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Neutron Skins and Neutron Stars
Physics with Intense Polarized Electron Beams
Organizing Committee
Chuck Horowitz (Indiana)
Kees de Jager (JLAB)
Jim Lattimer (Stony Brook)
Witold Nazarewicz (UTK, ORNL)
Jorge Piekarewicz (FSU
Sponsors: Jefferson Lab, JSA
PREX is a fascinating experiment that uses parity
violation to accurately determine the neutron
radius in 208Pb. This has broad applications to
astrophysics, nuclear structure, atomic parity non-
conservation and tests of the standard model. The
conference will begin with introductory lectures
and we encourage new comers to attend.
For more information contact [email protected]
Topics
Parity Violation
Theoretical descriptions of neutron-rich nuclei and
bulk matter
Laboratory measurements of neutron-rich nuclei
and bulk matter
Neutron-rich matter in Compact Stars / Astrophysics
Website: http://conferences.jlab.org/PREX
MIT - March 14-16, 2013
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 1 / 13
My FSU Collaborators
Genaro Toledo-SanchezKarim HasnaouiBonnie Todd-RutelBrad FutchJutri TarunaFarrukh FattoyevWei-Chia Chen
My Outside Collaborators
B. Agrawal (Saha Inst.)M. Centelles (U. Barcelona)G. Colò (U. Milano)C.J. Horowitz (Indiana U.)W. Nazarewicz (U. Tennessee)N. Paar (U. Zagreb)M.A. Pérez-Garcia (U.Salamanca)P.G.- Reinhard (U.Erlangen-Nürnberg)X. Roca-Maza (U. Milano)D. Vretenar (U. Zagreb)
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 2 / 13
Neutron Skins and Density Dependence of the Symmetry Energy
Neutron densities are as fundamental as proton (charge) densitiesYet, still elusive after more than 80 years of nuclear physics
Hinders our understanding of density dependence symmetry energyPenalty for breaking N=Z symmetry [B(Z ,N) = −aa(N−Z )2/A + . . .]
Neutron matter as a resonant Fermi Gas with large effective rangeUniversality of dilute Fermi gases with infinite scattering length
Neutron skin strongly correlated to the symmetry pressure L∝PPNMSlope (pressure) of pure neutron matter poorly constrained
Symmetry (or PNM) pressure pushes against surface tension⇒ n-skin
0.2 0.4 0.6 0.8 1.0 1.2kF (fm-1)
0
2
4
6
8
E/N
(MeV
)
Schwenk-PethickFriedman-PandharipandeHF-Vlow-k (S-P)Hebeler-SchwenkGandolfi et al.Gezerlis-CarlsonVidana et al.NL3FSUIU-FSU
Pure Neutron Matter
Ferm
i Gas
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 3 / 13
Neutron-Star StructureNeutron Stars satisfy the Tolman-Oppenheimer-Volkoff equationGeneral-Relativistic extension of Newtonian gravity (vesc/c . 1/2)Only unknown physics is the Equation of State [P = P(E)]EOS must span 10-11 orders of magnitude in baryon densityEnormous uncertainty in the prediction of neutron-star radiiPREX places a significant constraint on neutron-star radii
dMdr
= 4πr2E(r)
dPdr
= −GE(r)M(r)
r2
[1 +
P(r)E(r)
][1 +
4πr3P(r)M(r)
] [1− 2GM(r)
r
]−1
Need an E vs P relation!
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 4 / 13
Enhanced Cooling as signature for Quark Stars: the case of 3C58
Core-collapse supernovae generates hot (proto) neutron star T '1012KNeutron stars cool promptly by ν-emission (D-URCA process)Standard (“inefficient") cooling scenario takes over (M-URCA process)Thermal emissions from 3C58 far below standard cooling scenario
This requires the presence of exotic stellar cores!Neutrino “enhanced” cooling driven by exotic matter (π, K , q . . .)
Unless symm. energy is stiff: large neutron skin⇔ large Yp ⇔ DURCA
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 5 / 13
The Stellar Crust: Nuclear Crystals and Nuclear PastaFRIB ... will provide an understanding of matter in the crust of neutron stars (2007 Long Range Plan)
At crustal densities uniform state unstable against cluster formationCoulomb Crystal of neutron-rich nuclei immersed in a uniform e− gas56Fe, 62Ni, 68Ni, . . ., 118
36 Kr82(?)Coulomb frustration drives the formation of complex topological shapes“Nuclear Pasta” or “Micro-emulsions in 2D e-gas"Neutron-rich nuclei highly sensitive to symmetry energyNuclear Pasta highly sensitive to proton fractionSmall neutron skin⇔ large proton fraction⇔ Nuclear Pasta
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 6 / 13
Neutron Stars and Density Dependence of the Symmetry Energy
Stellar radius strongly correlated to the symmetry pressure L∝PPNM
Symmetry (or PNM) pressure pushes against gravity⇒ NS radius
Symmetry (or PNM) pressure correlated to a myriad of NS observablesNS-radii, proton fraction, core-crust transition density, DUrca cooling, ...
40 50 60 70 80L (MeV)
12
12.5
13
13.5
14
14.5
R NS [
M/M
sun]
(km
) RNS[0.8]RNS[1.4]
CAB=0.988
FSUGold
CAB=0.946
0 0.2 0.4 0.6 0.8 1Correlation with L
t
skin 132Sn
RNS[1.4]
skin 48Ca
RNS[0.8]
skin 208Pb
L
MDUrca
PPNM
Yp
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 7 / 13
Heaven on Earth: Neutron Skins and Neutron Stars
Same dynamical origin to neutron skin and NS radiusSame pressure creates neutron skin and NS radius
Correlation among observables differing by 18 orders of magnitude!
NS radius sensitive to the high-density component of the EOSHence the model dependence ...
Large neutron skin and small neutron radius?May be evidence in favor of a phase transition to exotic matter
The larger the neutron skin, the larger the neutron-star radius ...
0.16 0.20 0.24 0.28rskin[208Pb] (fm)
12
12.5
13
13.5
14
R[1.4
] (km
)
phase transition?
FSUGold
NL3
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 8 / 13
PREX: The Lead Radius EXperiment [PRL 108, 112502 (2012)]
Ran for 2 months on April-June 2010 Organizing Committee
Chuck Horowitz (Indiana)
Kees de Jager (JLAB)
Jim Lattimer (Stony Brook)
Witold Nazarewicz (UTK, ORNL)
Jorge Piekarewicz (FSU
Sponsors: Jefferson Lab, JSA
PREX is a fascinating experiment that uses parity
violation to accurately determine the neutron
radius in 208Pb. This has broad applications to
astrophysics, nuclear structure, atomic parity non-
conservation and tests of the standard model. The
conference will begin with introductory lectures
and we encourage new comers to attend.
For more information contact [email protected]
Topics
Parity Violation
Theoretical descriptions of neutron-rich nuclei and
bulk matter
Laboratory measurements of neutron-rich nuclei
and bulk matter
Neutron-rich matter in Compact Stars / Astrophysics
Website: http://conferences.jlab.org/PREX
First purely electroweak (clean!) measurement of Rn(208Pb)
Promised a 1% measurement of Rn(208Pb)
Uses parity violation as Z0 couples preferentially to neutrons[Donnelly, Dubach, Sick, NPA 503, 589 (1989)]
up-quark down-quark proton neutronγ-coupling +2/3 −1/3 +1 0Z0-coupling ≈ +1/3 ≈ −2/3 ≈ 0 −1
gv=2tz − 4Q sin2 θW≈2tz−Q
A Physics case for PREX-II and beyond!J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 9 / 13
The Case for PREX-II, Super-PREX, CREX, and beyond
R208skin correlated to a myriad of NS observables (radii, cooling, glitches ...)
How accurate measure R208skin to constrain L to within a given error?
Many observables with realistic ± to constrain L to within a given error?R208
skin ,R48skin, α
208D , . . .
0 0.2 0.4 0.6 0.8 1Correlation with skin of 208Pb
skin 132Sn
RNS[0.8]RNS[1.4]
skin 48Ca
lt
skin 208Pb
L
Ypt
MDUrca
Icrust[0.8]
Stru
ctur
ePa
sta
Cooling
Glitches
40 50 60 70 80L (MeV)
0.18
0.2
0.22
0.24
R ski
n[20
8 Pb] (
fm) 6L/2
lAB=0.995
6Lmin=1.18 MeV
0.01
5 fm
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 10 / 13
Systematic Theoretical Errors: Comparison among EDFs
Correlation between E1 polarizability and R208skin remains robust (0.77)
Piekarewicz et al., PRC 85, 041302(R) (2012)
... the impact of a 1% measurement of R208n is much smaller on the EOS
Reinhard-Nazarewicz, PRC 81, 051303(R) (2010)
... although very demanding, an accuracy of 0.02 fm in R208skin is desired
Roca-Maza et al., PRL 106, 252501 (2011)
... in order to constrain theory an accuracy of .0.03 fm is requiredPiekarewicz et al., PRC 85, 041302(R) (2012)
We suggest a 0.5% Super-PREX measurement to constrain the EOSFattoyev-Piekarewicz, PRC 86, 015802 (2012)
v090MSk7
HFB-8SkP
HFB-17SkM
*DD-M
E2DD-M
E1FSUGoldDD-PC1Ska
PK1.s24Sk-Rs
NL3.s25Sk-T4G2
NL-SV2PK1NL3
NL3*NL2
NL1
0 50 100 150 L(MeV)
0.1
0.15
0.2
0.25
0.3
0.35r sk
in[20
8 Pb](
fm)
Linear Fit, r = 0.979Mean Field
D1S
D1NSGII
Sk-T6SkX SLy5
SLy4
MSkA
MSL0
SIVSkSM
*SkM
P
SkI2SV
G1
TM1
NL-SHNL-RA1
PC-F1
BCP
RHF-PKO3Sk-GsRHF-PKA1
PC-PK1
SkI5
PREX-II
S-PREX
(63±16)Roca-Maza et al.
PRL106,252501(2011)
0.12 0.16 0.2 0.24 0.28 0.32rskin[208Pb](fm)
18
19
20
21
22
23
24
25
26
_D[20
8 Pb](f
m3 )
PREX-IIS-PREX
NL3/FSUDD-MESkyrmeSkyrme (SV)
RCNP
CABmodels =0.769
Few observables with realistic uncertainty to constrain the EOSJ. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 11 / 13
PREX-II, Super-PREX, CREX as Anchors for FRIB Physics“One of the main science drivers of FRIB is the study of nuclei with neutron skins 3-4 times thicker than is currently possible.FRIB will provide rare isotopes to explore the properties of halos and skins. JLab uses parity violation to measure the neutronradius of stable lead and calcium nuclei. Studies of neutron skins at JLab and FRIB will help pin down the behavior of nuclearmatter at densities below twice typical nuclear density” 2013 Subcommittee Report to NSAC
The Traditional Approach: Proton-Nucleus ScatteringFRIB will scatter protons from radioactive nuclei in inverse kinematicsLarge and uncontrolled uncertainties in the reaction mechanismEnormous ambiguities yield an energy dependent neutron skinFRIB must use PREX-II and CREX as calibrating anchors
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 12 / 13
Conclusions and OutlookSole ingredient required to understand neutrons stars is theEOS of neutron-rich matter in beta-equilibriumNeutron skins play a critical role in elucidating the richstructure, composition, and dynamics of neutron starsCovariance analyses uncover correlations and dictate therequired accuracy of laboratory experimentsElectroweak measurements of neutron skins should serveas anchors for hadronic experiments at FRIB-type facilitiesThe combination of precise data on dipole polarizabilityand neutron skins will provide stringent constraints onnuclear structure modelsAccurate measurements of neutron radii will continue toplay a fundamental role in elucidating the physics ofneutron-rich systems in both heaven and earth!
J. Piekarewicz (FSU) Neutron Skins and Neutron Stars MIT - March 14-16, 2013 13 / 13