$H \rightarrow e^+ e^- $ at CEPC: ISR effect with MadGraph

TL;DR

This paper investigates the Higgs decay to electron pairs at the CEPC, focusing on the ISR effect using MadGraph, and estimates the potential upper limit on the branching ratio with full simulation data.

Contribution

It introduces a method to incorporate ISR effects in MadGraph for e+e- colliders and evaluates the Higgs to e+e- decay at CEPC with detailed simulation.

Findings

Upper limit of Higgs to e+e- branching ratio could reach 0.024% at 95% CL

First implementation of ISR in MadGraph for electron-positron collider studies

Simulation results inform future Higgs decay measurements at CEPC

Abstract

The Circular Electron Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240-250 GeV. The CEPC will accumulate an integrated luminosity of 5 ab$^{\rm{-1}}$ in ten years' operation. With GEANT4-based full simulation samples for CEPC, Higgs boson decaying into electron pair is studied at the CEPC. The upper limit of ${\cal B}(H \rightarrow e^+ e^-)$ could reach 0.024\% at 95\% confidence level. The signal process is generated by MadGraph, with Initial State Radiation (ISR) implemented, as a first step to adjust MadGraph for a electron positron Collider.