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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 (15 sections, 50 equations, 7 figures, 4 tables)

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