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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) Ashes Duration H burning 2x10 7 He few x 10 6 yrs

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core collapse supernovae neutrinos and the omnis project

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

Alex Murphy

www.hep.man.ac.uk/omnis/

www.physics.ohio-state.edu/OMNIS

slide2

The 7 stages of Core Collapse...

For a ~10M star…

Stage Temp (K) AshesDuration

H burning 2x107Hefew x 106 yrs

He 2x108C, Ofew x 104 yrs

C 8x108Ne, O~600 yrs

Ne 1.4 x109O, Mg~1 yr..

O 2x109Si, S~6 mo..

Si 3.5x109Fe, Ni~1 day

Collapse ~40 x 109 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!

CERN

inside a supernova
Inside a Supernova

Extreme temp: photodissociates nuclei back to protons, neutrons and alphas.

>8 M evolves ~107 yr

3000 km

3x107 km

Neutronisation: p+e-  n+ne

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

e++e- g+g ; g+g nx + nx(all flavours equally)

r ~ few x rnuclear

CERN

sn1987a
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 netype:

ne+p  n+e+

CERN

supernovae facts and figures
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 that’s enough to make it as bright as an entire galaxy.
    • Probably site of the r-process.

¼ MT test (Dominic Truckee, 1962)

CERN

importance of neutrinos in core collapse
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

CERN

detecting sn neutrinos
Detecting SN Neutrinos…
  • Cross section: Weak coupling constants are small  s~10-42 cm2
    • ~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)
    • 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

CERN

slide8

n’s

Q [ 208Pb(n,n’2n)206Pb] = -14.1 MeV

n’s

Q [ 208Pb(n,n’n)207Pb] = -7.4 MeV

n’s

Q [ 208Pb(ne,e+n)207Bi] = -9.8 MeV

208Pb

207Bi

Reaction thresholds

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

CERN

neutron detection
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

0

200

400

Time (ns)

Delayed pulse

Energy deposited

0

50

100

Time (ms)

CERN

so how to build omnis

n

g

n

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

CERN

lead perchlorate
Lead Perchlorate

2.8m

½ kT module

  • Pb(Cl2O4)2
    • S. Elliott PRC 62 (2001)
    • Diluted 20% (w/w) with H2O
    • 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

PMTs

~3000 5” pmts

Includes reactions on H2O

CERN

neutrino physics potential
Neutrino Physics Potential

Dt=1.6 [R/8kpc] [m(nt)/50eV]2 [25MeV/E(nt)]2

  • Presence of neutrino mass

s t e t c h e s arrival time

profile. Rise of leading edge is probably best

measure of massBeacom, et al PRL 85, 3568

(2000); PRD 63, 073011 (2001).

  • Direct way to measure mass (not inferred from oscillations)
    • ne is light (<1eV/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.

CERN

slide13

OMNIS and Oscillations

Simulation: ‘Standard’ SN @ 8kpc. Calculate number of 1n and 2n eventsdetectedin 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)

CERN

slide14

NOMAD

MINOS

LSND

OMNIS-MSW

Super-K MSW

GALLEX MSW

OMNIS-Vacuum

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))

CERN

slide15

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))

CERN

omnis in the uk and us
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

CERN

omnis in the uk and us1
OMNIS in the UK and US.
  • US
    • 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

CERN

anl lead perchlorate test module
ANL Lead Perchlorate Test Module
  • Elliot’s tests did not test with neutron (or g) sources
  • Simple bath-tub design
    • Diffuse reflective inner lining (white Teflon)
    • No Cêrenkov rings from fast e’s
  • Measure
    • bulk attenuation lengths
    • Spectral response
    • Efficiency
    • Longevity
    • Purification techniques

CERN

omnisita
OMNISita
  • A technology test bed for the OMNIS project.

CERN

galactic supernova event rate
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 Kepler’s SN’
  • 1667? Cas A Flamsteed ? not seen ?

r=5 kpc

Somewhat more sophisticated analysis in progress by P.F. Smith

CERN

slide21

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 SN1987A’s
    • 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

CERN

summary

HST

Summary
  • 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!

ROSAT

Chandra

CERN

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