Global QCD Analysis and the CTEQ Parton Distributions
H. L. Lai, J. Botts, J. Huston, J. G. Morfin, J. F. Owen, J. W. Qiu, W. K. Tung, H. Weerts
TL;DR
The paper presents the CTEQ global QCD analysis program and its iterative evolution from CTEQ1 through CTEQ3, detailing data selection, methodology, and parametrization choices. It demonstrates how incorporating diverse data sets (DIS, Drell-Yan, direct photon, collider measurements, and flavor-sensitive results) improves constraints on PDFs, especially flavor differentiation and the small-$x$ gluon, while addressing systematic uncertainties and theoretical scales. The results show a progression toward a balanced, largely consistent description of a wide range of data, with CTEQ3 delivering a robust, 15-parameter PDF set (CTEQ3M being the preferred) and highlighting remaining challenges such as precise strange-quark treatment and gluon uncertainties. The study underscores the importance of combining multiple processes to test QCD's universality and informs future measurements (e.g., W and Drell-Yan asymmetries) to further refine parton distributions.
Abstract
The CTEQ program for the determination of parton distributions through a global QCD analysis of data for various hard scattering processes is fully described. A new set of distributions, CTEQ3, incorporating several new types of data is reported and compared to the two previous sets of CTEQ distributions. Comparison with current data is discussed in some detail. The remaining uncertainties in the parton distributions and methods to further reduce them are assessed. Comparisons with the results of other global analyses are also presented.