neutrino hierarchy determination from a galactic supernova burst
DESCRIPTION
Neutrino hierarchy determination from a galactic supernova burst. David Webber August 20, 2010. Neutrino energies at infinity (1 second time-slice of 10-second burst spectrum?). H. Duan and A. Friedland , http://arxiv.org/abs/1006.2359. Consider 3 detector possibilities. - PowerPoint PPT PresentationTRANSCRIPT
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Neutrino hierarchy determination from a galactic supernova burst
David WebberAugust 20, 2010
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H. Duan and A. Friedland, http://arxiv.org/abs/1006.2359
Neutrino energies at infinity(1 second time-slice of 10-second burst spectrum?)
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Consider 3 detector possibilities
• Water Cherenkov (WC) with 30% phototube coverage and high quantum-efficiency tubes– This is roughly equivalent to Super-K’s coverage
• WC, 15% coverage, HQE• Liquid Argon
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n reaction cross-sections
https://wiki.bnl.gov/dusel/index.php/Event_Rate_Calculations
nepe nDominant reaction:
Water Argon
Dominant reaction:KeAr 40-40 en
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Normal Hierarchy: Observed Spectra(accounts for detector acceptance)
WC 30% coverage
n flux at detector
WC 15% coverage Liquid Ar
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Inverted Hierarchy: Observed Spectra(accounts for detector acceptance)
WC 30% coverage
n flux at detector
WC 15% coverage Liquid Ar
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How many events are needed to distinguish normal from inverted hierarchy in water?
Normal Hierarchy Inverted Hierarchy
102 eventsindistinguishable
•Water Detector•30% PMT coverage•HQE tubes•IBD reaction•c2 shown for “wrong” fit
105 eventsclearly distinguishable
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How many events for 3 sigma exclusion?
• Note: c2 is not the same as Gaussian• “3 sigma” = 99.73% confidence• 99.73% confidence is…– c2/NDF of 1.6 for 57 degrees of freedom– c2/NDF of 1.8 for 34 degrees of freedom
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c2 vs. events, WC, 30% coverage
Normalhierarchy
Invertedhierarchy
Normal fit Inverted fit
•Water Detector•30% PMT coverage•HQE tubes•IBD reaction ~103.5-3.6 = 3200-4000 events are needed
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c2 vs. events, WC, 15% coverage
Normalhierarchy
Invertedhierarchy
Normal fit Inverted fit
•Water Detector•15% PMT coverage•HQE tubes•IBD reaction ~103.5-3.6 = 3200-4000 events are needed
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How many events are needed to distinguish normal from inverted hierarchy in argon?
Normal Hierarchy Inverted Hierarchy
102 eventsindistinguishable
105 eventsclearly distinguishable
•Liquid Argon•c2 shown for “wrong” fit
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c2 vs. events, liquid argon
Normalhierarchy
Invertedhierarchy
Normal fit Inverted fit
~102.7-2.8 = 500-630 events are needed
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Normal and inverted hierarchy neutrino spectra for 99.7% confidence.
Normal Hierarchy Inverted Hierarchy
Water Cherenkov30% PMT coverage4000 events
Liquid Argon630 events
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Summary• WC phototube coverage has little impact on resolving the
hierarchy.– 15% is as good as 30%
• To resolve the hierarchy…– ~4000 events must be observed in water, or– ~630 events must be observed in argon
• If a SNB occurs at 8.5 kpc…– Need 18.3 kT water– Need 7.6 kT Ar– a 100kT water module would have better statistics than a 17 kT LAr
module– The LAr module would show more interesting spectral features
Volume estimates based on http://arxiv.org/abs/astro-ph/0701081This study was based on repository revision 754