Research Papers in Physics and Astronomy


Date of this Version

October 2004


Published by American Physical Society. Phys. Rev. D 70, 074008 (2004). Copyright © 2004 American Physical Society. Permission to use.


We present a measurement of the isolated direct photon cross section in pp̅ collisions at √s =1.8 TeV and |η|<0.9 using data collected between 1994 and 1995 by the Collider Detector at Fermilab (CDF). The measurement is based on events where the photon converts into an electron-positron pair in the material of the inner detector, resulting in a two track event signature. To remove π0→γγ and η→γγ events from the data we use a new background subtraction technique which takes advantage of the tracking information available in a photon conversion event. We find that the shape of the cross section as a function of photon pT is poorly described by next-to-leading-order QCD predictions, but agrees with previous CDF measurements.

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