The dead-cone effect in charm, bottom and top quark jets in angular and momentum space
Abstract
The dead-cone effect reflects the mass dependence of QCD radiation from heavy quarks. We investigate this phenomenon from charm and bottom to top quarks using two-dimensional angular distributions and single-particle inclusive momentum spectra. The angular distributions illustrate the depletion of radiation around the heavy-quark direction, while the momentum spectra provide a quantitative observable of the effect. For charm and bottom jets, fragmentation functions reconstructed from LEP data at the Z pole exhibit a strong suppression of high-momentum particles, quantitatively described within the Modified Leading Logarithmic Approximation of perturbative QCD. The analysis is extended to √s=1 TeV using Monte Carlo simulations. A hypothetical stable-top sample isolates the primary top-quark radiation pattern, whereas the physical decay t→ bW introduces coherent radiation from the tb colour dipole, obscuring the primary dead cone. By exploiting the dependence on the b-quark emission angle Θb, we reconstruct the primary top-quark parton momentum spectrum through extrapolation to Θb→0. In contrast, the small-angle gluon and parton distributions do not converge to the stable-top dead-cone pattern because of radiation from the decay b quark. These findings establish the inclusive momentum spectrum as a robust quantitative observable of the top-quark dead-cone effect and provide a unified description of mass-dependent QCD radiation from charm to top.
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BibTeX
@misc{perezramos2026deadcone,
title = {{The dead-cone effect in charm, bottom and top quark jets in angular and momentum space}},
author = {Redamy Perez-Ramos and Stefan Kluth and Wolfgang Ochs},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20164},
eprint = {2610.20164},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20164},
}
RIS
TY - UNPB
TI - The dead-cone effect in charm, bottom and top quark jets in angular and momentum space
AU - Redamy Perez-Ramos
AU - Stefan Kluth
AU - Wolfgang Ochs
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.20164
UR - https://arxiv.org/abs/2610.20164
AB - The dead-cone effect reflects the mass dependence of QCD radiation from heavy quarks. We investigate this phenomenon from charm and bottom to top quarks using two-dimensional angular distributions and single-particle inclusive momentum spectra. The angular distributions illustrate the depletion of radiation around the heavy-quark direction, while the momentum spectra provide a quantitative observable of the effect. For charm and bottom jets, fragmentation functions reconstructed from LEP data at the Z pole exhibit a strong suppression of high-momentum particles, quantitatively described within the Modified Leading Logarithmic Approximation of perturbative QCD. The analysis is extended to √s=1 TeV using Monte Carlo simulations. A hypothetical stable-top sample isolates the primary top-quark radiation pattern, whereas the physical decay t→ bW introduces coherent radiation from the tb colour dipole, obscuring the primary dead cone. By exploiting the dependence on the b-quark emission angle Θ_b, we reconstruct the primary top-quark parton momentum spectrum through extrapolation to Θ_b→0. In contrast, the small-angle gluon and parton distributions do not converge to the stable-top dead-cone pattern because of radiation from the decay b quark. These findings establish the inclusive momentum spectrum as a robust quantitative observable of the top-quark dead-cone effect and provide a unified description of mass-dependent QCD radiation from charm to top.
ER -