L. E. Gordon

New parton distribution functions for the photon

Abstract We present new improved parton distributions for the photon. We fit all available data on the photon structure function, F 2 γ ( x , Q 2 ), with Q 2 ⩾ 3 GeV 2 , in order to determine the quark distributions. We also pay particular attention to the gluon distribution in the photon, g γ (x),Q 2 ) which has been poorly constrained in earlier analyses which only include structure function data. We use large PT jet production in yy collisions from TRISTAN to constrain g γ . We also see what information can be gleaned from yp collisions at HERA on g γ and on the quark distributions at large x , where there are no structure function data. We review future prospects of elucidating the parton distributions of the photon.

Polarized and unpolarized double prompt photon production in next-to-leading order QCD

Abstract We calculate O ( α s ) corrections to inclusive and isolated double prompt photon production, both for the unpolarized case, and for longitudinal polarization of the incoming hadrons. The calculation is performed using purely analytical techniques for the inclusive case, and a combination of analytical and Monte Carlo techniques to perform the phase space integration in the isolated case. A brief phenomenological study is made of the process pp → γγX at c.m.s. energies appropriate for the RHIC heavy ion collider.

Prompt photon plus jet photoproduction at DESY HERA at next-to-leading order in QCD

The cross section for photoproduction of an isolated prompt photon in association with a jet is studied in next-to-leading order. The kinematics are those appropriate for the DESY ep collider HERA. The effects on the cross section of various experimental cuts including isolation cuts on the photon are examined. Comparisons with the ZEUS preliminary data using two parametrizations of the photon structure function are made, and good agreement is found. The data are not yet precise enough to make a distinction between various models for the photon structure function. {copyright} {ital 1997} {ital The American Physical Society}

Spin-dependent Drell-Yan in QCD to O(αs2) (I). The non-singlet sector

A study of the order α 2 corrections to the Drell-Yan (non-singlet) differential cross section for incoming states of arbitrary longitudinal helicities is presented. The transverse momentum distributions, qT, of the lepton pair are studied and the calculations of Ellis, Martinelli, and Petronzio (EMP) are extended to include polarized initial states. We use the MS scheme and the t’Hooft-Veltman regularization for the helicity projectors. From our results one can obtain the bulk of the totally inclusive NNLO cross section for the production of a Drell-Yan pair in the non-singlet sector by a simple integration over the virtual photon momentum. We show that in the MS scheme helicity is not conserved along the quark lines, unless a finite renormalization is done and one adapts the physical (MSp) scheme. This aspect of the calculation is similar to the O(α 2 ) polarized production of single and double photons. Our spin averaged unpolarized differential cross sections agree with the EMP calculations.

Inclusive prompt photon production in polarized pp collisions at HERA-N

Abstract We present a NLO study of inclusive polarized prompt photon production in a conceivable fixed target pp mode of HERA with longitudinally polarized protons at s = 39 GeV . We analyze the sensitivity of the corresponding double spin asymmetry to the protons polarized gluon distribution Δg and estimate the expected statistical precision in its determination. The main theoretical uncertainties in the predictions are examined.

Prompt photon production in γγ collisions and the gluon content of the photon

Abstract We calculate the cross section for inclusive prompt photon production in γγ collisions, i.e. the reaction e + e − → γγ → γX , in next-to-leading order QCD. We show that at LEP2 energies this cross section is measurable and is sensitive to the gluon distribution of the photon, g γ , which is currently very poorly constrained by data.

Production of a prompt photon in association with a charm quark at next-to-leading order in QCD.

A second order

Isolated photons at hadron colliders at O(ααs2) (I): Spin-averaged case

O({\ensuremath{\alpha}}_{s}^{2})

Isolated photons at hadron colliders at O(ααS2) (II): Spin-dependent case

calculation in perturbative quantum chromodynamics of the two particle inclusive cross section is presented for the reaction

Analytic calculation of prompt photon plus associated heavy flavor at next-to-leading order in QCD.

p+\overline{p}\ensuremath{\rightarrow}\ensuremath{\gamma}+c+X