Extending Precision Perturbative QCD with Track Functions

Aug 3, 2021, 5:45 PM



Yibei Li (Department of Physics, Zhejiang University, CHINA) Yibei Li (Department of Physics, Zhejiang University, CHINA)


Using the tracking system at the LHC, one can efficiently suppress pile-up contamination and im- prove angular resolution. Observables that only depend on charged particles (tracks) are not in- frared safe in perturbation theory, so any calculation of track-based observables must account for hadronization effects. This can be done by matching the partonic cross section onto perturbative objects that absorb the infrared divergences, called track functions. These track functions describe the energy fraction of a hard parton which is converted into charged hadrons. We demonstrate the validity of the track function approach at order alpha_s^2 by calculating its renormalisation group evolution at this order, using two different approaches: The first uses analytic results for the projected Energy-Energy Correlator to extract the evolution for moments of the track function. The second involves a calculation of a track-based jet function in Soft-Collinear Effective Theory. This result is also an important input for higher-order calculations of track-based observables. Our results open the door to the application of advances in perturbative quantum field theory to observables defined on a subset of final-state particles, with a wide range of applications from the LHC to the EIC.

Primary authors

Huaxing Zhu (ZJU - Zhejiang University (CN)) Solange Schrijnder van Velzen Ian James Moult Wouter Waalewijn (University of Amsterdam) Yibei Li (Department of Physics, Zhejiang University, CHINA)

Presentation materials