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Supernova Watches and HALO

Supernova Watches and HALO. SNOLAB Grand Opening Workshop May 14-16, 2012. Clarence J. Virtue. Supernova neutrinos – First order expectations. Approximate equipartition of neutrino fluxes

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Supernova Watches and HALO

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  1. Supernova Watches and HALO SNOLAB Grand Opening Workshop May 14-16, 2012 Clarence J. Virtue

  2. Supernova neutrinos –First order expectations • Approximate equipartition of neutrino fluxes • Several characteristic timescales for the phases of the explosion (collapse, burst, accretion, cooling) • Time-evolving νe, νe, ν”μ” luminosities reflecting aspects of SN dynamics • Presence of neutronization pulse • Hardening of spectra through accretion phase then cooling • Fermi-Dirac thermal energy distributions characterized by a temperature, Tν, and pinching parameter,ην • Hierarchy and time-evolution of average energies at the neutrinosphere T(ν”μ” ) > T(νe) > T(νe ) • ν-νscattering collective effects and MSW oscillations SNOLAB Grand Opening

  3. Put another way... An observed SN signal potentially has information in its: The time evolution of the luminosities The time evolution of the average energies The values of the pinching parameters Deviation from the equiparition of fluxes Modifications of the above due to ν-νscattering collective effects and MSW oscillations SNOLAB Grand Opening

  4. What is to be learned? • Astrophysics • Explosion mechanism • Accretion process • Black hole formation (cutoff) • Presence of Spherical accretion shock instabilities (3D effect) • Proto-neutron star EOS • Microphysics and neutrino transport (neutrino temperatures and pinch parameters) • Nucleosynthesis of heavy elements • Particle Physics • Normal or Inverted neutrino mass hierarchy, θ13 • Presence of axions, exotic physics, or extra large dimensions (cooling rate) • Etc. SNOLAB Grand Opening

  5. Opportunity to alert the astronomical community • Through participation in a global network of neutrino sensitive detectors - SNEWS • Provide prompt and positive alert to astronomical community in event of galactic SN in the event of a coincidence between experiments • Also provides machinery for an “INDIVIDUAL” announcement of SN by participating experiments • Design: • Coincidence server(s) – 10 second UT time window • Maximum rate of alarms is 1 per 10 days per experiment • For 2-fold coincidence, 4 experiments  < 1 false alarm/century SNOLAB Grand Opening

  6. SNEWS– current configuration LVD Super-Kamiokande Bologna SSL SSL Redundant Secure Coincidence Servers 10 s window (UT time) 2-fold coincidence SSL SSL Alert to the Astronomical Community PGP signed e-mail Borexino IceCube SNOLAB Grand Opening

  7. PGP-signed e-mail To amateur astronomers Via Sky & Telescope Go to skyandtelscope.com to “subscribe to astroalert” > 2000 subscribers To neutrino physicists and astronomers Subscribe to receive an alert at snews.bnl.gov > 250 subscribers • Direct clients: • Gravitational wave detectors • Dark Matter detectors • Gamma-ray burst Coordinates Network (GCN) • etc. • operating since March 23, 2004 • live since March 30, 2006 • all experiments sending automated alarms since April 17, 2006 SNOLAB Grand Opening

  8. Super-Kamiokande ES NC νe CC • 50 kton water Cerenkov • For 10 kpc SN • 7000 IBD • 410 NC on 16O • 300 ES • 4◦ pointing SNOLAB Grand Opening

  9. Large Volume Detector (LVD) M. Selvi, arXiv:hep-ex/0608061v1 1000 tonne liquid scintillator with PMTs and limited streamer tubes 5 MeV threshold SNOLAB Grand Opening

  10. Astronomy and Astrophysics 535 (2011) A109 5160 PMTs monitoring ~ 1 km3 of ice ~0.6 kt / PMT (~3Mt for SN) Statistical increase in dark current / singles rate (20 σ at 30 kpc) SNOLAB Grand Opening

  11. Borexino NC νe CC νe CC ES Includes ~100 νx + p L. Cadonati et al., Astropart.Phys.16:361-372,2002 • Liquid scintillator (PC) • 100 ton fiducial • 300 ton viewed (SN) • For 10 kpc SN • CC (IBD) 79 • CC (12C) 5 • NC (12C) 23 • ES 5 SNOLAB Grand Opening

  12. Near future experiments • Gadzooks! (S-K plus Gd) • For DSNB detection through tagged IBD • MicroBoone (170 t LArTPC) 2014 • SNEWS client (would buffer 1500 TB / ~30 minutes of data containing 17 SN events for 10 kpc SN) • ICARUS • Noνa • HALO • SNO+ SNOLAB Grand Opening

  13. Generically, how do we detect a SN? We can instrument as large a mass as possible, for as long as possible, and watch for a burst of the subtle effects of the SN neutrino’s weak interactions We get to chose the target and the technology To date we’ve concentrated almost exclusively on electrons, protons, and PMTs Some other “nuclear” targets are “along for the ride” and only a few others seem worthy of consideration SNOLAB Grand Opening

  14. The ideal SN detector would... • Be reliable • Target and detector would be stable and reliable for decades • Low tech • Good aging properties  longevity • Be large and scalable • Target and detector technology should be modular and easily expanded • Have large neutrino cross-sections • Very helpful, constrains shielding and costs • Additionally, secondaries need sufficient mean free paths to permit detection, constrains # readout channels and costs SNOLAB Grand Opening

  15. The ideal detector would... Have diverse sensitivities to different reaction channels and the ability to tag those channels on an event-by-event basis Have a day job that does not conflict with supernova readiness Be able to measure the energy and direction of the SN neutrinos Have low background / noise levels above a threshold that permits reliable SNEWS alerts from the far-side of the galaxy, or much further. Be able to record the data without loss from the nearest conceivable SN We don’t achieve all of this with any one technology! ... But HALO fills a niche SNOLAB Grand Opening

  16. HALO - a Helium and Lead Observatory A “SN detector of opportunity” / An evolution of LAND – the Lead Astronomical Neutrino Detector, C.K. Hargrove et al., Astropart. Phys. 5 183, 1996. “Helium” – because of the availability of the 3He neutron detectors from the final phase of SNO + “Lead” – because of high -Pb cross-sections, low n-capture cross-sections, complementary sensitivity to water Cerenkov and liquid scintillator SN detectors HALO is using lead blocks from a decommissioned cosmic ray monitoring station SNOLAB Grand Opening

  17. Comparative ν-nuclear cross-sections Kate Scholberg SNOwGLoBES SNOLAB Grand Opening

  18. Pb nuclear physics High Z increases νeCC cross-sections relative to νe CC and NC due to Coulomb enhancement. CC and NC cross-sections are the largest of any reasonable material though thresholds are high ( CC-1n: 10.3 MeV, CC-2n: 18.4 MeV, NC-1n: 7.4 MeV, NC-2n: 14.1 MeV) Neutron excess (N > Z) Pauli blocks further suppressing the νe CC channel Results in flavour sensitivity complimentary to water Cerenkov and liquid scintillator detectors Other Advantages High Coulomb barrier  no (α, n) Low neutron absorption cross-section (one of the lowest in the table of the isotopes)  a good medium for moderating neutrons down to epithermal energies SNOLAB Grand Opening

  19. Flavour Sensitivities Liquid Scintillator Water Cherenkov NC νe CC NC νe CC ES νe CC νe CC Lead Liquid Argon (needs updating for large θ13) NC NC Iron SNOLAB Grand Opening

  20. Goals and Philosophy Goals • to provide νe (dominantly) and νx sensitivity to the SN detection community as soon as possible • to build a long-term, high live-time dedicated supernova detector • to explore the feasibility of scaling a lead-based detector to kt mass Philosophy • Achieve these goals by keeping HALO • Very low cost • Low maintenance • Low impact in terms of lab resources SNOLAB Grand Opening

  21. Design Overview • Lead Array (79 +/- 1% tonnes) • 32 three meter long columns of annular Lead blocks • 864 blocks total at 91kg each • Neutron detectors • 4 three meter long 3He detectors per column • 384 meters total length • 200 grams total 3He • Moderator • HDPE tubing • Shielding (12 tonnes) • 30 cm of water (5 sides) • ~18 cm average PE (bottom) SNOLAB Grand Opening

  22. CC: NC: Supernova signal In 79 tonnes of lead for a SN @ 10kpc†, • Assuming FD distribution with T=8 MeV for μ’s, τ’s. • 68 neutrons through e charged current channels • 30 single neutrons • 19 double neutrons (38 total) • 20 neutrons through νx neutral current channels • 8 single neutrons • 6 double neutrons (12 total) ~ 88 neutrons liberated; ie. ~1.1 n/tonne of Pb †- cross-sections from Engel, McLaughlin, Volpe, Phys. Rev. D 67, 013005 (2003) For HALO neutron detection efficiencies of 50% have been obtained in MC studies optimizing the detector geometry, the mass and location of neutron moderator, and enveloping the detector in a neutron reflector. SNOLAB Grand Opening

  23. HALO – March 2010 SNOLAB Grand Opening

  24. 3He neutron detectors Cutting apart welded sections from SNO installation and adding new endcaps. Six months of careful work! SNOLAB Grand Opening

  25. Status today 4/5th of shielding in place Cabling complete Readout complete HV on all channels and full detector being read-out since May 8th 2012. Upgrade of electronics pending Calibration / characterization started Plans shielding compete in June Participate in SNEWS by year end SNOLAB Grand Opening

  26. Signal and Backgrounds SNOLAB Grand Opening

  27. Performance Preamp / ADC pairing with best resolution (left) Preamp / ADC pairing with best γ/ n separation (right) SNOLAB Grand Opening

  28. Backgrounds and SNEWS A trigger condition of 6 neutrons in a 2 second window gives sensitivity out to ~20 kpc (for T=8 MeV for ”μ” ) Fast and thermal neutrons in SNOLAB occur at 4000 and 4100 neutrons/m2/day respectively A background event rate of 150 mHz from all sources will randomly satisfy the trigger condition once per month. We take this as the target false alert rate for SNEWS (presently at 170 mHz with partial shielding) Bulk αcontamination in the CVD nickel tubes gives a negligible 22 +/- 1 events in neutron window per day for the whole array (α, n) reactions not simulated in the HALO GEANT MC but the threshold in Pb is 15.2 MeV Cosmic ray muon rate is < 2 per day. Rate of spallation events not yet calculated. SNOLAB Grand Opening

  29. Physics with HALO K. Scholberg March 2012 APS SNOLAB Grand Opening

  30. Physics with HALO K. Scholberg March 2012 APS SNOLAB Grand Opening

  31. Summary HALO is effectively complete and continuous operation of the full detector began on May 8th providing sensitivity to the νe and νxcomponents of a supernova HALO will participate in SNEWS once the behaviour of the detector is well understood Experience gained will feed into the design of a next generation detector taking advantage of the scalability of the lead plus neutron detector technology SNOLAB Grand Opening

  32. The HALO Collaboration • With assistance this past year from: • Kurt Nicholson – Guelph U. • Axel Boeltzig – TU Dresden • Ben Bellis, Leigh Schaefer, Zander Moss – Duke U. • Victor Buza, Olivia Zigler – U. Minnesota Duluth • Brian Redden – Armstrong Atlantic State U • Thomas Corona – U. North Carolina • Andre-Philippe Olds – Laurentian U. SNOLAB Grand Opening

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