J. F. Owens

Global parton distributions with nuclear and finite-Q 2 corrections

We present three new sets of next-to-leading order parton distribution functions (PDFs) determined by global fits to a wide variety of data for hard scattering processes. The analysis includes target mass and higher twist corrections needed for the description of deep inelastic scattering data at large x and low Q 2 , and nuclear corrections for deuterium targets. The PDF sets correspond to three different models for the nuclear effects, and provide a more realistic uncertainty range for the d quark PDF, in particular, compared with previous fits. We describe the PDF error sets for each choice of the nuclear corrections, and provide a user interface for utilizing the distributions.

k{sub T} effects in direct-photon production

We discuss the phenomenology of initial-state parton-k{sub T} broadening in direct-photon production and related processes in hadron collisions. After a brief summary of the theoretical basis for a Gaussian-smearing approach, we present a systematic study of recent results on fixed-target and collider direct-photon production, using complementary data on diphoton and pion production that provide empirical guidance on the required amount of k{sub T} broadening. This approach provides a consistent description of the observed pattern of deviation of next-to-leading order QCD calculations relative to the direct-photon data, and accounts for the shape and normalization difference between fixed-order perturbative calculations and the data. We also discuss the uncertainties in this phenomenological approach, the implications of these results on the extraction of the gluon distribution of the nucleon, and the comparison of our findings to recent related work. {copyright} {ital 1999} {ital The American Physical Society}

Uncertainties in determining parton distributions at large x

We critically examine uncertainties in parton distribution functions (PDFs) at large x arising from nuclear effects in deuterium F2 structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, from the use of relativistic kinematics, and from the use of a less restrictive parametrization of the d/u ratio. We find in particular that the d-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure functions, and on W boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the d-quark and gluon distributions but insensitive to nuclear corrections.

Order-. alpha. sub s calculation of hadronic ZZ production

An order-{alpha}{sub {ital s}} calculation of {ital pp}{sup ({minus})}{r arrow}{ital ZZ}+{ital X} is presented. Results are given for the total cross section and differential distributions for Fermilab Tevatron, CERN Large Hadron and Collider, and Superconducting Super Collider energies. The calculation utilizes a combination of analytic and Monte Carlo integration methods which makes it easy to calculate a variety of observables and to impose experimental cuts.

New parton distributions from large-

We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on

x

W

and low-

and

Q^2

Q

data

are relaxed, thereby including more data at high values of

Probing gluon and heavy-quark nuclear PDFs with γ + Q production in pA collisions

x