Supernova Watches and HALO Workshop May 14-16, 2012 Clarence J. Virtue
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 2
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-ν scattering collective effects and MSW oscillations 3
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 SNOLAB neutrino transport (neutrino Grand Opening 4
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 5
o edit Master text styles d level hird level Fourth level Fifth level SNEWS current configuration Super-Kamiokande LVD Bologna SSL SSL Redundant Secure Coincidence Servers SSL 10 s window (UT time) SSL 2-fold coincidence Alert to the Astronomical Community PGP signed e-mail Borexino IceCube 6
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 7
Super-Kamiokande 50 kton water Cerenkov For 10 kpc SN 7000 IBD ES NC 410 NC on 16O 300 ES 4 pointing νe CC 8
Large Volume Detector (LVD) 1000 tonne liquid scintillator with PMTs and limited streamer tubes 5 MeV threshold M. Selvi, arxiv:hep-ex/0608061v1 9
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) Astronomy and Astrophysics 535 (2011) A109 10
Borexino Liquid scintillator (PC) 100 ton fiducial 300 ton viewed (SN) For 10 kpc SN νe CC ES CC (IBD) 79 CC (12C) 5 L. Cadonati et al., Astropart.Phys.16:361-372,2002 NC (12C) 23 ES 5 νe CC NC Includes ~100 νx + p 11
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 12
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 13 consideration
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 SNOLAB Grand Opening Have large neutrino cross-sections 14
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 15
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 crosssections, 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 16
Comparative ν-nuclear cross-sections Kate Scholberg SNOwGLoBES 17
Pb nuclear physics High Z increases νe CC 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 May 14, 2012 complimentary to watersnolab Cerenkov and Grand Opening liquid scintillator detectors 18
Flavour Sensitivities Liquid Scintillator Water Cherenkov νe CC NC νe CC NC ES νe CC NC νe CC Lead Liquid Argon (needs updating for large θ13) Iron NC 19
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 20
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 21
Supernova signal CC: In 79 tonnes of lead for a SN @ 10kpc, NC: 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) 22
HALO March 2010 23
3He neutron detectors Cutting apart welded sections from SNO installation and adding new endcaps. Six months of careful work! 24
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 25
Signal and Backgrounds 26
Performance Preamp / ADC pairing with best resolution (left) Preamp / ADC pairing with best γ / n separation (right) 27
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) 28 Bulk α contamination in the CVD nickel tubes gives a
Physics with HALO K. Scholberg March 2012 APS 29
Physics with HALO K. Scholberg March 2012 APS 30
Summary HALO is effectively complete and continuous operation of the full detector began on May 8th providing sensitivity to the νe and νx components 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 31 technology
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. 32