Measurements of Reactor Neutrinos at Long Baselines: KamLAND and Beyond Brian Kurt Fujikawa Lawrence Berkeley National Laboratory 2011 APS April Meeting 2011-05-01 1
Reactor Anti-Neutrino Disappearance Experiments Beta Decay of Neuron Rich Fission Fragments ( A, Z ) → ( A, Z + 1) + e − + ν e → → ν e + p → n + e + → ν µ + p → n + µ + → ν τ + p → n + τ + N e + N µ + = 0 ν e N τ + = 0 P ( ν e → ν e ) = 1 − sin 2 2 θ sin 2 1 . 27∆ m 2 L E L 2011-05-01 2
Long Baseline Reactor Neutrino Experiments 2011-05-01 3
Large Mixing Angle (LMA) Solution to the Solar Neutrino Problem 1.4 1.2 1.0 N obs /N no-osc 0.8 ILL 0.6 LMA Savannah River Bugey 0.4 Rovno Prediction Goesgen Krasnoyarsk 0.2 Palo Verde Chooz 0.0 10 1 10 2 10 3 10 4 10 5 Distance to Reactor (m) (2004) http://hitoshi.berkeley.edu/neutrino/ 2011-05-01 4
Updated Reactor Neutrino Spectrum Predictions arXiv:1101.2663 arXiv:1101.2755 Th. Lasserre (CEA-Saclay, Irfu APC & SPP) 1.4 1.2 1.0 N obs /N no-osc 0.8 ILL 0.6 Savannah River Bugey 0.4 Rovno Goesgen Krasnoyarsk 0.2 Palo Verde Chooz 0.0 10 1 10 2 10 3 10 4 10 5 Distance to Reactor (m) 2011-05-01 5
Motivation • Test Solar LMA solution with a terrestrial experiment that uses a man-made neutrino source. • The LMA region is very “flat” with respect to Δ m 2 from the Solar Neutrino experiments alone. Long Baseline Reactor Neutrino experiment compliment the Solar Neutrino experiments by measuring Δ m 2 . 2011-05-01 6
Scaling Short Baseline Reactor Neutrino Experiments to Long Baselines 2011-05-01 7
ν e + p → e + + n ¯ ¯ ν e n � ∆ T � ∼ 200 µs p p n np → d γ e + E γ = 2 . 2 MeV e − e + γ γ E ¯ ν e ∼ E e + + 0 . 8 MeV Backgrounds: • accidental coincidences • spallation products from cosmic-ray μ ‘s ‣ 9 Li/ 8 He β -delayed neutron emitters • neutrons produced externally by μ ‘s • ( α ,n) reactions 2011-05-01 8
Geoneutrino Background (or Signal)? • Geoneutrinos is a background when measuring Reactor Neutrinos • Ironically, Reactor Neutrinos are a background when measuring Geoneutrinos • Simultaneous measurement of Geo and Reactor Neutrinos 2011-05-01 9
Long Baseline Reactor Neutrino Experiments Require: 1. High Reactor Power 2. Large Target Mass 3. Low Background ‣ Underground to shield from cosmic ray μ ’s ‣ Radiopurity 2011-05-01 10
泊 東海第二 カムランド （km) 距離 川内 女川 福島第二 福島第一 柏崎刈羽 ふげん 志賀 敦賀 大飯 美浜 高浜 島根 伊方 玄海 浜岡 LMA and KamLAND 9 x10 7000 ) 2 fission/cm 6 U235 6000 Pu239 5000 U238 1.4 12 Pu241 Fission number flux(10 4000 4 1.2 3000 2 2000 1.0 N obs /N no-osc 1000 0.8 0 0 0 100 200 300 400 500 600 700 800 900 1000 ILL 0.6 Savannah River Bugey 0.4 Rovno Goesgen 180km Krasnoyarsk 0.2 Palo Verde Chooz 0.0 10 1 10 2 10 3 10 4 10 5 Distance to Reactor (m) 180 km 2011-05-01 11
The KamLAND Detector 1000m rock = 2700 mwe long. 137 ◦ 18 � 43 . 495 �� lat. 36 ◦ 25 � 35 . 562 �� alt. 358 m 2011-05-01 12
1st KamLAND Reactor Result 1.4 1.2 1.0 N obs /N no-osc 0.8 N obs − N bkgd ILL = 0 . 611 ± 0 . 085 stat ± 0 . 041 syst 0.6 Savannah River N no − osc Bugey Rovno 0.4 Goesgen Krasnoyarsk Palo Verde 0.2 Chooz KamLAND 0.0 10 1 10 2 10 3 10 4 10 5 Distance to Reactor (m) 2011-05-01 13
Latest (4th) KamLAND Reactor Neutrino Result Please see R7.00002: “A three-flavor oscillation analysis of a new KamLAND data set” Thomas O’Donnell (1:42 pm, May 2, Grand E) 2011-05-01 14
Exposure: • 3.49 × 10 42 target-proton-years Candidate Event Selection: • Delayed coincidence pairs (in time & space) • Prompt energy window • Delayed energy window (near 2.2 MeV or 4.7 MeV) • Likelihood discriminator • Isolation from cosmic ray μ ’s ( μ veto) 2011-05-01 15
Events expected from reactors (no oscillation) 2879 +/- 118 Events expected from background (ex. geo-nu) 325.9 +/- 26.1 Observed events 2106 2011-05-01 16
( α ,n) Background α np → np 13 C p n � ∆ T � ∼ 200 µs p n 16 O ∗ np → d γ γ /e + − e − • Primarily from 210 Po α ’s • 2007-2009 KamLAND liquid scintillator purification campaigns (in preparation for solar 7 Be neutrino detection) • Reduced 210 Po contamination by a factor of 20. • ( α ,n) backgrounds are greatly reduced for the post-purification period. 2011-05-01 17
3-Flavor Analysis PMNS Matrix Survival Probability at KamLAND 2011-05-01 18
Matter Effects from Propagating Through the Earth 2011-05-01 19
Un-binned Maximum Likelihood Analysis Include Time Depend Effects: • Fluctuations in reactor power. • Pre/Post-Purification changes in background, e.g. ( α ,n). • Pre/Post-Purification changes in detector performance. 2011-05-01 20
Systematic Error Table data set before purification / data set after purification 2011-05-01 21
Results of the 3-Flavor Analysis 20 4 σ 15 2 χ 3 σ ∆ 10 2 σ 5 1 σ KamLAND Best Fit Solar KamLAND 2 1 2 3 4 (b) σ σ σ σ 95% C.L. 95% C.L. 99% C.L. 99% C.L. 1.8 99.73% C.L. 99.73% C.L. ) 2 1.6 best fit best fit eV 1.4 KamLAND+Solar -4 95% C.L. (10 1.2 99% C.L. 99.73% C.L. 21 1 2 best fit m ∆ 0.8 0.6 θ free 0.4 13 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5 10 15 20 2 2 tan θ ∆ χ 12 2011-05-01 22
Prompt Energy Distribution 100 Efficiency (%) Selection efficiency 80 60 KamLAND data 350 no-oscillation best-fit osci. 300 accidental Events/0.425MeV 16 13 C( ,n) O α 250 best-fit Geo ν e best-fit osci. + BG 200 + best-fit Geo ν e 150 100 50 0 0 1 2 3 4 5 6 7 8 E (MeV) p 2011-05-01 23
Shape Distortion and Evidence for Neutrino Oscillations 1 Survival Probability 0.8 0.6 0.4 0.2 3- best-fit oscillation Data - BG - Geo ν ν e 2- best-fit oscillation ν 0 20 30 40 50 60 70 80 90 100 110 L /E (km/MeV) 0 ν e (L 0 = 180 km chosen for scale) 2011-05-01 24
2-Flavor/3-Flavor Analysis Comparison 2-Flavor 3-Flavor 20 20 4 σ 4 σ 15 15 2 2 χ χ 3 σ 3 σ ∆ 10 ∆ 10 5 2 σ 5 2 σ 1 σ 1 σ Solar KamLAND Solar KamLAND 2 2 1 2 3 4 1 2 3 4 (a) (b) σ σ σ σ σ σ σ σ 95% C.L. 95% C.L. 95% C.L. 95% C.L. 99% C.L. 99% C.L. 99% C.L. 99% C.L. 1.8 1.8 99.73% C.L. 99.73% C.L. 99.73% C.L. 99.73% C.L. ) ) 2 2 1.6 1.6 best-fit best-fit best fit best fit eV eV 1.4 KamLAND+Solar 1.4 KamLAND+Solar -4 -4 (10 95% C.L. (10 95% C.L. 1.2 1.2 99% C.L. 99% C.L. 99.73% C.L. 99.73% C.L. 21 21 1 1 2 2 best-fit best fit m m ∆ ∆ 0.8 0.8 0.6 0.6 θ = 0 θ free 0.4 0.4 13 13 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5 10 15 20 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5 10 15 20 2 2 2 2 tan θ ∆ χ tan θ ∆ χ 12 12 2011-05-01 25
0.2 Solar KamLAND 95% C.L. 95% C.L. 0.18 99% C.L. 99% C.L. 99.73% C.L. 99.73% C.L. 0.16 best-fit best-fit 0.14 KamLAND+Solar 95% C.L. 0.12 13 99% C.L. θ 99.73% C.L. 2 0.1 sin best-fit 0.08 0.06 0.04 0.02 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 tan θ 12 2011-05-01 26
Global Analysis 10 99.73% C.L. CHOOZ + Atmospheric + LBL 9 Global 8 7 r a l 6 o S Global: 2 + χ D 5 N ∆ A L 95% C.L. m 4 a Solar K 90% C.L. 3 2 D N A L 1 m a K 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 2 sin θ 13 2011-05-01 27
Visualization of KamLAND’s Sensitivity to θ 13 Survival Probability: 1 0.8 Survival Probability Dependent on θ 13 : 0.6 Mostly Dependent on θ 12 : 0.4 0.2 ν Data - BG - Geo 3- ν best-fit osci. e no-oscillation ν 2- best-fit osci. 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 2 2 2 ≡ 〈 θ ∆ 〉 θ sin 2 sin (1.27 m L/E ) /sin 2 x 21M 12M ν 12 e 2011-05-01 28
5th KamLAND Reactor Neutrino Result? • Slightly increased exposure compared to the 4th result. • Full volume calibration campaign is scheduled for June 2011 which will reduce the fiducial volume uncertainties for the post-purification period. • Consider the implications of the updated reactor neutrino spectrum predictions. 2011-05-01 29
Future of Long Baseline Reactor Neutrino Experiments 2011-05-01 30
KamLAND-Zen 136 Xe 400 kg: 2.7 wt% dissolved into LS easy handling/ enrichment (90%) longer 2 ν beta decay life time T 2 ν >10 22 years (cf: ~10 19-20 ) KamLAND exists: ultra pure environment (U/Th~10 -17 g/g) LS techniques Balloon experience LS Density control techniques Reactor/Geo neutrino 136 Xe 400 kg loaded LS Slide courtesy of Dr. K Nakamura, in mini-balloon, R=1.7m RCNS Tohoku University, Jp Neutrino 2010 31 2011-05-01 31
Neutrinoless Double Beta Decay Search 2011-05-01 32
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