Study of the Jet Shape at 920 GeV/c in Proton-Nucleus Intereactions with   HERA-B Detector
  We performed a measurement of differential and integral jet shapes in proton-carbon, proton-tungsten and proton-aluminium collisions at 920 GeV/c proton momentum with the HERA-B detector at HERA for the jet transverse energies in the range 4 < E_T(jet) < 12 GeV. Jets were identified using the k_T-clustering algorithm. The measurements were performed for the hardest jet in the event, directed towards the opposite side with respect to the trigger direction. Jets become narrower with increasing transverse energy and measured distributions agree well with predictions of the PYTHIA 6.2 model. We do not observe any significant difference in the jet shape for the carbon and the aluminium targets. Nevertheless, the transverse energy flow at small and large radii for the tungsten sample is slightly less than for light nuclei. This observation indicates some influence of the nuclear environment on the formation of jets in heavy nuclei, especially at lower transverse energies, 5 < E_T(jet) < 6 GeV. 
D.Yu. Golubkov (1) and Yu.A. Golubkov (2) ((1) Moscow Physical   Engineering Institute (MEPhI), (2) Institute of Nuclear Phy...