Mass and spin determination of new particles at hadron collider using $M_{T2}$ and on-shell reconstruction

Abstract

If new physics signals are discovered in collider experiments then it will be crucial to determine the mass and spin of new particles to demonstrate that they are indeed the predicted new physics. A wide class of new physics that provides a candidate of dark matter often preserves a discrete $Z_2$ symmetry, which results in a certain type of event topology in the experiment. We give a brief survey of the new physics scenarios which were motivated by solving the hierarchy problem, and typical collider signature of them. We then introduce the methods of mass measurement at hadron collider, and discuss the $\It{M_{T2}}$-kink method to determine the masses of both the dark matter WIMP, and its parent particle. To provide kinematic variables useful for the determination of new particle properties, we propose a scheme to assign a systematic approximation of four-momentum to each WIMP in the generic new physics processes. This $\It{M_{T2}}$-assisted on-shell (MAOS) reconstruction of missing momenta can be applied to the spin determination, which is vital to discriminate among different classes of models. As an application of MAOS momentum to the mass measurement, we examine the possibility to determine the standard model Higgs boson mass by constructing the MAOS Higgs mass.