Emilio Royo
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Emilio Royo has a total of 10 co-authors. Here are the top co-authors by number of shared publications:
- Rafel Escribano
Universitat Autónoma de Barcelona
15 shared publications - Sergi Gonzàlez-Solís
Departament de Física Quàntica i Astrofísica (FQA) Universitat de Barcelona (UB) c.Martí i Franquès 1 08028 Barcelona Spain
6 shared publications - Pablo Sanchez-Puertas
Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, Granada, Spain
3 shared publications - Renata Jora
Natl Inst Phys & Nucl Engn, POB MG-6, Bucharest, Romania
2 shared publications - Antonio Sala
Instituto de Automática e Informática Industrial Universitat Politècnica de València Valencia Spain
1 shared publication - Bernardo Tormos
CMT-Clean Mobility & Thermofluids, Universitat Politècnica de València, 46022 Valencia, Spain
1 shared publication
Latest Publications
- Open Access
- 3 December 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (11)
Assessment of the a 2 ( 1320 ) tensor-meson contribution to η / η ′ → π 0 γ γ decays
In light of the recent measurement of the η → π 0 γ γ decay by the KLOE-2 Collaboration, a previous analysis including vector- and scalar-meson exchange contributions using the vector meson dominance and linear sigma model frameworks, respectively, is extended in the present study to incorporate the effects of the a 2 ( 1320 ) tensor meson within a chiral context. Although the individual contribution of the a 2 is negligible, its destructive interference with the vector-meson resonances is found to be significant, representing approximately 18% of the total signal and substantially affecting the diphoton invariant-mass distribution, especially at low m γ γ 2 values. The total decay rate is calculated to be Γ ( η → π 0 γ γ ) = 0.154 ( 22 ) eV , which corresponds to a branching ratio of BR ( η → π 0 γ γ ) = 1.17 ( 17 ) × 10 − 4 . This result is approximately 5 σ below the reported value of the particle data group, 2.55 ( 22 ) × 10 − 4 , while it is in very good agreement with the KLOE-2 measurement, 0.98 ( 1 1 stat ) ( 1 4 syst ) × 10 − 4 . In contrast, the total contribution of the a 2 is found to be negligible in η ′ → π 0 γ γ , as this process is completely dominated by the exchange of an on-shell ω vector resonance.
- 3 December 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 112 (11)
Open AccessAssessment of the a 2 ( 1320 ) tensor-meson contribution to η / η ′ → π 0 γ γ decays
In light of the recent measurement of the η → π 0 γ γ decay by the KLOE-2 Collaboration, a previous analysis including vector- and scalar-meson exchange contributions using the vector meson dominance and linear sigma model frameworks, respectively, is extended in the present study to incorporate the effects of the a 2 ( 1320 ) tensor meson within a chiral context. Although the individual contribution of the a 2 is negligible, its destructive interference with the vector-meson resonances is found to be significant, representing approximately 18% of the total signal and substantially affecting the diphoton invariant-mass distribution, especially at low m γ γ 2 values. The total decay rate is calculated to be Γ ( η → π 0 γ γ ) = 0.154 ( 22 ) eV , which corresponds to a branching ratio of BR ( η → π 0 γ γ ) = 1.17 ( 17 ) × 10 − 4 . This result is approximately 5 σ below the reported value of the particle data group, 2.55 ( 22 ) × 10 − 4 , while it is in very good agreement with the KLOE-2 measurement, 0.98 ( 1 1 stat ) ( 1 4 syst ) × 10 − 4 . In contrast, the total contribution of the a 2 is found to be negligible in η ′ → π 0 γ γ , as this process is completely dominated by the exchange of an on-shell ω vector resonance.
- Open Access
- 6 February 2024
- Published by Sissa Medialab Srl
- Vol. 413, 024
Theoretical analysis of $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^{\prime}\to\eta l^+l^-$ decays, and new-physics signatures via $CP$ violationA complete theoretical analysis of the $C$-conserving semileptonic decays $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0$, $\omega$, $\phi$ and $P=\pi^0$, $\eta$, $\eta^{\prime}$). Theoretical predictions for the six decay widths and associated dilepton energy spectra are calculated and presented. In addition, we investigate the prospect of observing new-physics signatures via $CP$ violation in $\eta^{(\prime)}\to\pi^0\mu^+\mu^-$ and $\eta^\prime\to\eta\mu^+\mu^-$ decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics $CP$-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments for these particular processes.- 6 February 2024
- Published by Sissa Medialab Srl
- Vol. 413, 024
Open AccessTheoretical analysis of $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^{\prime}\to\eta l^+l^-$ decays, and new-physics signatures via $CP$ violationA complete theoretical analysis of the $C$-conserving semileptonic decays $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0$, $\omega$, $\phi$ and $P=\pi^0$, $\eta$, $\eta^{\prime}$). Theoretical predictions for the six decay widths and associated dilepton energy spectra are calculated and presented. In addition, we investigate the prospect of observing new-physics signatures via $CP$ violation in $\eta^{(\prime)}\to\pi^0\mu^+\mu^-$ and $\eta^\prime\to\eta\mu^+\mu^-$ decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics $CP$-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments for these particular processes. - Open Access
- 6 February 2024
- Published by Sissa Medialab Srl
- Vol. 413, 027
A primer analysis of $\pi^0$-$\eta$-$\eta^{\prime}$ mixing from $V\!\rightarrow\!P\gamma$ and $P\!\rightarrow\!V\gamma$ decaysA primer analysis of $\pi^0$-$\eta$-$\eta^{\prime}$ mixing from $V\!\rightarrow\!P\gamma$ and $P\!\rightarrow\!V\gamma$ ($V=\rho$, $K^*$, $\omega$, $\phi$ and $P=\pi$, $K$, $\eta$, $\eta^{\prime}$) decays is performed using an enhanced phenomenological model that includes isospin-symmetry breaking. When the model is contrasted with the most recent experimental data for these radiative transitions, estimations for the mixing angles amongst the three pseudoscalar states with vanishing third-component of isospin are obtained. The current experimental uncertainties allow for isospin-symmetry violations with a confidence level of approximately $2.5\sigma$.- 6 February 2024
- Published by Sissa Medialab Srl
- Vol. 413, 027
Open AccessA primer analysis of $\pi^0$-$\eta$-$\eta^{\prime}$ mixing from $V\!\rightarrow\!P\gamma$ and $P\!\rightarrow\!V\gamma$ decaysA primer analysis of $\pi^0$-$\eta$-$\eta^{\prime}$ mixing from $V\!\rightarrow\!P\gamma$ and $P\!\rightarrow\!V\gamma$ ($V=\rho$, $K^*$, $\omega$, $\phi$ and $P=\pi$, $K$, $\eta$, $\eta^{\prime}$) decays is performed using an enhanced phenomenological model that includes isospin-symmetry breaking. When the model is contrasted with the most recent experimental data for these radiative transitions, estimations for the mixing angles amongst the three pseudoscalar states with vanishing third-component of isospin are obtained. The current experimental uncertainties allow for isospin-symmetry violations with a confidence level of approximately $2.5\sigma$. - Open Access
- 22 December 2022
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 274, 06002
Searching for a leptophobicBboson throughη→π0γγandηʹ→π0γγdecays
The sensitivity of the decaysη→π0γγandηʹ→π0γγto a leptophobicBboson in the sub-GeV mass range is summarised in this work. By adding an explicitB-boson resonance exchange to the dominant Standard Model contribution from vector meson exchanges, and employing experimental measurements of the associated branching ratios, the current constraints on theB-boson massmBand coupling to Standard Model particlesαBare significantly improved. From these constraints and the analysis of the available experimentalγγinvariant mass distribution ofη→π0γγ, we conclude that a B-boson signature in the resonant mass rangemπ0≲mB≲mηis strongly suppressed and would be very difficult to experimentally identified. Theη΄→π0γγdecay is not as powerful as theη→π0γγat constrainingB-boson parameters belowmηbut allow exploring largerB-boson masses. Yet, the task of identifying aB-boson withmB∼mωwould be very challenging.
- 22 December 2022
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 274, 06002
Open AccessSearching for a leptophobicBboson throughη→π0γγandηʹ→π0γγdecays
The sensitivity of the decaysη→π0γγandηʹ→π0γγto a leptophobicBboson in the sub-GeV mass range is summarised in this work. By adding an explicitB-boson resonance exchange to the dominant Standard Model contribution from vector meson exchanges, and employing experimental measurements of the associated branching ratios, the current constraints on theB-boson massmBand coupling to Standard Model particlesαBare significantly improved. From these constraints and the analysis of the available experimentalγγinvariant mass distribution ofη→π0γγ, we conclude that a B-boson signature in the resonant mass rangemπ0≲mB≲mηis strongly suppressed and would be very difficult to experimentally identified. Theη΄→π0γγdecay is not as powerful as theη→π0γγat constrainingB-boson parameters belowmηbut allow exploring largerB-boson masses. Yet, the task of identifying aB-boson withmB∼mωwould be very challenging.
- Open AccessSensitivity of the $η^{(\prime)}\toπ^{0}γγ$ and $η^{\prime}\toηγγ$ decays to a sub-GeV leptophobic $U(1)_{B}$ bosonThe sensitivity of the rare decays $\eta^{(\prime)}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ to signatures of a leptophobic $B$ boson in the MeV-GeV mass range is analyzed in this work. By adding an explicit $B$-boson resonance exchange, $\eta\to B\gamma\to\pi^{0}\gamma\gamma$, to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the $B$-boson mass $m_{B}$ and coupling to Standard Model particles $\alpha_{B}$. From these constraints and the analysis of the available experimental $\gamma\gamma$ invariant mass distribution, we show that a $B$-boson signature in the resonant mass range $m_{\pi^{0}}\lesssim m_{B}\lesssim m_{\eta}$ is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic $B$ boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding $t$- and $u$-channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model $\rho$, $\omega$ and $\phi$ meson exchanges. In addition, we make use of experimental data from the $\eta^{\prime}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ decays to explore larger $B$-boson masses. Our results are relevant for the $B$-boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.Open AccessSensitivity of the $η^{(\prime)}\toπ^{0}γγ$ and $η^{\prime}\toηγγ$ decays to a sub-GeV leptophobic $U(1)_{B}$ bosonThe sensitivity of the rare decays $\eta^{(\prime)}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ to signatures of a leptophobic $B$ boson in the MeV-GeV mass range is analyzed in this work. By adding an explicit $B$-boson resonance exchange, $\eta\to B\gamma\to\pi^{0}\gamma\gamma$, to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the $B$-boson mass $m_{B}$ and coupling to Standard Model particles $\alpha_{B}$. From these constraints and the analysis of the available experimental $\gamma\gamma$ invariant mass distribution, we show that a $B$-boson signature in the resonant mass range $m_{\pi^{0}}\lesssim m_{B}\lesssim m_{\eta}$ is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic $B$ boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding $t$- and $u$-channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model $\rho$, $\omega$ and $\phi$ meson exchanges. In addition, we make use of experimental data from the $\eta^{\prime}\to\pi^{0}\gamma\gamma$ and $\eta^{\prime}\to\eta\gamma\gamma$ decays to explore larger $B$-boson masses. Our results are relevant for the $B$-boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.
- Open Access
- 8 December 2022
- Published by American Physical Society (APS) in Physical Review D
- Vol. 106 (11) , 114007
Sensitivity of the and decays to a sub-GeV leptophobic bosonThe sensitivity of the rare decays and to signatures of a leptophobic boson in the MeV–GeV mass range is analyzed in this work. By adding an explicit -boson resonance exchange, , to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the -boson mass and coupling to Standard Model particles . From these constraints and the analysis of the available experimental invariant mass distribution, we show that a -boson signature in the resonant mass range is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding - and -channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model , and meson exchanges. In addition, we make use of experimental data from the and decays to explore larger -boson masses. Our results are relevant for the -boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.- 8 December 2022
- Published by American Physical Society (APS) in Physical Review D
- Vol. 106 (11) , 114007
Open AccessSensitivity of the and decays to a sub-GeV leptophobic bosonThe sensitivity of the rare decays and to signatures of a leptophobic boson in the MeV–GeV mass range is analyzed in this work. By adding an explicit -boson resonance exchange, , to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the -boson mass and coupling to Standard Model particles . From these constraints and the analysis of the available experimental invariant mass distribution, we show that a -boson signature in the resonant mass range is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding - and -channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model , and meson exchanges. In addition, we make use of experimental data from the and decays to explore larger -boson masses. Our results are relevant for the -boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments. - Open Access
- 24 August 2022
- Published by Springer Nature in The European Physical Journal C
- Vol. 82 (8) , 1-4
Erratum to: A theoretical analysis of the semileptonic decays $\eta ^{(\prime )}\rightarrow \pi ^0l^+l^-$ and $\eta ^\prime \rightarrow \eta l^+l^-$This erratum corrects Eqs. (6) and (15), Table 1, and Fig. 2 of the original article. An additional footnote is added at the end of the first paragraph in Section III. Finally, the paragraph discussing the use of the energy-dependent width for the $$\rho ^0$$ propagator is modified.- 24 August 2022
- Published by Springer Nature in The European Physical Journal C
- Vol. 82 (8) , 1-4
Open AccessErratum to: A theoretical analysis of the semileptonic decays $\eta ^{(\prime )}\rightarrow \pi ^0l^+l^-$ and $\eta ^\prime \rightarrow \eta l^+l^-$This erratum corrects Eqs. (6) and (15), Table 1, and Fig. 2 of the original article. An additional footnote is added at the end of the first paragraph in Section III. Finally, the paragraph discussing the use of the energy-dependent width for the $$\rho ^0$$ propagator is modified. - Open AccessA theoretical analysis of the semileptonic decays $η^{(\prime)}\toπ^0l^+l^-$ and $η^\prime\toηl^+l^-$A complete theoretical analysis of the $C$-conserving semileptonic decays $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0$, $\omega$, $\phi$ and $P=\pi^0$, $\eta$, $\eta^{\prime}$). The decay widths and dilepton energy spectra for the two $\eta\to\pi^0l^+l^-$ processes obtained using this approach are compared and found to be in good agreement with other results available in the published literature. Theoretical predictions for the four $\eta^{\prime}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ decay widths and dilepton energy spectra are calculated and presented for the first time in this work.Open AccessA theoretical analysis of the semileptonic decays $η^{(\prime)}\toπ^0l^+l^-$ and $η^\prime\toηl^+l^-$A complete theoretical analysis of the $C$-conserving semileptonic decays $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0$, $\omega$, $\phi$ and $P=\pi^0$, $\eta$, $\eta^{\prime}$). The decay widths and dilepton energy spectra for the two $\eta\to\pi^0l^+l^-$ processes obtained using this approach are compared and found to be in good agreement with other results available in the published literature. Theoretical predictions for the four $\eta^{\prime}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ decay widths and dilepton energy spectra are calculated and presented for the first time in this work.
- Open AccessNew-physics signatures via $C\!P$ violation in $η^{(\prime)}\toπ^0μ^+μ^-$ and $η^\prime\toημ^+μ^-$ decaysIn this work we investigate the prospect of observing new-physics signatures via $C\!P$ violation in $\eta^{(\prime)}\to\pi^0\mu^+\mu^-$ and $\eta^\prime\to\eta\mu^+\mu^-$ decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics $C\!P$-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments. This reasserts the $\eta\to\mu^+\mu^-$ process as the most promising channel to find $C\!P$-violation at this experimental facility.Open AccessNew-physics signatures via $C\!P$ violation in $η^{(\prime)}\toπ^0μ^+μ^-$ and $η^\prime\toημ^+μ^-$ decaysIn this work we investigate the prospect of observing new-physics signatures via $C\!P$ violation in $\eta^{(\prime)}\to\pi^0\mu^+\mu^-$ and $\eta^\prime\to\eta\mu^+\mu^-$ decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics $C\!P$-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments. This reasserts the $\eta\to\mu^+\mu^-$ process as the most promising channel to find $C\!P$-violation at this experimental facility.
- Open Access
- 23 May 2022
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2022 (5) , 1-14
New-physics signatures via CP violation in η(′) → π0μ+μ− and η′ → ημ+μ− decays
In this work we investigate the prospect of observing new-physics signatures via CP violation in η(′) → π0μ+μ− and η′ → ημ+μ− decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics CP-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments. This reasserts the η → μ+μ− process as the most promising channel to find CP-violation at this experimental facility.
- 23 May 2022
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2022 (5) , 1-14
Open AccessNew-physics signatures via CP violation in η(′) → π0μ+μ− and η′ → ημ+μ− decays
In this work we investigate the prospect of observing new-physics signatures via CP violation in η(′) → π0μ+μ− and η′ → ημ+μ− decays at the REDTOP experiment. We make use of the SMEFT to parametrise the new-physics CP-violating effects and find that the projected REDTOP statistics are not competitive with respect to nEDM experiments. This reasserts the η → μ+μ− process as the most promising channel to find CP-violation at this experimental facility.