Two-lepton tales: Dalitz decays of heavy quarkonia

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Hauptverfasser: Colangelo, Pietro, De Fazio, Fulvia, Pinto, Riccardo
Format: Preprint
Veröffentlicht: 2025
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author Colangelo, Pietro
De Fazio, Fulvia
Pinto, Riccardo
author_facet Colangelo, Pietro
De Fazio, Fulvia
Pinto, Riccardo
contents We study the Dalitz decays of heavy quarkonia, which result from the internal virtual photon conversion into an $\ell^+ \ell^-$ lepton pair. Heavy-quark symmetries allow us to establish systematic relations between transitions of different quarkonium states, and to precisely determine the branching fractions for several charmonium and bottomonium decay modes. For charmonium, existing data on $χ_{cJ}(1P)\to J/ψ\ell^+ \ell^-$ and $ψ(2S)\to χ_{cJ}(1P) \ell^+ \ell^-$ enable us to determine the parameters of the transition form factors and to predict the rates of yet-unobserved modes. The Dalitz transitions of $χ_{c1}(3872)$ are important, as they can help assessing the structure of this meson. For bottomonium, recent LHCb measurements allow us to predict the branching fractions of $χ_{bJ}(nP)\to Υ(1S)\ell^+ \ell^-$ and $h_b(nP)\to η_b(1S) \ell^+ \ell^-$ ($n=1,\,2)$. We also investigate the sensitivity of heavy quarkonia Dalitz modes to the contribution of a new light vector mediator, such as the putative $X(17)$.
format Preprint
id arxiv_https___arxiv_org_abs_2512_17672
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Two-lepton tales: Dalitz decays of heavy quarkonia
Colangelo, Pietro
De Fazio, Fulvia
Pinto, Riccardo
High Energy Physics - Phenomenology
High Energy Physics - Experiment
High Energy Physics - Lattice
We study the Dalitz decays of heavy quarkonia, which result from the internal virtual photon conversion into an $\ell^+ \ell^-$ lepton pair. Heavy-quark symmetries allow us to establish systematic relations between transitions of different quarkonium states, and to precisely determine the branching fractions for several charmonium and bottomonium decay modes. For charmonium, existing data on $χ_{cJ}(1P)\to J/ψ\ell^+ \ell^-$ and $ψ(2S)\to χ_{cJ}(1P) \ell^+ \ell^-$ enable us to determine the parameters of the transition form factors and to predict the rates of yet-unobserved modes. The Dalitz transitions of $χ_{c1}(3872)$ are important, as they can help assessing the structure of this meson. For bottomonium, recent LHCb measurements allow us to predict the branching fractions of $χ_{bJ}(nP)\to Υ(1S)\ell^+ \ell^-$ and $h_b(nP)\to η_b(1S) \ell^+ \ell^-$ ($n=1,\,2)$. We also investigate the sensitivity of heavy quarkonia Dalitz modes to the contribution of a new light vector mediator, such as the putative $X(17)$.
title Two-lepton tales: Dalitz decays of heavy quarkonia
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
High Energy Physics - Lattice
url https://arxiv.org/abs/2512.17672