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
Neutrino hierarchy determination from a galactic supernova burst
David WebberAugust 20, 2010
H. Duan and A. Friedland, http://arxiv.org/abs/1006.2359
Neutrino energies at infinity(1 second time-slice of 10-second burst spectrum?)
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
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
Normal Hierarchy: Observed Spectra(accounts for detector acceptance)
WC 30% coverage
n flux at detector
WC 15% coverage Liquid Ar
Inverted Hierarchy: Observed Spectra(accounts for detector acceptance)
WC 30% coverage
n flux at detector
WC 15% coverage Liquid Ar
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
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
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
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
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
c2 vs. events, liquid argon
Normalhierarchy
Invertedhierarchy
Normal fit Inverted fit
~102.7-2.8 = 500-630 events are needed
Normal and inverted hierarchy neutrino spectra for 99.7% confidence.
Normal Hierarchy Inverted Hierarchy
Water Cherenkov30% PMT coverage4000 events
Liquid Argon630 events
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