Abstract
The algebraic singularity method is a framework for analyzing collider events with missing energy. It provides a way to draw out a set of singularity variables that can catch singular features originating from the projection of full phase space onto the observable phase space of measured particle momenta. It is a promising approach applicable to various physics processes with missing energy but still requires more studies for use in practice. Meanwhile, in the double-sided decay topology with an invisible particle on each side, the MT2 variable has been known to be a useful collider observable for measuring particle masses from missing energy events or setting signal regions of collider searches. We investigate the relation between the two different types of kinematic variables in double-sided decay topology. We find that the singularity variables contain the MT2 variable in many cases, although the former is not a strict superset of the latter.
Highlights
JHEP11(2021)042 has never been considered in the following works by different authors [17–20]
We anticipate that our attempt of comparing the MT 2 with the singularity variables in doublesided decay topology will help the reader to gain an understanding of the method and to apply the method to find the signals of unexplored decay topologies at colliders
The MT 2 variable is served as the observable of choice when analyzing the collider events of double-sided decay topology with invisible particles in the final state
Summary
We begin our discussion with the definition and the properties of the MT 2 variable before looking into the algebraic singularity method. The MT 2 variable is a function of visible particle momenta pa, missing transverse momentum P/ T , and the guessed value of invisible particle mass Mχ. Because we here assume that the upstream momentum is vanishing, the missing transverse momentum is given by the negative vector sum of the visible particle momenta from the decays of Y and Y , P/ T = −p1T − p2T. The invisible transverse momentum of the second decay chain is given by k2T = −p1T This expression matches that identified in the study of MT 2 for the h → W W → +ν −νprocess, where the visible and invisible particles in the final state are all massless [42, 43]. We will revisit the fully massless case in the last section before conclusions
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