KamLAND Update Lauren Hsu Lawrence 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 chain 4p  4 He + 2e e Chlorine Experiment Homestake 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/ : 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( l  l’ ) = sin 2 2  sin 2 (1.27  m 2 (eV 2 ) L (m) /E (MeV) ) U MNSP = oscillations imply neutrinos have mass! e -i  / e i  / cos  12 sin  sin  12 cos  cos  23 sin  sin  23 cos  23 cos  13 0 e -i  sin  e -i  sin  13 0 cos  13    Solar and KamLAND Atmospheric Future reactor or accelerator 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 effects Well-understood man-made source Anti-neutrino vs neutrino oscillations Basics 1955 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 235 U + n  X 1 + X 2 + 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!) – combats 1/R 2 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/

The KamLAND Detector (1879)

The Target Volume Serves as both the target and the detector, > protons 20% Pseudocume + 80% Mineral Oil 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 ” tubes ” tubes (since 2/03) Transit time spread < 3 ns Separated from inner buffer by acrylic panels ” 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 = E prompt MeV -   2.2 MeV  n e+e+ 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

Calibration Radioactive 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 He 8 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

13 C( ,n) 16 O Background low energy 4.4 MeV ~6 MeV Background Prompt E (MeV)

KamLAND Reactors Total reactor power uncertainty in analysis is 2% (conservative estimate)

III. KamLAND Results

First Result: Disappearance PRL 90 (2003) KamLAND is the first reactor experiment to observe e disappearance! live-days (7 months) of data-taking: 99.95% CL

Second Result: Spectral Distortion PRL (2005) 258 events observed 365 expected 515 live days, better optimized cuts, discovery of 13 C 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 fit 1.8% goodness of fit Simplified expression for two flavor oscillations in a vacuum: P( l  l’ ) = sin 2 2  sin 2 (1.27  m 2 (eV 2 ) L (m) /E (MeV) )

Unparalled Sensitivity to  m 12 PRL (2005) 2 Extract Oscillation Parameters and Combine with Solar Data Solar + KamLAND:  m 12 =7.9  eV 2, tan 2  12 = PRL (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 TW of Earth’s radiated heat

Candidate Events U signal Th signal -- reactor BG C BG -- accidental BG Expected Spectra w/ extended x-axis Total Background

Geoneutrino Results Observed signal = 28 (at 90% C.L.) Results set an upper limit of 60 TW on the radiogenic power Demonstrating “proof of principle” theoretical prediction

IV. The Future of KamLAND

Future Improvements: Reactor Analysis Systematic Unc. on Rate% Fiducial Volume4.7 un-oscillated e spectrum (theor.) 2.5 Energy Threshold2.3 Reactor Power2.1 Cut Efficiency1.6 Fuel Composition1.0 Cross Section0.2 Livetime0.06 Total7.1 Compare to statistical uncertainty: 6.7% Further Improvements Require Reducing Systematic Uncertainty! Better understanding of 13 C( ,n) 16 O 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 boundary positions

Muon Tracker Gold-plated muon events to cross-check the muon track reconstruction. Module and Frame Testing Testing at LBNL

A Full-Detector Simulation Includes Full Light Propagation Model Geant4 visualization of KamLAND Geometry reduce systematic uncertainty increase understanding of detector model backgrounds laser light reflected light indirect light

Shika II Effect Second Unit at Shika Power Station commissioned May 2005 Impact on baseline depends on the oscillation parameters! Thermal Power (GW)

Projected Future Sensitivity KamLAND will continue to make the most sensitive measurements on  m 2 for the forseeable future 12

Papers In the Works High Energy B 8 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

Be 7 : 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 210 Pb by 5 orders of magnitude! reduce 85 Kr by 6 orders of magnitude!

New Distillation System Purification system commissioned in October 2006 circulation from KamLAND to begin ~next week 1.5 m 3 /hr

Summary Phase II of KamLAND: 7 Be neutrinos from the sun. Purification starting and low-background measurements to start in  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  m 2 = 7.9  eV 2 and tan 2  = Further improvements to reactor measurement still to come…

Acknowledgements Tohoku U. LBNL Stanford CalTech KSU U. of TN U. of AL TUNL Drexel U. of NM U. 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 (E prompt = 2.6 MeV) Correcting for Nonlinearity of Energy Scale -

Sampling of -Oscillation Experiments Reactor (KamLAND) tan  12 &  m 12 e disappearance  +  appearance Energy: ~5-15 MeV Baseline: 1.5  10 8 km By no means comprehensive!  m 23 & sin2  23 v  (   ?) disappearance Energy: ~ GeV Baseline: ,000 km 2  m 23 & sin2  23 v u (   ?) disappearance Energy: ~ GeV Baseline: 250 km 2  m 12 & sin2  12 e disappearance Energy: few MeV Baseline: 180 km - 2 2

Physics Implications for the First Result

What Were Improvements? More Statistics: live days compared to live days. 13 C( ,n) 16 O 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 parameters o Detailed geometry (photocathode, calibration devices, detector itself) o Nonlinear response of scintillator o 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 238 U and 232 Th 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 : 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/

Dip in Nuclear Power Output KamLAND no-osc rate e events/day Falsified saftey records prompted shutdown of several nuclear power plants

Looking for Correlations in Un-Oscillated Rate Changes

Neutrino Mass Heirarchy m2m2 ? e   0.0 m21m21 m22m22 m23m23  m 12  m 23 = (1-3)  eV 2 = (7.9  0.06)  eV 2 atmospheric Solar and KamLAND 2 2 Normal or Inverted?