Transverse Energy in Forward/Backward Directions from RHIC Au+Au Collisions at Several Beam Energies

In 2010, RHIC produced Au+Au collisions at $\sqrt{s_{NN}}=200, 62.4, 39$, and $7.7 $~GeV. Progress in measuring transverse energy in the range $3.1<|\eta|<3.8$ using the PHENIX Muon Piston Calorimeter will be reported. Transverse energy has been used to estimate energy density in ultra-relativistic heavy ion collisions and to discriminate between competing models of hadronic interactions. At forward rapidities the net baryon densities are much higher than those at mid-rapidity, so one can probe these models at high baryon chemical potential. Furthermore, fluctuations in transverse energy might signal the presence of a critical point in the phase diagram of nuclear matter.