Properties of the Initial Participant Interaction Zone in Near Fermi-Energy HI Collision Jiansong Wang for NIMROD Collaboration Institute of Modern Physics, Lanzhou China Texas A&M University, TX, USA Title 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Outline Motivation Experimental set up Coalescence model analysis Properties of the participant zone Summary 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Motivation Hot topics of HI collisions at intermediate energy: Isospin Physics and Liquid-Gas Phase Transition Does the equilibrium reach during the dynamic evolution? If yes, when? ( J. Wang et al., Phys. Rev. C 72(2005)024603) Entry channel independence in HI collision at near Fermi energies?(J. Wang et al., Phys. Rev. C71(2005)054606) Studying the impact parameter dependence of the interaction zones is of interest too. (J. Wang et al., nucl-ex/0603009 ) What is the properties of the nuclear matter in the interaction zone? What is the relationship between the Coalescence radius and the interaction zone Nucl-ex/0410024 P. Chomaz 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

NIMROD (Neutron Ion Multidetector for Reaction Oriented Dynamics) 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

The NIMROD Collaboration E. Bell1, M. Cinausero2, Y. El Masri 6,D. Fabris3, K. Hagel1, J. Iglio1, A. Keksis1, T. Keutgen6, M. Lunardon3, Y.G. Ma1, Z. Majka4, A. Martinez-Davalos,5 A. Menchaca-Rocha5, S. Kowalski1,T. Materna1, J. B. Natowitz1, G. Nebbia3, L. Qin1, G. Prete,2 R. Murthy1, V. Rizzi,3 D. V. Shetty1, S. Soisson1, B. Stein1, G. Souliotis1, P. M. Veselsky1, A. Wieloch1, G. Viesti,3 R. Wada1, J. Wang1, S. Wuenshel1, and S. J. Yennello1 1Texas A&M University, College Station, Texas 2INFN Laboratori Nazionali di Legnaro, Legnaro, Italy 3INFN Dipartimento di Fisica, Padova, Italy 4Jagellonian University, Krakow, Poland 5UNAM, Mexico City, Mexico 6UCL, Louvain-la-Neuve, Belgium 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Reaction Systems 47MeV/u 65Zn+92Mo 40MeV/u 40Ar+112Sn 55MeV/u 27Al + 124Sn Dividing the events into four bins with total multiplicity 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Selection of time clock the surface velocity of the emitted particle is used as a clock based on the dynamic model calculations J. Wang et al., Phys. Rev. C， 72(2005) 024603 v// (cm/ns) vl - K. Hagel et al., Phys. Rev. C62(2000)034607 R. Wada et al. Phys. Rev. C, 69 (2004) 044610 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Energy spectra of particle emitted from spherical thermal source Surface emission Volume emission 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Moving Source Fits Target-like Source (surface emission) Mid-Rapidity Source (volume emission) Projectile-like Source (surface emission) R. Wada et al. PRC39(1989)p497, D. Prindle et al PRC57(1998)p1305, 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

An example of moving fit 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Results of three source fits Multiplicity decrease from central bin to peripheral bin. Temperatures and velocities of NN source keep similar for different bins while they are reasonably changing from central events to peripheral events 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Coalescence Model I : determining P0 In Coalescence Model, the density of composite particle momentum space with Z protons and N neutrons is directly related to the density of free neutrons and protons momentum space as the following formula. ( T. Butler and C.A.Pearson, PRL7(1961)69, PhysRev129(1963)836, A Mekjian PRL38(1977)640 ) Because of the difficulty to measure the neutron spectra, we assume the neutron has the same shape of momentum distribution and the yield is related to the isospin of the system, then the equation become as the following. 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Coalescence Model II: determining size of the system In Mekjian thermal Coalescence model, assuming the chemical equilibrium is reached and the particle are emitted at the freeze-out density. The relationship of coordinate volume and momentum volume is as the following, EB is the binding energy and ‘s’ is spin of the composite particle and T is the temperature of the source A. Mekjian et al. PRL38(1977)640, PRC17(1978)1051 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Evolution of the t/3He Ratios 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Temperature Determination Double Ratio Isotope Temperature (S. Albergo et al., Nuovo Cimento A 89(1985)p1) Assumptions in the model: Free nucleons and composite fragments are contained within a certain volume The thermal and chemical equilibrium are reached The yield follows the Maxwell distribution The experimental yield of a fragment is proportional to the density inside the volume All detected fragment originate from a single source For the isotopes of d,t,he3,he4, The formula of temperature for a certain velocity zone is as the following 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Evolution of HHe Isotope Ratio Temperature ZnMo47 ArSn40 AlSn55 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Evolution of coalescence Parameter P0 Coalescence Parameter P0 changes with surface velocity for different particle and different bins Peaks at Vsurf about 5 cm/ns 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Evolution of the Coalescence Radii Coalscence Radii of different particle for reaction ZnMo47 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Glauber Model Nucleon density a RA r(fm) (r) “Spectators” “Participants” b impact l Sampling the positions of the nucleons according to Woods-Saxon density Sampling an impact parameter Calculate the distance d between the nucleon in projectile and that in target If d < R_interaction, these two nucleons are counted as participant nucleons 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Results of Glauber model simulation Impact Parameter (fm) 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

The Coalescence radii at different surface velocities 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

Relationship Between Coalescence Radii and the Participant number 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai Summary The dynamic evolution of the interaction zone from the central to the peripheral collisions are very similar. The Radius from the coalescence analysis is well correlated with the impact parameter. The total multiplicity is sensitive to the impact parameter The coalescence analysis is a good technique for experimentally understanding the process of dynamic evolution in HI collisions 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai

6th China-Japan Joint Nuclear Physics Symposium @ Shanghai The End Thank you ! 2018/9/20 6th China-Japan Joint Nuclear Physics Symposium @ Shanghai