Why $$\alpha _s$$ αs cannot be determined from hadronic processes without simultaneously determining the parton distributions

• Main Authors: Stefano Forte, Zahari Kassabov
• Format: Article
• Language: English
• Published: SpringerOpen 2020-02-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-020-7748-6

Abstract We show that any determination of the strong coupling $$\alpha _s$$ αs from a process which depends on parton distributions, such as hadronic processes or deep-inelastic scattering, generally does not lead to a correct result unless the parton distributions (PDFs) are determined simultaneously along with $$\alpha _s$$ αs . We establish the result by first showing an explicit example, and then arguing that the example is representative of a generic situation which we explain using models for the shape of equal $$\chi ^2$$ χ2 contours in the joint space of $$\alpha _s$$ αs and the PDF parameters.