Common Partial Wave Analysis Framework

One of the main topics of interest in physics is the composition and structure of matter. Especially for hadrons, which are bound states of quarks and gluons such as the proton and neutron, the description is incomplete. Quantum chromodynamics (QCD), the theory of the strong inter­action, is able to describe most experimental results. However, neither QCD nor derived effective theories or lattice-QCD calculations are able to fully explain the rich hadron spectrum. When trying to extract information on bound states produced in particle reactions, partial wave analysis (PWA) or amplitude analysis is a powerful technique, which gives access to a broad spectrum of bound states. However, there is more than one theoretical approach to such processes. The comparison between the results of various formalisms on data sets is of high value, as this can provide information on the interpretation of states and on the accuracy and limitations of the results. These techniques are also needed in other fields of particle physics, in particular in heavy-flavour physics. Besides the study of bound states, the search for CP violating effects is of particular interest. Here, the analysis of multi-body decays of B and D mesons requires a decomposition of the final state into its CP-even and –odd components by means of amplitude analysis.

The software package ComPWA (Common Partial Wave Analysis Framework) is designed precisely to facilitate this kind of comparisons. One of the most important design guidelines for ComPWA has been the greatest possible modularization. This allows avoiding restrictions imposed by most other PWA tools on the market. As of now, the first formalisms, such as the helicity formalism and a simple Dalitz plot analysis, have been implemented in ComPWA and are being used in analyses of data of the BESIII experiment in the field of meson spectroscopy.

The goal of this project is to extend ComPWA with further formalisms in order to broaden the base for comparison of the various theoretical descriptions. We also plan to extend ComPWA to allow the analysis of baryonic final states using e. g. BESIII data, and to prepare for the extraction of parameters necessary for Standard Model tests with BESIII and Belle II data. Furthermore, we will implement the necessary formalisms to describe antiproton-proton reactions, especially in preparation for the PANDA experiment. Strict adherence to the modular design of ComPWA will finally allow simultaneous fits to more than one data set from the same or even different experiments.

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