Leading proton production in e^+p collisions at HERA
  Events with a final-state proton carrying a large fraction of the proton-beam momentum, x_L>0.6, and the square of the transverse momentum p_T^2 <0.5 GeV^2, have been studied in e^+p collisions with the ZEUS detector at HERA. Data with different photon virtualities were used: Q^2<0.02 GeV^2, 0.1 <Q^2<0.74 GeV^2 and 3<Q^2<254 GeV^2. 
ZEUS Collaboration