Neutrino hierarchy determination from a galactic supernova burst
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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.

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Neutrino hierarchy determination from a galactic supernova burst

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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

  • 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

Water

Argon

Dominant reaction:

Dominant reaction:

https://wiki.bnl.gov/dusel/index.php/Event_Rate_Calculations


Normal Hierarchy: Observed Spectra(accounts for detector acceptance)

n flux at detector

WC 30% coverage

WC 15% coverage

Liquid Ar


Inverted Hierarchy: Observed Spectra(accounts for detector acceptance)

n flux at detector

WC 30% coverage

WC 15% coverage

Liquid Ar


How many events are needed to distinguish normal from inverted hierarchy in water?

Normal Hierarchy

Inverted Hierarchy

102 events

indistinguishable

105 events

clearly distinguishable

  • Water Detector

  • 30% PMT coverage

  • HQE tubes

  • IBD reaction

  • c2 shown for “wrong” fit


How many events for 3 sigma exclusion?

  • Note: c2is 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

Normal fit

Inverted fit

Normal

hierarchy

Inverted

hierarchy

  • Water Detector

  • 30% PMT coverage

  • HQE tubes

  • IBD reaction

~103.5-3.6 = 3200-4000 events are needed


c2 vs. events, WC, 15% coverage

Normal fit

Inverted fit

Normal

hierarchy

Inverted

hierarchy

  • 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 events

indistinguishable

105 events

clearly distinguishable

  • Liquid Argon

  • c2 shown for “wrong” fit


c2 vs. events, liquid argon

Normal fit

Inverted fit

Normal

hierarchy

Inverted

hierarchy

~102.7-2.8 = 500-630 events are needed


Normal and inverted hierarchy neutrino spectra for 99.7% confidence.

Normal Hierarchy

Inverted Hierarchy

Water Cherenkov

30% PMT coverage

4000 events

Liquid Argon

630 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 kTAr

    • a 100kT water module would have better statistics than a 17 kTLAr module

    • The LAr module would show more interesting spectral features

This study was based on repository revision 754

Volume estimates based on http://arxiv.org/abs/astro-ph/0701081


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