Supernova Watches and HALO

Supernova Watches and HALO

SNOLAB Grand Opening WorkshopMay 14-16, 2012

Clarence J. Virtue

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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-ν scattering collective effects and MSW oscillations

SNOLAB Grand OpeningMay 14, 2012

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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


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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.


5SNOLAB Grand Opening

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

May 14, 2012


SNEWS – current configuration

May 14, 2012

Alert to theAstronomicalCommunity

PGP signed e-mail

Bologna

RedundantSecure

CoincidenceServers

10 s window(UT time)

2-fold coincidence

SSL

SSL

SSL

SSL

Super-Kamiokande LVD

IceCubeBorexino

7SNOLAB Grand OpeningMay 14, 2012

PGP-signed e-mail

To amateur astronomersVia Sky & Telescope

Go to skyandtelscope.comto “subscribe to astroalert”

> 2000 subscribers

To neutrino physicistsand astronomers

Subscribe to receive analert 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


Super-Kamiokande 50 kton water

Cerenkov For 10 kpc SN

7000 IBD 410 NC on 16O 300 ES 4◦ pointing

May 14, 2012

νe CC

NCES


Large Volume Detector (LVD)

1000 tonne liquid scintillator with PMTs and limited streamer tubes

5 MeV threshold

May 14, 2012

M. Selvi, arXiv:hep-ex/0608061v1


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)

May 14, 2012

Astronomy and Astrophysics 535 (2011) A109


Borexino 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

May 14, 2012

NC

νe CC ES

νe CCL. Cadonati et al., Astropart.Phys.16:361-372,2002

Includes~100νx + p


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+May 14, 2012

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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


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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


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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


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HALO - a Helium and Lead Observatory

“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

A “SN detector of opportunity” / An evolution of LAND – the Lead Astronomical Neutrino Detector, C.K. Hargrove et al., Astropart. Phys. 5 183, 1996.


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Comparative ν-nuclear cross-sections

Kate ScholbergSNOwGLoBES


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 complimentary to water

Cerenkov and liquid scintillator detectorsOther 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

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Pb nuclear physics


NC

νe CC

νe CC

ES

WaterCherenkov

NC

LiquidScintillator

LiquidArgon(needs updatingfor large θ13)

Lead

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NCNC

νe CC

νe CC

Iron

Flavour Sensitivities


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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

Goals and Philosophy


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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)


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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.

CC:

NC:


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HALO – March 2010


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Cutting apart welded sections from SNO installation and adding new endcaps. Six months of careful work!

3He neutron detectors


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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

Status today


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Signal and Backgrounds


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Preamp / ADC pairing with best resolution (left) Preamp / ADC pairing with best γ / n separation (right)

Performance


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 α contamination 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.

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Backgrounds and SNEWS


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Physics with HALO

K. ScholbergMarch 2012 APS


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Physics with HALO

K. ScholbergMarch 2012 APS


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 technology

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Summary


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.

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The HALO Collaboration


Supernova Watches and HALO

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