The HALO-2 Supernova Detector

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1 The HALO-2 Supernova Detector Vucano Workshop 2016 FRONTIER OBJECTS IN ASTROPHYSICS AND PARTICLE PHYSICS Carence J. Virtue

2 Outine Science Motivation Supernovae in genera Lead-based detectors in particuar Supernova Neutrinos Lead as a Supernova Neutrino Target Event Rates / kt of Lead The HALO Detector HALO-2 at LNGS Status of HALO-2 May 24, 2016 Vucano Workshop

3 Science Motivation - supernovae in genera the potentia to: BUT earn more about supernova dynamics earn more about properties of neutrinos maximize the science opportunity from the next gaactic supernova by prompty aerting the astronomica community (SN Watch / SNEWS) Whie the probabiity of a gaactic SN in a ifetime are good there are issues: most supernova-sensitive detectors have other primary objectives necessitating down-time; extensive caibration; reconfiguration; and end of ife Whie SN emit neutrinos and anti-neutrinos of a favours in roughy equa numbers, and vauabe information is present in a channes, Water Cherenkov and iquid scintiator detectors have dominant ν e sensitivity future (mega-expensive) detectors can save costs by increasing their energy threshod at the expense of their supernova capabiities a risk May 24, 2016 Vucano Workshop

4 Science Motivation - Pb-based detectors in particuar So, with these issues in mind, it seems there s a niche for a ow cost ow maintenance robust ong ifetime dedicated supernova detector with compementary sensitivity Lead, as a supernova neutrino target, has a dominant ν e sensitivity and some other advantages HALO is 79 tonnes of ead instrumented with 3 He neutron detectors running since May 2012 at SNOLAB HALO-2 is a kio-tonne concept for LNGS being deveoped due to the avaiabiity of ~1 kiotonne of Pb from the decommissioning of OPERA May 24, 2016 Vucano Workshop

5 Supernova Neutrinos First Order Expectations Approximate equipartition of neutrino fuxes Severa characteristic timescaes for the phases of the exposion (coapse, burst, accretion, cooing) Time-evoving ν e, ν e, ν x uminosities refecting aspects of SN dynamics Presence of neutronization puse Hardening of spectra through accretion phase then cooing Fermi-Dirac therma energy distributions characterized by a temperature, T ν, and pinching parameter, η ν Hierarchy and time-evoution of average energies at the neutrinosphere T(ν x ) > T(ν e ) > T(ν e ) ν-ν scattering coective effects and MSW osciations further imprint physics on the F-D distributions K. Schoberg, Annu. Rev. Nuc. Part. Sci : May 24, 2016 Vucano Workshop 2016 GKVM (Gava-Kneer-Vope-McLaughin) mode Phys. Rev. Lett. 103: (2009) 5

6 What is to be Learned? Astrophysics Exposion mechanism Accretion process Back hoe formation (cutoff) Presence of Spherica accretion shock instabiities (3D effect) Proto-neutron star EOS Microphysics and neutrino transport (neutrino temperatures and pinch parameters) Nuceosynthesis of heavy eements Partice Physics Norma or Inverted neutrino mass hierarchy Presence of axions, exotic physics, or extra arge dimensions (cooing rate) Etc. May 24, 2016 Vucano Workshop

7 Lead as a Supernova Neutrino Target CC and NC cross-sections are the argest of any reasonabe materia though threshods are high Neutron excess (N > Z) Paui bocks n High Z increases ν e CC cross-sections reative to ν e CC and NC due to Couomb enhancement further suppressing the ν e CC channe Resuts in mainy ν e sensitivity - compementary to water Cerenkov and iquid scintiator detectors de-excitation of nuceus foowing CC or NC interactions is by 1n or 2n emission Other Advantages High Couomb barrier à no (α, n) Low neutron absorption cross-section (one of the owest in the tabe of the isotopes) à a good medium for moderating neutrons down to epitherma energies May 24, 2016 Vucano Workshop 2016 Limitations no directionaity no direct measure of neutrino energy 7

8 Comparative ν-nucear Cross-sections CC: NC: Threshods CC 1n 10.7 MeV CC 2n 18.6 MeV NC 1n 7.4 MeV NC 2n 14.4 MeV K. Schoberg, Annu. Rev. Nuc. Part. Sci : May 24, 2016 Vucano Workshop n cross-sections don t appear on pot but provide a hande on energy distribution 8

9 Favour Sensitivities for Different Technoogies ES ν e CC ν e CC ES Water Cherenkov ν e CC NC Liquid Scintiator ν e CC NC NC Liquid Argon Lead Iron Generay functions of neutrino temperatures and detector energy threshods, aso needs updating for arge θ 13 May 24, 2016 Vucano Workshop 2016 NC 9

10 Event Rates / kt of Lead (100% capture efficiency) from Väänänen and Vope, JCAP 1110 (2011) 019. Earier work, in 1kt of ead for a 10kpc, ú Assuming FD distribution with T=8 MeV for ν x. ú ú 860 neutrons through ν e charged current channes 380 singe neutrons 240 doube neutrons (480 tota) 250 neutrons through ν x neutra current channes 100 singe neutrons 75 doube neutrons (150 tota) May 24, 2016 Vucano Workshop 2016 cross-sections from Enge, McLaughin, Vope, Phys. Rev. D 67, (2003) (more conservative neutrino temperatures reduce these event numbers by a factor of ~2) 10

11 Sensitivity to neutrino energy Distinct 1n and 2n emission threshods in ead provide the possibiity to measure neutrino temperatures and pinching parameters. N 1n and N 2n per kt from Väänänen and Vope, JCAP 1110 (2011) 019 May 24, 2016 Vucano Workshop 2016 March 2012 APS, K. Schoberg. 11

12 HALO - a Heium and Lead Observatory A SN detector of opportunity / An evoution of LAND the Lead Astronomica Neutrino Detector, C.K. Hargrove et a., Astropart. Phys , Heium because of the avaiabiity of the 3 He neutron detectors from the fina phase of SNO + Lead because of high ν-pb crosssections, ow n-capture cross-sections, compementary sensitivity to water Cerenkov and iquid scintiator SN detectors HALO is using ead bocks from a decommissioned cosmic ray monitoring station May 24, 2016 Vucano Workshop

13 HALO at SNOLAB SNOLAB 6800 campus 6000 mwe depth 0.27 µ/m 2 /day 8000 n/m 2 /day HALO is a dedicated ead-based supernova detector May 24, 2016 Vucano Workshop

14 The HALO Coaboration Funded by: hao.snoab.ca May 24, 2016 Vucano Workshop

15 Neutron detection in HALO Re-using SNO s NCD 3 He proportiona counters 5 cm diameter x 3m and 2.5m in ength, utra-pure CVD Ni tube (600 micron wa thickness) 2.5 atm (85% 3 He, 15% CF 4, by pressure) Four detectors with HDPE moderator tubes in each of 32 coumns of ead rings 128 counters (~370 m) paired for 64 channes of readout an additiona ~200m of 3 He proportiona counters are aso avaiabe May 24, 2016 Vucano Workshop

16 Neutron detection in HALO Neutron detection via 3 He + n à p + t kev 764 kev FE peak pus LE tai due to wa effects measured neutron capture efficiency ~30% voume averaged; 47% centra **new** α s present at rate of ~20 events per day in ROI for the entire array Compton and beta events at ow energies Background n in room at eve of 4000 fast pus 4000 therma per m 2 per day. Cosmic muons < 2 per day Intrinsic tritium rate (18.6 kev endpoint) above 12 kev threshod ~10 Hz / detector but running at threshod of ~50 kev for tota rate of 5 Hz Current neutron rate in HALO is Hz (~1300 / day) May 24, 2016 Vucano Workshop

17 Status today Fu detector being read-out since May 8 th Daiy shift-taking since Juy 27 th Burst trigger impemented and connected to SNEWS since October 8, 2015 Fu caibration done with and without front shieding wa Apri 2016 work continues on redundant systems and monitoring toos May 24, 2016 Vucano Workshop

18 HALO-2 at LNGS the decommissioning of OPERA has made avaiabe ~ 1 kiotonne of Pb for new ideas concepts for HALO-2 are preiminary have ~500 m of 3 He counters (very quiet) pus 120 m of 10 BF 3 counters ikey more is desirabe and/or an aternative technoogy (coud be ess quiet if not used in trigger) cosmic muon rate ~x100 higher in LNGS veto might be desirabe, not absoutey necessary modest (water) shieding shoud reduce ambient neutrons to negigibe eve, as we as isoate and define the target voume May 24, 2016 Vucano Workshop

19 HALO-2 at LNGS Starting Point distribute a avaiabe 3 He detectors in a 4m x 4m x 5.5m voume of Pb simuate MeV neutrons in Pb find 1/4 capture on 3 He; 1/3+ capture on Pb; 1/3+ escape voume reca neutron capture efficiency in HALO is ~30%; so gain factor of 12 in Pb mass; ose some efficiency May 24, 2016 Vucano Workshop

20 HALO-2 at LNGS Next. add water ayer as refector for HALO (smaer voume; arger surface/ voume ratio) this had significant benefits for HALO-2 capture on Pb increases; detection on 3He ~unchanged needed as part of the design, in any case, to isoate from environmenta neutrons and to define target voume May 24, 2016 Vucano Workshop

21 HALO-2 at LNGS not satisfied with 25% neutron capture efficiency HALO achieved 47% in centra voume so with more favourabe surface/voume ratio HALO-2 shoud do better increasing density of neutron detection wi increase capture efficiency / scientific reach of detector AND costs more 3 He detectors not feasibe with greaty increased cost of 3He; ooking towards BF 3 and Gd-cad pastic scintiator exporation with detaied simuations in progress backgrounds in 3 He counters are ower than required for setting a ow threshod SN trigger à ikey design feature woud be a centra voume of detector instrumented with 3 He and surrounding voume with aternative technoogy to be expored May 24, 2016 Vucano Workshop

22 HALO-2 at LNGS Insights from MC studies scaing with detector densities and gas pressures not quite intuitive choice of moderator (pastic, graphite, water, heavy water) has ony weak effects on capture efficiency geometry matters moderating cose to neutron detectors is better and aows an increase in capture efficiency over the naïve moe.barn fraction of the detectors fraction of neutrons escaping Pb voume is important and not greaty affected by the geometrica detais interior to the voume finding a way to detect the escaping neutrons is ikey the argest win in detection efficiency; additiona detectors an expensive option; studying Gd ayer and gamma catcher options May 24, 2016 Vucano Workshop

23 HALO-2 Status sti in the fun conceptua stage ~unconstrained but conscious that increasing costs diminish ikeihood of reaization expressed an interest in the OPERA ead to the LNGS Scientific Committee in Apri 2015 have formed a working group with bi-weeky meetings to discuss simuations 6 HALO members 9 new Itaians 4 new Canadians 4 new Americans made a submission to the LNGS 10 year Pan for UG Resources exercise in February 2016 panning to grow and transition working group to a coaboration and produce an LOI and technica design study on a 1 year timescae May 24, 2016 Vucano Workshop

24 Interested? To hep in the deveopment of the LOI and TDS pease contact Carence Virtue Thanks for your attention! May 24, 2016 Vucano Workshop