L. Oberauer, Paris, June 2004 Measurements at Reactors Neutrino 2004 CdF, Paris, June...
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![Page 1: L. Oberauer, Paris, June 2004 Measurements at Reactors Neutrino 2004 CdF, Paris, June 2004...chasing the missing mixing angle.](https://reader031.fdocuments.in/reader031/viewer/2022013101/56649f305503460f94c4b728/html5/thumbnails/1.jpg)
L. Oberauer, Paris, June 2004
Measurements at Reactors
Neutrino 2004
CdF, Paris, June 2004
...chasing the missing mixing angle
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L. Oberauer, Paris, June 2004
ex
Why reactors?
The actual best limit is coming from a reactor experiment ! Chooz,
Paolo Verde
sin22
m2 = 2 10-3 eV2
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L. Oberauer, Paris, June 2004
Experimental method
nepe
• Nuclear reactors are a powerful source of low energy (up to ~ 8 MeV) electron anti-neutrinos
• Detection via inverse beta decay:
• Q-value ~ 1.8 MeV
• E~ Ee - Q ( spectroscopy)
• suppress background via use delayed coincidence method
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L. Oberauer, Paris, June 2004
How to improve the sensitivity?The problem: Reactor exp. = Disappearance exp.
• compare total flux (and spectrum) with the
no- oscillation hypothesis
• one depends on systematic uncertainties, like:
absolute source strength,
cross section,
detection efficiency,
fuel development over time...
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L. Oberauer, Paris, June 2004
The basic idea:Use 2 identical detectors
• oscillation frequency basically known
L/2 ~ 1.0 km - 2.0 km
• choose the right distance for the signal with the far detector
• monitor the reactor with the close detector (100m) (cancels also uncertainties like cross section, efficiencies etc.)
m2 = ( 2.0 - 2.5 ) 10-3 eV2
osc.length L
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L. Oberauer, Paris, June 2004
The aims:
• Statistics N(far) ~ 5 104
• energy uncertainty (E) < 1%
• normalization uncertainty rel < 1%
number of target protons
efficiencies (positron, neutron) rel
excellent calibrations required...
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L. Oberauer, Paris, June 2004
Additional uncertainties:
• shape (~ 2%)
• cross section (~ 1.9%)
should cancel !
• fuel composition (235U, 238U, 239Pu, 241Pu)
should cancel !
Bugey; comparison with spectrum deconvoluted from exp. determined beta spetra
Feilitzsch, Schreckenbach; used for analysis of the Gösgen experiment
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Background?• accidental background
determine online not critical
radiopurity experiencies from CTF, Chooz, KamLAND
• correlated background (muon induced)
fast neutrons
beta - neutron cascades
• in Chooz signal/background ~ 25 -> 100 (aim)
• backgrounds in both detectors identical ??
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L. Oberauer, Paris, June 2004
Sensitivity ?
• around few 10-2 for sin2 2after ~3 years (20t, 8GW)
• impact of systematics fairly modest
Huber, Lindne
r, Schw
etz & W
inter: hep-ph/0303
232
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L. Oberauer, Paris, June 2004
Approach towards an experiment...• 3 workshops on „Future Low Energy -Experiments“
spring 2003 Alabama, USA
fall 2003 Munich, Germany
spring 2004 Niigata, Japan
• White paper
thanks to Maury Goodman.
paper available hep-ex/0402041
(or http://www.hep.anl.gov/minos/reactor13/white.html)
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L. Oberauer, Paris, June 2004
Which site for the experiment ?
Diablo Canyon
Byron
Angra
PenlyChoozCruas
Krasnoyarsk
Taiwan
Kashiwasaki
One reactor complexTwo underground cavities @0.1- 1 km & ~1- 2 km
Daya Bay
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L. Oberauer, Paris, June 2004
Requirements:
• Strong power plant
• Shielding (300m.w.e. or better) for at least the far detector
• Only one (or two) cores (=sources) preferred
• Support from the power plant responsibles
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L. Oberauer, Paris, June 2004
Sites under discussion:
ANGRA, Brazil (reactor II)
BRAIDWOOD, BYRON, LA SALLE, Illinois, USA
CHOOZ, France
DAYA BAY, China
DIABLO CANYON, California, USA
KASHIWAWASAKI, KARIWA, Japan
KRASNOYARSK, Russia (first proposal)
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L. Oberauer, Paris, June 2004
The Diablo Canyon site (USA)
• Close to San Francisco (500 km), California • Two cores (2 x 3.1 GWth) • D1 ~ 0.5 – 1 km & D2 ~ 1.5 – 3 km • Overburden: horizontal tunnel 800 mwe Leader Group : Berkeley LBL
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L. Oberauer, Paris, June 2004
The Diablo Canyon site (USA)
• Close to San Francisco (500 km), California • Two cores (2 x 3.1 GWth) • D1 ~ 0.5 – 1 km & D2 ~ 1.5 – 3 km • Overburden: horizontal tunnel 800 mwe Leader Group : Berkeley LBL
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L. Oberauer, Paris, June 2004
The Kashiwasaki site (Japan)
Kashiwasaki power plant : 24.3 GWth 7 cores 2 near detectors needed ! R&D budget approved 3 identical detector of ~8 tons
shielding 350 - 440 mwe Data taking ~ 2008
Sensitivity (3 years): sin2(213)<0.026 @90% C.L
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L. Oberauer, Paris, June 2004
...even SuperK was proposed (Kornoukhov, Starostin)(Phys. Of Atom. Nucl., Vol. 67, 4, (2004) 672)
...with a near detector (KamLAND size) and a russian type 300 MW reactor !
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L. Oberauer, Paris, June 2004
Letter of Intent: Double-Chooz
• d~1.05 km
• P~8.4 GW
• 300mwe far detector
• no excavation for far detector
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L. Oberauer, Paris, June 2004
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L. Oberauer, Paris, June 2004
Chooz (site of far detector)
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Detector design, Double-Chooz
-target
Gd-scintillator
-catcher, scintillator
buffer, non-scintillating
Muon Veto, scintillator
2.4m3.6m
5.5m6.7m
)
)
)
)
)
)
PMs 2.8m
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Sensitivity ?
• sensitivity between 0.02 and 0.03
for sin2 2 after ~3 years (for m2 = 2.0 10-3 eV2 )
P. Huber et al. hep-ph/0403068
Poster: G. Mention, systematics and sensitivities for Double-Chooz
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L. Oberauer, Paris, June 2004
Comparison to LBL-projects?P
. Huber et al. hep-ph/0403068
• D-Chooz: funding French side 2.2 - 2.5 M€ approved
• Aim for start data taking ~ 2008
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L. Oberauer, Paris, June 2004
Background studies for Double-Chooz
Correlated background events:
• Monte-Carlo simulation of fast neutrons, generated by cosmic muons
• first check: simulation of the old Chooz experiment
MC - result: 0.8 < bg/day < 4.5 (limited by statistics)
Exp. - result: bg = 1.1 / day
• MC reliable !
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L. Oberauer, Paris, June 2004
Background spectrum Double-Chooz
Neutron spectrum - veto off Neutron spectrum - veto on
Shielding 100mwe, t = 33.7 h 1 background event
prelim
inary
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L. Oberauer, Paris, June 2004
Background Double-Chooz
• expected rate far detector (300mwe) ~ 0.15 / day
(lower than 0.3 / day at 90% cl)
• signal / background far det. > 100
• expected rate close detector (60mwe) ~ 2 / day
• signal / background close det. > 500
(if distance is ~ 150m)
• spectral shape of background quite flat (unequal to signal spectrum)
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L. Oberauer, Paris, June 2004
Example: beta-n from 8He
(generated by cosmic muon on 12C in organic liquid scintillator)
• monitor 8He rate by special beta - alpha delayed coincidence
• data from other candidates (9Li) available from T. Hagner et al. (muon beam @ SPS, CERN), Chooz, CTF, KamLAND
Beta - neutron cascades
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L. Oberauer, Paris, June 2004
Spectral information ?Y(‚close‘) - Y(‚far‘)
• ~ 3.5 years
• sin22
m2 = 2 10-3 eV2
very valuable cross-check if one obeserves an effect in the total rates !
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L. Oberauer, Paris, June 2004
Conclusions
Search for 13 with a new reactor experiment is very promising
„next future“ experiments
Large expertise available from low energy, low background projects (Chooz, CTF/Borexino, KamLAND)
White paper available
LOI for a new Double-Chooz, France
Poster, A. Ianni, C
TF &
M. Göger, LENA