Study of the effective transverse momentum of partons in the proton using prompt photons in photoproduction at HERA - Chekanov, S; Derrick, M; Krakauer, D; Magill, S; Musgrave, B; Pellegrino, A; Repond, J; Stanek, R; Yoshida, R; Mattingly, MCK; Antonioli, P; Bari, G; et al. (PHYSICS LETTERS B, 2001)