We present a measurement of the $\sqrt{s}%
$ dependence of isolated prompt photon production in hadronic collisions.
Prompt photon samples from 1.8~TeV and 0.63 TeV $p \bar
p$ collisions were recorded with the Collider Detector at Fermilab.  Two independent background subtraction methods, shower shape and conversion rates, were calibrated and used to calculate the photon cross sections. 
The measured shapes of the cross sections as a function of photon transverse momentum are consistent with each other yet disagree with current calculations of perturbative Quantum Chromodynamics (QCD). When comparing the cross sections as a function of photon $x_T$ (=$2P_T/\sqrt{s}$), the two cross sections disagree by more than 3 $\sigma$.  Therefore, the parameterized parton distributions of the proton are excluded as an explanation of the discrepancy between data and theory.


Posted to /cdf/pub/thesis/cdf5721_photon_xsec_thesis.ps
    http://www-cdf.fnal.gov/thesis/cdf5721_photon_xsec_thesis.ps

Posted by partos@cdfsga