Search for High-mass Resonances in Z(ll)gamma Final State at CMS

Kyungwook Nam

doi:10.22323/1.282.0767

Abstract

A search for a heavy resonance decaying to Zγ, with the Z boson further decaying to pairs of electrons or muons is presented. The search strategy is to look for an excess above the non- resonant Standard Model background on the l+l−γ invariant mass spectrum. The search is based on 13 TeV proton-proton collision data collected with the CMS detector, corresponding to the integrated luminosity of 12.9/fb.

Highlights

The discovery of a Higgs boson at 125 GeV [1][2], while generally seen as the completion of the Standard Model (SM) of particle physics, can be a first hint for a more fundamental theory of nature to which the SM might be only a low-energy approximation
The signal Monte Carlo (MC) is used in the analysis for two parts: first, it provides the shape of the signal invariant mass spectrum, which is parametrized by a function with a Gaussian core and two power-law tails, an extended form of the Crystal Ball function [11]; second, acceptance and selection efficiency are measured using the signal MC
No significant excess above expected backgrounds is observed in mZγ spectrum

Summary

Introduction

The discovery of a Higgs boson at 125 GeV [1][2], while generally seen as the completion of the Standard Model (SM) of particle physics, can be a first hint for a more fundamental theory of nature to which the SM might be only a low-energy approximation. A variety of models beyond the SM predict the existence of a new scalar boson, which may decay into Zγ. This paper describes the results of a search for such heavy resonances decaying to Zγ, with further decay of Z → e+e−/μ+μ− [3]. The search is based on 13 TeV proton-proton collision data collected by the CMS experiment [4] in 2016, corresponding to the integrated luminosity of 12.9 fb−1. The search strategy measures the non-resonant SM background directly on data, and looks for localized excesses, to what is done in Ref. The search strategy measures the non-resonant SM background directly on data, and looks for localized excesses, to what is done in Ref. [5] and [6]

Event Selection

Background

Results

Conclusion