No abstract

a b s t r a c tA time-projection chamber (TPC) called the SAMURAI Pion-Reconstruction and Ion-Tracker (SπRIT) has recently been constructed at Michigan State University as part of an international effort to constrain the symmetry-energy term in the nuclear Equation of State (EoS). The SπRIT TPC will be used in conjunction with the SAMURAI spectrometer at the Radioactive Isotope Beam Factory (RIBF) at RIKEN to measure yield ratios for pions and other light isospin multiplets produced in central collisions of neutron-rich heavy ions, such as 132 Sn þ 124 Sn. The SπRIT TPC can function both as a TPC detector and as an active target. It has a vertical drift length of 50 cm, parallel to the magnetic field. Gas multiplication is achieved through the use of a multi-wire anode plane. Image charges, produced in the 12096 pads, are read out with the recently developed Generic Electronics for TPCs.

A B S T R A C TEfficiency corrected single ratios of neutron and proton spectra in central 112 Sn+ 112 Sn and 124 Sn+ 124 Sn collisions at 120 MeV/u are combined with double ratios to provide constraints on the density and momentum dependencies of the isovector mean-field potential. Bayesian analyses of these data reveal that the isoscalar and isovector nucleon effective masses, * − * are strongly correlated. The linear correlation observed in * − * yields a nearly independent constraint on the effective mass splitting Δ * = ( * − * )∕ = −0.05 +0.09 −0.09 . The correlated constraint on the standard symmetry energy, 0 and the slope, at saturation density yields the values of symmetry energy ( ) = 16.8 +1.2 −1.2 MeV at a sensitive density of ∕ 0 = 0.43 +0.05 −0.05 .

Particle-decaying states of the light nuclei 11,12 N and 12 O were studied using the invariant-mass method. The decay energies and intrinsic widths of a number of states were measured, and the momentum correlations of three-body decaying states were considered. A second 2p-decaying 2 + state of 12 O was observed for the first time, and a higher energy 12 O state was observed in the 4p+2α decay channel. This 4p+2α channel also contains contributions from fission-like decay paths, including 6 Beg.s.+ 6 Beg.s.. Analogs to these states in 12 O were found in 12 N in the 2p+ 10 B and 2p+α+ 6 Li channels. The momentum correlations for the prompt 2p decay of 12 Og.s. were found to be nearly identical to those of 16 Neg.s., and the correlations for the new 2 + state were found to be consistent with sequential decay through excited states in 11 N. The momentum correlations for the 2 + 1 state in 12 O provide a new value for the 11 N ground-state energy. The states in 12 N/ 12 O that belong to the A=12 isobaric sextet do not deviate from the quadratic isobaric multiplet mass equation (IMME) form.