KamLAND Status and Prospects

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KamLAND Status and Prospects

KamLAND Status and Prospects

Jean-stéphane Ricol

(Tohoku University)

J.S. Ricol KamLAND status and prospects APPI 2004


Contents

• Description of KamLAND experiment

• Results on reactor antineutrinos oscillation

• New limit on 8 to 15 MeV antineutrinos flux

Status

• Future results

J.S. Ricol KamLAND status and prospects APPI 2004


1 km

Description of experiment:

KamLAND Site

Mozumi mine in Mt Ikenoyama

Existing cavern from

KamioKANDE

experiment

New infrastructure installed for KamLAND

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

KamLAND Site

70 GW are generated at 130-240 km

distance from KamLAND

Flux ~ 5 10 6 / cm 2 / sec

a few events per day in KamLAND

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

KamLAND Detector

Scintillation light is detected by 1325+554 photomultipliers (~ 300 pe / MeV)

Waveform data acquired by DAQ is converted offline to pulse times and

charges from which event times, positions and energies are reconstructed

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Antineutrino detection

ν e

Inverse beta decay

e -

e +

2 γ

Prompt event

E p ~ E ν − 0.78 MeV

p

n

γ

2

H

in coincidence

Delayed event

E d = 2.22 MeV

p

~ ns ~ 200 s

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Fiducial Volume Calibration

68

Ge : 1.012 MeV (γ+γ) 65 Zn : 1.116 MeV (γ)

60

Co : 2.506 MeV (γ+γ) AmBe : 2.20, 4.40, 7.6 MeV (γ)

~ 25 cm

- 5 m + 5 m

Spallation neutrons

induced by muons

V fid /V fid = 4.1%

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Energy Calibration

Sources deployment + spallation neutrons

(2.2 MeV on p, 4.9 MeV on 12 C)

∆E/E ~ 7.5% / E [MeV]

∆E syst = 1.9% at 2.6 MeV

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

238

U, 232 Th Contamination

238

U … 214 Bi (+γ, 28.7 min) 214 Po(, 237 s) 210 Pb

∆T = |t prompt – t delayed |

τ =


Note: not a

background

since totally

unlike neutron

Likewise from 212 (Bi,Po) decay:


Requirement for reactor experiment < 10 -14 g/g

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Spallation cuts

We can get coincidence events from spallation

products up to few times 200 s after muon

We can get beta-neutron coincidence up to few times

200 ms after muon from 9 Li (half-life time is 178.3 ms) !!

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Geo-neutrinos background

16 TW model

Antineutrino from the Earth have

never been observed before.

Many different models.

Uncertainties in flux prediction.

Analysis threshold fixed to 2.6 MeV

If observed it opens a new field in geo-neutrino physics

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Reactor antineutrino selection

Temporal coincidence : 0.5 s < T < 660 s

Spatial coincidence : R < 1.6 m

Neutron energy : |E delayed -2.2MeV| < 0.4 MeV

Fiducial volume : R prompt < 5 m, R delayed < 5 m

R xy delayed > 1.2 m

Total efficiency : 78.3%

Analysis Threshold : E prompt > 2.6 MeV

Spallation cuts : dead time ~ 11%

J.S. Ricol KamLAND status and prospects APPI 2004


Description of experiment:

Remained background and

systematic errors

Source BG in data sample

Accidental 0.0086±0.0005

9 Li/ 8 He 0.94±0.85

Fast Neutrons


First antineutrino oscillation results:

Rate suppression




N obs /N no-osc = 0.611 0.085 (stat) 0.041 (syst)

neutrino disappearance at 99.95C.L.

J.S. Ricol KamLAND status and prospects APPI 2004


First antineutrino oscillation results:

Impact of rate suppression

J.S. Ricol KamLAND status and prospects APPI 2004


First antineutrino oscillation results:

Spectral distortion ?

2-ν oscillation: best-fit No oscillation, flux suppression

Data and best oscillation fit

consistent at 93% C.L.

Data and scaled no-oscillation

shape consistent at 53% C.L

J.S. Ricol KamLAND status and prospects APPI 2004


First antineutrino oscillation results:

Impact of spectrum

Rate + Spectrum analysis

J.S. Ricol KamLAND status and prospects APPI 2004


Recent result:

Flux of 8 to 15 MeV antineutrinos

from any source in 0.28 kt-yr exposure

< 370 cm -2 s -1 As limit on solar antineutrinos :

Flux < 2.8x10 -4 x solar 8 B neutrino flux

Factor 30 improvement over SuperK

In context of spin flavor precession:

ν


KamLAND Status

• HV system upgraded

• Radon free air system

operational

• “4” off axis calibration

system expected before

summer

• Data now includes shutdown

of Kashiwazaki and

Fukushima sites

J.S. Ricol KamLAND status and prospects APPI 2004


Future results

• Direct measurement of fiducial volume

using off-axis calibration system.

• Consistency check using brief period of

50% lower flux.

• More data, better statistics.

• Geo-neutrinos ?

J.S. Ricol KamLAND status and prospects APPI 2004


Future results:

Sensitivity after 5 years of data

• Measure m 2 to ±3%

• Modest improvement in

12 of antineutrinos

J.S. Ricol KamLAND status and prospects APPI 2004


Future results:

Solar 7 Be phase

Improve KamLAND purification system.

210 Pb; 10 -20 g/g 10 -25 g/g (Water extraction)

Air tight valve housings.

Radon free air system

Testing the water extraction.

J.S. Ricol KamLAND status and prospects APPI 2004


Future results:

Solar 7 Be phase

± 4.4%(99%

CL)

J.S. Ricol KamLAND status and prospects APPI 2004


Future results:

Promising results will come soon,

keep an eye open on KamLAND

J.S. Ricol KamLAND status and prospects APPI 2004

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