arXiv subjects

Antonio Rojas

Publications and source records attributed to Antonio Rojas.

4 recordsLinked to original sources

arXiv2026

Effect of $K^*$ meson magnetic dipole moment on the $e^+e^- \to K^+ K^-π^0 π^0 $ cross section

We explore the sensitivity of the $e^{+} e^{-} \to K^+ K^- 2 π^0$ cross section to the magnetic dipole moment (MDM) of the $K^*$ vector meson. We describe the $γ^* \to 2K2π$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant for energies below 2.4 GeV. Using BaBar data for this process, we show that this observable is indeed sensitive to the MDM of the $K^*$; we obtain a central value for the MDM of $μ_{K^*}=4.5$ and an upper bound of $\barμ_{K^*} = 6.3$, in units of $e/2 m_{K^*}$. We emphasize the need for higher precision data to provide a first data-driven determination of this parameter to confront it with theoretical predictions.

hep-ph↗

arXiv2024

The $ρ$ meson magnetic dipole moment from BaBar $e^+e^- \to π^+ π^-π^0 π^0 $ cross section measurement

We obtain the value of the magnetic dipole moment of the $ρ$ meson, using data from the BaBar Collaboration for the $e^{+} e^{-} \to π^+ π^- 2 π^0$ process. The considered center of mass energy range is from 0.9 to 1.8 GeV. We describe the $γ^* \to 4π$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant at these energies. We find $μ_ρ= 2.7 \pm 0.3 $ in $e/2 m_ρ$ units. We improve on the previous extracted value, where preliminary data from the same collaboration was used, by considering definite data, better grounded values of the parameters involved and explicit gauge invariant description of the process.

hep-ph↗

arXiv2024

Sizing the double pole resonant enhancement in $e^{+}e^{-} \to π^{0} π^{0} γ$ cross section and $τ^{-} \to π^{-}π^{0} ν_τγ$ decay

The enhancement mechanism due to the resonant properties of the $ρ$ and $ω$ mesons, which are close in mass, are analysed when such resonances carry different momenta. Considerations from the particular process where they appear to the individual resonant features are at play for the appearance of the global resonant manifestation. In this work, we first consider the $e^+e^- \to π^0 π^0 γ$ process. We use the differential cross section at a given angle of emission of one of the pions, to tune the individual features of the two resonances and exhibit how both resonances combine to produce the enhancement. Then, we incorporate the $ρ^\prime$ using the information obtained from the $ e^+e^- \to π^0 π^0 γ$ total scattering process and show that, it becomes important thanks to the same enhancement mechanism between the $ρ$ and the $ω$. In a second step, we use a similar approach to describe a model dependent contribution to the $τ^- \to π^-π^0ν_τγ$ decay, the so-called $ω$ channel. We show that the dipion invariant mass distribution at particular angles is sensitive to the individual resonant states. We compute the interference of this channel with the known dominant model independent contribution, and show how a better knowledge of the $e^+e^- \to π^0 π^0 γ$ process can help to properly account for such model dependent effects. The implication on the isospin symmetry breaking correction to tau-based estimates of the muon magnetic dipole moment is assessed.

hep-ph↗

arXiv2023

Role of the $ρ(1450)$ in low-energy observables from an analysis in the meson dominance approach

The $ρ(1450)$ vector meson ($ρ^\prime$) is becoming increasingly important to properly describe precision observables. We analyse a set of decay modes and cross sections, in the low-energy regime, to determine the role played by this meson. This is done through the extraction of the parameters for its description, in the context of the vector meson dominance model and its effective hadronic interactions, involving the low mass lying hadrons ($ρ$, $ω$ and $π$). In a first step, we determine the parameters of the model from ten decay modes which are insensitive to the $ρ^\prime$. Then, we consider the $ω\rightarrow 3π$ decay and exhibit the need to extend the description, by incorporating the $ρ^\prime$ and a contact term as prescribed by the Wess-Zumino-Witten anomaly. In a second step, we incorporate the data from the $e^+e^- \rightarrow 3π$ cross section (as measured by SND, CMD2, BABAR and BESIII) and then the $e^+e^- \rightarrow π^0 π^0 γ$ data (as measured by SND and CDM2) to further restrict the $ρ^\prime$ parameters validity region. As an application of the results, we compute the $e^+e^- \rightarrow 4π$ cross section for the so-called omega channel, measured by BABAR, and find a good description of the data considering the parameters found. As a byproduct, the coupling between $ρ$, $ω$ and $π$ ($g_{ρωπ}= 11.314 \pm 0.383$ GeV$^{-1}$) is found to be consistent with all the relevant observables, upon the inclusion of the $ρ^\prime$ and the contact term.

hep-ph↗