1 / 26

Maria Colonna and Hua Zheng IN F N - Laboratori Nazionali del Sud (Catania )

This paper discusses the use of mean-field models and effective interactions to study dissipative reaction mechanisms in heavy ion collisions. The study focuses on the sensitivity of selected observables to specific ingredients of the effective interaction, such as symmetry energy and effective mass splitting. The results provide insights into the nuclear equation of state and the interplay between isovector channel effects.

eotto
Download Presentation

Maria Colonna and Hua Zheng IN F N - Laboratori Nazionali del Sud (Catania )

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Inputs from SMF (BNV) simulations Maria Colonnaand HuaZheng INFN - Laboratori Nazionali del Sud (Catania) ASY-EOS II Collaboration MeetingDecember 14-15, 2017 LNS-Catania

  2. Dissipative reactionmechanisms, involvingheavyions, can probe severalaspectsof the nucleareffectiveinteraction and nuclear EOS Outline • The tool: mean-fieldmodels(SMF, BNV) and • effectiveinteractions • Studyof HIC at 400 MeV/A, of interest forAsy-EOS II • Sensitivityofselectedobservablestospecificingredients • of the effectiveinteraction • (symmetryenergy, effective mass splitting)

  3. Mean-fieldmodels and effectiveinteractions Residualinteraction: in-medium NN cross sectionσNN 2-body correlations, Fluctuations One-body description ρ1 : one-body density k δk ETDHF semi-classicalapproximation Vlasov BUU, SMF Heff : effectiveHamiltonian • Effectiveinteractions are phenomenological • (ex: Skyrmeinteractions, …) • Fittedparameters incorporate the effectsof • correlationsbeyondmean-field functionsofisoscalar, spin, isospindensities, currents … • Expectationvalueofphysicalquantities : TDHF DTF, Nuclearmatter EOS

  4. The nuclearEquationof State (T = 0) Energy per nucleon E/A (MeV) SymmetryenergyEsym (MeV) soft expansionaroundnormal density poorly known … stiff or J predictionsofseveral effectiveinteractions symm. energy symm. matter β = asymmetryparameter = (ρn - ρp)/ρ • analogywithWeizsacker • mass formula for nuclei (symmetryterm) ! 25 ≤ J ≤ 35 MeV 20 ≤ L ≤ 120 MeV

  5. 1.Semi-classicalapproximation Transportequationfor the one-bodydistributionfunctionf Chomaz,Colonna, Randrup Phys. Rep. 389 (2004) Baran,Colonna,Greco, Di Toro Phys. Rep. 410, 335 (2005) (semi-classicalanalogofWignerfunction) Residualinteraction: Correlations, Fluctuations k δk vrel Vlasov Two-body Collision Integral (BUU) 2 3 4 1 (1,2) (3,4) Boltzmann-Langevin (BL) equation StochasticMean-Field(SMF) model Fluctuations are projected in coordinate space (density profile) Fluctuations in collisionintegral

  6. 2. Molecular Dynamics approaches (AMD, ImQMD, CoMD,…) A.Ono, Phys.Rev.C59,853(1999) Zhang and Li, PRC74,014602(2006) J.Aichelin, Phys.Rep.202,233(1991) M. Papa et al., PRC64, 024612 (2001), …… stochastic NN collisions Collision integral fully stochastic, but approx. description of mean-field effects… Colonna, Ono, Rizzo, Phys. Rev..C82,054613(2010) A. Ono, IWM 2011

  7. Probing the isovectorchannelof the nucleareffectiveinteractionwith SMF model SAMi-Jinteractions: Skyrmeinteractions especiallydevisedtoimprove the spin-isospin propertiesof nuclei effective mass splitting

  8. stiff Density dependence ofSymmetryEnergy soft Effective mass splitting stiff, m*n < m*p stiff, m*p < m*n β = 0.2 β = 0.2

  9. Lane potential data m*n < m*p n m*n < m*p n Density dependence ofSymmetrypotential m*p < m*n p m*p < m*n p stiff soft k = 2 kF, β = 0.2 Momentumdependence ofSymmetrypotential m*n < m*p m*n < m*p m*n > m*p ρ = ρ0, β = 0.2

  10. = - 1 full out V2 = 0 spherical = + 1 full in Isospin Collective flows In-plane (transverse) Out-of-plane (elliptic) y = rapidity = vparallel /vbeam pt = transverse momentum X Z V1 vs. y V2 vs pt Flow observables expressed as the 1st and 2nd coefficient of the Fourier expansion of the azimuthal distribution of particles dN/dφ(y,pt ) = 1 + v1 cos(φ) + 2v2 cos(2φ) B-A Li et al. PRL2002

  11. asy-stiff asy-soft Mass splitting: N/Z of Fast Nucleon Emission Light isobar 3H/3He yields n/p ratio yields 197Au+197Au 400 AMeV central, y  0.3 asy-stiff • m*n>m*p • m*n<m*p asy-soft Observablevery sensitive at high pTto the mass splitting and notto the asy-stiffnessQualitative trend : ratioincreasesonlywithm*n <m*p seealsoG.C.Yonget al., PHYSICAL REVIEW C 80, 044608 (2009) V.Giordano et al., PRC 81(2010)

  12. m*n<m*p n/p ratio: Preliminaryresultsfor106Sn+112Sn 400 AMeV b = 5 fm, y  0.3 stiff m*n>m*p soft stiff Preliminaryresultsfor132Sn+124Sn 400 AMeV b = 5 fm, y  0.3 soft m*n<m*p m*n>m*p

  13. y(0)0.3 v2 vs pT m*n>m*p m*n<m*p Mass splitting impact on Elliptic Flow 197Au+197Au, 400 AMeV, b=5 fm, y(0)0.3 Fast nucleon emission m*n<m*p : largerneutronsqueeze out at mid-rapidity - Largerneutronrepulsionforasy-stiff Coulomb effects Comparableresults: Interplay betweenasy-stiffness and effective mass effects ! Qualitative trend: n flow is more negative than p flow onlyfor the choicem*n < m*p

  14. V2 : Preliminaryresultsfor 132Sn+124Sn 400 AMeV b = 5 fm, y  0.3 Au + Au soft m*n>m*p stiff soft m*n<m*p stiff

  15. Experimental data and comparison withUrQMDcalculations P. Russottoet al. Phys. Rev. C 94, 034608 (2016)

  16. Tobedone … More quantitative and systematicstudyof the interplay betweenisovectorchanneleffects:  symmetryenergyvs effective mass splitting(MD effects) • Evolutionof the relative roleof the twoingredients • with the beamenergy: • Importanttoextract the density dependenceofEsym

  17. Low-energyreactionmechanisms: a studywithinmean-fieldmodels • Fusion vs Quasi fission or • DeepInelastic • Ternarybreaking • Chargeequilibration • Fragmentation • Isospindiffusion • (Fermi energies)

  18. Fusion vs. Quasi Fission: towards the synthesisof SHE 50Ti +249Bk 233 MeV FUSION Umar, Oberacker, Simenel tip side TDHF calculations soft • Fusionprobabilitydepends on the • deformation/orientationofcolliding nuclei • Possiblesummetryenergyeffects ?? stiff SMF calculationswithneutronrichsystems l (ћ) C.Rizzo et al., PRC83, 014604 (2011)

  19. A recentinvestigation: Ternary Quasi Fission SMF Skyrmeforces 197Au + 197Aucollisions - 15 and 23 MeV/A Mass distributionoffragments emittedby DF fragment ShapeObservables: Quadrupole and Octupolemoments D F S F D F S F A1 A2 “PLF-TLF separationtime” D F: deformedfragment A1: lightestfragment A2: heaviestfragment S F: “spherical” fragment C.Rizzoet al., PRC 90 (2014)

  20. Ternary breakup in n-richsystems: SensitivitytoEsym & MultidimensionalAnalysis 124Sn + 64Ni , E/A = 10 MeV, b = 6-8 fm DF PLF-TLF configurationat separation time PLF Sliced Inverse Regression (SIR) algorithm : a multidimensionalanalysis techniqueto discriminate and combine the most sensitive observables Quad. Oct. shiftedto the left forstiff P.Cammarataet al., NIM A761, 1-6 (2014)

  21. Dipoleexcitations in heavyionreactions (Dyn. Dipole) TDHF calculations A1 A2 Relative motionofneutron and protoncentersof mass Simenel et al, PRC 76, 024609 (2007) InitialDipole D(t) : bremss. dipoleradiationCompound: stat. GDR If N1/Z1≠ N2/Z2 + 2-body collisionaldamping 130 MeV SMF simulations 132Sn + 58Ni , D0 = 45 fm E/A = 10 MeV dampedoscillations Oberackeret al., PRC 85, 034609 (2012) C.Rizzo et al., PRC 83, 014604 (2011) Time (fm/c) 3000 6000

  22. DynamicalDipole in heavyionreactions (DD) • The restoringforceisprovidedby the symmetryterm (as in the standard GDR) • probe the symmetryenergy in the density conditions and configurations • reachedalong the reactionpath • Coolingmechanism in the formationof SHE • Fewexperimental data: more systematicanalysisneeded • Theory: a more systematicstudyof the sensitivityofthismechanismto • the ingredientsofof the effectiveinteraction and two-bodydissipationneeded • Ground state deformationimportant ??? DD in the fusion-evaporation of the 40Ca + 152Sm heavy system, C.Parascandolo et al., PRC 93, 044619(2016)

  23. DD oscillations: dependence on the effectiveinteraction MI 132Sn + 58Ni , D0 = 45 fm, E/A = 10 MeV MD J-L correlations SAMi-J: MI MD Skyrme (MI) : H.Zhenget al., - free n-n cross section • The DD emissionlooks sensitive toEsym at ρ = 0.6ρsat • Largerstrengthseen in the MD case: • similarto the enhancementfactor in the GDR sum rule (dampedharmonicoscillator)

  24. Correlations: observables vs. parameters Covarianceanalysis A set of 8 parameterizations in SMF simulations: Skyrme (MI) and SAMi-J31 + σNN = 40 mb, *2, /2 Observables (A): DDcentroid, D”(ω) integral and N/Zofpre-equilibriumnucleon emission Parameters (B): SymmetryenergyslopeL, effective mass m* and NN cross section (cs) τcoll : collisionaldampingtime seealsoZhanget al, PLB 749, 262 (2015) (n) (n) Blue: negative Red: positive neutrons protons compare with (energy-integratedyield)

  25. Conclusions • Reactionswith RIB’s open the opportunitytolearnaboutfundamental • propertiesof the nucleareffectiveinteraction, of interest also in the • astrophysicalcontext • Low energycollisions: • Reactionmechanisms at the borderline withnuclearstructure: • roleofeffectiveinteraction, 2-body dissipation • n-skin, g.s.deformation • -Competitionbetweenreactionmechanisms (n-richneckdynamics) • -Pre-equilibriumγ and particleemission Collaborators: HuaZheng(LNS), Stefano Burrello(LNS), V.Baran (UniversityofBucharest, Romania)

More Related