OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints

TL;DR

OPTIMASS is a C++ software package that efficiently performs constrained minimization of kinematic mass functions, facilitating advanced analyses in collider physics for new physics searches.

Contribution

It introduces a flexible, general-purpose tool for calculating complex mass variables with constraints, extending the capabilities beyond existing methods.

Findings

Successfully applied to top quark decay analysis

Demonstrated efficient constrained minimization with MINUIT

Enhanced analysis potential for collider physics

Abstract

Reconstructed mass variables, such as $M_2$, $M_{2C}$, $M_T^\star$, and $M_{T2}^W$, play an essential role in searches for new physics at hadron colliders. The calculation of these variables generally involves constrained minimization in a large parameter space, which is numerically challenging. We provide a C++ code, OPTIMASS, which interfaces with the MINUIT library to perform this constrained minimization using the Augmented Lagrangian Method. The code can be applied to arbitrarily general event topologies and thus allows the user to significantly extend the existing set of kinematic variables. We describe this code and its physics motivation, and demonstrate its use in the analysis of the fully leptonic decay of pair-produced top quarks using the $M_2$ variables.