Reconstructing particle masses from pairs of decay chains

TL;DR

This paper introduces a robust method for reconstructing the masses of new particles in collider events with decay chains, effectively utilizing all kinematic information and handling experimental uncertainties.

Contribution

It presents a novel approach that determines particle masses from decay chain events by analyzing invariant mass spectra and mass-squared differences, improving robustness and efficiency.

Findings

Method successfully reconstructs particle masses with small data samples.

Approach is robust against measurement errors and combinatorial ambiguities.

Utilizes full kinematic information for accurate mass determination.

Abstract

A method is proposed for determining the masses of the new particles N,X,Y,Z in collider events containing a pair of effectively identical decay chains Z to Y+jet, Y to X+l_1, X to N+l_2, where l_1, l_2 are opposite-sign same-flavour charged leptons and N is invisible. By first determining the upper edge of the dilepton invariant mass spectrum, we reduce the problem to a curve for each event in the 3-dimensional space of mass-squared differences. The region through which most curves pass then determines the unknown masses. A statistical approach is applied to take account of mismeasurement of jet and missing momenta. The method is easily visualized and rather robust against combinatorial ambiguities and finite detector resolution. It can be successful even for small event samples, since it makes full use of the kinematical information from every event.