SUPERNOVA NEUTRINOS AND THE r- AND n-PROCESSES OF NUCLEOSYNTHESIS

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SUPERNOVA NEUTRINOSAND THE r- AND n-PROCESSES
OF NUCLEOSYNTHESIS
Richard N. Boyd Ohio State University NDM03,
June, 2003 1. Understanding the stellar core
collapse process with SN neutrinos black
holes. 2. Understanding neutrinos from their
supernova signatures. 3. r-process and n-process
nucleosynthesis. 4. Detecting nucleon decay. 5.
OMNIS, the Observatory of Multiflavor Neutrinos
from Supernovae
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STAGES OF STELLAR EVOLUTION
During each stage, each shell of a star
establishes hydrostatic equilibrium between
gravity and the energy it produces. When that
stages fuel is gone, the star contracts,
converts gravitational potential energy to heat,
and burns the next fuel. When its gone, the star
contracts, ... Stage T9 r(g/cm3) t(y) React
ions Ashes H 0.02 102 107 pp-Chains He,
... CNO He 0.2 104 105 34He?12C C, O,
... 12C(a,g)16O C 0.8 105 103 12C12C? Ne,
O, ... 20Nea Ne 1.4 107
3 20Ne(g,a)16O O, Mg, ... O 2.0 107 .8 16O16O?
Si, S, ... 28Sia, 31Pp, ... Si
3.5 108 1 w. 28Si(g,a)24Mg, ... Fe,
Ni 28Si(a,g)32S, ... NSE Collapse 40 1014 1
d. gx?n,p,a ns,ps,as NSE Nuclear
Statistical Equilibrium it makes everything up
to mass 100 u in lt 1s out of ns and as.
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BASICS OF COLLAPSE PROCESS
Gravitational binding energy EGrav ? (3/5)
GMNS2/RNS ? 3x1053 ergs (MNS/1.4Mo)2
(10 km/RNS) Neutrino Diffusion time tn 3
s Typical Luminosity per Neutrino Species Ln
(GMNS2/RNS)/1/tn 1x1052 ergs/s Epochs of
Supernova Neutrino Emission I. Infall
Principal n emission, high energy ne from e-
p ? n ne II. Shock ReHeating/Explosion
Thermal emission from neutron star surface of
ne, nm, and nt in roughly equal fluxes.
Fermi-Dirac black body spectra. (?) Ln ? 1052
ergs/s per flavor. ltE(ne)gt ? 11 MeV, ltE(ne)gt ?
16 MeV, ltE(nx)gt ? 25 MeV. III. Post-Explosion,
r-Process Epoch Time scale 10 s. Neutron star
contracts from 40 km to 10 km. Low Lns, but
ltEgts slowly rising. (?)
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NEUTRINOS FROM STELLAR COLLAPSE
The energy in the core is (a few)x1053 ergs most
of it is emitted in a few seconds, ultimately to
produce a stable neutron star. The reactions p
e- ? n ne (neutronization spike) n e
? p ne (URCA process) g ? e e- e
e- ? g g e e- ? ni ni (once in 1019
times) A ? A ni ni Nearly all of the
neutrinos emitted are from the last process
1053 ergs of them in the order of a second (as
seen in SN 1987a). After the neutronization
spike, E(ne)?E(nm)?E(nt), but the mean energies
are NOT the same ltE(ne)gt lt ltE(ne)gt lt ltE(nm,t)gt.
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DETECTING SUPERNOVA NEUTRINOS--WHY?
1. Checking the Standard Model of core collapse
and cooling of the protoneutron star. Are
cooling times consistent with prediction? A
low-entropy core collapse? Neutrino opacities
correct? Neutrino energies correct? ltEm,tgt
? 25 MeV, ltEegt ? 16 MeV, ltEegt ? 11 MeV? Or might
other mechanisms affect ltEm,tgt? Are the
distributions Fermi-Dirac? Might oscillations
affect these? Are there signatures of rotation
(mixing)? 2. Neutrino physics. Measure
neutrino masses from their time of flight? Or
from timing signals from collapse to a black
hole. But need to detect all the flavors! And
mixing could confuse this. Measure/check
some types of oscillations might measure ?13
with incredible sensitivity. 3.
Nucleosynthesis. Measure the neutrino
spectratheyre crucial for understanding the
r-process and the n-process. 4. Black hole
astrophysics. Observe the collapse to a
black hole via the abrupt termination of the
neutrino signal. Do diagnostics on the
black hole collapse process via differences in
termination times of signals from different
neutrino flavors?
L
t
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MODIFICATIONS ON THE STANDARD MODEL
1. Atmospheric n observations from Super-K,
Soudan 2, and MACRO nm ? nt vacuum
oscillations. (Theyre nx either way.) 2. Solar
n observations from Super-K and SNO ne ? nm MSW
transitions. As the ns emerge from their
n-spheres near the stars core The nms,
nms, nts, and nts have high mean energies. As
the ns emerge from the periphery of the star
The nes, nms, nts, and nts have high
energies. These transformations will
produce mostly high energy nes. Furthermore, a
non-zero ?13 (which is very difficult to measure)
could produce an additional enhancement in the
high energy nes. RESULT the nes detected by
OMNIS will be high-energy, so reflect the energy
distribution of the nms and nts emitted from
the core of the star. This results from OMNISs
leads selectivity, via its thresholds, to only
high-energy neutrinos.
nm
En
sin22?12 0.8
ne
MSW region
Log R
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For ne p ? e n (CC Interaction) in
Super-Kamiokande
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DETECTING NEUTRINOS FROM SUPERNOVAE--HOW?
nes and nes interact via both charged-current and
neutral-current interactions. s for the former is
larger, so use ne p ? e n, and ne O ?
e N Can use Cerenkov detectors in water for
this--SuperK, SNO. m- and t-neutrinos (at SN
energies) interact only via the NC interaction,
but OMNIS can detect them by observing neutrons
from nm,t 208Pb ? 208Pb nm,t
? 207Pb n (Q -7.4 MeV) 206Pb 2n (Q
-14.1 MeV) The relative yields of 1n to 2n
events test the energy distribution, the NC
interaction doesnt provide a direct way to
measure neutrino energies. The NC interactions
also have a zero-neutron mode that emits a
distinguishable g-ray.
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Detecting Neutrinos from SNe--More on How?
Electron neutrinos can also undergo CC
interactions ne 208Pb ? e- 208Bi
? 207Bi n (Q-9.77 MeV)
206Bi 2n (Q-17.86 MeV) With lead perchlorate
(a clear liquid that dissolves easily in water)
one can detect the e-, providing a direct
measurement the energy of the nes from E(e-) and
the number of neutrons emitted. In most cases
(except the no-neutron NC case), detect neutrons.
Need several thousand events to do a decent
statistical analysis 2 kT Pb slabs (2000 events)
1.0 kT PbClO42 (1000 events) will do
that. The CC events will measure the
distribu- tion of the high-energy ns as they
were emitted the (two-threshold) NC events will
provide a consistency check of the oscillation
modes and a sensitive measure of the high-energy
tails of the distributions. Super-K will observe
some NC ns from the O in the H2O, a very useful
additional (high threshold) datum.
Flux
Energy
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MEASURING NEUTRINO ENERGIES IN CC INTERACTIONS
E, MeV
First forbidden states
25 20 15 10 5 0
G-T states
2-n thd.
IAS
2-n emitting transitions
1-n thd.
1-n emitting transitions
208Bi
208Pb
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NUCLEAR PHYSICS OF NEUTRINO DETECTION Pb
////////// //////////// ////////////// ///
/////////// ____ ____
//////////
//////////////
//////////////
n207Bi threshold
2n206Pb, Q-14.1 MeV
n207Pb, Q-7.4 MeV
n207Pb threshold
nPb?nPb?Pbn (NC Interaction)
(n,n)
But also, for 208Pb
208Pb
2n206Bi, Q-17.9 MeV
n207Bi, Q-9.8 MeV
208Pb(n,e-)208Bi
nePb?e-Bi? e-Bin (CC Interaction)
208Bi
208Pb
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CALIBRATING OMNIS?

• Using the neutrino beams from a stopped pion
  facility isnt perfect the neutrinos arent the
  right energy (which we dont know!).
• So, use 208Pb(3He,t)208Bi reaction (Fujiwara et
  al.). Identify the transitions to the states of
  interest by their angular distribution, and
  measure the neutrons that they emit. This is also
  very important information it determines the
  detection efficiency!

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How to Detect nes? And nxs?
Two types of detection schemes. 1. Use vertical
lead slabs alternated with planes of neutron
detectors. n Pb interactions produce ns via
NC and CC interactions nx APb ? nx A-1Pb
n, ne APb ? e- A-1Bi n. The neutrons
escape the lead slabs and are detected when they
ther- malize and are captured in the neutron
detectors. These detectors produce lots of
events and some E information. 2. Use lead
perchlorate (a clear liquid). NC interactions
again produce neutrons, which are captured on the
Cl. The e- from the CC interactions produce
Cerenkov radiation, which identifies the CC
event, and gives the energy of the incident ne.
Also neutrons. Only neutrons means its a NC
event. These detectors produce the NC to CC event
ratio and measure the high E ne, hence nx,
spectrum.
nx
n
n
ne
e-
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A Site for OMNIS?
Site I Waste Isolation Pilot Plant, Carlsbad,
NM Nuclear waste repository. This is in a salt
deposit, 2000 feet underground. Drifts and much
infrastructure exist, and waste is distant from
where OMNIS would be, so is not an issue. WIPP
will be there for a very long time! And the WIPP
has been very supportive, providing much
infrastructure support. Furthermore, everything
we would need is already in place! We plan to
begin building OMNIS in the WIPP. Site II Deep
Underground Science Engineering Lab DUSEL
would be NSF supported. It is strongly supported
by the physics community, but isnt a reality
yet. Its support structure is unknown, but would
be expected to be similar, at least for our
purposes, to that of the WIPP. It would be as
deep as 8000 feet. The nucleon decay studies
would require a deep site. Site III Boulby
Mine, UK. This is also a salt deposit, depth
comparable to that of WIPP. This is currently
being used for dark matter searches, but OMNIS
group in UK wants to put an OMNIS component there
too. Why multiple sites? Coincidences required
for REAL supernova events!
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DUSEL
Deep Underground Science and Engineering Lab,
Homestake Mine, Lead, South Dakota
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DIAGNOSING STELLAR COLLAPSE
Stellar collapse depends on hydrodynamics, the
EOS, and the interactions between the ns and the
nuclei in the collapsing region of the star.
SN1987A confirmed that the collapse is
low-entropy the ns took seconds to get out
rather than the tens of 10 ms in which theyre
produced. ltE(ne)gt 11 MeV, ltE(ne)gt16 MeV, and
ltE(nm,t)gtltE(nm,t)gt 25 MeV?? But the neutrino
energy and time distributions could be affected
by Neutrino transport Equation of state 1-D vs.
2-D vs. 3D Hydrodynamics, e.g.,
turbulence Pinching of energy distributions by
scattering (inevitable?) Neutrino Bremsstrahlung
(n n ? n n ni ni) Neutrino inelastic
scattering (n n n ? n n n) Convection
(!) Neutrino oscillations (!) In addition, the
time distributions (especially late time) could
exhibit interesting features such
as Schirato-Fuller anomalies from neutrino
oscillations. Reddy late-time spikes from phase
transition from neutron matter to quark matter
(?). Cutoff from collapse to a black hole? Would
all flavors terminate at the same instant?
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Supernova Neutrinosand the r-Process
The r-process makes half the nuclides heavier
than iron, and all nuclides heavier than 209Bi.
It is thought to occur in second in the bubble
just outside the nascent neutron star, in a hot n
wind. The r-process requires a neutron density
1020 cm-3 in order to have it go fast enough to
circumvent some short-lived nuclides (it must get
to Uranium). PROBLEMS 1. The nes will tend to
equilibrate the neutrons and protons that will
kill the r-process. 2. They also make 3H and 3He
via n4He, which then capture 4Hes to make 7Li
and 7Be, which then can make too many light
nuclei to seed the r-process. SOLUTIONS The
r-process would work if one could have neutrino
oscillations involving a sterile neutrino (e.g.,
Caldwell, Fuller, Qian mass scheme). Or perhaps
the energy spectral differences might solve the
problem? REQUIREMENT MUST know the energy
spectra!
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Supernova Neutrinos and the n-Process
The n-process is thought to make some of the
rarest nuclides in the periodic table, e.g.,
138La and 180Ta. It must occur in the n-wind from
a collapsing core in a supernova. 138La from
139La(n,n)138La and 138Xe(ne,e-)138La. 180Ta
from 181Ta(n,n)180Ta and 180Hf(ne,e-)180Ta. And
half come from 181Ta(g,n)180Ta. But, also, 19F
from, e.g., 20Ne(n,n)19Ne ?19F. And 7Li from,
e.g., 4He(n,n)3He 4He(3He,g)7Be?7Li. Satellite
yields just below the r-process abundance
peaks suggest n-processing at the end of the
r-process, supporting this model of the
n-process (Haxton et al. Qian et al.). The
actual n-spectrum is crucial to the predictions
of n-process models. Its uncertain at present,
but OMNIS will provide this.
.6 .5 .4 .3 .2 .1 0
.04 .02 0
r-Process Abundances
170 180 190 200 A
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Detecting Nucleon Decay in OMNIS
Nucleon decay Tests most fundamental theories of
particle physics. Has been looked for in large
underground detectors. Has good experimental
limits for decay modes that emit charged
particles, especially Cerenkov light. Has much
poorer limits for processes that dont emit
charged or strongly interacting particles. Lead
perchlorate PbCl O42 VERY soluble in
water--will give Cerenkov light. But what would
Pb and Cl do for nucleon decay observations? n ?
n n n Decay of a neutron in 35Cl ? 34Cl ?
34Cl ? 34S b. Signature Slow coincidence
between g-rays from 34Cl de-excitation, then b
from 34Cl ? 34S (T1/2 1.5 s). Then
determination of correct 34Cl lifetime! T1/2
1029y/year. Most troublesome background High
energy atmospheric neutrino causing 35Cl ? 34Cl
n. Use n for a veto!
g
b
3 n
x x
x
x
x
x x
x o
x x
x x
x x
x x
x x
x x
x x x x x x
x x x x x x
x x x x x x
x x x x x x
x x x x x x
x x x x x x
x x
x x
x x
x o
x x
x x
x x x x
x x x x
x x x x
x x x x
x x x x
x x x x
x
x
x
x
x
x
x x
x x
x x
N Z
N Z
N Z
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Nucleon Decay in Lead of Lead Perchlorate
Signature of nucleon decay in 208Pb 208Pb ?
207Pb 3n ? 206Pb n
? 205Pb n ( n)
? 205Pb g 2n (and other
branches are possible). In general, 208Pb ?
208-jPb 3n (j-1)n g. In the LPC, multiple
neutrons would be observed, and gs in excess of 3
MeV would be observed. Obvious background n
208Pb ? 207Pb n ?
? 205Pb g 3n. This is
identical to neutron decay except that theres an
extra neutron. This would be VERY difficult to
identify. But could measure the same process with
nes, convert NC to CC cross sections, and infer
the background to subtract. Should be able to
achieve a half-life limit of 1030 y/y (Boyd,
Rauscher, Reitzner, Vogel)
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DO SUPERNOVAE AND/ORBLACK HOLES EVER HAPPEN?
Rate of Core-Collapse SN van den Bergh 3
? 1 per century Strom, Hatano et al., The
historical SNe were in a few of the galaxy
its 5-10 per century. Bahcall and Piran
Arnett, Schramm, and Truran 10 per century.
Large UG detectors over past 20 years 10 per
century is excluded at 85 confidence
limit. How many Core-Collapse SNe produce black
holes? Bahcall Piran Ratnatunga and van
den Bergh 1 b.h./4 n-stars Bethe and
Brown 1 b.h./1 n-star Qian, Vogel,
Wasserburg 9 b.h./1 n-star Both areas clearly
need more work!
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COMPARING OMNIS TO OTHER SN-NEUTRINO
DETECTORSFOR AN 8 kpc DISTANT SN
nm nmntnt
ne
ne (nmnt)