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Determining the neutrino hierarchy from a galactic supernova using a next-generation detector

Determining the neutrino hierarchy from a galactic supernova using a next-generation detector. http://www.spitzer.caltech.edu/search/image_set/20?search=sig08-016. http://chandra.harvard.edu/photo/printgallery/2004/. http://www.spitzer.caltech.edu/search/image_set/20?search=ssc2005-14c.

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Determining the neutrino hierarchy from a galactic supernova using a next-generation detector

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  1. Determining the neutrino hierarchy • from a galactic supernova • using a next-generation detector http://www.spitzer.caltech.edu/search/image_set/20?search=sig08-016 http://chandra.harvard.edu/photo/printgallery/2004/ http://www.spitzer.caltech.edu/search/image_set/20?search=ssc2005-14c SN 1572 “Tycho’s Nova” 7,500 light years (2.3 kPc) SN 1604 “Kepler’s Nova” ~20,000 light years (6 kPc) Cassiopeia A ~300 years ago 11,000 light years (3.4 kPc) David M. Webber APS April Meeting May 3, 2011

  2. Neutrino emission: • 10% gravitational binding energy • Ln ~ 1051-1053 erg s-1 • 10-30 seconds • Neutrino spectral swaps D. M. Webber Adapted from Fuller, NDM09

  3. Initial neutrino spectra • “Pinched thermal” distribution1 • ne “freeze-out” later than nm, nt, at lower temp • Initial Spectrum will be modified by • Spectral (flavor) swaps • Turbulence and shockwave • Detector resolution 0 60 MeV Ignore Fig adapted from: Duan and Friedland, Phys. Rev. Lett. 106, 091101 (2011) D. M. Webber 1Keil, Raffelt, Janka. Astrophys. J. 590,971(2003)

  4. The initial flux is modified by spectral swaps Near the Supernova, at high neutrino densities, neutrinos self-interact Self-interaction will introduce a collective flavor swap |nx>+|ne> |ne> |nx> |ne>+|nx> Normal Hierarchy 0 60 MeV 0 60 MeV Fig adapted from: Duan and Friedland, Phys. Rev. Lett. 106, 091101 (2011) Fig adapted from: Duan and Friedland, Phys. Rev. Lett. 106, 091101 (2011)

  5. The features of the flavor swap depend on the neutrino hierarchy “Normal” “Inverted” n2 n1 n3 n2 n1 n3 0 60 MeV http://www.lbl.gov/Science-Articles/Archive/sabl/2006/Jul/03.html The energy shape gives a handle on the hierarchy Normal Hierarchy Inverted Hierarchy Energy spectra figs adapted from: Duan and Friedland, Phys. Rev. Lett. 106, 091101 (2011)

  6. Next-generation detectors will see lots of (anti)neutrinos from a galactic SN LBNE Water-Cherenkov 100 kT 10 kPc to supernova ~20000 events LBNE Liquid Argon 17 kT 10 kPc to supernova ~1500 events http://hubblesite.org/newscenter/archive/releases/1995/49/image/a/ Fig: Steve Hentschel Via Bruce Baller SN 1987A 160,000 LY (50 kPc) (galactic SN 5-15 kPc) How many events are needed to distinguish the neutrino hierarchy? Kamiokande II (1 kton) detected 11  IMB (3.3 kton) detected 8 Baksan (0.2 kton) detected 5 Fig: S. Kettell D. M. Webber

  7. n reaction cross-sections Water Argon 102 102 ne40Ar ne160 inverse beta decay ne40Ar Cross-section (10-38 cm2) ne160 Cross-section (10-38 cm2) NC160 elastic scattering elastic scattering 10-7 10-7 10 Neutrino Energy (MeV) 100 Neutrino Energy (MeV) 10 100 Dominant reaction: Dominant reaction: D. M. Webber SNOwGLoBES K. Scholberg L11 6 http://www.int.washington.edu/PROGRAMS/10-2b/LBNEPhysicsReport.pdf

  8. Observed spectral shapes Water 100kT Argon 17kT Normal Hierarchy Inverted Hierarchy Normal Hierarchy Inverted Hierarchy Events/0.5 MeV/s* Events/0.5 MeV/s* Energy (MeV) Energy (MeV) Larger detector, more events Sharper, nonthermal features D. M. Webber * one-second late-time slice

  9. A log-likelihood ratio discriminates between neutrino hierarchies 1000 simulated spectral fits 1000 events “Normal” 10% 1000 events “Inverted” 12.6 s log likelihood NH – log likelihood IH Define “significance (s)” as hierarchy distinguishability D. M. Webber *fit assuming known spectrum

  10. Finding the required number of events to distinguish the neutrino hierarchy Significance (s) D. M. Webber *fit assuming known spectrum

  11. 189 events in argon Normal Hierarchy Inverted Hierarchy D. M. Webber

  12. Finding the required number of events to distinguish the neutrino hierarchy Significance (s) D. M. Webber *fit assuming known spectrum

  13. 1645 events in water Normal Hierarchy Inverted Hierarchy D. M. Webber

  14. Finding the required number of events to distinguish the neutrino hierarchy Significance (s) D. M. Webber *fit assuming known spectrum

  15. 1014 events in water, 76 events in argon water normal hierarchy argon normal hierarchy argon inverted hierarchy water inverted hierarchy

  16. Fitting simultaneously is better than fitting separately Significance (s) SN Distance from Earth, O(10’s kPc) D. M. Webber *fit assuming known spectrum

  17. Summary • Core-collapse supernovae emit a lot of neutrinos • Spectra will not be known ab-initio • ~40% chance to observe a galactic supernova in next-gen detectors • Non-thermal features in the observed energy-spectrum will distinguish hierarchy • Water and argon detectors, fit simultaneously, will give the most information • Further study • More neutrino flux models • Time-evolution of neutrino flux • Parameterize uncertainty http://chandra.harvard.edu/photo/2008/g19/ G1.9+0.3 circa 1870* 25,000 light years away (7.7 kPc) *City of Anaheim, CA incorporated Feb 10, 1870. D. M. Webber

  18. Backup

  19. Fitting simultaneously is better than fitting separately most probable distance Significance (s) SN Distance from Earth, O(10’s kPc) Crab Nebula (SN1054) galactic center Milky Way diameter SN1987A D. M. Webber *fit assuming known spectrum

  20. To study different SNB spectra, need “effective” spectra generator Use basis: (ne, ne, nx, nx, ny, ny) nx=cos(q23)nm-sin(q23)nt ny=cos(q23)nm+sin(q23)nt Tunable Knobs: Relative flavor luminosity, eg. L(ne)/L(ne), L(nx)/L(ne) Average Energies, <Ei> Luminosity: (1.0, 1.0, 1.5, 1.5, 1.5, 1.5) <Energy> (MeV): (12, 15, 20, 20, 20, 20) D. M. Webber

  21. Miscellaneous • Supernova • 10% of rest energy emitted • 99% of energy emitted as neutrinos • Caveats • Neglected Turbulence • Assumed energy spectrum known exactly • Have not explored time-dependence • Distances • Milky Way is 30 kPc across • Sun is 8.5 kPc from center of Milky Way • Energy resolution • 10-12% for water from 10-100 MeV (docDB 2687) • 15% PMT coverage D. M. Webber

  22. A more robust estimator uses log likelihood 10% 14.5 s • Water Detector • 30% PMT coverage • HQE tubes • IBD reaction D. M. Webber

  23. Slide created by: Fuller, NDM09 D. M. Webber

  24. Galactic supernovae occur roughly twice per century Core-Collapse Supernova rate From 26Al abundance: 1.9 +/- 1.1 per century Diehl et. al., Nature 439 Known galactic supernovae in the last 2000 years http://www.spaceacademy.net.au/watch/snova/galactic.htm http://chandra.harvard.edu/photo/2008/g19/ G1.9+0.3 ~1870* 25,000 light years (7.7 kPc) ~40% chance to see SN with next-gen n detector, even if optically invisible. D. M. Webber *City of Anaheim, CA incorporated Feb 10, 1870.

  25. D. M. Webber Fig 4 from Duan and Friedland, Phys. Rev. Lett. 106, 091101 (2011)

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