# Simulation of $e^+e^-\rightarrow\mbox{Hadrons}$ and Comparison to ALEPH Data at Full Detector Simulation with an Emphasis on Four-Jet States

## TL;DR

This paper uses advanced Monte Carlo simulations to model $e^+e^-
ightarrow$ hadrons, focusing on four-jet states, and compares the results to ALEPH data, showing improved agreement with higher-order matrix elements.

## Contribution

It introduces SHERPA simulations with up to six partons at NLO and LO, enhancing four-jet observable modeling and comparison to experimental data.

## Key findings

- NLO SHERPA improves four-jet observable modeling.
- Reweighting dijet masses enhances agreement with ALEPH data.
- SHERPA outperforms KK2f for four-jet clustering observables.

## Abstract

We use the SHERPA Monte Carlo generator to simulate the process $e^+e^-\rightarrow\mbox{hadrons}$ using matrix elements with up to six partons in the final state. Two samples of SHERPA events are generated. In the "LO" sample, all final states are generated with leading order matrix elements; in the "NLO" sample, matrix elements for final states with up to four partons are generated at next-to-leading order, while matrix elements for final states with five or six partons are generated at leading order. The resulting samples are then passed through the ALEPH detector simulation. We compare the Monte Carlo samples to each other, to samples generated using the KK2f generator interfaced with PYTHIA, and to the archived ALEPH data at both LEP1 and LEP2 energies. We focus on four-jet observables with particular attention given to dijet masses. The LO and NLO SHERPA samples show significant improvement over the KK2f generation for observables directly related to clustering events into four jets, while maintaining similar performance to KK2f for event-shape variables. We additionally reweight the dijet masses using LEP1 data and find that this greatly improves the agreement between the three Monte Carlo samples at LEP2 energies for these observables.