ASY-EOS experiment at GSI: constraining the symmetry energy with neutron and proton elliptic flows

Transcription

1 Società Italiana di Fisica XCVI Congresso Nazionale Bologna, Settembre, 2010 ASY-EOS experiment at GSI: constraining the symmetry energy with neutron and proton elliptic flows Amorini F., Boiano C., Bassini R., Brzychczyk J., Cardella G., Chartier M., D Andrea M., De Filippo E., Geraci E., Grassi L., Guazzoni C., Guazzoni P., Kis M., La Guidara E., Lanzalone G., Leifels Y., Lemmon R.C., Li Q., Lombardo I., Lukasik J., Moser S., Pagano A., Papa M., Pawlowski P., Pirrone S., Politi G., Porto F., Rizzo F., Riccio F., Russotto P.*, Trautmann W., Trifirò A., Verde G., Wu P., Zetta L. and the ASY-EOS collaboration *LNS-INFN and CSFNSM Catania, Italy /09/10

2 E( ρ, I ) / B A 2 = E( ρ ) + E ( ρ ) I + O( I B Symmetry Energy??? sym B I = 4 N Z N + Z ) +... Suprasaturation densities supernovae, nucleosynthesis (rel. HIC, neutron stars) E sym (ρ Β ) (MeV) 0 Asy-stiff Asy-soft 1 ρ Β /ρ From H. Wolter talk at ASYEOS 2010, Noto, May 2010

3 High density symmetry energy in relativistic heavy ion collisions Au+Au 1AGeV central: phase space evolution in a CM cell High densities about 2.5 ρ 0 Non-spherical momentum distribution, non-equilibrium even at highest densities Observable (qualitative): Pre-equilibrium emission of p, n, light clusters Differential and difference of collective flows Particle production, π,k

4 Constraints on the symmetry energy 197 Au+ 197 Au Current state at low densities (Fermi energy): various extrapolations, generally consistent with each other, but still uncertainties. More work necessary, also on consistency of codes (see E. De Filippo talk) Ferini, at al., NPA 762 (05) NLρ NL NLρδ Current state at high densities (E/A>100 MeV): Few experimental data on isospin effects, Few extrapolations, inconsistent with each other, Big uncertainties More work necessary on consistency of codes Main example: π - /π + ratio Z. Xiao et al., PRL 102 (09) FOPI data, W.Reisdorf et al. NPA781 (2007) 459 Z.Q. Feng, PLB 683 (2010)

5 Constraints on the symmetry energy Ferini, at al., NPA 762 (05) NLρδ NLρ NL Current state at high densities (E/A>100 MeV): Few experimental data on isospin effects, Few extrapolations, inconsistent with each other, Big uncertainties More work necessary on consistency of codes Main example: π - /π + ratio Z. Xiao et al., PRL 102 (09) Pion ratio->high densities: Some increase, some decrease with increasing stiffness. Inconsistent with each other! Understand better mechanism! Z.Q. Feng, PLB 683 (2010) models for symmetry energy (SE)

6 Transverse and elliptic flow dn ( y, pt ) 1+ V cos( φ) + 2V 2 dφ cos(2 Y = rapidity = 1 φ p t = transverse momentum ) V 1( y, pt ) = p p x t Transverse flow: it provides information on the angular distribution in the reaction plane V 2 ( y, pt ) = p 2 x p 2 t p 2 y Elliptic flow: it measures the competition between in-plane (V 2 >0) and out-of-plane ejection (V 2 <0) L-W Chen arxiv.org y z x V 2

7 URQMD simulations (by Qingfeng Li) UrQMD vs. FOPI data: 400 A MeV STIFF b<2.5 fm (*) SOFT See Qingfeng Li, J. Phys. G (2005) and references therein Coalescence condition: DR <3 fm and DP< 275 MeV/c (*) W. Reisdorf et al., NPA (1997)

8 differential elliptic flow UrQMD vs. FOPI data: 400 A MeV 5.5<b<7.5 fm stiff inversion of neutron and hydrogen flows soft A. Andronic et al., Eur. Phys. J. A 30 (2006) 31. Z=1 squeeze-out more sensitive than the directed flow 400 AMeV maximum V2

9 Present constraints on the high density symmetry energy Au+Au, 400AMeV, FOPI-LAND data (1991)* S(ρ) (MeV) π+/π- ratio, Feng, et al. (ImQMD) ρ/ρ 0 Fermi Energy HIC, MSU π+/π- ratio B.A. Li, et al. * Y.Leifels PRL 71 (1993) 963

10 ASY-EOS experiment approved by GSI-PAC (possible) 1 st phase toward FAIR??? (e.g. 132 Sn, 106 Sn beams) 400 AMeV 96 Zr AMeV 96 Ru AMeV FairRoot simulation (Geant 3-4,Fluka, Montecarlo)

11 From B.Tsang NUFRA2009

12 GSI TEST with U BEAM, September 2009 Quasi-Standard analogical acquisition Z=3 Z=2 stopping Z=2 punchingthrought Si CsI(Tl) γ Z=1 U pps 350 A.MeV + Pb

13 GSI TEST with U BEAM, September 2009 Digital Pulse Shape acquisition DSPA U pps 350 A.MeV + Pb

14 GSI TEST with U BEAM, September 2009 Digital Pulse Shape acquisition DSPA U pps 350 A.MeV + Pb

15 Conclusions Several heavy Ion reactions observables have been useful in order to get information on symmetry energy at sub-saturation densities (giant and pigmy dipole resonances, isobaric analogue states and masses, isospin diffusion, n/p ratios, 3 H/ 3 He ratio ). Viceversa, more extended data sets and consistency checks (π - /π + ) are needed in order to arrive at firm conclusions at supra-saturation densities Neutron-proton elliptic flow is a promising observable In the ASY-EOS experiment at GSI we will try to measure such (and other) crucial observables. a good constraint of symmetry energy at supra-saturation density?