Mesure d'effet de spin dans la réaction inclusive $pp \uparrow \to \pi^{0} X$ a 24 GeV/C dans la région centrale et à grande impulsion transversale

This. thesis presents the measurement of the spin dependent production of n° mesons at Pt > 1 GeV/c produced in the central region in pp collisions. One uses an intense proton beam of 24 GeV/c incident on a polarized proton target. The n° energy is measured with lead-glass counters. The "up"-"down" asymmetry is negative and grows with Pt up to more than -50% for Pt greater than 2. GeV/c. This effect suggests a constituant picture of the interaction. Such an effect would, if confirmed at higher energy, modify the current hard scatterring models. A theoretical investigation of soft processes explaining such an effect would certainly improve our present knowledge of confinement.