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

Alex MurphyAlex Murphy

www.physics.ohio-state.edu/OMNISwww.hep.man.ac.uk/omnis/

17/1/2002 CERN 2

The 7 stages of Core Collapse...

For a ~10M star…

Stage Temp (K) Ashes DurationH burning 2x107 He few x 106 yrsHe 2x108 C, O few x 104 yrsC 8x108 Ne, O ~600 yrsNe 1.4 x109 O, Mg ~1 yr..O 2x109 Si, S ~6 mo..Si 3.5x109 Fe, Ni ~1 dayCollapse ~40 x 109 90%n ~few ms

10%p +Ejecta (some of surface

layers, rich in heavy elements)

Fe core

SiO

NeCHeH

Not to scale!

17/1/2002 CERN 3

Inside a Supernova

Dense core

100 km M.

3x107 km

3000 km

n*10 km M

.

>8 M evolves ~107 yrExtreme temp: photodissociates nuclei back to protons, neutrons and alphas.

Neutronisation: p+e- n+e

e++e- + ; + x + x (all flavours equally) ~ few x nuclear

Huge thermal emission of neutrinos ~5-10 seconds

17/1/2002 CERN 4

SN1987AAnglo Australian Observatory

Progenitor: Sanduleak -69°202, LMC about 50 kpc away. Remnant neutron star unseen

maybe it went to ablack 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 e type:

e+p n+e+

17/1/2002 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)

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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

17/1/2002 CERN 7

Detecting SN Neutrinos… Cross section: Weak coupling constants are small ~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 e+n p+e- than e+p n+e+

CC reactions (changes np) 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(e)> = 11 MeV <E(e)> = 16 MeV <E(x)> = 25 MeV

Measurement of energies: primary physics goal EOS, neutrino transport

17/1/2002 CERN 8

A New Detection Strategy…

Utilize CC & NC reactions from ‘hi-z’ materials with low n-threshold.Use the higher energies of and -neutrinos to enhance their yields – ‘flavour filter’ Results in 2 observables:1 neutron emission from Pb2 neutron emission from Pb

The Observatory for Multiflavor NeutrInos from Supernovae

208Pb207Bi

Q [ 208Pb(,’2n)206Pb] = -14.1 MeV

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

Q [ 208Pb(,’n)207Pb] = -7.4 MeV

n’s

n’s

n’s

Reaction thresholds

Strong dependence of neutron yield on temperature Sensitivity to oscillationsDependence on temperature different for 1n and 2n channels Sensitivity to shape of energy spectrum

17/1/2002 CERN 9

Neutron Detection

Time (ns)

En

erg

y d

eposi

ted

4002000

Time (s)50 1000

En

erg

y d

eposi

ted

Prompt pulse

Delayed pulse

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 (~30s)

capture on Gd; release of several -rays (total 8 MeV). Delayed pulse

Allows two level trigger ‘Singles’ while flux high ‘Double Pulse’ when flux low

17/1/2002 CERN 10

So – how to build OMNIS

Underground to reduce cosmic ray rate

Need large blocks of lead interleaved with scintillator planes

n

Lead

Loaded scintillator (liquid or plastic)

PF Smith Astroparticle Physics 8 (1997) 27 Astroparticle Physics 16 (2001) 75JJ Zach, AStJ Murphy, RN Boyd, NIMS, 2001, accepted

17/1/2002 CERN 11

Lead Perchlorate Pb(Cl2O4)2

S. Elliott PRC 62 (2001) Diluted 20% (w/w) with H2O Transparent Cêrenkov light Bulk attenuation length >4m Neutron capture time ~100s

8.6 MeV in ’s recoil electrons Cêrenkov ‘flash’

‘Interesting’ chemical properties CC e events have well defined

Cêrenkov cone energy spectrum

2.8m

~3000 5” pmts

½ kT module

8 kpc, ½ kT e e x

No osc’ 17 23 140

e 570 23 110Includes reactions on H2O

PMTsPMTs

17/1/2002 CERN 12

Neutrino Physics Potential

Presence of neutrino mass s t e t c h e s arrival timeprofile. 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) e is light (<1eV/c2); confirmed by -

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.

DefinitiveDefinitive mass range for hot dark matter candidate.

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

17/1/2002 CERN 13

OMNIS and Oscillations

Simulation: ‘Standard’ SN @ 8kpc. Calculate number of 1n and 2n events detected in lead.

Simulation assumes {sin2m2} P(e)=0.5

What combinations of range, temperature, oscillation scenario and probability of oscillation is this compatible with?

Caveat! – Assumes shape of energy spectra known, but if solution to SP is LMA or LOW MSW then Pb(Cl2O4)2 gives us that for ! Which dominate event yields

P(

e)

P(

e

e)

17/1/2002 CERN 14

-10 –9 –8 –7 –6 –5 –4 –3 –2 –1 0

4

2

0

-2

-4

-6

-8

-10

-12

-14

-16

-18

Log(sin2(2)

Log(

m2)

MINOS

LSNDLSND

NOMAD

Super-K MSW

GALLEX MSW

OMNIS-Vacuum

OMNIS-MSWOMNIS-MSW

Neutrino Mixing – Parameter space

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)

17/1/2002 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’ - and -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?!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))

How the yield in the lead-slab modules would be affected by a cutoff in x 2ms earlier than a complete shut off at 0.2 second. Simulation is for Betelgeuse.

17/1/2002 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

17/1/2002 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

17/1/2002 CERN 18

ANL Lead Perchlorate Test Module

Elliot’s tests did not test with neutron (or ) 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

17/1/2002 CERN 19

OMNISita A technology test bed for the OMNIS project.

17/1/2002 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 ?

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

r=5 kpc

17/1/2002 CERN 21

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

17/1/2002 CERN 22

Summary Core Collapse Supernovae are

immensely important in astronomy, galactic evolution, nucleosynthesis,…

A new method of observing them, that of neutrino astronomyneutrino astronomy, offers a way of ‘seeing’ the core collapse process, allowing tests of many areas of tests of many areas of physics/astrophysicsphysics/astrophysics

Neutrino oscillations as observed at S-K are the first hints of physics beyond the standard model. SN neutrinos offer a a new, direct, method to observe effects new, direct, method to observe effects of neutrino mass and oscillations.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 - and -neutrinos must be observed in detail. OMNIS offers the most cost OMNIS offers the most cost efficient method of doing so. efficient method of doing so.

Keep watching the skies!Chandra

HST

ROSAT