Parton Fragmentation within an Identified Jet at NNLL
Keywords
parton fragmentation_s19 gluon jet_s19 jet pair production_s19 jet mass_s19 hadronization_s19 fragmentation function_s19 quark jet_s19 infrared problem_s19 electron positron annihilation_s19 jet electroproduction_s19 leading logarithm approximation: higher-order_s19 dimensional regularization_s19 soft collinear effective theory_s19 pi_s16 electroproduction_s19 thrust_s19 differential cross section_s19 renormalization group_s19 optical theorem_s19 numerical calculations_s19 10.6 GeV-cms
Abstract
The fragmentation of a light parton i to a jet containing a light energetic hadron h, where the momentum fraction of this hadron as well as the invariant mass of the jet is measured, is described by _s15fragmenting jet functions_s15. We calculate the one-loop matching coefficients J_{ij} that relate the fragmenting jet functions G_i^h to the standard, unpolarized fragmentation functions D_j^h for quark and gluon jets. We perform this calculation using various IR regulators and show explicitly how the IR divergences cancel in the matching. We derive the relationship between the coefficients J_{ij} and the quark and gluon jet functions. This provides a cross-check of our results. As an application we study the process e_s16 e- to X pi_s16 on the Upsilon(4S) resonance where we measure the momentum fraction of the pi_s16 and restrict to the dijet limit by imposing a cut on thrust T. In our analysis we sum the logarithms of tau=1-T in the cross section to next-to-next-to-leading-logarithmic accuracy (NNLL). We find that including contributions up to NNLL (or NLO) can have a large impact on extracting fragmentation functions from e_s16 e- to dijet _s16 h.
