Measurements of Reactor Neutrinos at Long Baselines: KamLAND and - - PowerPoint PPT Presentation

Measurements of Reactor Neutrinos at Long Baselines: KamLAND and Beyond

2011 APS April Meeting Lawrence Berkeley National Laboratory

Brian Kurt Fujikawa

1 2011-05-01

Reactor Anti-Neutrino Disappearance Experiments

L

P(νe → νe) = 1 − sin2 2θ sin2 1.27∆m2L E

νe Ne+ Nµ+ = 0 Nτ + = 0

(A, Z) → (A, Z + 1) + e− + νe → → νe + p → n + e+ → νµ + p → n + µ+ → ντ + p → n + τ +

Beta Decay of Neuron Rich Fission Fragments

2 2011-05-01

Long Baseline Reactor Neutrino Experiments

3 2011-05-01

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Nobs/Nno-osc 101 102 103 104 105 Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

Large Mixing Angle (LMA) Solution to the Solar Neutrino Problem

LMA Prediction

http://hitoshi.berkeley.edu/neutrino/

(2004)

4 2011-05-01

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Nobs/Nno-osc 101 102 103 104 105 Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

• Th. Lasserre (CEA-Saclay, Irfu APC & SPP)

arXiv:1101.2663 arXiv:1101.2755 Updated Reactor Neutrino Spectrum Predictions

5 2011-05-01

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 Δm2

from the Solar Neutrino experiments alone. Long Baseline Reactor Neutrino experiment compliment the Solar Neutrino experiments by measuring Δm2.

6 2011-05-01

Scaling Short Baseline Reactor Neutrino Experiments to Long Baselines

7 2011-05-01

Backgrounds:

• accidental coincidences
• spallation products from cosmic-ray μ‘s
• 9Li/8He β-delayed neutron emitters
• neutrons produced externally by μ‘s
• (α,n) reactions

¯ νe

e+

n

p p

e−

e+

γ γ

Eγ = 2.2MeV

E¯

νe ∼ Ee+ + 0.8MeV

n

∆T ∼ 200µs ¯ νe + p → e+ + n

np → dγ

8 2011-05-01

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

9 2011-05-01

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

10 2011-05-01

LMA and KamLAND

川内 玄海 伊方 島根 高浜 美浜 大飯 敦賀 志賀 柏崎刈羽 東海第二 福島第一 福島第二 女川 泊

距離 （km) 100 200 300 400 500 600 700 800 900 1000

1000 2000 3000 4000 5000 6000 7000

x10

)

fission/cm

Fission number flux(10 2 4 6

U235 Pu239 U238 Pu241

ふげん 浜岡

180km

カムランド

180 km

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Nobs/Nno-osc 101 102 103 104 105 Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

11 2011-05-01

358 m 36◦2535.562 137◦1843.495

long. lat. alt. 1000m rock = 2700 mwe

The KamLAND Detector

12 2011-05-01

1st KamLAND Reactor Result

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Nobs/Nno-osc 101 102 103 104 105 Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

KamLAND

Nobs − Nbkgd Nno−osc = 0.611 ± 0.085stat ± 0.041syst

13 2011-05-01

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)

14 2011-05-01

Exposure:

• 3.49 × 1042 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)

15 2011-05-01

Events expected from reactors (no oscillation) 2879 +/- 118 Events expected from background (ex. geo-nu) 325.9 +/- 26.1 Observed events 2106

16 2011-05-01

n

p

n

∆T ∼ 200µs

p

np → dγ

13C

α

16O∗

γ/e+ − e− np → np

(α,n) Background

• Primarily from 210Po α’s
• 2007-2009 KamLAND liquid scintillator purification campaigns

(in preparation for solar 7Be neutrino detection)

• Reduced 210Po contamination by a factor of 20.
• (α,n) backgrounds are greatly reduced for the post-purification

period.

17 2011-05-01

3-Flavor Analysis

PMNS Matrix Survival Probability at KamLAND

18 2011-05-01

Matter Effects from Propagating Through the Earth

19 2011-05-01

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.

20 2011-05-01

data set before purification / data set after purification

Systematic Error Table

21 2011-05-01

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

(b)

free

13

θ

12

θ

2

tan )

2

eV

• 4

(10

21 2

m ∆

KamLAND+Solar KamLAND Solar

95% C.L. 99% C.L. 99.73% C.L. best fit

95% C.L. 99% C.L. 99.73% C.L. best fit 95% C.L. 99% C.L. 99.73% C.L. best fit

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

Results of the 3-Flavor Analysis

KamLAND Best Fit

22 2011-05-01

Efficiency (%)

60 80 100

Selection efficiency

50 100 150 200 250 300 350

1 2 3 4 5 6 7 8

KamLAND data no-oscillation best-fit osci. accidental O

16

,n) α C(

13 e

ν best-fit Geo best-fit osci. + BG

e

ν + best-fit Geo

(MeV)

p

E Events/0.425MeV

Prompt Energy Distribution

23 2011-05-01

(km/MeV)

e

ν

/E L

20 30 40 50 60 70 80 90 100 110

Survival Probability

0.2 0.4 0.6 0.8 1

e

ν Data - BG - Geo

best-fit oscillation ν 3- best-fit oscillation ν 2-

(L0 = 180 km chosen for scale)

Shape Distortion and Evidence for Neutrino Oscillations

24 2011-05-01

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

(a)

= 0

13

θ

12

θ

2

tan )

2

eV

• 4

(10

21 2

m ∆

KamLAND+Solar KamLAND Solar

95% C.L. 99% C.L. 99.73% C.L. best-fit

95% C.L. 99% C.L. 99.73% C.L. best-fit 95% C.L. 99% C.L. 99.73% C.L. best-fit

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

2-Flavor/3-Flavor Analysis Comparison

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

(b)

free

13

θ

12

θ

2

tan )

2

eV

• 4

(10

21 2

m ∆

KamLAND+Solar KamLAND Solar

95% C.L. 99% C.L. 99.73% C.L. best fit

95% C.L. 99% C.L. 99.73% C.L. best fit 95% C.L. 99% C.L. 99.73% C.L. best fit

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

5 10 15 20

σ 1 σ 2 σ 3 σ 4

2

χ ∆

2-Flavor 3-Flavor

25 2011-05-01

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

12

θ

2

tan

13

θ

2

sin

KamLAND Solar KamLAND+Solar

95% C.L. 95% C.L. 95% C.L. 99% C.L. 99% C.L. 99% C.L. 99.73% C.L. 99.73% C.L. 99.73% C.L. best-fit best-fit best-fit

26 2011-05-01

0.01 0.02 0.03 0.04 0.05 0.06 0.07 1 2 3 4 5 6 7 8 9 10

90% C.L. 95% C.L. 99.73% C.L.

K a m L A N D Solar K a m L A N D + S

• l

a r CHOOZ + Atmospheric + LBL Global

13

θ

2

sin

2

χ ∆

Global Analysis

Global:

27 2011-05-01

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Survival Probability 0.2 0.4 0.6 0.8 1

x

12

θ 2

2

/sin 〉 )

e

ν

L/E

21M 2

m ∆ (1.27

2

sin

12M

θ 2

2

sin 〈 ≡

best-fit osci. ν 3- best-fit osci. ν 2-

e

ν Data - BG - Geo no-oscillation

Mostly Dependent on θ12: Dependent on θ13: Survival Probability:

Visualization of KamLAND’s Sensitivity to θ13

28 2011-05-01

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.

29 2011-05-01

Future of Long Baseline Reactor Neutrino Experiments

30 2011-05-01

136Xe 400 kg:

2.7 wt% dissolved into LS easy handling/ enrichment (90%) longer 2ν beta decay life time T2ν >1022 years (cf: ~1019-20) KamLAND exists: ultra pure environment (U/Th~10-17 g/g) LS techniques Balloon experience LS Density control techniques Reactor/Geo neutrino

136Xe 400 kg loaded LS

in mini-balloon, R=1.7m

KamLAND-Zen

31

Slide courtesy of

• Dr. K Nakamura,

RCNS Tohoku University, Jp Neutrino 2010

31 2011-05-01

Neutrinoless Double Beta Decay Search

32 2011-05-01

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G654A) A8G) C'.$")

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P#,+)!"#$%&'()) V<,(%#+$"()(3#;;"')%0#+) )B66>3)%&)%0")<"%"$%&'XY)

• )C'.$")'"#$%&')L,;;)$&+%',-.%")3#,+;F)%&)%0")$"+%'#;)2"#>=)
• )W")$#+)%#>")#<D#+%#T")Z'&3)#+F)[(0.%J&\])2"',&<)

^_M)R+#;F(,()

Steve Biller ANT 2011

33 2011-05-01

Intermediate Baseline Reactor Neutrino Experiments

34 2011-05-01

Can the neutrino mass hierarchy be determined by a reactor experiment?

Petcov & Piai, PLB 533, 94 (2002) Choubey et al., PRD 68, 113006 (2003) Learned et al., PRD 78, 071302 (2008) Zhan, et al., PRD 78, 111103 (2008) Zhan, et al., PRD 79, 073007 (2009) Ghosha & Petcov, arXiv:1011.1646

Normal Inverted

35 2011-05-01

!"

Fourier transformation of L/E spectrum

• Frequency regime is in fact the

M2 regime enhance the visible features in M2 regime

• Take M2

32 as reference

– NH: M2

31 > M2 32 , M2 31

peak at the right of M2

32

– IH: M2

31 < M2 32 , M2 31

peak at the left of M2

32

L/E spectrum

Yifang Wang ANT 2011

36 2011-05-01

Features of Mass Hierarchy

• A different Fourier formalism:
• Clear distinctive features:

– FCT:

• NH: peak before valley
• IH: valley before peak

– FST:

• NH: prominent peak
• IH: prominent valley
• Better than power spectrum
• No pre-condition of m2

23

!"

• L. Zhan et al., PRD78(2008)111103

Yifang Wang ANT 2011

37 2011-05-01

Quantify Features of FCT and FST

• To quantify the symmetry

breaking, we define:

RV/LV: amplitude of the right/left valley in FCT P/V: amplitude of the peak/valley in FST

• For asymmetric Pee

– NH: RL>0 and PV>0 – IH: RL<0 and PV<0

• L. Zhan et al., PRD78:111103,2008

Baseline: 46-72 km Sin2(213): 0.005-0.05 Others from global fit

Two clusters of RL and PV values show the sensitivity of mass hierarchy determination

Yifang Wang ANT 2011

38 2011-05-01

In reality

• L. Zhan, et. al., Phys.Rev.D79:073007,2009

Unfortunately, M2

21 / M2 23 ~ 3%

Yifang Wang ANT 2011

39 2011-05-01

Requirement

• To determine mass hierarchy at > 90% CL:

– Baseline: ~ 58 km, determined by 12 – Reactor power > 24 GWth – Flux and detector size: ~ (250-700) ktyear – Ideally, sin2213 > 0.02 & energy resolution < 2%

• IF sin2213=0.01, energy resolution < 2% & 700 ktyear
• For sin2213=0.02 , energy resolution < 3% & 700 ktyear
• Overburden > 1000 MWE
• A huge e detector with mass >20kt

– currently the largest on is 1kt (KamLAND & LVD)

• Yifang Wang ANT 2011

40 2011-05-01

A possible location

60 km from Daya Bay and Haifeng Thermal power > 40 GW

Yifang Wang ANT 2011

41 2011-05-01

Technical challenges

• Requirements:

– Large detector: >10 kt LS – Energy resolution: 2%/E 2500 p.e./MeV

• Ongoing R&D:

– Low cost, high QE “PMT”

• New type of PMT

– Highly transparent LS: 15m >25m

• Understand better the scintillation mechanism
• Find out traces which absorb light, remove it from the

production

Now: 1kt 250 p.e./MeV 20” UBA/SBA photocathode PMT is also a possibility

Yifang Wang ANT 2011

42 2011-05-01

Summary

• KamLAND observes a neutrino survival probability

that is consistent with the solar LMA solution.

• At the present time, KamLAND has the most

precise measurement of Δm221.

• Experiments will continue to measure reactor

neutrinos at long baselines (parasitically).

• If sin22θ13 is large enough (>0.02), then

intermediate baseline reactor neutrino experiments may have the capability of determining the neutrino mass hierarchy.

43 2011-05-01