KamLAND Update NuFact 05 Lauren Hsu June 21, 2005 Lawrence Berkeley National Laboratory For the KamLAND Collaboration Add a slide that discusses FIDUCIAL VOLUME? Include picture of effective baseline? Somewhere we need a slide(s) of how the analysis is done!

KamLAND KAMioka Liquid scintillator Anti-Neutrino Detector Looking for disappearance of anti-neutrinos 1 km beneath Mt. Ikeyama Inside the Kamioka Mine KamLAND is looking for disappearance of anti-neutrinos, located 1 km beneath a mountain in central Japan, shares the same mine as Super- Surrounded by 53 Japanese Nuclear Reactors

Liquid Scintillator: 20% Pseudocume + 80% Mineral Oil + 1.5 g/l PPO The KamLAND Detector (1879) ~2.5 m thick Do this fast! Most people will be familiar with this! Spiel: 1 kTon detecting volume (LS), encased by thin nylon balloon, viewed by ~2000 17 and 20” PMT’s, separated from PMT’s by 2.5m thick layer of mineral oil. Liquid Scintillator: 20% Pseudocume + 80% Mineral Oil + 1.5 g/l PPO H:C ~2

Anti-Neutrino Signal Detection Use coincident energy deposits of inverse beta-decay: Signal Selection: T = [0.5, 1000]s R < 2m rvertex < 5.5m Eprompt = [2.6, 8.5] MeV Edelayed = [1.6, 2.6]MeV e + p  e+ + n Prompt Energy: positron energy deposit (K.E. + annihilation ’s) Candidate Coincidence Events: T = [0.5, 1000]s Coincidence events *suppress* background – i.e. distint from anything else that can happen. Efficiency of all events is 89.8% Neutron capture on H is 0.33 barns Delayed Energy: n-capture releases 2.2 MeV , ~200 s later - e energy: E = Eprompt + 0.8 MeV

Uniform spallation products off-z Energy Estimation Evis/Ereal Correcting for Nonlinearity of Energy Scale 60Co, 68Ge, 65Zn, deployed along z Uniform spallation products off-z Ereal (MeV) - Only observe e above 3.4 MeV (Eprompt = 2.6 MeV) Say precise energy estimation is important both for having well-defined cut efficiencies and for measuring the energy spectrum of the neutrinos…. Prl says ~3000 spallation neutrons per kTon*day.

Fiducial Volume Estimate Events/bin z deviation (cm) z-axis (cm) (R/6.5m) Fiducial Volume Uncertainty To determine how many neutrinos you would have observed in the case of no-oscillations… Fiducial volume: 0.595 +/- 0.013 from flow meters Measure position distribution of beta-decays of 12B and 12N (60 combined events per kton per day) Gives 0.607+/-0.006(stat)+/-0.006(sys) (number measured in fiducial volume compared to total – systematic error arises from reconstruction of events near balloon edge). Additional 2.7% uncertainty comes from fact that energy is higher Flow Meters: 0.595 +/- 0.013 12B/12N spallation: 0.607  0.006  0.006 Energy Dependence: 2.7% Total: 4.7%

Backgrounds 13C(,n)16O Prompt Energy Uncorrelated Backgrounds from trace radioactive isotopes. Fiducial Volume: R < 5.5m Correlated 13C(,n)16O Background Troublesome and new! ’s produced indirectly through decay of 210Pb, a long-lived daughter of 222Rn 13C(,n)16O Prompt Energy quenched n ~6 MeV excited 16O 4.4 MeV excited 12C Prompt E (MeV) Correlated Muon Spallation Backgrounds: fast neutrons or delayed-n -decay of 9Li cylinder cut veto (2 s) whole detector veto (2 s)

Reactor Flux 235U:238U:239Pu:241Pu = 0.563: 0.079: 0.301:0.057 Total reactor power uncertainty is 2% (conservative estimate) Averaged Relative Fission Yields: 235U:238U:239Pu:241Pu = 0.563: 0.079: 0.301:0.057 Say somewhere that the neutrinos are a by-produce of fission. Instantaneous power generation, burn-up and fuel exchange records provided by Japanese power companies Neutrino spectra measured this way from power company data has been tested to a few percent accuracy in previous reactor neutrino experiments (which ones?) The nuebar spectrum per fiession and its error are taken from literature (which ones?).

Improvements Over First Result First KamLAND Result 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 to 6%/E(MeV)) Reactor off-time  study correlation of signal with reactor flux. PRL 90 (2003) 021802 State: The analysis is basically the same, but

Observation of Spectral Distortion Measurement of Energy Spectrum Distortion Due to e Oscillation (Latest KamLAND Result) - PRL 94 081802 (2005) What points do you want to make here? Spectral distortions, background, point out when this is from Make way for next slide.

Neutrino Oscillations Favored 0.7% goodness of fit 1.8% goodness of fit Goodness of fit = confidence level? Probability of getting a worse X2. Just another way to bin the data, shows the oscillatory behavior (washed out by the multi-baselines). Simplified expression for two flavor oscillations in a vacuum: P(ll’) = sin22 sin2(1.27m2(eV2)L(m)/E (MeV))

Unparalled Sensitivity to m12 Extract Oscillation Parameters and Combine with Solar Data PRL 94 081802 (2005) PRL 94 081802 (2005) What difference did the alpha-n background make?? Say the words LMA-I favored and LMA-II disfavored (98% confidence). Solar + KamLAND: m12 =7.9 10-5 eV2, tan212 =0.4 2 +0.6 -0.5 +0.10 -0.07

Future Improvements: Reactor Analysis Further Improvements Require Reducing Systematic Uncertainty! 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 Make sure how you understand the impact on the shape analysis – these uncertainty are for rate only? Compare to statistical uncertainty: 6.7% Better understanding of 13C(,n)16O will also improve shape analysis

Full Volume Calibration A new full-volume calibration device Off-axis calibration to improve energy and vertex estimation Reduce fiducial volume uncertainty Testing 4 at LBNL Make sure how you understand the impact on the shape analysis – these uncertainty are for rate only? Source placement uncertainty of 2 cm will measure fiducial volume to 2-3% uncertainty

A flexible tool for systematic studies. More Improvements A Muon Tracker A Full-Detector Simulation Include discussion on MC? Gold-plated events ~200 events/day x-y resolution of 2-3 cm. A flexible tool for systematic studies.

A Change in Effective Baseline? Shika upgrade will be complete in 2006. Impact on baseline will depend on the oscillation parameters! (sin212, m2) 12 Possibly leave this out if there’s no time. What are the LMA parameters? And why does it have such a huge variation?? – from first KamLAND result? (Inoue had it at the beginning of this talk). CLARIFY the (lefthand) y-axis.

Geo-Anti-Neutrinos - - surface heat flux measurements First search for geologically produced e! 16 TW of Heat predicted from decay of 238U and 232Th concentrated in earth’s crust Total Heat radiated by Earth is ~44 TW Th + U signal What is the source of heat and antineutrinos? Never been measured before! Say wha y anti neurtinos have to do with all this (measure u an Th). No one has done this before, so whether or not kamland sees anything, we will at least put the first upper limit on this. - reactor - e background Sorry, no results yet, but paper to be released soon!

Future KamLAND: 7Be Phase Detect e from 7Be via elastic scattering (not a coincidence signal) Make sure how you understand the impact on the shape analysis – these uncertainty are for rate only? KamLAND needs to reduce 210Pb and 85Kr by 5-6 orders of magnitude!

Timeline for KamLAND Excavation of new purification chamber started in April and nearly finished. Mention what the timeline is for the reactor analysis and data-taking. How much data do we have, and how much more will we take before shutting down. (what did the last datset include?)

Summary KamLAND has observed disappearance of reactor anti-neutrinos at 99.998% significance. Latest results (PRL 94 081802 2005) show evidence for spectral distortion, combined solar and KamLAND results give the most precise determination to date: m2 = 7.9 10-5eV2 and tan2 = 0.40 Future KamLAND measurements to benefit from: full-volume calibration, muon tracker, full-detector simulations, and purification. Results coming soon on geo-neutrinos – the first limit or observation of anti-neutrinos produced from the earth. Phase II of KamLAND: 7Be neutrinos from the sun. Purification stage is already beginning, and measurements to start in 2007. +0.10 -0.07 +0.6 -0.5 12 12 What is the balloon made out of?

Rate of Muons hitting KamLAND is ~1 Hz Muon Tracking Rate of Muons hitting KamLAND is ~1 Hz Reconstruction of Tracks: Pattern recognition based on expected timing of inner detector hits Good agreement with simulation of muons passing through detailed mountain topography Don’t forget to mention why we are so concerned about muons!! Roughly describe how the tracker works

Looking for Correlations in Un-Oscillated Rate Changes Datapoints correspond to areas of equal flux. What’s the point here? – Leave it out?

Changes from Extra BG What is the balloon made out of?