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Summary of EOS working group Z. Chajecki,B . Tsang . Neutron stars. HICs, Structure. Tan Ahn. Additional contributions from: Garg , Brown, Pagano. Neutron skin. ICNT —International Collaborations in Nuclear Theory http:// /content/ ICNT.

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Summary of EOS working groupZ. Chajecki,B. Tsang

Neutron stars

HICs, Structure

Tan Ahn

Additional contributions from:Garg, Brown, Pagano

Neutron skin

icnt international collaborations in nuclear theory http frib msu edu content icnt
ICNT—International Collaborations in Nuclear Theory
  • MSU, GSI, & RIKEN directors contribute $50k/year to host 10-20 theorists’ get-together for 2-4 weeks.
  • ICNT2013 held at NSCL/FRIB- Symmetry-energy in the context of new radioactive beam facilities and astrophysics (Chuck Horowitz)
    • Week I (July 15 - 19): Symmetry energy at low nuclear densities
    • Week II (July 22 - 26): NuSYM13
    • Week III (July 29 – Aug 2): Symmetry energy at high densities including astrophysical environment
    • Week IV (Aug 5 - 9): Future Directions
  • Deliverable: Write-up of a document after the ICNT

ICNT reflected the international nature of EOS investigations.

There are new results and initiatives from ICNT/NuSYM13.

EOS working group - Summary

equation of state of nuclear matter
Equation of State of Nuclear Matter

E/A (,) = E/A (,0) + d2S()

d = (n- p)/ (n+ p) = (N-Z)/A

Strategies used to study the Symmetry Energy with HICs

  • Vary the N/Z compositions of projectile and targets
    • e.g, 108,132Sn+112,124Sn,52Ca+48Ca
  • Measure N/Z compositions of emitted particles
  • At low energies: isotopes yields isospindiffusion
  • Simulate collisions with transport theory
  • Find the symmetry energy density dependence that describes the data.
  • Constrain the relevant input transport variables.

adapted from

M.B. Tsang, PRL 102, 122701 (2009)

Brown, Phys. Rev. Lett. 85, 5296 (2001)



Super soft

EOS working group - Summary

updated constraints on symmetry energy
Updated constraints on Symmetry Energy

E/A (,) = E/A (,0) + d2S()

d = (n- p)/ (n+ p) = (N-Z)/A

Updated from ICNT/NuSYM13

Consistent constraints establish HIC and structure as viable probe to study symmetry energy at supra-saturation density

EOS working group - Summary

astrophysics and nuclear physics
Astrophysics and Nuclear Physics

Neutron star

Skyrme interactions


MNS ~ 2Msun

RNS ~ 9 km

Equation of State

stiff EoS at high r

softening EoS at r~2r0

EOS working group - Summary

astrophysics and nuclear physics1
Astrophysics and Nuclear Physics


Wiringa, Fiks, & Fabrocini 1988

Neutron star


Equation of State

softening EoS at r~ 2r0

stiff EoS at high r

Pions at r~2r0(J. Hong and P. Danielewicz, pBUU)

EOS working group - Summary

how to probe sym en at r 2 r 0
How to probe Sym En at r~2r0


Spirit TPC @ MSU (for RIKEN)

Cosmic tracks observed

  • TPC and active target
  • 4p acceptance of reaction products including pions
  • AT-TPC prototype successful
  • Final AT-TPC being assembled and electronics being tested.
  • Will reside inside Twist solenoid magnet
  • Construction completed, electronics testing underway
  • To be shipped to RIKEN in Jan 2014
  • To be placed inside SAMURAI magnet
  • Commissioning and first experiment 2015

EOS working group - Summary

improve constraints gmr gdr
Improve constraints: GMR, GDR


  • Giant Monopole Resonances in neutron-rich nuclei
    • Kt,Kcoreand Kskin

“soft GMR” akin to pigmy GDR’s.

    • Need inverse reactions

2H, 4He, or 6Li targets

beams of 35-100 MeV/A

    • TPC’s offer the best options for now.
    • AT-TPC (NSCL); CAT (CNS, Tokyo), MAYA (GANIL)
    • Experiments being planned/proposed at RIKEN and NSCL.

U. Garg

  • TPC as active target where TPC gas is the target
  • Provides good energy resolution for a thick target
  • 4p acceptance of inelastically scattered target gas atoms
  • Will reside inside Twist solenoid magnet
  • For ALL EoS measurements, we need to move AT-TPC to fast beam area

EOS working group - Summary

establishing the mom dependence of the sym en
Establishing the mom-dependence of the Sym En

Isospinmultiplet ratios in112Sn+112Sn and 124Sn+124Sn @ 50 and 120 MeV/A

  • Improvements for Neutron Walls
  • Veto charged particles directly in front of NW
    • Construct new PV scintillator array
    • Increase segmentation
    • Reduce scattering of charged particles through PV’s
    • Already have PMTs
    • Estimated cost: $50,000 (~$1,000/scintillator w/o PMTs)

Protons (LASSA)

ΘCM (deg)

Neutrons (NW)


horizontal(or vertical)

PV array

EOS working group - Summary

experiments to provide additional constraints
Experiments to provide additional constraints
  • Measuring time scale of N/Z equilibration
  • Pagano et al, INFN, Catania
  • S. Hudan, de Souza et al., Indiana University
  • Isospin diffusions with RIBs
  • New observables: projectile-like residues
  • NSCL--112,118,124Sn+112,118,124Sn
  • RIKEN --109In+112Sn

EOS working group - Summary

new mona lisa program
New MONA-LISA Program
  • Use RIBs from NSCL; enhances sensitivityto Esym
  • Dedicated experiment approved (concept tested on previous data)
  • Couple with light fragment detection (HiRA?)

EOS working group - Summary

sub barrier fusion x section of n rich nuclei
Sub-barrier fusion x-section of n-rich nuclei

Physics Motivations: Neutron Star Crust Fusion Dynamics ⇒ EOS

Fusion of n-rich light nuclei may be important for heating the crust and to determine its chemical composition

Need RIBs!


Relatively small floor space requirement (9ft x 3ft on beamline)

Few days of beam time per isotope to measure the excitation function

EOS working group - Summary

  • There is a rich program to constrain the symmetry energy at both low and high densities with RIBs
  • Next frontier is the high density region observation of small NS radius and high mass suggests a softening of SE at r~2r0
  • Progress in theory is important – transport model workshop scheduled in Jan, 2014 in China (ICNT)
  • Future needs:
  • Moving AT-TPC to the fast beam area for both giant resonances and pion measurements
  • Neutron wall veto detector to improve the identifications of charge particles
  • Chamber for charge particle detection with MONA-LISA
  • General beam line for fusion measurements at REA3

EOS working group - Summary