SπRIT-TPC experiment with neutron rich Sn + Sn collisions in RIKEN-RIBF

Investigation of nuclear Equation of State (EoS) is one of the most attractive topics not only for nuclear physics but also astrophysics since the neutron star merger was discovered with the gravitational wave.

Nuclear EoS indicates large uncertainly in theory, because of lack of information above the normal nuclear density. Neutron rich heavy ion collisions are suitable to investigate isospin symmetry dependence of nuclear EoS at supra-saturation.

The first experiment using SAMURAI Pion-Reconstruction and Ion-Tracker-Time-Projection Chamber (SπRIT-TPC) was performed at RIKEN-RIBF-SAMURAI in 2016. The nuclear collisions with ¹³²Sn and ¹⁰⁸Sn beams at 270MeV/u on ¹²⁴Sn and ¹¹²Sn targets were utilized for the systematic study. To trigger central collision events effectively, a multiplicity trigger, a large fragment beam veto and an active beam collimator systems were employed. And fast trigger worked to brock unnecessary electron through a gating-grid-driver. Tracking software has been developed based on FairROOT framework and analysis is on going.

In this talk, the properties of SπRIT-TPC and the recent results of obtained by day-one experiment will be shown and discussed.