Nuclear modification factor of inclusive charged particles in Au+Au collisions at sNN = 19.6 and 27 GeV with the STAR experiment

The Quantum Chromodynamics (QCD) phase diagram, characterized by temperature (T) and baryon chemical potential (Formula: see textB), features a transition from hadronic matter to a deconfined quark-gluon plasma (QGP) at a certain values of T and Formula: see textB. The Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) explores this phase structure by systematically varying the collision energy of AuFormula: see textAu collisions, with a key focus on locating the QCD phase boundary and the critical point. During the first phase (BES-I, 2010−2014), STAR experiment measured the nuclear modification factor (Formula: see text) of inclusive charged particles in Au+Au collisions in the energy range from Formula: see text = 7.7 to 39 GeV. In 2018, the STAR experiment initiated the second phase of the BES program (BES-II), which has a tenfold increase in statistics compared to the first phase. This enables better precision RCP measurements. By 2018- 2019, STAR collected more than 500 million Au+Au events at Formula: see text = 19.6 and 27 GeV, two orders of magnitude larger than the BES-I dataset at these energies. In these proceedings, we present new measurements of charged-particle production and Formula: see text measurements on the high-statistics BES-II data at Formula: see text = 19.6 and 27 GeV, comparing them with BES-I results. We further evaluate theoretical expectations using UrQMD and hydrodynamic (SMASHFormula: see textvHLLE) model predictions, testing their description of the experimental observations. By extending the analysis to higher transverse momenta Formula: see text, we probe potential jet quenching effects and assess implications for QGP formation and properties at lower collision energies.