Jianwei Qiu

k{sub T} factorization is violated in production of high-transverse-momentum particles in hadron-hadron collisions

We show that hard-scattering factorization is violated in the production of high-p{sub T} hadrons in hadron-hadron collisions, in the case that the hadrons are back-to-back, so that k{sub T} factorization is to be used. The explicit counterexample that we construct is for the single-spin asymmetry with one beam transversely polarized. The Sivers function needed here has particular sensitivity to the Wilson lines in the parton densities. We use a greatly simplified model theory to make the breakdown of factorization easy to check explicitly. But the counterexample implies that standard arguments for factorization fail not just for the single-spin asymmetry but for the unpolarized cross section for back-to-back hadron production in QCD in hadron-hadron collisions. This is unlike corresponding cases in e{sup +}e{sup -} annihilation, Drell-Yan, and deeply inelastic scattering. Moreover, the result endangers factorization for more general hadroproduction processes.

Upsilon transverse momentum at hadron colliders.

We predict the shape of the transverse momentum pT spectrum of ϒ production. The distribution at low pT is dominated by the region of small impact parameter b and may be computed reliably in perturbation theory. We resum to all orders in the strong coupling αs the process-independent large logarithmic contributions that arise from initial-state gluon showers in the small pT(≤ Mϒ) region. The cross section at large pT is represented by the lowest-order non-vanishing perturbative contribution.

Hadronic production of W and Z bosons at large transverse momentum

We introduce a modified factorization formalism in quantum chromodynamics for hadronic production of

Gluonic contribution to g sub 1 and its relationship to the spin-dependent parton distributions

W

QCD parton recombination and applications to nuclear structure functions

and

New derivation of the Altarelli-Parisi equations

Z

Probing gluon polarization in hadronic direct photon production

bosons at large transverse momentum

QCD and Hadron Physics

p_T

Modeling parton spin-transfer densities

. When

Prompt Photon Production With a Polarized Deuteron Target

p_T