrinos
 Energy Resolution 14% at 10 MeV
 Charged Current off D - 26.7 ev/day
 measure NEUTRINO energy
- look for spectral distortion with high
sensitivity
- seasonal variation over entire spectrum
 Neutral Current 7.7 ev/day
 CC/NC ratio “smoking gun”
 Electron Scattering 3.0 ev/day
SNO Sensitivity
1) CC/NC Ratio
2) Spectrum
Borexino
-300 Tonnes of
Scintillator
-2200 Pmt’s
-Gran Sasso
 Detector Performance
 Electron Threshold low enough to
observe 7Be (863 keV) neutrinos
 Real time measurement of 7Be & 8B
 46 events/day in 100 ton fiducial volume
 First Measurement of only the 7Be flux
 final ingredient
Solar Neutrinos in Near Future
Possible
Super-K
Solutions
(Boron)
*
No
Flux low
Solar
No spec
Osc
No D/N
No Seas
Small
Angle
Spectral
MSW
Distortion?
Large
Angle
Day/Night
MSW
Vacuum
Osc
Spectrum
Season?
Small
Angle
Sterile
SNO
(Boron)
Borexino
(Be)*
Boone
(Acc)
Flux low? Meas/exp
No Spec
Possible
CC/NC
1
signal
OK
Spectrum
CC/NC
~1/4
No
low
Signal
Day/Night
CC/NC
~1/2
No
low
Signal
Spectrum
Season
~1/2
No
CC/NC
Signal
low
Spectrum
Spectrum? CC/NC
~.01
Possible
OK
signal
*Bahcall Phys Rev D 58
(http://www.sns.ias.edu/~jnb/)
Atmospheric Neutrino
Oscillations
 Need Confirmation of Evidence
 Further Running of Super-k, Soudan,
MACRO
 Accelerator Experiments planned
 MINOS at FNAL
 CERN to Gran Sasso
- Disappearance experiments?
 Future Possibilities
 Megaton underground Atmospheric
Neutrino detector
 Appearance Experiment?
 5 GeV Neutrinos
 L/E ~ 1 x 103
L ~ 5000 km