Exploring forward physics with the PHENIX MPC-EX upgrade

The MPC-EX detector is a Si-W preshower extension to the existing Muon Piston Calorimeter (MPC) at PHENIX. Located at forward rapidity, $3.1 < |\eta| < 3.8$, the MPC-EX consists of eight layers of alternating W absorber and Si minipad sensors. Covering a large range at forward rapidity makes the MPC-EX and MPC ideal to access low-x partons in the A nucleus of p+A collisions. The neutral pion and direct photon are excellent probes to separate between the initial and final state effects of the pA collisions. Isolating the direct photon signal requires the MPC-EX to be able to distinguish single showers from double showers. The single versus double shower separation was tested with an electron beam at the SLAC test beam facility. Results from the test beam data will be presented in this talk.