Comparison of Horace and Photos Algorithms for Multi-Photon Emission in the Context of the W Boson Mass Measurement

TL;DR

This paper compares two algorithms, Horace and Photos, for modeling multi-photon emission in W boson mass measurements, highlighting their impact on the accuracy of the measurement at the Tevatron.

Contribution

It provides a detailed comparison of Horace and Photos algorithms for final-state photon emission in W mass analysis, which was previously not thoroughly evaluated.

Findings

Differences in photon emission modeling affect the W mass measurement.

The study quantifies the impact of each algorithm on the mass shift.

Results inform the choice of photon emission models in precision measurements.

Abstract

The W boson mass measurement is sensitive to QED radiative corrections due to virtual photon loops and real photon emission. The largest shift in the measured mass, which depends on the transverse momentum spectrum of the charged lepton from the boson decay, is caused by the emission of real photons from the final-state lepton. There are a number of calculations and codes available to model the final-state photon emission. We perform a detailed study, comparing the results from the Horace and Photos implementations of the final-state multi-photon emission in the context of a direct measurement of the W boson mass at the Tevatron. Mass fits are performed using a simulation of the CDF II detector.