Extending a User Interface Class for the KinFit Library*

In particle physics, kinematic fitting is a technique used to improve the resolution of experimental measurements. This is done using conservation laws and different constraints, such as mass or momentum constraints. One widely used constraint is the 3-constraint (combination of geometric and kinematic constraints) which is implemented in the KinFit library that is used in the HADES experiment. Within KinFit is a user interface class that aims to ease the process of using the library as compared to using all of the library’s individual classes in an analysis, which can be very cumbersome and error prone. The class contains functions to apply constraints for various fits, and the goal is to add a function to enable the UI to successfully do 3C fits. The fit quality obtained using the method was compared to the quality of a manual fit without the UI class. The constraint was applied by generating an undetected candidate using known decay products of this particle and other particles in the event. The class was modified, and the fit was then applied. The results such as the χ2 and probabilities and comparison to the manual fit will be presented. The UI should be further modified to also include pull distributions to better know the quality of the fit, as well to make the UI more accessible.