Transcript Nuclear Astrophysics Studies

Current quests in Nuclear
Astrophysics
Karlheinz Langanke
GSI, TU Darmstadt, FIAS
• Core-collapse Supernovae
• The neutrino-p process
• The r-process
• Evolution of neutron star crust
Electron capture: Lab vs Stars
Capture is dominated by Gamow-Teller transitions
During collapse, electrons are described by Fermi-Dirac distribution
with chemical potentials of order a few MeV
Parent nuclei are described by thermal ensemble
Calculating stellar capture rates
data KVI Groningen
Capture on nuclei in mass range A~45-65 calculated by large-scale shell model
Capture rates are smaller than assumed before!
Unblocking GT for nuclei with
neutron numbers N>40
In Independent Particle Model, GT are Pauli-blocked for N>40
In reality, blocking does not occur due to correlations and finite T.
Calculations of rates by SMMC/RPA model.
76Se: Experimental GT strength
There is GT strength across the N=40 shell gap!
(Frekers and collaborators)
Neutron occupancies
Data from transfer reactions: J.P Schiffer and collaborators
B(GT) strengths
Zhi, Martinez-Pinedo, Sieja, Nowacki
Electron capture rate on 76Se
Convergence with truncation level
Cross-shell correlations converge slowly. Hence, models like
thermofield dynamics model or finite temperature QRPA, which
consider only 2p-2h correlations, do not suffice.
Effects of Nuclear Electron Capture during
Core Collapse
The electron capture at high
densities results in lower Ye
and generates neutrino wind
which is necessary for driving
the shock.
Hix, Messer, Mezzacappa, et al ‘03
Electron captures on nuclei dominate
Inelastic neutrino-nucleus scattering
validation of nu-nucleus cross sections
from precision (e,e') M1 data
Martinez-Pinedo, Richter, Neumann-Cosel
neutrino scattering on nuclei acts as
additional obstacle – in particular
for high-energy neutrinos
supernova neutrino spectrum shifts
to lower energies
smaller event rates for earthbound
supernova neutrino detectors
Janka, Hix, Martinez-Pinedo,
Juogadalvis, Sampaio
Explosive Nucleosynthesis
Neutrino reactions with nucleons
determine the proton-to-neutron
ratio
• Neutrino-Proton Process
(early ejecta, proton rich)
• R-Process
(late ejecta, neutron rich)
Possible consequences of high
neutrino flux in shock-front
Neutrino capture on protons
1H(+,e+)n, neutron production
which influence the reaction
path by neutron capture.
•Anti-neutrino capture on protons produce neutrons at late times
•(n,p) reactions simulate beta decays and overcome waiting points
p-process in hydrogen rich, high
neutron flux environments
On-site neutron production
through neutrino induced
interaction: 1H(+,e+)n!
By-passing waiting
point nuclei 64Ge,
68Se by n-capture
reactions.
Collective neutrino oscillations
In Normal Hierarchy
electron and (muon,tau) neutrinos
swap spectra above
split energy Ec
Fuller,, Qian, Raffelt, ….
Collective neutrino oscillations
Collective neutrino
oscillations enhance
neutron production rate
larger neutron abundance
results in enhanced nup
process nucleosynthesis
enhancement factor quite
insensitive to split energy
Nup nucleosynthesis considering
collective neutrino oscillations
Enhanced production of
nuclides with A>80
reduction of waiting point
‚successors‘
Martinez-Pinedo, Fischer,
Ziebarth
The R-Process
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Courtesy: K.-L. Kratz
Masses
Half lives
Neutron capture rates
Fission
Neutrino reactions
Robust R-Process for A>130?
J. Cowan, C. Sneden,...
r-process abundances in very old stars
the same as solar for A>130, but not
for lighter nuclides
are there two r-process sites?
robustness due to fission?
Impact of masses
FAIR
impact of nuclear half-lives
Impact of nuclear half-lives
on r-process abundances
Knowing the half-lives we will
constrain the dynamics of the
supernova explosion
New Era due to RIB Facilities
At present, except for
a few cases (blue),
output of models
cannot be matched to
measured
abundances.
today
Existing facilities
FRIB+
FAIR+
RIA
RIKEN
Future RIB facilities
will allow one to
constrain r-process
models using
abundance data
A colored dot means that the relevant nuclear
data (mass,
P(βn)) could
environment
byhalflife,
comparison
ofbe measured.
Constrain r-process
simulations with observation!
Island of stability
Theories predict long-lived
Nuclei around Z~120
Can long-lived nuclei be produced
In r-process and survive?
Courtesy: Y. Oganessian
Mass flow into fission region
FRDM
ETFSI
T
I
M
E
Long-lived nuclei due to r-process?
R-process makes superheavy nuclei as progenitors
• they can only make long-lived superheavies if
• they do not fission on way to stability
FRDM
ETFSI
Decay to stability passes through region with fission dominance -> no SHE
FAIR Chance: Neutron Stars
• Neutron Stars are
laboratories for matter
at extreme densities
• Neutron rich nuclei
• Equation of State for
nuclear matter
• Exotic phases?
X-Ray Burst and RP-Process
 = 106 g/cm3
End Point
Sn
Pd
66
62
Mo
58
Sr
Waiting Points
54
Se
50
46
Zn
42
38 5 ·1038
Fe
34
Ti
30
Ar
26
22
106g/cm3
Ne
Si
18
14
C
10
He
2
6
Ignition
Luminosity [erg/s]
105g/cm3
70 74
AW max
AW min
4
3
2
1
0
100
200
Time [s]
300
Fate of ashes on neutron star
surface
Neutron star surface
Radiative
H,He Nuclear
cooling
reactions
gas
thermonuclear
ashes
ocean
outer
crust
Inner
crust
 cooling
thermonuclear
Electron
capture
pycnonuclear
Crust processes
106Pd
Ouellette, Gupta & Brown 2005
Haensel & Zdunik 1990, 2003
Beard & Wiescher 2003
Known mass
4.8 x 1011 g/cm3
106Ge
Increase with Z1Z2
56Fe
1.8 x 1012 g/cm3
68Ca
2.5 x 1011 g/cm3
56Ar
1.5 x 1012 g/cm3
34Ne
72Ca
4.4 x 1012 g/cm3
The RIB Chance: New Horizons