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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. 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.

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  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) 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

  3. 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

  4. 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

  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 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. OMNISita • A technology test bed for the OMNIS project. CERN

  20. 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

  21. 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

  22. 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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