Abstract
We present a Monte Carlo approach to soft-gluon resummation at subleading color which can be used to improve existing parton shower algorithms. At the single-emission level, soft-collinear enhancements of the splitting functions are explicitly linked to quadratic Casimir operators, while wide angle single-soft enhancements are connected to nontrivial color correlators. We focus on a numerically stable implementation of color matrix element corrections to all orders and approximate the virtual corrections by requiring unitarity at the single-emission level. We provide a proof-of-concept implementation to compute nonglobal event shapes at lepton colliders.
Highlights
Soft-gluon resummation is one of the most important tools in perturbative QCD, as it allows one to systematically and fairly straightforwardly compute radiative corrections to all orders for a large class of observables [1]
We find that the impact of subleading color evolution on all these observables is less than 10%, which agrees with the intuitive notion that corrections to improved leading color evolution should be of order 1=N2c
We have presented a novel Monte Carlo method for softgluon resummation that allows one to generate parton-level events and can be incorporated into existing parton showers in order to improve their formal precision
Summary
Soft-gluon resummation is one of the most important tools in perturbative QCD, as it allows one to systematically and fairly straightforwardly compute radiative corrections to all orders for a large class of observables [1]. Nonglobal observables require a more sophisticated treatment, which was first discussed in the context of eþe− and deep inelastic scattering (DIS) event shape resummation [9,10] using a Monte Carlo (MC) approach at leading color accuracy [9]. Based on the independence of color and kinematics operators, the color matrix elements are integrated with Monte Carlo methods at each step of the evolution. This allows one to reach good precision on the color coefficients, while limiting the run-time of computer simulations at high multiplicity.
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