A short comparison between m_T2 and m_CT

TL;DR

This paper compares two kinematic variables, m_T2 and m_CT, used for analyzing pair-produced particles with symmetric decay chains, highlighting their differences, advantages, and specific use cases.

Contribution

The paper provides a detailed comparison of m_T2 and m_CT, identifying conditions where they are equivalent and discussing their relative advantages in mass analysis.

Findings

m_CT equals m_T2 for massless visible particles in a specific limit

m_T2 is more robust under initial state radiation

m_T2 better facilitates mass extraction from decay chains

Abstract

We compare m_T2 with m_CT; both are kinematic variables designed to find relationships between masses of pair-produced new states with symmetric decay chains. We find that for massless visible particles m_CT equals m_T2 in a particular limit. We identify advantages and disadvantages to the use of each variable. Tovey's paper on m_CT also introduced a powerful concept of extracting mass information from an analysis at intermediate stages of a symmetric decay chain. We suggest that m_T2 is a better tool for performing this analysis than m_CT due to m_T2's better properties under initial state radiation.