Diffraction dissociation of photons on hydrogen

We report results from a measurement of the inclusive diffraction dissociation of photons on hydrogen, \ensuremath{\gamma}p\ensuremath{\rightarrow}Xp, in the range 75${p}_{\ensuremath{\gamma}}$148 GeV/c, 0.02\ensuremath{\Vert}t\ensuremath{\Vert}0.1 (GeV/c${)}^{2}$, and ${M}_{X}$${\mathrm{}}^{2}$/s0.1. Our data show an exponential t dependence and a dominant 1/${M}_{X}$${\mathrm{}}^{2}$ behavior for ${M}_{X}$${\mathrm{}}^{2}$>4 ${\mathrm{GeV}}^{2}$. We test the finite-mass sum rule and, by comparing \ensuremath{\gamma}p with ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p data obtained in the same apparatus, we test factorization.