Abstract
We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A weighting algorithm is implemented, that allows to consistently treat potentially negative values of the splitting functions and the parton distributions. We provide two independent, publicly available implementations for the two event generators Pythia and Sherpa.
Highlights
Parton showers and fragmentation models have been used for more than three decades to predict the dynamics of multi-particle final states in collider experiments [1,2]
The traditional approaches implemented in Herwig [3,4], Pythia [5,6] and Sherpa [7,8] were supplemented by methods based on dipole and antenna factorization [9,10,11,12,13,14,15,16,17]
We have introduced an observable, O, that measures the kinematics of the final state
Summary
Parton showers and fragmentation models have been used for more than three decades to predict the dynamics of multi-particle final states in collider experiments [1,2]. The model is a hybrid of dipole and parton shower These choices will eventually allow one to compare with analytic approaches, such as CSS [22,23,24,25,26,27] and SCET [28,29,30,31]. When comparing the results of different event generators at the hadron level it is often unclear whether differences should be ascribed to the hadronization model, to the simulation of multiple scattering/rescattering effects, or to the parton shower.
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