arXiv subjects

Eleftheria Solomonidi

Publications and source records attributed to Eleftheria Solomonidi.

6 recordsLinked to original sources

arXiv2026

Implications of two-channel rescattering for charm CP violation from precise dispersive data

The experimental observation of large CP violation in charm-meson hadronic decays remains theoretically unexplained within the Standard Model. The data-driven approach which accounts for the rescattering between the final-state pion and kaon pairs provides predictions that fall short of the experimental values. However, it relies on a set of inputs that exhibit large uncertainties. In this work, we make optimal use of the available information on branching ratios and of only one strong-scattering input parameter that is well determined. We find that it remains unlikely to explain the experimental signal within this approach and obtain predictions for sum rules that constrain CP asymmetries of the pion and kaon channels.

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arXiv2026

Impact of the $a_1(1260) π$ cascade contribution on $D^0 \to π^+ π^- \ell^+ \ell^-$ decays

We revisit the Standard Model description of the recently measured rare decays $D^0\toπ^+π^-\ell^+\ell^-$. Because of the effectiveness of the Glashow-Iliopoulos-Maiani mechanism in charm flavour-changing neutral currents, those decays are driven by non-local insertions of four-quark operators. Following previous work, we consider the mediation of resonances both for the dipion and dilepton pairs. For the first time, we incorporate the effect of the cascade-type topology $D^0\to π^- a_1^+(1260)(\toπ^+ρ^0(\to\ell^+\ell^-))$, which manifests distinctly in the invariant-mass and angular distributions. We find that this partial amplitude comprises one of the largest contributions to the decay rate and obtain an unprecedented agreement of the Standard Model prediction with the available LHCb data. Finally, we compare to the available CLEO-c, LHCb, and BESIII amplitude analyses for the analogous four-body hadronic decays and find that similar values of the hadronic parameters of our model successfully describe the two classes of decays.

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arXiv2025

Cascade topologies in rare charm decays and implications for CP violation

The CP violation observed in the hadronic decays of charmed mesons remains a puzzling open question for theorists. Calculations relying on the assumption of inelastic final-state interactions occurring between the pairs of pions and kaons fall short of the experimental value. It has been pointed out that a third channel of four pions can leave imprints on the CP asymmetries of the two-body decays. At the same time, plenty of data are available for the $4π$ decays of charmed mesons, as well as for the rare decays $D^0\toπ^+π^-\ell^+\ell^-$. With this motivation, we study the cascade topology $D^0\to a_1(1260)^+(\to ρ(770)^0π^+)\,π^-$, which has been measured to contribute significantly to the $4π$ decays, and estimate its effect on the branching ratio of the rare decays. We also explore the possibility of this topology contributing to the decay amplitude of $D^0\toπ^+π^-$ and by extension to the related CP asymmetry.

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arXiv2024

Resonances in $D^0\toπ^+π^-\ell^+\ell^-$ and sensitivity to New Physics

The study of processes involving the weak decays of the charm quark offers unique possibilities to test the Standard Model from the up-type sector and to probe different New Physics scenarios. In here we focus on the rare decays $D^0\toπ^+π^-\ell^+\ell^-$. The effectiveness of the Glashow-Iliopoulos-Maiani mechanism in charm results in a series of observables that serve as null tests of the Standard Model. Simultaneously, the dominant Standard Model contribution to such decays comes from long-distance dynamics. Following previous literature we describe this with the mediation of resonances. Motivated by recent experimental results on analogous semileptonic decays we investigate the effect of the $S$-wave of the pion pair by considering the scalar resonance $f_0(500)$. The experimental mass distributions and angular observables are described well with our model and there is a significant improvement on the agreement when accounting for $f_0(500)$, which amounts to around 20\% of the total branching ratio. Furthermore, we propose and estimate the size of a series of additional observables to be measured, which can help probe the $S$-wave and act as complementary null tests of the Standard Model.

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arXiv2023

$S$-wave contribution to rare $D^0 \to π^+ π^- \ell^+ \ell^-$ decays in the Standard Model and sensitivity to New Physics

Physics of the up-type flavour offers unique possibilities of testing the Standard Model (SM) compared to the down-type flavour sector. Here, we discuss SM and New Physics (NP) contributions to the rare charm-meson decay $ D^0 \to π^+ π^- \ell^+ \ell^- $. In particular, we discuss the effect of including the lightest scalar isoscalar resonance in the SM picture, namely, the $f_0 (500)$, which manifests in a big portion of the allowed phase space. Other than showing in the total branching ratio at an observable level of about $ 20\% $, the $f_0 (500)$ resonance manifests as interference terms with the vector resonances, such as at high invariant mass of the leptonic pair in distinct angular observables. Recent data from LHCb optimize the sensitivity to $P$-wave contributions, that we analyse in view of the inclusion of vector resonances. We propose the measurement of alternative observables which are sensitive to the $S$-wave and are straightforward to implement experimentally. This leads to a new set of null observables, that vanish in the SM due to its gauge and flavour structures. Finally, we study observables that depend on the SM interference with generic NP contributions from semi-leptonic four-fermion operators in the presence of the $S$-wave.

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arXiv2023

Final-state interactions in the CP asymmetries of charm-meson two-body decays

Urgent theoretical progress is needed in order to provide an estimate in the Standard Model of the recent measurement by LHCb of direct CP violation in charm-meson two-body decays. Rescattering effects must be taken into account for a meaningful theoretical description of the amplitudes involved in such category of observables, as signaled by the presence of large strong phases. We discuss the computation of the latter effects based on a two-channel coupled dispersion relation, which exploits isospin-zero phase-shifts and inelasticity parameterizations of data coming from the rescattering processes $ ππ\to ππ$, $ πK \to πK $, and $ ππ\to K \overline{K} $. The determination of the subtraction constants of the dispersive integrals relies on the leading contributions to the transition amplitudes from the $ 1/N_C $ counting, where $N_C$ is the number of QCD colours. Furthermore, we use the measured values of the branching ratios to help in selecting the non-perturbative inputs in the isospin limit, from which we predict values for the CP asymmetries. We find that the predicted level of CP violation is much below the experimental value.

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