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β-beam background in a Water Cherenkov Detector. Elena Couce (IFIC - U. Valencia) Based on a collaboration with D. Casper, JJ Gomez-Cadenas and P. Hernandez. April 27 2006 ISS meeting at RAL (UK). Experimental Challenge. Next generation neutrino oscillation experiments: - PowerPoint PPT Presentation
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Elena Couce (IFIC - U. Valencia)Based on a collaboration with D. Casper, JJ Gomez-Cadenas and P.
Hernandez
April 27 2006ISS meeting at RAL (UK)
Experimental ChallengeExperimental Challenge
Next generation neutrino oscillation Next generation neutrino oscillation experiments:experiments:
Need for precision measurements of very small Need for precision measurements of very small oscillation probabilities oscillation probabilities at E/L at E/L mm22
atmatm :: High StatisticsHigh Statistics Low SystematicsLow Systematics
CP-VIO??? 2
23
23
sign
octant
?
?
m
13 ?
So why a Water Cherenkov So why a Water Cherenkov Detector?Detector?
Because water is cheap… so we can make it Because water is cheap… so we can make it large!large!
Let’s say… 20 x !Let’s say… 20 x !
It has other uses: It has other uses: atmospherics, proton decay, atmospherics, proton decay, supernova…supernova…
However it cannot detect the charge…However it cannot detect the charge…
Is signal/background ratio good enough?Is signal/background ratio good enough?
SK
≈ 1000 kTon
SuperBeamSuperBeam -Factory-Factory β-beamβ-beam√ √
At least ~10 times larger than for any other technology!
In this talk we’re presenting the results of a complete and In this talk we’re presenting the results of a complete and realistic realistic
MC simulation of a MC simulation of a Water CherenkovWater Cherenkov detector exposed to a detector exposed to a β-β-beambeam
ProcedureProcedure Fluxes:Fluxes:
Nature’s oscillation parameters:Nature’s oscillation parameters:
Analysis cuts:Analysis cuts:
L = 700 Km = 350 5 + 5 years 5.8 1018 d.p.y. of 6He 2.2 1018 d.p.y. of 18Ne
L = 130 Km = 100 5 + 5 years 5.8 1018 d.p.y. of 6He 2.2 1018 d.p.y. of 18Ne
High High β-Beam β-BeamLow Low β-Beam β-Beam
mm221212 sinsin22θθ1212 mm22
2323 sinsin22θθ2323 sinsin22θθ1313 7.92 10-5 eV2 0.314 2.4 10-3 eV2 0.44 2.74 10-3 40º
G.L. Fogli hep-ph/0506083
Fiducial:Fiducial:
Selection:Selection: PID Michel e-
Distance to walls > 2 m Maximum of 10 hits in outer det.
Fiducial cuts: Fiducial cuts: Signal and Background spectra
High- -beam
Low- -beam
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
1
Fiducial cuts : Fiducial cuts : Absolute # of events
High- -beam after fiducial cuts:
Low- -beam after fiducial cuts:
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
1
0
10000
20000
30000
40000
50000
60000
1
0
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1
66HeHe
66HeHe1818NNee
1818NNee
-- oo++ -- oo++
-- oo++ -- oo++
PID cutPID cut
Electron/muon separation:Electron/muon separation:μ-like event e-like event
Selecting 1 ring -like events
PID cut : PID cut : Signal and Background spectra
High- -beam:
PID cut
Low- -beam:
PID cut
FIDUCIAL
FIDUCIAL
0
100
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1
0
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1
0
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6000
1
0
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1000
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3000
3500
4000
4500
5000
1
PID cut: PID cut: Absolute # of events
High- -beam after fiducial + PID cuts:
Low- -beam after fiducial + PID cuts:
66HeHe
66HeHe1818NNee
1818NNee
-- oo++ -- oo++
-- oo++ -- oo++
Michel e- cutMichel e- cut
ee
Signal
Selecting events with a second delayed ring after the
first
Michel e-
t ~ decay time
Michel e- cut: Michel e- cut: Signal and Background spectra
High- -beam:
Low- -beam:
Delayedring cut
Delayedring cut
PID
PID
0
100
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1
0
50
100
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1
0
500
1000
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1
0
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1000
1500
2000
2500
1
Michel e- cut: Michel e- cut: Absolute # of events
High- -beam after fiducial + PID + Michel e- cuts:
Low- -beam after fiducial + PID + Michel e- cuts:
66HeHe
66HeHe1818NNee
1818NNee
-- oo++ -- oo++
-- oo++ -- oo++
0
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1
0
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1
0
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1
0
50
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1
High- -beam after fiducial + PID + Michel e- + Energy > 500 MeV cuts:
Low- -beam after fiducial + PID + Michel e- cuts:
66HeHe
66HeHe1818NNee
1818NNee
-- oo++
-- oo++ -- oo++
-- oo++
Michel e- cut: Michel e- cut: Absolute # of events
Signal/Bkgd final compositionSignal/Bkgd final composition
High- -beam after fiducial + PID + Michel e- cuts:
Low- -beam after fiducial + PID + Michel e- cuts: 1818NN
ee
66HeHe
BKGNDSIGNAL SIGNAL BKGND
SIGNAL BKGND
1818NNee
BKGNDSIGNAL
66HeHe
SIGNAL BKGND
High- -beam after fiducial + PID + Michel e- + Energy > 500 MeV cuts:
Low- -beam after fiducial + PID + Michel e- cuts: 1818NN
ee
66HeHe
BKGNDSIGNAL SIGNAL BKGND
SIGNAL BKGND
1818NNee
BKGNDSIGNAL
66HeHe
SIGNAL BKGND
Signal/Bkgd final compositionSignal/Bkgd final composition
Cuts evaluationCuts evaluation: : Relative effect of each cut
Low- -beam:
1818NNee
66HeHe
0%
20%
40%
60%
80%
100%
0%
20%
40%
60%
80%
100%
e
Normalized to fiducial events
High- -beam:
0%
20%
40%
60%
80%
100%
1818NNee
0%
20%
40%
60%
80%
100%
66HeHe
e
Normalized to fiducial events
Cuts evaluationCuts evaluation: : Relative effect of each cut
Low- -beam
Cuts evaluationCuts evaluation: : Signal to noise ratio
High- -beam
ConclusionsConclusions
AA β-beamβ-beam with a Water Cherenkov should have with a Water Cherenkov should have good signal to noise ratio well below good signal to noise ratio well below θθ13 13 = = 3º 3º (s/n = 60)(s/n = 60)
Water Ckov detectors might not be the best Water Ckov detectors might not be the best choice in terms of performance for β-beam choice in terms of performance for β-beam experiments (particularly at high experiments (particularly at high ). However ). However the increase in statistics compensates, up to the increase in statistics compensates, up to ~ ~ 350350
The s/n is better for high The s/n is better for high β-beam, particularly β-beam, particularly for for . In addition it allows energy binning.. In addition it allows energy binning.
ConclusionsConclusions
From this study we know the relevant From this study we know the relevant processes contributing to signal and processes contributing to signal and background. With some knowledge on the background. With some knowledge on the corresponding corresponding cross section errorscross section errors it it should be possible to obtain, if not a good should be possible to obtain, if not a good estimate, at least an educated guess on the estimate, at least an educated guess on the systematic errors… possibly good enough?systematic errors… possibly good enough?
HELP WANTED!
Study of T2HK signal and backgroundand
Realistic comparison of β-beam and Superbeam performances
to be continued…