Experimental studies of N/Z equilibration in peripheral collisions using fragment yield ratios

Journal Article · Sat May 15 00:00:00 EDT 2010 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.81.054602· OSTI ID:21389033

Keksis, A L; May, L W; Kohley, Z; Soisson, S N; Stein, B C; Wuenschel, S; Yennello, S J ^[1]; Souliotis, G A ^[1]; Veselsky, M ^[1]; Galanopoulos, S; Shetty, D V; Tripathi, R ^[1]; Li, B A ^[2]

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1. Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
2. Department of Physics, Texas A and M University-Commerce, Commerce, Texas 75429 (United States)

Peripheral collisions of {sup 40}Ca and {sup 48}Ca projectiles at 32 MeV/nucleon on {sup 112}Sn and {sup 124}Sn targets were studied in this work. The fragments of the projectile-like source (quasiprojectile) were collected with a charged-particle multidetector array. The average value of the neutron-to-proton ratio N/Z of the quasiprojectiles formed in the reactions was determined with two approaches. The first is a direct reconstruction approach using isotopically resolved fragments and is hindered by undetected neutrons leading to lower N/Z values. The second approach, based on the assumption of early fragment formation, employs yield ratios of fragment isobars and is not hindered by undetected neutrons. Using this approach, the amount of N/Z mixing that occurred in the quasiprojectiles (compared to a fully N/Z equilibrated system) was found to be approximately 53%. The experimental results were compared with model calculations. First, the phenomenological DIT (deep inelastic transfer) model was used, followed by the statistical multifragmentation model (SMM). The results of these calculations are in close agreement with the data and indicate that the mean number of undetected neutrons increases with the N/Z of the composite system, accounting for the difference observed between the two approaches of quasiprojectile N/Z determination. Second, the microscopic transport model IBUU (isospin-dependent Boltzmann-Uehling-Uhlenbeck) was employed, providing preliminary results in reasonable agreement with the data. The determination of the degree of N/Z equilibration employing the present fragment yield ratio approach may provide a valuable probe to study the isospin part of the nuclear equation of state in conjunction with detailed microscopic models of the collisions in the Fermi energy regime.

• OSTI ID: 21389033
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 81, Issue 5; Other Information: DOI: 10.1103/PhysRevC.81.054602; (c) 2010 The American Physical Society; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CALCIUM 40
CALCIUM 48
CHARGED PARTICLES
COLLISIONS
DEEP INELASTIC SCATTERING
EQUATIONS OF STATE
ISOSPIN
MEV RANGE 10-100
MIXING
NEUTRONS
PERIPHERAL COLLISIONS
PROTONS
TIN 112 TARGET
TIN 124 TARGET
TRANSPORT THEORY
ALKALINE EARTH ISOTOPES
BARYONS
BASIC INTERACTIONS
CALCIUM ISOTOPES
ELEMENTARY PARTICLES
ENERGY RANGE
EQUATIONS
EVEN-EVEN NUCLEI
FERMIONS
HADRONS
INELASTIC SCATTERING
INTERACTIONS
INTERMEDIATE MASS NUCLEI
ISOTOPES
LEPTON-BARYON INTERACTIONS
LEPTON-HADRON INTERACTIONS
LEPTON-NUCLEON INTERACTIONS
LIGHT NUCLEI
MEV RANGE
NUCLEI
NUCLEONS
PARTICLE INTERACTIONS
PARTICLE PROPERTIES
SCATTERING
STABLE ISOTOPES
STRONG INTERACTIONS
TARGETS