Core-collapse Supernovae, Neutrinos, and the OMNIS project.

1
Core-collapse Supernovae, Neutrinos, and the
OMNIS project.

• Alex Murphy

www.hep.man.ac.uk/omnis/
www.physics.ohio-state.edu/OMNIS
2
The 7 stages of Core Collapse...
For a 10M? star Stage Temp (K) Ashes
Duration H burning 2x107 He few x 106
yrs He 2x108 C, O few x 104 yrs C
8x108 Ne, O 600 yrs Ne 1.4 x109 O,
Mg 1 yr.. O 2x109 Si, S 6 mo.. Si
3.5x109 Fe, Ni 1 day Collapse 40 x 109
90n few ms 10p Ejecta (some of
surface layers, rich in heavy elements)
H
He
C
Ne
O
Si
Fe core
Not to scale!
3
Inside a Supernova
Extreme temp photodissociates nuclei back to
protons, neutrons and alphas.
gt8 M? evolves 107 yr
3000 km
3x107 km
Neutronisation pe- ? nne
Huge thermal emission of neutrinos 5-10 seconds
n
n
n
n
n
n
Dense core
n
.
.
10 km
M
M
100 km
n
n
n
n
ee- ? gg gg ? nx nx (all flavours
equally)
r few x rnuclear
4
SN1987A
Anglo Australian Observatory

• Progenitor Sanduleak -69202,
• LMC about 50 kpc away.
• Remnant neutron star unseen
• maybe it went to a black hole?
• Neutrinos preceded light by
• 2 hours

• 20 events seen in IMB, Kamiokande
• First (and only) extra-solar neutrinos
• Water detectors, therefore almost certainly
  these were ne type
• nep ? ne

5
Supernovae Facts and Figures

• Energy release 3x1046 J (the gravitational
  binding energy of the core), in about 10 seconds
• Equivalent to 1000 times the energy emitted by
  the Sun in its entire lifetime.
• Energy density of the core is equivalent to 1MT
  TNT per cubic micron.
• 99 of energy released is in the form of
  neutrinos
• 1 is in the KE of the exploding matter
• 0.01 is in light and thats enough to make it
  as bright as an entire galaxy.
• Probably site of the r-process.

¼ MT test (Dominic Truckee, 1962)
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Importance of Neutrinos in Core Collapse

• They facilitate the explosion
• The prompt explosion stalls due to photo-nuclear
  dissociation
• Tremendous density - Core is opaque to neutrinos!
  Coupling of energetic neutrinos with core
  material ? Delayed explosion.
• Flux, energy, time profile of neutrinos provide
  detail of explosion mechanism
• Energy transport is dominated by neutrinos
• Less trapped than any other radiation
• Cooling via neutrinos (evidenced by 99
  luminosity)
• The last interaction of the neutrinos will have
  been with the collapsing/radiating core
• Allows us to look directly at the core of a
  collapsing massive star!
• Caveat! NO self consistent core collapse computer
  simulations have yet been successful
• May REQUIRE neutrino oscillations, or maybe
  convection/rotation/strong magnetic fields

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Detecting SN Neutrinos

• Cross section Weak coupling constants are small
  ? s10-42 cm2
• 1015 times smaller that traditional nuclear
  physics (e.g. mb)
• Energies thermal, weighted by number of ways
  to interact before decoupling (G. Raffelts talk
  yesterday for more details)
• More n than p ? More nen ? pe- than nep ?
  ne
• CC reactions (changes n?p) easier that NC
  (elastic scattering)
• Some recent work suggests neutrino Bremsstrahlung
  may pinch high and low ends of spectrum. Such
  an observation would tell us about the EOS of
  dense matter
• ? Neutrinospheres at different radii

ltE(ne)gt 11 MeV ltE(ne)gt 16 MeV ltE(nx)gt 25
MeV
Measurement of energies primary physics goal
? EOS, neutrino transport
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A New Detection Strategy
Utilize CC NC reactions from hi-z materials
with low n-threshold. Use the higher energies of
m and t-neutrinos to enhance their yields
flavour filter
Results in 2 observables 1 neutron emission from
Pb 2 neutron emission from Pb
Strong dependence of neutron yield on n
temperature ? Sensitivity to oscillations
Dependence on n temperature different for 1n and
2n channels ? Sensitivity to shape of n energy
spectrum
The Observatory for Multiflavor NeutrInos from
Supernovae
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Neutron Detection

• Require
• Large
• Efficient
• Provide adequate discrimination against
  background
• Fast timing
• CHEAP
• Gadolinium loaded scintillator (liquid of
  plastic)
• Fast neutron enters
• High H content results in rapid energy loss.
  Prompt pulse
• After thermalisation (30ms) capture on Gd
  release of several g-rays (total 8 MeV). Delayed
  pulse
• Allows two level trigger
• Singles while flux high
• Double Pulse when flux low

Prompt pulse
Energy deposited
400
200
0
Time (ns)
Delayed pulse
Energy deposited
50
100
0
Time (ms)
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So how to build OMNIS

• Underground to reduce cosmic ray rate
• Need large blocks of lead interleaved with
  scintillator planes

Loaded scintillator (liquid or plastic)
Lead
PF Smith Astroparticle Physics 8 (1997)
27 Astroparticle Physics 16 (2001) 75 JJ
Zach, AStJ Murphy, RN Boyd, NIMS, 2001,
accepted
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Lead Perchlorate
2.8m

• Pb(Cl2O4)2
• S. Elliott PRC 62 (2001)
• Diluted 20 (w/w) with H2O
• Transparent ? Cêrenkov light
• Bulk attenuation length gt4m
• Neutron capture time 100ms
• ? 8.6 MeV in gs
• recoil electrons
• Cêrenkov flash
• Interesting chemical properties
• CC ne events have well defined Cêrenkov cone ?
  energy spectrum

½ kT module
PMTs
8 kpc, ½ kT ne ne nx
No osc 17 23 140
nm?ne 570 23 110
3000 5 pmts
Includes reactions on H2O
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Neutrino Physics Potential

• Presence of neutrino mass
• s t e t c h e s arrival time
• profile. Rise of leading edge is probably best
• measure of mass Beacom, et al PRL 85, 3568
• (2000) PRD 63, 073011 (2001).
• Direct way to measure mass (not inferred from
  oscillations)
• ne is light (lt1eV/c2) confirmed by b-spectra
  endpoint
• Massive neutrino ? travels slower. Over 10 kpc, a
  typical energy mass 50 eV/c2 neutrino would
  arrive 2 seconds later (after traveling 33,000
  years!)
• Including statistics and experimental effects, we
  expect OMNIS sensitivity to be 10 eV/c2.
• Definitive mass range for hot dark matter
  candidate.

Dt1.6 R/8kpc m(nt)/50eV2 25MeV/E(nt)2
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OMNIS and Oscillations
Simulation Standard SN _at_ 8kpc. Calculate
number of 1n and 2n events detected in lead.
Simulation assumes sin22q,Dm2 ?
P(nm?ne)0.5 What combinations of range, nm
temperature, oscillation scenario and
probability of oscillation is this compatible
with? Caveat! Assumes shape of energy spectra
known, but if solution to SnP is LMA or LOW MSW
then Pb(Cl2O4)2 gives us that for nm ! Which
dominate event yields
P(nm? ne)
P(ne? ne)
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Neutrino Mixing Parameter space
4
2
Extreme long base line gives sensitivity to very
small mass differences Extreme nuclear density
in a supernova gives sensitivity to very small
mixing angles (under the MSW effect)
0
-2
-4
-6
Log(Dm2)
-8
-10
-12
-14
-16
-18
-10 9 8 7 6 5 4
3 2 1 0
Log(sin2(2q))
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Black hole scenarios

• Observational evidence of BHs association with
  SNRs currently weak
• Sudden (!) termination
• Black hole is predicted to form at centre, and
  expand outwards
• BH will swallow-up m- and t-neutrino-spheres
  first, then electron neutrino-sphere
• Diff in cutoff due to this is predicted to be
  1-5 ms
• Could chart out neutrino-spheres?!

How the yield in the lead-slab modules would be
affected by a cutoff in nx 2ms earlier than a
complete shut off at 0.2 second. Simulation is
for Betelgeuse.
Allows for incredible timing sensitivity,
including a mass measurement at the few eV level
(Beacom, et al PRL 85, 3568 (2000) PRD 63,
073011 (2001))
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OMNIS in the UK and US.

• UK and US groups are highly interested in
  developing an OMNIS project
• Differences, primarily in the funding mechanisms,
  require different approaches in the US and UK
• UK
• Location Boulby. Institute for Underground
  Science
• UKDMC (central institutions RAL, Sheffield,
  Imperial). Manchester also a collaborator for
  OMNIS.
• Edinburgh just joined!
• UKDMC Received JIF award. Facilities being
  upgraded.
• Current philosophy is for a parasitic OMNIS,
  i.e. combining with Gd nuclear excitation in
  SIREN, or muon veto shield for DRIFT, ZEPLIN
• Full scale OMNIS could then be built by extending
  in a modular fashion
• Neutrino Factory Far Detector

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OMNIS in the UK and US.

• US
• Location WIPP or Homestake NUSL
• Ohio State, UCLA, ANL, UTD, UNM
• Dedicated OMNIS detector. Larger scale.
• RD funding at OSU. West coast groups applying
  for more
• OSU test module
• OMNISita
• Argonne NL Pb2(ClO4)2 test detector
• UCLA lithium loaded fibers RD

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ANL Lead Perchlorate Test Module

• Elliots tests did not test with neutron (or g)
  sources
• Simple bath-tub design
• Diffuse reflective inner lining (white Teflon)
• No Cêrenkov rings from fast es
• Measure
• bulk attenuation lengths
• Spectral response
• Efficiency
• Longevity
• Purification techniques

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OMNISita

• A technology test bed for the OMNIS project.

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Galactic supernova event rate

• The historical record contains
• 7 (8?) SNe in the last 1000 years.
• 5 are core-collapse
• All within 8-12 of Galaxy
• Suggests real waiting time is 15-30 years.
  Comparable with some high energy experiments
• Suggests there are many dark supernovae (but we
  would still see then in neutrinos!)
• 1006 Apr 30 SNR 1006 Arabic also Chinese,
  Japanese, European
• 1054 Jul 4 Crab Chinese, North American (?)
  also Arab, Japan
• 1181 Cas -1 3C 58 Chinese and Japanese
• 1203 ? Sco 0
• 1230 ? Aql
• 1572 Nov 6 Tycho Brahe's SN
• 1604 Oct 9 Johannes Keplers SN
• 1667? Cas A Flamsteed ? not seen ?

r5 kpc
Somewhat more sophisticated analysis in progress
by P.F. Smith
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Candidate supernovae?

• No supernova has ever been predicted, but there
  are several candidates
• Betelgeuse red supergiant,
• 20M?. 425 light years close.
• Sher 25 - Very similar to SN1987As
• progenitor. Blue super giant, distance
• 6 kpc, out burst creating nebula
• 6600 yrs ago.
• Eta Carinae originally 150M?,
• now 50-100 M?. Created nebula in
• 1840. 3kpc distant. Recently
• doubled in brightness maybe a
• hypernova candidate, the possible
• cause of gamma-ray bursters

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Summary
HST

• Core Collapse Supernovae are immensely important
  in astronomy, galactic evolution,
  nucleosynthesis,
• A new method of observing them, that of neutrino
  astronomy, offers a way of seeing the core
  collapse process, allowing tests of many areas of
  physics/astrophysics
• Neutrino oscillations as observed at S-K are the
  first hints of physics beyond the standard model.
  SN neutrinos offer a new, direct, method to
  observe effects of neutrino mass and
  oscillations.
• Given the rate of Galactic SN, its vitally
• important to maximise an event.
• Hence a statistically significant
• number of m- and t-neutrinos
• must be observed in detail.
• OMNIS offers the most cost
• efficient method of doing so.
• Keep watching the skies!

ROSAT
Chandra