Studying the Phase Diagram on QCD Matter at RHIC

In first phase of the Beam Energy Scan program at RHIC (BES-I), collisions energies of 200, 62.4, 39.0, 27.0, 19.6, 14.5, 11.5, and 7.7 GeV were studied. This program has allowed access to a region of the QCD phase diagram which statistical hadronization models suggest covers a range of baryon chemical potential ($\mu_B$) from 20 to 420 MeV. Some, but nor all, lattice QCD models suggest that interesting features of the phase diagram (i.e. the possible first-order phase transition and a possible critical point) may be accessible in this search region. Several analyses of BES-I data have further explored lines of analysis that have been used to support the claim of quark-gluon plasma (QGP) discovery at the top RHIC energy $\sqrt{s_{NN}}$ = 200 GeV. Results and conclusions from the BES-I program will be reviewed. Upgrades to the collider and to the STAR detector in the next few years will enable a second phase of the Beam Energy Scan (BES Phase-II) at RHIC in 2018 and 2019. These upgrades and the physics analyses which they make possible will be presented.