Ultrarelativistic heavy ion collisions constitute the main experimental arena where different properties of the QCD phase diagram are being currently probed by the nuclear programs conducted at RHIC and LHC. The deconfined phase of QCD corresponding to a nearly inviscid, strongly interacting quark-gluon plasma (QGP) has been produced in such collisions since 2005 and its properties are the focus of intensive experimental and theoretical efforts. Of particular importance for investigating the behavior of QCD matter in the plane of temperature (T) and baryon chemical potential (mu_B) are the Beam Energy Scan (BES) program at RHIC and future experiments at the FAIR and NICA facilities exploiting low energy collisions with a center of mass energy of a few GeV, in which cases mu_B/T ~ 1 (contrary to the TeV scale collisions at the LHC, where baryon density effects are effectively washed out by the high temperatures achieved within the QGP medium).

In this talk, I will discuss how the holographic gauge/gravity duality may be used as a powerful nonperturbative tool to quantitatively investigate the properties of the QGP in the baryon dense regime, which is very hard to grasp using first principle lattice QCD simulations. An ensemble containing approximately 2,000,000 numerically generated 5D dilatonic black holes is employed to populate the (T,mu_B) phase diagram of a bottom-up Einstein-Maxwell-Dilaton (EMD) holographic setup, which is shown to be in an unprecedented agreement with state-of-the-art lattice data for the QCD equation of state and higher order baryon susceptibilities at finite baryon density. Taking also into account that the nearly perfect fluidity of the strongly coupled QGP is naturally enclosed in such setup, the holographic EMD construction constitutes, by far, the best option available in the literature to investigate higher baryon densities which are currently out of the reach of lattice QCD simulations.

By looking at divergencies in the baryon susceptibilities of the EMD setup, we provide a strong candidate for the long-sought QCD critical point in the (T,mu_B) phase diagram. A chemical freeze-out analysis employing recent experimental data from the STAR collaboration for the moments of fluctuations of conserved charges measured in heavy ion collisions at the BES program is used to predict the location of the critical region in terms of the center of mass energy of the collisions. We predict that the QCD critical point will be at the reach of upcoming low energy heavy ion collision experiments.

I will also discuss how the behavior of the kurtosis times the variance of the net-proton multiplicity distributions measured by STAR may behave very differently depending on the actual freeze-out trajectory realized in heavy ion collisions. In particular, this observable may develop a non-monotonic profile even far away from the critical region, such that one must be very careful in trying to directly associate data for this observable with possible experimental signatures of the QCD critical point.