new results from kamland and prospects for observation of terrestrial neutrinos nikolai tolich

New Results from KamLAND and Prospects for Observation of

Terrestrial Neutrinos

Nikolai Tolich

July 9, 2004 LBL Journal Club Meeting 2

KamLAND CollaborationT. Araki1, K. Eguchi1, S. Enomoto1, K. Furuno1, K. Ichimura1, H. Ikeda1, K. Inoue1, K. Ishihara1, T. Iwamoto1,T. Kawashima1, Y. Kishimoto1, M. Koga1, Y. Koseki1, T. Maeda1, T. Mitsui1, M. Motoki1, K. Nakajima1, H. Ogawa1,K. Owada1, J.-S. Ricol1, I. Shimizu1, J. Shirai1, F. Suekane1, A. Suzuki1, K. Tada1, O. Tajima1, K. Tamae1, Y. Tsuda1,H. Watanabe1, J. Busenitz2, T. Classen2, Z. Djurcic2, G. Keefer2, K. McKinny2, D-M. Mei2, A. Piepke2, E. Yakushev2, B.E. Berger3, Y.D. Chan3, M.P. Decowski3, D.A. Dwyer3, S.J. Freedman3, Y. Fu3, B.K. Fujikawa3, J. Goldman3,F. Gray3, K.M. Heeger3, K.T. Lesko3, K.-B. Luk3, H. Murayama3, A.W.P. Poon3, H.M. Steiner3, L.A. Winslow3,G.A. Horton-Smith4, C. Mauger4, R.D. McKeown4, P. Vogel4, C.E. Lane5, T. Miletic5, P.W. Gorham6, G. Guillian6,J.G. Learned6, J. Maricic6, S. Matsuno6, S. Pakvasa6, S. Dazeley7, S. Hatakeyama7, A.Rojas7, R. Svoboda7,B.D. Dieterle8, J. Detwiler9, G. Gratta9, K. Ishii9, N. Tolich9, Y. Uchida9, M. Batygov10, W. Bugg10, Y. Efremenko10,Y. Kamyshkov10, A. Kozlov10, Y. Nakamura10, H.J. Karwowski11, D.M. Markoff11, J.A. Messimore11, K. Nakamura11,R.M. Rohm11, W. Tornow11, R. Wendell11, A.R. Young11, M.-J. Chen12, Y.-F. Wang12, and F. Piquemal13

1Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan2Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA 3Physics Department, University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA4W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA5Physics Department, Drexel University, Philadelphia, Pennsylvania 19104, USA6Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA7Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA8Physics Department, University of New Mexico, Albuquerque, New Mexico 87131, USA9Physics Department, Stanford University, Stanford, California 94305, USA10Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA11Triangle 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 Hill12Institute of High Energy Physics, Beijing 100039, People's Republic of China13CEN Bordeaux-Gradignan, IN2P3-CNRS and University Boreaux I, F-33175 Gradignan Cedex, France


An Attractive Group


Detecting Anti-neutrinos at KamLAND

• KamLAND (Kamioka Liquid scintillator Anti-Neutrino Detector)

dpe+

0.5 MeV 2.2 MeV

np

0.5 MeV

e

e-

• Inverse beta decay

e + p → e+ + n

• The positron losses its energy then annihilates with an electron

• The neutron first thermalizes then captures on a proton with a mean capture time of ~200s

PromptDelayed


DetectorElectronics Hut

Steel Sphere

Water Cherenkov outer detector 225 PMTs

1 kton liquid-scintillator

PMTs1325 17”554 20”34% coverage

1km Overburden


Inside the Detector


KamLAND Situated to Detect Reactor Anti-neutrinos

Kashiwazaki

Takahama

Ohi

KamLAND


History Repeating

Fred Reines preparing a neutrino detector (circa 1953)


So were Fred Reines background from Terrestrial Anti-neutrinos?


Total Heat from the Earth

• Conductive heat flow measured from bore-hole temperature gradient and conductivity

• Total heat flow 44TW• In 1862 Lord Kelvin used the

temperature gradient to estimate the age of the Earth to be 20-400 million years old


Radiogenic Heat

• 238U generates 8.0TW of radiongenic heat in the Earth

• 232Th generates 8.3TW of radiongenic heat in the Earth

• Beta decays produce electron anti-neutrinos


Terrestrial Anti-neutrino signal

238U decay chain 232Th decay chain

• KamLAND is only sensitive to anti-neutrinos above 1800keV


Terrestrial Anti-neutrino signal at KamLAND

Reactor Background

U+Th

U


Structure of the Earth

Image by Colin Rose

• Structure of the Earth determined from Seismic data


Convection in the Earth

• The mantle convects even though it is solid • Oceanic crust is being renewed at mid-ocean ridges and

recycled at subduction zones


U and Th in the Earth

• U and Th are thought to be absent from the core and present in the Silicate Earth at ~2.75 times CI carbonaceous chondrites concentrations

• The U concentration in the silicate Earth is 20ppm

• The Th concentration in the silicate Earth is 80ppm

• The Th/U ratio is ~4


The Expected TerrestrialAnti-neutrino Flux

• The activity per unit mass

• The number of neutrinos per decay chain per unit energy

• The mass concentration as a function of position in the Earth

• The density as a function of position in the Earth

• The neutrino survival probability as a function of distance from KamLAND

2

4

,

d

d

d

d

L

LLLL

EPad

E

nA

E

• Given a model of the Earth the anti-neutrino flux per unit energy at KamLAND can be calculated


Reference Earth Model

Conc. [ppm]UCC 2.7MCC 1.6LCC 0.6OC 0.08UM 0.01LM 0.01CS 2.7OS 1.7

• Earth split into eight sections:Upper Continental Crust (UCC),Middle Continental Crust (MCC),Lower Continental Crust (LCC),Oceanic Crust (OC),Upper Mantle (UM),Lower Mantle (LM),Continental Sediment (CS),Oceanic Sediment (OS)


Cumulative Terrestrial Anti-neutrino Flux Expected at KamLAND


Terrestrial Anti-neutrino map of the Earth


Measurement at KamLAND

Total

Measured Total Heat Flow

New Reactor Results*

*T. Araki et al. arXiv:hep-ex/0406035 June 13, 2004 submitted to Phys. Rev. Lett.


Introduction to reactor measurement

Nuclear Reactor

KamLAND

L

e


Determining the Event Vertex

(2.5MeV)

(1.1MeV)

(1.0MeV)


Tagged Cosmogenics used as Calibration Device

12B

12N

τ=29.1msQ=13.4MeV

τ=15.9msQ=17.3MeV

μ


Energy Calibration Using Sources and 12B/12N

68Ge

65Zn

60Co

n-p

n-12C


Selecting Electron Anti-neutrinos• Rprompt, Rdelayed < 5.5m• ΔR < 2m• 0.5μs < ΔT < 1ms• 1.8MeV < Edelayed < 2.6MeV• 2.6MeV < Eprompt < 8.5MeV

• 89.8% tagging efficiency• 33% increase in volume

e+

0.5 MeV 2.2 MeV

0.5 MeV

PromptDelayed


Japan Nuclear Reactor Scandal


2003 saw a substantial dip in reactor anti-neutrino flux


Good correlation with reactor flux

Fit constrained through known background 2/dof=2.1/4

90% CL

No os

cillat

ion e

xpec

ted


Energy spectrum shows distortion

• Best fit 2/dof=18.3/18 (goodness of fit is 42%)

• Fit to rescaled reactor spectrum 2/dof=43.4/19 (excluded at 99.89% CL)


Oscillations with L/EKamLAND sees reactor neutrinos from different distances

Hypothetical oscillation curve for single reactor distance


Alternative neutrino propagation models

• Decay* excluded at 95% CL

• Decoherence† excluded at 94% CL

*V.Barger et al. Phys. Rev. Lett., 82 (1999) 2640†E.Lisi et al. Phys. Rev. Lett., 85 (2000) 1166


Two flavor rate and shape analysis

• Best fitm2=8.3×10-5eV2

sin22=0.83

• LMA0 excluded at 94% CL

• LMA2 excluded at 99.6% CL

Previous ResultNew Result


Combined solar and KamLAND two flavor result

09.007.0

2

256.05.0

2

40.0tan

eV102.8

m

new results from kamland and prospects for observation of terrestrial neutrinos nikolai tolich

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