Precision physics with inclusive QCD processes

Abstract

The inclusive production of hadrons through electroweak currents can be rigorously analysed with short-distance theoretical tools. The associated observables are insensitive to the involved infrared behaviour of the strong interaction, allowing for very precise tests of Quantum Chromodynamics. The theoretical predictions for ( + − → hadrons) and the hadronic decay widths of the lepton and the , and Higgs bosons have reached an impressive accuracy of ( 4 ). Precise experimental measurements of the and hadronic widths have made possible the accurate determination of the strong coupling at two very different energy scales, providing a highly significant experimental verification of asymptotic freedom. A detailed discussion of the theoretical description of these processes and their current phenomenological status is presented. The most precise determinations of from other sources are also briefly reviewed and compared with the fully-inclusive results.

Global fits in the Aligned Two-Higgs-Doublet model

“…Thus, the statistical relevance of the (g − 2) µ anomaly could be magnified by underestimated uncertainties. The most recent lattice calculations seem in fact to suggest that the SM prediction could be much closer to the current (g − 2) µ measurement [94]. While waiting for a possible confirmation (or not) of this intriguing anomaly, and in order not to bias the results, we will not include (g − 2) µ in the global fit.…”

SU(3) analysis of four-quark operators: K → ππ and vacuum matrix elements

“…A more precise knowledge arises in inclusive semileptonic processes involving three light quark flavours, such as hadronic tau decays or electron-positron annihilation into hadrons [8]. Although they have a quite different nature, the former being a weakinteraction transition and the latter an electromagnetic one, their associated hadronic distributions can be studied with the same theoretical formalism, since rigorous dispersion relations [9,10] connect them with two-point correlation functions of quark currents, leading to very precise predictions [11].…”

“…1) play a central role in the study of hadronic production through electroweak currents [8]. Here, J = V, A and the superscripts denote the transverse (T ) and longitudinal (L) components.…”

“…The inclusive invariant-mass distributions of the final hadrons in τ decay directly measure the hadronic spectral functions associated with the ud and us two-point current correlators in eq. (4.1), up to the τ mass scale [8,11]:…”

“…The so-called singlet topologies that only contribute to the neutral correlators are absent in the threeflavour theory because q eq = 0[8].…”