State-of-the-Art Predictions for C-parameter and a Determination of alpha_s

• Main Authors: Hoang, Andre H, Kolodrubetz, Daniel W, Mateu, Vicent, Stewart, Iain W
• Format: Journal Article
• Language: English
• Published: 20-01-2015
• Subjects: Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.1501.04753

The C-parameter event-shape distribution for e+e- annihilation into hadrons
is computed in the framework of SCET including input from fixed-order
perturbation theory. We calculate all missing ingredients for achieving N3LL
resummation accuracy in the cross section, which is then matched onto
O(alpha_s^3) fixed-order results. Hadronization power corrections are
incorporated as a convolution with a nonperturbative shape function. Wide-angle
soft radiation effects introduce an O(Lambda_QCD) renormalon ambiguity in the
cross section, which we cure by switching to the Rgap short-distance scheme. We
also include hadron mass effects, but find their effect is rather small.
Performing fits to the tail of the C-parameter distribution for many center of
mass energies we find that the strong coupling constant is alpha_s(mZ) = 0.1123
+-0.0015, with chi^2/dof=0.99.