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Multiphoton Radiation in Leptonic W-Boson Decays

W. Placzek, S. Jadach

TL;DR

This work delivers the first implementation of multiphoton radiation in leptonic W decays using YFS exclusive exponentiation, embedded in the WINHAC Monte Carlo for single-W production at parton level. It provides fully massive spin amplitudes for W production and decay, including single-real-photon radiation, and constructs a numerically stable YFS framework with non-IR beta functions for event generation. Numerical tests show that total cross-section corrections are at the 10^-4 level, while certain distributions can receive much larger YFS-enhanced corrections, especially without calorimetric recombination. The authors plan to extend the approach to full pp collisions, incorporate NLO EW and QCD effects, and apply the method to W-pair production and future collider studies.

Abstract

We present the calculation of multiphoton radiation effects in leptonic W-boson decays in the framework of the Yennie-Frautschi-Suura exclusive exponentiation. This calculation is implemented in the Monte Carlo event generator WINHAC for single W-boson production in hadronic collisions at the parton level. Some numerical results obtained with the help of this program are also presented.

Multiphoton Radiation in Leptonic W-Boson Decays

TL;DR

This work delivers the first implementation of multiphoton radiation in leptonic W decays using YFS exclusive exponentiation, embedded in the WINHAC Monte Carlo for single-W production at parton level. It provides fully massive spin amplitudes for W production and decay, including single-real-photon radiation, and constructs a numerically stable YFS framework with non-IR beta functions for event generation. Numerical tests show that total cross-section corrections are at the 10^-4 level, while certain distributions can receive much larger YFS-enhanced corrections, especially without calorimetric recombination. The authors plan to extend the approach to full pp collisions, incorporate NLO EW and QCD effects, and apply the method to W-pair production and future collider studies.

Abstract

We present the calculation of multiphoton radiation effects in leptonic W-boson decays in the framework of the Yennie-Frautschi-Suura exclusive exponentiation. This calculation is implemented in the Monte Carlo event generator WINHAC for single W-boson production in hadronic collisions at the parton level. Some numerical results obtained with the help of this program are also presented.

Paper Structure

This paper contains 15 sections, 50 equations, 7 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Spin amplitudes
  3. Born level
  4. ${\cal O}(\alpha)$ corrections
  5. Virtual and real soft-photon corrections
  6. Real hard-photon radiation
  7. The YFS exponentiation in leptonic $W$ decays
  8. Numerical results
  9. General tests
  10. Distributions
  11. Summary and outlook
  12. Spinorial string functions
  13. The YFS IR functions
  14. The virtual-photon IR function
  15. The real-photon IR function

Figures (7)

  • Figure 1: The Born-level Feynman diagram for single-$W$ production in fermion--antifermion collisions.
  • Figure 2: The Born-level Feynman diagram for $W$-boson decay.
  • Figure 3: The Feynman diagrams for $W$-boson decay including single real-photon radiation (in the unitary gauge).
  • Figure 4: Production of a single $W^-$ in quark--antiquark collisions with multiphoton radiation in $W$-boson decay.
  • Figure 5: Distributions of the charged-lepton energy for BARE and CALO acceptances.
  • ...and 2 more figures