PHENIX study of the initial state with forward hadron measurements in 200 GeV p(d)+A and He-3+Au collisions

Forward hadron measurements in p(d)+A provide a signal to study nuclear shadowing, initial state energy loss and/or gluon saturation effects as a function of rapidity, centrality and energy. High pT identified π0 measurements are an essential first step toward measuring prompt photon production. The π0 measurements are enabled by the PHENIX MPC-EX detector, a Si-W preshower detector located in front of the Muon Piston Calorimeter (MPC), expanding the neutral pion reconstruction capabilities in the rapidity range 3.1 < η < 3.8 out to high energies, E < 80 GeV. Previous PHENIX measurements of punch-through charged hadrons in the muon arms in the rapidity range 1.4 < |η| < 2.2 were significantly improved through the capability of the forward silicon vertex detector (FVTX) to determine the transversemomentum and rapidity with high precision and reject background from secondary hadrons. PHENIX collected d+Au data with the MPC-EX in the 2016 run at √sNN = 200, 62, 39 and 19.6 GeV; and p+p andp+Au(Al) data with the FVTX in 2015 at 200 GeV. In this talk, we will present first results for high pT π0 production from the √sNN = 200 GeV dataset, the status of the prompt photon measurement, as well as charged hadron nuclear modification factors in p+Au(Al) and 3He+Au