Abstract
We provide a quantum field theory based description of the nonperturbative effects from hadronization for soft drop groomed jet mass distributions using the soft- collinear effective theory and the coherent branching formalism. There are two distinct regions of jet mass mJ where grooming modifies hadronization effects. In a region with intermediate mJ an operator expansion can be used, and the leading power corrections are given by three universal nonperturbative parameters that are independent of all kinematic variables and grooming parameters, and only depend on whether the parton initiating the jet is a quark or gluon. The leading power corrections in this region cannot be described by a standard normalized shape function. These power corrections depend on the kinematics of the subjet that stops soft drop through short distance coefficients, which encode a perturbatively calculable dependence on the jet transverse momentum, jet rapidity, and on the soft drop grooming parameters zcut and β. Determining this dependence requires a resummation of large logarithms, which we carry out at LL order. For smaller mJ there is a nonperturbative region described by a one-dimensional shape function that is unusual because it is not normalized to unity, and has a non-trivial dependence on β.
Highlights
Measurements of jet observables in QCD provide a key tool to test perturbative, resummed, nonperturbative, and Monte Carlo descriptions of QCD dynamics and are used to probe the presence of new physics
We have presented a study of the dominant nonperturbative corrections to the groomed jet mass spectrum based on quantum field theory calculations in the framework of soft collinear effective theory and the coherent branching formalism
We considered the operator expansion region (SDOE), where the hadronization effects are power corrections, and the nonperturbative region (SDNP) of the jet mass spectrum, where they become leading order effects
Summary
Measurements of jet observables in QCD provide a key tool to test perturbative, resummed, nonperturbative, and Monte Carlo descriptions of QCD dynamics and are used to probe the presence of new physics. Often the most important information about hadronization can be encoded in a single parameter, which is the first moment of an underlying nonperturbative shape function Another method of accounting for hadronization corrections is to rely on hadronization models that are implemented within Monte Carlo parton shower event generators like Pythia [33] and Herwig [34]. We consider two distinct regions for the jet mass, each having a distinct description for their leading hadronization corrections: soft drop operator expansion (SDOE) region: soft drop nonperturbative (SDNP) region: QΛQCD m2J
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