Transcript Core-collapse Supernovae, Neutrinos, and the OMNIS project. Alex Murphy www.hep.man.ac.uk/omnis/

Core-collapse Supernovae,
Neutrinos, and the OMNIS project.
Alex Murphy
www.hep.man.ac.uk/omnis/
www.physics.ohio-state.edu/OMNIS
The 7 stages of Core Collapse...
For a ~10M star…
Stage
Temp (K)
H burning 2x107
He
2x108
C
8x108
Ne
1.4 x109
O
2x109
Si
3.5x109
Collapse ~40 x 109
Ashes Duration
He
few x 106 yrs
C, O
few x 104 yrs
Ne, O ~600 yrs
O, Mg ~1 yr..
Si, S ~6 mo..
Fe, Ni ~1 day
90%n ~few ms
10%p
+Ejecta (some of surface
layers, rich in heavy elements)
H
He
C
Ne
O
Si
Fe core
Not to scale!
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Inside a Supernova
Extreme temp: photodissociates nuclei
back to protons, neutrons and alphas.
>8 M evolves ~107 yr
3000 km
3x107 km
Huge thermal
emission of
neutrinos
~5-10 seconds
Neutronisation: p+e-  n+ne
n
n
n
10 km
n
n*
n
n
.
M
n
100 km
Dense
core
n
n
.
M
n
e++e-  g+g ; g+g  nx + nx (all flavours equally)
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r ~ few x rnuclear
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SN1987A
Anglo Australian Observatory
 Progenitor: Sanduleak -69°202,
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:
ne+p  n+e+
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Supernovae: Facts and Figures
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Energy release ~3x1046 J (the
gravitational binding energy of the
core), in about 10 seconds
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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 that’s enough to
make it as bright as an entire galaxy.
¼ MT test (Dominic Truckee, 1962)
Probably site of the r-process.
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Importance of Neutrinos in Core Collapse
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They facilitate the explosion:
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Energy transport is dominated by neutrinos
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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
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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
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’
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May REQUIRE neutrino oscillations, or maybe
convection/rotation/strong magnetic fields
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Detecting SN Neutrinos…
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Cross section: Weak coupling constants are small  s~10-42 cm2
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~1015 times smaller that traditional nuclear physics (e.g. mb)
Energies: “thermal”, weighted by number of ways to interact
before decoupling (G. Raffelt’s talk yesterday for more details)
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More n than p  More ne+n  p+e- than ne+p  n+e+
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
<E(ne)> = 11 MeV
<E(ne)> = 16 MeV
<E(nx)> = 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 –
n’s
Q [ 208Pb(n,n’2n)206Pb] = -14.1 MeV
n’s
Q [ 208Pb(n,n’n)207Pb] = -7.4 MeV
‘flavour filter’
n’s
Results in 2 observables:
Q [ 208Pb(ne,e+n)207Bi] = -9.8 MeV
1 neutron emission from Pb
2 neutron emission from Pb
208Pb
207Bi
Reaction thresholds
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:
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CHEAP
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Gadolinium loaded scintillator
(liquid of plastic)
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0
Fast neutron enters
High H content results in rapid
energy loss. Prompt pulse
After thermalisation (~30ms)
capture on Gd; release of several grays (total 8 MeV). Delayed pulse
Allows two level trigger
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200
400
Time (ns)
Delayed pulse
0
‘Singles’ while flux high
‘Double Pulse’ when flux low
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Prompt pulse
Energy deposited
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Large
Efficient
Provide adequate discrimination
against background
Fast timing
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Energy deposited
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50
Time (ms)
100
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So – how to build OMNIS
n
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g
Underground
to reduce
cosmic ray rate
Need large
blocks of lead
interleaved
with scintillator
planes
n
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
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2.8m
Pb(Cl2O4)2
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S. Elliott PRC 62 (2001)
Diluted 20% (w/w) with H2O
½ kT module
Transparent  Cêrenkov light
Bulk attenuation length >4m
Neutron capture time ~100ms
  8.6 MeV in g’s
 recoil electrons
 Cêrenkov ‘flash’
‘Interesting’ chemical properties
CC ne events have well defined Cêrenkov
cone  energy spectrum
8 kpc, ½ kT
ne
ne
nx
No osc’
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23
140
nmne
570
23
110
~3000 5” pmts
Includes reactions on H2O
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Neutrino Physics Potential
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Presence of neutrino mass
Dt=1.6 [R/8kpc] [m(nt)/50eV]2 [25MeV/E(nt)]2
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).
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Direct way to measure mass (not inferred
from oscillations)
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ne is light (<1eV/c2); confirmed by bspectra 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.
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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
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P(ne ne)
Simulation: ‘Standard’ SN @
8kpc. Calculate number of 1n
and 2n events detected in
lead.
P(nm ne)
OMNIS and Oscillations
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Neutrino Mixing – Parameter space
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NOMAD
MINOS
2
Extreme long base
line gives sensitivity to
very small mass
differences
-2
LSND
OMNIS-MSW
GALLEX MSW
-6
-8
-10
-12
-14
OMNIS-Vacuum
-16
-18
-10
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Super-K MSW
-4
Log(Dm2)
Extreme nuclear
density in a
supernova gives
sensitivity to very
small mixing angles
(under the MSW
effect)
0
–9
–8
–7
–6
–4 –3
Log(sin2(2q))
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–5
–2
–1
0
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Black hole scenarios…
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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 neutrinosphere
Diff’ in cutoff due to this is
How the yield in the lead-slab modules would
predicted to be ~1-5 ms
be affected by a cutoff in nx 2ms earlier than
a complete shut off at 0.2 second. Simulation
Could chart out neutrinois for Betelgeuse.
spheres?!
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.
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UK and US groups are highly interested in
developing an OMNIS project
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Differences, primarily in the funding mechanisms,
require different approaches in the US and UK
UK
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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.
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US
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Location: WIPP or Homestake
NUSL
 Ohio State, UCLA, ANL, UTD,
UNM…
Dedicated OMNIS detector. Larger
scale.
R&D funding at OSU. West coast
groups applying for more
 OSU test module
 OMNISita
 Argonne NL Pb2(ClO4)2 test
detector
 UCLA lithium loaded fibers
R&D
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ANL Lead Perchlorate Test Module
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Elliot’s tests did not test with neutron (or g) sources
Simple bath-tub design
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Diffuse reflective inner lining (white Teflon)
No Cêrenkov rings from fast e’s
Measure
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bulk attenuation lengths
Spectral response
Efficiency
Longevity
Purification techniques
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OMNISita
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A technology test bed for the OMNIS project.
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Galactic supernova event rate
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The historical record contains
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7 (8?) SNe in the last 1000 years.
5 are core-collapse
All within ~8-12% of Galaxy
r=5 kpc
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 Kepler’s SN’
1667? Cas A Flamsteed ? not seen ?
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:
o Betelgeuse – red supergiant,
~20M. 425 light years close.
o Sher 25 - Very similar to SN1987A’s
progenitor. Blue super giant, distance
6 kpc, out burst creating nebula
6600 yrs ago.
o 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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HST
Summary
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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, it’s 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!
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ROSAT
Chandra
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