126 research outputs found
Measurement of direct photon production at Tevatron fixed target energies
Measurements of the production of high transverse momentum direct photons by
a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions
with beryllium and hydrogen targets are presented. The data span the kinematic
ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in
rapidity. The inclusive direct-photon cross sections are compared with
next-to-leading-order perturbative QCD calculations and expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 23 pages, 32 figures, submitted to Phys. Rev.
Evidence for Parton kT Effects in High pT Particle Production
Inclusive pizero and direct-photon cross sections in the kinematic range 3.5
< pT < 12 GeV/c with central rapidities are presented for 530 and 800 GeV/c
proton beams and a 515 GeV/c pi- beam incident on beryllium targets. Current
Next-to-Leading-Order perturbative QCD calculations fail to adequately describe
the data for conventional choices of scales. Kinematic distributions from these
hard scattering events provide evidence that the interacting partons carry
significant initial-state parton transverse momentum (kT). Incorporating these
kT effects phenomenologically greatly improves the agreement between
calculations and the measured cross sections.Comment: 11 pages including 6 pages of figures with caption
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