kT factorization is violated in production of high-transverse-momentum particles in hadron-hadron collisions
Abstract
We show that hard-scattering factorization is violated in the production of high-pT hadrons in hadron-hadron collisions, in the case that the hadrons are back-to-back, so that kT 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+e- annihilation, Drell-Yan, and deeply inelastic scattering. Moreover, the result endangers factorization for more general hadroproduction processes.
- Publication:
-
Physical Review D
- Pub Date:
- June 2007
- DOI:
- 10.1103/PhysRevD.75.114014
- arXiv:
- arXiv:0705.2141
- Bibcode:
- 2007PhRvD..75k4014C
- Keywords:
-
- 12.39.St;
- 13.85.Ni;
- 13.87.-a;
- 13.88.+e;
- Factorization;
- Inclusive production with identified hadrons;
- Jets in large-Q<sup>2</sup> scattering;
- Polarization in interactions and scattering;
- High Energy Physics - Phenomenology
- E-Print:
- 10 pages. V. 2: Title change, misprints and minor corrections, as in journal version