Model-independent partial wave analysis using a massively-parallel fitting framework

Abstract

The functionality of GooFit, a GPU-friendly framework for doing maximum-likelihood fits, has been extended to extract model-independent -wave amplitudes in three-body decays such as D+ → h+h+h−. A full amplitude analysis is done where the magnitudes and phases of the -wave amplitudes are anchored at a finite number of m2(h+h−) control points, and a cubic spline is used to interpolate between these points. The amplitudes for -wave and -wave intermediate states are modeled as spin-dependent Breit-Wigner resonances. GooFit uses the Thrust library, with a CUDA backend for NVIDIA GPUs and an OpenMP backend for threads with conventional CPUs. Performance on a variety of platforms is compared. Executing on systems with GPUs is typically a few hundred times faster than executing the same algorithm on a single CPU.