Amplification of endpoint structure for new particle mass measurement at the LHC

Abstract

We introduce a new collider variable, ${M}_{CT2}$, named as constransverse mass. It is a mixture of ``stransverse mass (${M}_{T2}$)'' and ``contransverse mass (${M}_{CT}$)'' variables, where the usual endpoint structure of ${M}_{T2}$ distribution can be amplified in the ${M}_{CT2}$ basis by a large Jacobian factor which is controlled by a trial missing particle mass. Thus, the ${M}_{CT2}$ projection of events increases our observability to measure several important endpoints from new particle decays, which are usually expected to be buried by irreducible backgrounds with various systematic uncertainties at the LHC. In this paper we explain the phenomenology of endpoint amplification in ${M}_{CT2}$ projection, and describe how one may employ this variable to measure several meaningful mass constraints of new particles.