Improving the sensitivity of Higgs boson searches in the golden channel

TL;DR

This paper enhances Higgs boson search sensitivity in the ZZ* channel by applying the matrix element method, leveraging full kinematic information to improve discovery and exclusion capabilities at the LHC.

Contribution

It introduces a multivariate analysis using the matrix element method to exploit full decay kinematics for better Higgs search sensitivity.

Findings

10-20% improvement in discovery significance and exclusion limits at high masses

Effective at integrated luminosities of 2.5 fb^-1 or more

Significant angular correlation differences aid background discrimination

Abstract

Leptonic decays of the Higgs boson in the ZZ* channel yield what is known as the golden channel due to its clean signature and good total invariant mass resolution. In addition, the full kinematic distribution of the decay products can be reconstructed, which, nonetheless, is not taken into account in traditional search strategy relying only on measurements of the total invariant mass. In this work we implement a type of multivariate analysis known as the matrix element method, which exploits differences in the full production and decay matrix elements between the Higgs boson and the dominant irreducible background from q bar{q} -> ZZ*. Analytic expressions of the differential distributions for both the signal and the background are also presented. We perform a study for the Large Hadron Collider at sqrt{s}=7 TeV for Higgs masses between 175 and 350 GeV. We find that, with an integrated luminosity of 2.5 fb^-1 or higher, improvements in the order of 10 - 20 % could be obtained for both discovery significance and exclusion limits in the high mass region, where the differences in the angular correlations between signal and background are most pronounced.