The Previous Results and Future Possibilities of KamLAND

1
The Previous Results and Future Possibilities of
KamLAND

• Kazumi Tolich
• Stanford University
• 2/6/2007

2
Outline

• KamLAND
• Previous Reactor Neutrino Result
• Previous Geoneutrino Result
• Future Possibilities
• Full Energy Analysis
• Solar Neutrinos
• Supernova

3
KamLAND
Introduction to the KamLAND experiment
4
KamLAND Collaboration
T. Ebihara,1 S. Enomoto,1 K. Furuno,1 Y. Gando,1
K. Ichimura,1 H. Ikeda,1 K. Inoue,1 Y. Kibe,1 Y.
Kishimoto,1 M. Koga,1 Y. Konno,1 Y. Minekawa,1 T.
Mitsui,1 K. Nakajima,1 K. Nakajima,1 K.
Nakamura,1 K. Owada,1 I. Shimizu,1 J. Shirai,1
F. Suekane,1 A. Suzuki,1 K. Tamae,1 S.Yoshida,1
J. Busenitz,2 T.Classen,2 C. Grant,2 G. Keefer,2
D.S.Leonard,2 D. McKee,2 A. Piepke,2 B.E.
Berger,3 M.P. Decowski,3 D.A. Dwyer,3 S.J.
Freedman,3 B.K. Fujikawa,3 F. Gray,3 L. Hsu,3
R.W. Kadel,3 C. Lendvai,3 K.-B. Luk,3 H.
Murayama,3 T. ODonnell,3 H.M. Steiner,3 L.A.
Winslow,3 C. Jillings,4 C. Mauger,4 R.D.
McKeown,4 C. Zhang,4 C.E. Lane,5 J. Maricic,5 T.
Miletic,5 J.G. Learned,6 S. Matsuno,6 S.
Pakvasa,6 G.A. Horton-Smith,7 A. Tang,7 K.
Downum,8 G. Gratta,8 K. Tolich,8 M.Batygov,9 W.
Bugg,9 Y. Efremenko,9 Y. Kamyshkov,9 A.Kozlov,9
O. Perevozchikov,9 H.J. Karwowski,10
D.M.Markoff,10 W. Tornow,10 J.S. Ricol,11 F.
Piquemal,11 and K.M. Heeger,12 1. Research
Center for Neutrino Science, Tohoku University,
Sendai 980-8578, Japan 2. Department of Physics
and Astronomy, University of Alabama, Tuscaloosa,
Alabama 35487, USA 3. Physics Department,
University of California at Berkeley and Lawrence
Berkeley National Laboratory, Berkeley,
California 94720, USA 4. W. K. Kellogg Radiation
Laboratory, California Institute of Technology,
Pasadena, California 91125, USA 5. Physics
Department, Drexel University, Philadelphia,
Pennsylvania 19104, USA 6. Department of Physics
and Astronomy, University of Hawaii at Manoa,
Honolulu, Hawaii 96822, USA 7. Department of
Physics, Kansas State University, Manhattan,
Kansas 66506, USA 8. Physics Department,
Stanford University, Stanford, California 94305,
USA 9. Department of Physics and Astronomy,
University of Tennessee, Knoxville, Tennessee
37996, USA 10. Triangle Universities Nuclear
Laboratory, Durham, North Carolina 27708, USA and
Physics Departments at Duke University, North
Carolina State University, and the University of
North Carolina at Chapel Hill 11. CEN
Bordeaux-Gradignan, IN2P3-CNRS and University
Bordeaux I, F-33175 Gradignan Cedex, France 12.
Department of Physics, University of Wisconsin at
Madison, Madison, Wisconsin, USA
5
KamLAND Location

• KamLAND was designed to measure reactor
  anti-neutrinos.
• KamLAND is surrounded by nuclear reactors in
  Japan.

KamLAND
6
KamLAND Detector
1km (2700 m.w.e) Overburden
Electronics Hut
Steel Sphere of 8.5m radius
Inner detector 1325 17 PMTs 554 20 PMTs 34
coverage
1 kton liquid-scintillator
Transparent balloon of 6.5m radius
Buffer oil
Water Cherenkov outer detector 225 20 PMTs
7
Detecting Anti-neutrinos with KamLAND
Delayed
Prompt

• KamLAND (Kamioka Liquid scintillator
  Anti-Neutrino Detector)

2.2 MeV g
0.5 MeV ?
e-
e
0.5 MeV ?
n
p

• Inverse beta decay
• ne p ? e n

p
d
ne

• The positron loses its energy then annihilates
  with an electron.

• The neutron first thermalizes then gets captured
  on a proton with a mean capture time of 200ms.

• Neutrino energy can be estimated by the kinetic
  energy of the positron plus 1.8MeV.

8
Major Background Events for Antineutrino Detection

• Accidentals uncorrelated events due to the
  radioactivity in the detector mimicking the
  inverse beta decay signature.

• 13C(?,n) 210Po (introduced as 222Rn) emits an
  ??particle, which reacts with naturally occurring
  13C (1.1 of C).

1H(n,n)1H the neutron collides with protons
(prompt) and later captures on a proton (delayed).
12C(n,n?)12C the neutron excites a 12C producing
a 4.4 MeV ? (prompt), and later captures on a
proton (delayed).
13C(?,n?)16O the 16O de-excites with a 6 MeV
???(prompt), and the neutron later captures on a
proton (delayed).
9
Neutrino Oscillation Results

• Phys. Rev. Lett. 90, 021802 (2003)
• First Results from KamLAND
• Evidence for Reactor Anti-Neutrino Disappearance
• 1269 citations as of last week!
• The most cited paper in physics in 2003
• The 2nd most cited paper in all sciences in 2003

• Phys. Rev. Lett. 94, 081801 (2005)
• Measurement of Neutrino Oscillation with
  KamLAND
• Evidence of Spectral Distortion
• 425 citation as of last week!

10
Neutrino Oscillations in Vacuum

• The weak interaction neutrino eigenstates may be
  expressed as superpositions of definite mass
  eigenstates
• The electron neutrino survival probability can be
  estimated as a two flavor oscillations

11
Selecting Reactor Anti-neutrino Events

• ?r lt 2m
• 0.5µs lt ?T lt 1000µs
• 2.6MeV lt Ee, p lt 8.5MeV
• 1.8MeV lt E?, d lt 2.6MeV
• Veto after muons
• Rp, Rd lt 5.5m

Delayed
Prompt
2.2 MeV g
0.5 MeV ?
e
0.5 MeV ?
12
Dataset and Rate Analysis

• From March 9 2002 to January 11 2004.
• 365.2 23.7 expected reactor antineutrinos with
  no oscillation.
• 17.8 7.3 expected background events.
• 258 candidate events.
• The average survival probability is 0.658
  0.044(stat) 0.047(syst).
• We confirmed antineutrino disappearance at
  99.998 C.L. (4?).

13
Prompt Energy Distribution

• KamLAND saw an antineutrino energy spectral
  distortion at 99.6 significance.

14
Oscillation Analysis

• Shape distortion is the key factor in determining
  ?m2.

Shape Rate
Shape Only
15
Average Distance, L0
KamLAND
L0 180 km
80 of total flux comes from reactors 140 to
210km away.
16
L0/E
Observed/No Oscillation Expected
Would the data come back up again???
17
Geoneutrino Result

• Nature 436, 499-503 (28 July 2005)
• Experimental investigation of
• geologically produced antineutrinos
• with KamLAND

18
Convection in the Earth
Image http//www.dstu.univ-montp2.fr/PERSO/bokelm
ann/convection.gif

• The mantle convection is responsible for the
  plate tectonics and earthquakes.
• The mantle convection is driven by the heat
  production in the Earth.

19
Heat from the Earth

• Heat production rate from U, Th, and K decays is
  estimated from chondritic meteorites to be 19TW.
• Heat flow is estimated from bore-hole
  measurements to be 44 or 31TW.
• Models of mantle convection suggest that the
  radiogenic heat production rate should be a large
  fraction of the total heat flow.
• Problem with
• Mantle convection model?
• Total heat flow measured?
• Estimated radiogenic heat production rate?

20
Geoneutrino Signal
Inverse Beta Decay Threshold

• ? decays in U and Th decay chains produce
  antineutrinos.
• Geoneutrinos can serve as a cross-check of the
  radiogenic heat production rate.
• KamLAND is only sensitive to antineutrinos above
  1.8MeV
• Geoneutrinos from K decay cannot be detected with
  KamLAND.

21
Selecting Geoneutrino Events
Delayed
Prompt

• ?r lt 1m
• 0.5µs lt ?T lt 500µs
• 1.7MeV lt E?,plt 3.4MeV
• 1.8MeV lt E?,dlt 2.6MeV
• Veto after muons
• Rp, Rd lt 5m
• ?dgt1.2m

2.2 MeV g
0.5 MeV ?
e
0.5 MeV ?
These cuts are tighter compared to the reactor
antineutrino event selection cuts because of the
excess background events for lower geoneutrino
energies.
22
Geoneutrino Candidate Energy Distribution
Expected total
Expected total background 127 13
Candidate data 152 events
Expected reactor 80.4 7.2
Expected (?,n) 42 11
Measured Accidental 2.38 0.01
Expected U 14.8 0.7
Expected Th 3.9 0.2
Data from March, 2002 to October, 2004.
23
How Many Geoneutrinos?
chondritic meteorites
Expected
3 U geoneutrinos 18 Th geoneutrinos
28 U Th geoneutrinos
24
Future Possibility IFull Energy Analysis
My Thesis in Progress
25
Combined Analysis

• Combined analysis probes lower energy reactor
  anti-neutrinos and should improve ?m2
  measurement.
• We will possibly observe the re-reappearance of
  reactor antineutrinos.
• Better understanding of reactor spectrum might
  improve the geoneutrino measurement.

Re-reappearance?
26
Previous and Planned Cuts

• Geoneutrino event selection cuts are tighter due
  to the low energy accidental background.
• Combined analysis requires consolidation of the
  difference in the event selection cuts.

27
Real and Visible Energies

• Ereal is the particles real energy.
• Evisible is determined from the amount of optical
  photons detected, including quenching and
  Cerenkov radiation effects.
• The model of Evisible/Ereal as a function of
  Ereal fits calibration data very well.
• Previous analyses were done in positron real
  energy, having to convert background energies
  (such as ?s) into effective positron real
  energies.

12C(n,?)13C
1H(n,?)2H
60Co
Fit to our model
65Zn
68Ge
203Hg
28
Expected Prompt Energy Spectra
Accidentals
Reactor neutrinos
(?,n)
Th geoneutrinos
U geoneutrinos
Scaled approximately to the number of events
expected.
29
Expected Delayed Energy Spectra
n-capture on p
Accidentals
Scaled approximately to number of events expected
30
Expected ?t Spectra
Previous Geoneutrino Analysis Cut
n-capture on p
Accidentals
Scaled approximately to number of events expected
31
Time Variation of Reactor Neutrino Flux

• Shika reactor 90km (half of L0) away turned on
  from May 26 2005 to July 4 2006.
• Shika contributed 14 of total flux.
• May help distinguish LMA I and LMA II.

32
Probability Density Functions

• Expected prompt energy spectra and time variation
  of reactor neutrino flux were used in the
  previous analyses.
• Expected delayed energy and ?t spectra will be
  added to distinguish accidental background.

33
Future Possibility II7Be Solar Neutrino Detection
http//www.noaanews.noaa.gov/stories2005/images/su
n-soho011905-1919z.jpg
34
Solar Neutrinos from the p-p Chain Reactions
35
Solar Neutrino Spectrum
We expect to see a few hundred events per day.
Solar Neutrino Flux at the surface of the Earth
with no neutrino oscillations. Uses the solar
model, BS05(OP).
36
7Be Solar Neutrino Detection

• Solar ? scatters off e-.
• The electron recoil energy is

From ?e
From ?? ??
Detection resolution is not included.
37
Current Radioactivity in KamLAND
After fiducial volume cut is applied
38
Test Removal of Reducible Background

• Distillation removed 222Rn by a factor of 104 to
  105.
• Heating and distillation reduced the 212Pb
  activity by a factor of 104 to 105.
• Distillation reduced the 40K concentration in PPO
  by a factor of 102.
• Distillation reduced natKr by a factor of 105 to
  106.

39
Expected Energy Spectra after the Purification
40
Purification System Constructed

• The purification system is being commissioned
  right now.
• We have done some testing and are fixing bugs.
• We should be able to start the full purification
  operations soon.

From October 2006
41
Future Possibility IIISupernova Detection
http//upload.wikimedia.org/wikipedia/commons/4/43
/Supernova-1987a.jpg
42
Expected Signals

• For a standard supernova (d 10 kpc, E3x1053
  ergs, equal luminosity in all neutrino flavors),
  we expect to see (no neutrino oscillations)
• 310 events
• 20 events
• 60 events
• 45 events
• 20 events
• 10 events
• 300 events
• (0.2 MeV threshold)
• There should be 300 e events above 10 MeV, with
  an initial rate of 100 Hz (exponential decay with
  3s time constant).
• The proton scattering events (low visible energy)
  provide a determination of both luminosity of all
  neutrino flavors and temperature.

J. F. Beacom et al.
43
Expected Proton Scattering Events
Realistic energy threshold after purification of
scintillator
dN/dEvisible 1/MeV
Evisible MeV
J. F. Beacom et al.
44
Supernova Trigger

• 8 high energy inverse beta decay events (gt9MeV)
  within 0.8s causes a supernova trigger.
• With the supernova trigger, the trigger switches
  to a pre-determined supernova mode.
• The supernova mode has a lower energy threshold
  (0.6MeV) in order to detect low energy events
  (especially ? p ? ? p.)
• The energy threshold could be lowered after the
  purification.

45
Conclusions

• KamLAND has been producing some impressive
  results.
• I am analyzing the full energy range, reactor
  neutrinos and geoneutrinos simultaneously, to
  improve sensitivity.
• The planned purification of scintillator will be
  followed by the solar neutrino phase.
• If there is a supernova explosion, KamLAND is the
  only detector that can possibly detect the proton
  scattering events.

46
Questions?
47
Total Heat Flow from the Earth
Bore-hole Measurements

• Conductive heat flow measured from bore-hole
  temperature gradient and conductivity
• Deepest bore-hole (12km) is only 1/500 of the
  Earths radius.
• Total heat flow 44.2?1.0TW (87mW/m2), or 31?1TW
  (61mW/m2) according to more recent evaluation of
  same data despite the small quoted errors.

Image Pollack et. al
48
Radiogenic Heat

• U, Th, and K concentrations in the
• Earth are based on measurement
• of chondritic meteorites.
• Chondritic meteorites consist of
• elements similar to those in the
• solar photosphere.
• The predicted radiogenic total heat production is
  19TW.
• Th/U ratio of 3.9 is known better than the
  absolute concentrations of Th and U.

49
Reference Earth Model Flux

• 20 from nearby crust (within 30km).
• 20 from outside of a 4000km radius.
• 25 from the mantle.

50
MSW Effect in the Sun

• ?es experience MSW effect in the Sun.

• For 7Be ?es,

Possible sin22?
For E? 862keV ?m27.9x10-5eV2
51
Irreducible Radioactivity

• ?s (1.46MeV) and ?s from 40K in the balloon
• ?s (2.6MeV) from 208Tl decay in the surrounding
  rocks
• 14C throughout the detector (less than 200keV)
• 11C from cosmic muons (more than 700keV)
• Most of the 40K and 208Tl background is removed
  with fiducial volume cut.
• Most of the 14C and 11C background is removed
  with energy cut.

52
Detector Capability

• The electronics buffers can hold 10k high
  energy events (all PMTs hit).
• KamLAND handled a simulated supernova with 400 Hz
  high energy events (all PMTs hit) for 10 seconds
  with 0.6MeV detector threshold.