The P ̄ANDA experiment is one of the pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. The P ̄ANDA physics program is focused on answering fundamental questions re- lated to Quantum Chromodynamics (QCD), mostly in the non-perturbative energy regime, using antiproton collisions on proton and nucleon targets. The central Straw Tube Tracker (STT) will be the main tracking detector of the P ̄ANDA target spectrometer. The main tasks of the STT will be the measurement of the particle momentum from the reconstructed tracks (with a spatial resolution ≃ 150 μm transversal) and the measurement of the specific energy-loss for particle identification (with an energy resolution better than 10%), especially for particles with momenta below 1 GeV/c. In this work, results obtained with a prototype STT using a proton beam with different momenta are shown and discussed, with an emphasis to the spatial resolution and the energy-loss for the different momenta.