Quarkonium Decays and Production in NRQCD
Fabio Maltoni
TL;DR
This paper surveys NRQCD factorization applications to quarkonium phenomenology, with two main parts: NLO decay calculations for χ_cJ and Υ and an extraction of non-perturbative matrix elements (MEs) from hadronic fixed-target data to test universality. For χ_cJ, both color-singlet and color-octet Fock components contribute at leading order in v, and a global NLO fit using measured widths yields constrained MEs and a prediction for the h_c hadronic width. For Υ, color-octet contributions can be as large as color-singlet ones at NLO, complicating α_s extractions and highlighting the need for input from lattice or other methods to pin down MEs. The production section discusses factorized cross sections and uses fixed-target hadroproduction to test universality by relating production MEs to decay-derived singlets and constraining octets. Overall, the work illustrates the practical utility and challenges of NRQCD in both decays and production and the importance of universality tests.
Abstract
Some examples of the most recent applications of the NRQCD factorization approach to quarkonium phenomenology are presented. In the first part of the talk the NLO calculations for $\chicj$ and $Υ$ decays rates are compared to the data and the results critically analyzed. In the second part, I show how information on the non-perturbative matrix elements can be extracted from the hadronic fixed-target experiments and eventually used to test their universality.