Tuning and validation of hadronic event generator for $R$ value measurements in the tau-charm region

TL;DR

This paper develops and validates a hadronic event generator with second-order initial state radiation effects, tuned to experimental data, to improve $R$ value measurements in the tau-charm energy region.

Contribution

It introduces a new event generator incorporating second-order initial state radiation and tunes unknown process parameters using experimental data, validated across a broad energy range.

Findings

Generator accurately models $R$ values below the $Dar D$ threshold.

Optimized parameters are universally applicable in the specified energy range.

Validation shows good agreement with experimental data.

Abstract

To measure the $R$ value in an energy scan experiment with $\ee$ collisions, precise calculation of initial state radiation is required in event generators. We present an event generator for this consideration, which incorporates initial state radiation effects up to the second order accuracy, and the radiative correction factor is calculated using the totally hadronic Born cross section. The measured exclusive processes are generated according to their cross sections, while the unknown processes are generated using the LUND Area Law model, and its parameters are tuned with data collected at $\sqrt s=3.65$ GeV. The optimized values are validated with data in the range $\sqrt s=2.2324\sim3.671$ GeV. These optimized parameters are universally valid for event generation below the $D\bar D$ threshold.