KamLAND Update

Lauren HsuLawrence Berkeley National Laboratory

Fermi National Accelerator Laboratory

January 16, 2007

I. Reactor Experiments & Neutrino Oscillations

II. KamLAND overview

III. KamLAND Results

iV. The Future of KamLAND

Outline

The Solar Neutrino Problem

Pre-1950: p-p chain4p 4He + 2e+ + 2e

Chlorine ExperimentHomestake Mine

1968: Ray Davis pioneers the radiochemical experiment, Chlorine, and observes 1/3 of predicted solar neutrino flux.

1969: Pontecorvo and Gribov propose that neutrinos oscillate but…

…difficulty of Chlorine experiment and uncertainties in solar model lead to speculation that either one or both were wrong.

3 Decade Long Mystery

2001: SNO w/ sensitivity to both (e) and (x) measures total flux of x, consistent with Standard Solar Model

nucl-ex/0502021

1998: SuperKamiokande announces evidence for oscillations in atmospheric neutrinos

Neutrino Oscillations

Like quarks, neutrino flavor and mass eigenstates are not the same

Simplified expression for two flavor oscillations in a vacuum:

P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV))

UMNSP =

oscillations imply neutrinos have mass!

e-i /2 0 00 ei /2 00 0 1

cos12 sin12 0-sin12 cos12 0 0 0 1

1 0 00 cos23 sin23

0 -sin23 cos23

cos13 0 e-isin13

0 1 0-e-isin13 0 cos13

Solar and KamLAND Atmospheric Future reactor oraccelerator

Majorana phases

1

2

Why a Reactor Neutrino Experiment?

• Disappearance Experiment• Detect anti neutrino via inverse beta-decay• Energy range ~few MeV• Reactor anti-neutrino experiments performed since 1950’s

No matter effectsWell-understood man-made sourceAnti-neutrino vs neutrino oscillations

Basics1955 Reines & Cowan (Poltergeist)

Complimentary to the Solar Experiments

Anti-Neutrino Production in Reactors

• Anti-neutrinos from beta decay of daughter isotopes

• Production of anti-neutrinos well understood theoretically and fission yields precisely monitored by power companies

235U + n X1 + X2 + 2n

Calculated spectrum verified to 2% accuracy by earlier generation of reactor anti-neutrino experiments

(unoscillated)

II. KamLAND

Why KamLAND?

Long Baseline – optimizes sensitivity to oscillations

Large (1 kTon!) – combats1/R2 drop-off in intensity

More Overburden: Avoids Cosmogenic Backgrounds

KamLAND Optimizations:

KamLAND

Inside the Kamioka Mine

KAMioka Liquid scintillator Anti-Neutrino Detector

Surrounded by 53 Japanese Nuclear Reactors

Detecting reactor anti-neutrinos 1 km beneath Mt. Ikeyama

Physics Reach of KamLAND

Nature 436, 499 (2005)

n-Disappearance hep-ex/0512059

The KamLAND Detector

(1879)

The Target Volume

• Serves as both the target and the detector, > 1031 protons• 20% Pseudocume + 80% Mineral Oil + 1.5 g/l PPO • Optimal light yield while maintaining long attenuation length (~20 m).

• Separates target LS volume from buffer oil• 135 m Nylon/EVOH (ethylene vinyl alcohol copolymer)• Supported by kevlar ropes

Liquid Scintillator:

Balloon:

Welding the Balloon

KamLAND Photo-Multipliers

• 1325 17” tubes

• 554 20” tubes (since 2/03)

• Transit time spread < 3 ns

• Separated from inner buffer by acrylic panels

• 200 17” hits for 1 MeV energy deposit

PMT and acrylic panel installation

The Outer Detector

• 3.2 kT water Cerenkov detector (~200 PMT’s)• Detects 92% of muons passing through inner detector• Buffers inner detector from spallation products and radioactivity in rock.

Anti-Neutrino Signal Detection

Coincident energy deposits are a distinct signature of inverse beta-decay:

e + p e+ + n

Delayed Energy: n-capture releases 2.2 MeV , ~200 s later

Prompt Energy: positron energy deposit (K.E. + annihilation ’s)

e energy obtained from E = Eprompt + 0.8 MeV-

2.2 MeV

ne+

e

Basic KamLAND Data Reconstruction

Energy Reconstruction:• Energy Number of Hit PMT’s• Correction for Vertex Position• Correction for Quenching and Cherenkov Radiation

Vertex Reconstruction• Determined by Very Precise Timing of Hits (~ few ns):• Inherent Detector Resolution ~15cm.

How much energy deposited and where?

KamLAND Event Display

)(

%2.6

MeVEEE =

σ

CalibrationRadioactive Sources:

Co60, Ge68, Zn65, and AmBe deployed along the z-axis.

Backgrounds: Spallation Products throughout

fiducial volume

Muon Tracking

• Timing of inner detector hits• Good agreement with simulation of muons passing through detailed mountain topography

Rate of Muons hitting KamLAND is ~1 Hz

Source of cosmogenic backgrounds

Correlated Cosmogenic Backgrounds

Muons interact with material producing fast neutrons and delayed neutron - emitters

Spallation Products

He8 thought to be a negligeable contribution

Uncorrelated Backgrounds

• From radioactive isotopes in detector and surrounding material. • Activity concentrated near balloon

Uncorrelated backgrounds:

Lots of steel in the chimney region!

Reduced by fiducial volume and energy cut. Remaining accidental backgrounds are easily measured

13C(,n)16O Background

low energy

4.4 MeV

~6 MeV

Background Prompt E (MeV)

KamLAND Reactors

Total reactor power uncertaintyin analysis is 2%(conservative estimate)

III. KamLAND Results

First Result: Disappearance

PRL 90 (2003) 021802

KamLAND is the first reactor experiment to observe e disappearance!

-

145 live-days (7 months) of data-taking:

99.95% CL

Second Result: Spectral Distortion

PR

L 94 081802 (2005)

258 events observed365 expected

515 live days, better optimized cuts, discovery of 13C background

11% C.L. for best-fit oscillation paramters 0.4% C.L. for scaled no-oscillations spectrum

Looking for Oscillatory Behavior

0.7% goodness of fit1.8% goodness of fit

Simplified expression for two flavor oscillations in a vacuum:

P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV))

Unparalled Sensitivity to m12

PRL 94 081802 (2005)

2

Extract Oscillation Parameters and Combine with Solar Data

Solar + KamLAND: m12 =7.9 10-5 eV2, tan212 =0.4 2 +0.6-0.5

+0.10-0.07

PR

L 94 081802 (2005)

Pioneering Search for Geological e

Radioactive isotope decays produce same signal as reactor

e, but at lower energy

reactor - e

background

-

Th + U signal

Geoneutrino sensitivity of KamLAND

Geological structure of Earth

(core, mantle and crust)

-

-Decay of U, Th expected to generate 16 out of ~30-40 TWof Earth’s radiated heat

Candidate Events

-- 238U signal-- 232Th signal -- reactor BG-- 13C BG-- accidental BG

Expected Spectra w/ extended x-axis

Total Background

Geoneutrino Results

Observed signal = 28 (at 90% C.L.)+26.2- 23.5

Results set an upper limit of 60 TW on the radiogenic powerDemonstrating “proof of principle”

theoretical prediction

IV. The Future of KamLAND

Future Improvements: Reactor Analysis

Systematic Unc. on Rate %

Fiducial Volume 4.7

un-oscillated e spectrum (theor.) 2.5

Energy Threshold 2.3

Reactor Power 2.1

Cut Efficiency 1.6

Fuel Composition 1.0

Cross Section 0.2

Livetime 0.06

Total 7.1

Compare to statistical uncertainty: 6.7%

Further Improvements Require Reducing Systematic Uncertainty!

Better understanding of 13C(,n)16O will improve shape analysis

Full Volume Calibration

• Off-axis calibration to improve energy and vertex estimation• Reduce fiducial volume uncertainty

Testing 4 at LBNL

Using relative distances between sources, expect fiducial volume uncertainty of 1-2%.

Full volume calibration system commissioned in July 2006!

Since July:~200 hrs of 4 data

5 sources

4 positions

3 operators

A Typical Day of Off-Axis Calibration

In January:2 more sources

additional

more boundarypositions

Muon Tracker

Gold-plated muon events to cross-check the muon track reconstruction.

Module and Frame TestingTesting at LBNL

A Full-Detector Simulation

Includes Full Light Propagation ModelGeant4 visualization of KamLAND Geometry

reduce systematic uncertaintyincrease understanding of detector

model backgrounds

laser light

reflected light

indirectlight

Shika II Effect

Second Unit at Shika Power Station commissioned May 2005 Impact on baseline depends on the oscillation parameters!

The

rmal

Pow

er (

GW

)

Projected Future Sensitivity

KamLAND will continueto make the most sensitivemeasurements on m2 for the forseeable future

12

Papers In the Works

High Energy B8 Solar Neutrinos

NIM Detector Paper

Spallation Paper

KamLAND “First Phase” Paper• Includes all data up to purification

• geo, reactor, and high-energy antineutrinos

• includes 4 data

Be7: KamLAND Low-Background Phase

• Verification of low energy neutrino flux from Sun• Observe transition from vacuum to matter-enhanced oscillations• Significantly reduce bg in reactor and geoneutrino analyses

KamLAND

An Ambitious Purification Project

Detecting e via elastic Scattering(no coincidence to suppress radioactive backgrounds)

reduce 210Pb by 5 orders of magnitude!

reduce 85Kr by 6 orders of magnitude!

New Distillation System

Purification system commissioned in October 2006

circulation from KamLAND to begin ~next week

1.5 m3/hr

Summary

Phase II of KamLAND: 7Be neutrinos from the sun. Purification starting and low-background measurements to start in 2007.

• 4 off-axis calibration device commissioned in July, ~200 hrs data taken will reduce fiducial volume systematic uncertainty.

• KamLAND: First experiment to observe disappearance of reactor anti-neutrinos (99.998% significance).

Latest results (2004) show evidence for spectral distortion. Combined solar-experiment and KamLAND results give

m2 = 7.9 10-5eV2 and tan2 = 0.40 12

+0.6-0.5

+0.10-0.0712

Further improvements to reactor measurement still to come…

Acknowledgements

Tohoku U.

LBNLStanfordCalTechKSUU. of TNU. of ALTUNLDrexel U. of NMU. of HI

IHEP

CENBG

Many pieces of this talk borrowed liberally from my KamLAND colleagues

Toyama Oct. 2006

Mozumi 4/05

KL Control Room

to Kamioka Mine

Earlier Reactor Experiments

Pre-KamLAND, no oscillations found (baselines 1 km)These experiments demonstrate it can be done.

Energy Estimation

Only observe e above 3.4 MeV(Eprompt = 2.6 MeV)

Correcting for Nonlinearity of Energy Scale

-

Sampling of -Oscillation Experiments

Reactor(KamLAND)

tan12 & m 12

e disappearance+ appearance

Energy: ~5-15 MeV

Baseline: 1.5108 km

By no means comprehensive!

m23 & sin223

v (?) disappearance

Energy: ~ GeV

Baseline: 15 -13,000 km

2

m23 & sin223

vu (?) disappearance

Energy: ~ GeV

Baseline: 250 km

2

m12 & sin212

e disappearance

Energy: few MeV

Baseline: 180 km

-

22

Physics Implications for the First Result

What Were Improvements?

• More Statistics: 515.1 live days compared to 145.1 live days.

• 13C(,n)16O background discovered and included in analysis

• Better Optimized Cuts (fiducial volume increased from 5m to 5.5m)

• Addition of 20” tubes (improved energy resolution from 7%/E(MeV) to 6%/E(MeV))

• Reactor off-time allowed for study of correlation of signal with reactor flux.

Second results includes re-analysis of same data-sample used in first

KamLAND MC Laundry List

Verification:o light propagation model and optical parameterso Detailed geometry (photocathode, calibration devices, detector itself)o Nonlinear response of scintillatoro Shadowing effects

Detailed modeling of “electronic effects”

Most code has been written, but not much detailed comparison w/ data until recently.

Constraining Geothermal Heat

16 TW of Heat predicted from decay of 238U and 232Th concentrated in earth’s crust

surface heat flux measurements (bore-hole sampling)-

Total Heat radiated by Earth measured to be 44 1.0 TW and 31 1.0 TW

3 Decade Long Mystery

1990’s: Sage and Gallex radiochemical experiments confirm deficit in solar neutrino flux

Over next few decades:• Solar Model refined and x-checked with experimental observations• Chlorine systematics x-checked, no significant errors discovered.

1989: Kamiokande, real-time water Cherenkov detector, also observes deficit of solar neutrinos.

1988-1990: Kamiokande and IMB see hints of atmospheric neutrino deficits.

1998: SuperKamiokande announces that neutrinos have mass based on evidence for oscillations in atmospheric neutrinos

Resolution of the SNP

2001: SNO w/ sensitivity to both (e) and (x) measures• non-zero flux of from sun• total flux of x, consistent with Standard Solar Model

nucl-ex/0502021

Dip in Nuclear Power Output

KamLAND

no

-osc

rat

e e

eve

nts

/day

Falsified saftey records prompted shutdown of several nuclear power plants

Looking for Correlations in Un-Oscillated Rate Changes

Neutrino Mass Heirarchy

m2

?

e

0.0

m21

m22

m23

m12

m23= (1-3)10-3 eV2

= (7.90.06)10-5 eV2

atmospheric

Solar and KamLAND2

2

Normal or Inverted?