arXiv subjects

Luciano M. Abreu

Publications and source records attributed to Luciano M. Abreu.

At least 19 recordsLinked to original sources

arXiv2026

Final-state interactions in the $B^{\mp}\to K^+K^- π^{\mp} $ decays: traces of the $X(3700)$ state and CP asymmetry

In this work, we investigate final-state interaction effects in $B^{\mp}\to K^+K^- π^{\mp}$ decays above 3 GeV with a twofold objective: (i) to study $CP$ asymmetry, and (ii) to search for possible signatures of the $X(3700)$ state (also denoted as $X(3720)$). We consider both tree-level and resonant contributions, with the latter arising from a triangle mechanism $B^{\mp} \to \bar{D}^0 D^{\ast \mp} (\to π^{\mp} D^0) \to K^+K^- π^{\mp}$, in which the $D \bar D \to K \bar K$ rescattering process carries the signature of the exotic $X(3700)$ state. We analyze the dependence of our results on the relative phase between the tree-level and resonant contributions, as well as on other relevant parameters. We estimate the differential mass distribution in the region where the $X(3700)$ may leave a trace, and the $CP$ asymmetry driven by final-state interactions. Our findings are compared with available data for the differential mass distributions and the $CP$ asymmetry. Taken together, these results may contribute to a better understanding of the properties of exotic states and the role of $CP$ asymmetry in $B$-meson phenomenology.

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arXiv2026

Enigmatic properties of $Ξ(1620)$ and $Ξ(1690)$

Motivated by a considerable release of data on first two excited states of the doubly strange baryon, $Ξ(1620)$ and $Ξ(1690)$, from different experimental collaborations in recent years, we investigate meson-baryon interactions in a coupled-channel approach. The systems are composed of pseudoscalar and vector mesons and the calculations are done for the total spin 1/2 and isospin 1/2 configuration. The tree-level interactions are deduced from Lagrangians based on chiral and hidden local symmetries. Specifically, we make an attempt to describe (1) data on the $K^-Λ$ femtoscopic correlation function coming from $p\,p$ and $Pb\,Pb$ collisions, and (2) the available data on invariant mass distributions for different systems: $πΞ$, $\bar K Σ$ and $\bar K Λ$. We find that the amplitude which yields the correlation function close to the data results in mass distributions of different meson-baryon systems that are in discordance with the experimental data and vice-versa.

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arXiv2026

A pion-driven near-threshold enhancement in the $π\,T_{cc}$ system

Hadronic molecules are commonly viewed as products of near-threshold two-body dynamics. We investigate whether an experimentally established molecule can also serve as a building block for a more complex exotic hadron by studying pion scattering off $T^+_{cc}(3875)$. Treating $T_{cc}$ as a correlated isoscalar $D D^*$ molecular cluster, we describe the resulting $πD D^*$ dynamics in the $I(J^P)=1(1^-)$ channel within the Fixed Center Approximation to the Faddeev equations. The full three-body amplitude develops a pronounced enhancement slightly above the $πT_{cc}$ threshold, centered at $M_{\rm peak}\simeq 4055$~MeV, with an apparent width of approximately $60$~MeV. The associated behavior of the real and imaginary parts of the amplitude is compatible with a resonant-like interpretation. These results show that the lightest hadron can play an active dynamical role in promoting an observed hadronic molecule into a building block of a heavier near-threshold structure generated by the three-body dynamics. We propose searching for this enhancement in the $T_{cc}π$ invariant-mass distribution, particularly through the $D^0D^0π^+π^-$ final state.

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arXiv2026

Exotic states with charm and/or strangeness

In this talk, I will discuss the properties of several exotic states with charm and/or strangeness. These states can be interpreted either as being generated from two- or three-hadron dynamics. In particular, I will focus on $D_1(2420)$ and some predictions of three-body states obtained from $n\bar

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arXiv2026

Explicitly exotic heavy flavor mesons

In this talk, I summarize the highlights of our recent and ongoing work on exotic hadrons involving explicitly exotic heavy-flavor mesons. By heavy flavors, I refer in particular to strange and charm quarks. As discussed in this manuscript, several puzzle-like features appearing in recent experimental data can be understood in terms of coupled-channel interactions. The main result is the prediction of an exotic meson carrying both charm and strangeness quantum numbers, whose properties cannot be explained as those of a simple quark-antiquark bound state. I also discuss the future prospects of our research program on this topic.

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arXiv2026

Probing the $G(3900)$ State in Heavy-Ion Collisions

We investigate the interactions of the recently confirmed exotic hadron $G(3900)$ with the hadronic medium composed of light mesons produced in heavy-ion collisions. Using an effective Lagrangian approach, we compute both vacuum and thermally averaged cross sections for processes such as $G(3900) + π\to D^{(\ast)} + \bar{D}^{(\ast)}$ and their inverse reactions. Following recent proposals, the $G(3900)$ is interpreted as a $P$-wave $D\bar{D}^*/D^*\bar{D}$ molecular state. The resulting thermally averaged cross sections are employed in a rate equation to determine the time evolution of the $G(3900)$ multiplicity, with initial conditions provided by statistical and coalescence hadronization models. We compute the number of $G(3900)$'s produced in central Pb-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV and compare it with the number of produced $Z_c(3900)$'s . We obtain a considerably smaller final yield of $G(3900)$ compared to $Z_c(3900)$.

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arXiv2026

Searching for the pseudoscalar partner of $G(3900)$ via radiative $Y(4230)$ decays

Inspired by the $P$-wave molecular interpretation of the recently observed vector state $G(3900)$, we analyze the production of its possible pseudoscalar partner, denoted here as $G_0(3900)$, via the radiative decay $Y(4230) \to γG_0(3900)$. The $G_0(3900)$ is interpreted as a $P$-wave molecular state with quantum numbers $J^{PC}=0^{-+}$, dominated by the $D\bar{D}^{\ast}/\bar{D}D^{\ast}$ components. Although not yet experimentally established, such a structure is expected to appear near the $D\bar{D}^*$ threshold and to exhibit characteristic production patterns. The decay is assumed to proceed through a triangle mechanism. Depending on the model parameters and the binding energy of $G_0(3900)$, the resulting branching fraction lies in the range $\mathcal{B}(Y(4230) \to γG_0(3900)) = 3.8 \times 10^{-5} - 3.3 \times 10^{-4}$. Our results offer a pathway to search for signatures of $G_0(3900)$ in radiative channels and also provide a test of the consistency of loop-mediated radiative decays with a molecular description of the $Y(4230)$.

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arXiv2026

$D^*π$ interaction from the lineshape of $D_1(2420)$ in $B$-decays

We present a model calculation to reproduce the differential mass distribution for the $D^*π$ system in the reactions $B^- \to D^{*+} π^- π^-$ and $B^{+}\to D_s^+D^{*-}π^{+}$ analyzed by the LHCb Collaboration, which shows a dominant signal for $D_1(2420)$. %\textbf{We} (The idea is to) We consider a model based on coupled channel meson-meson interactions that can describe the properties of $D_1(2420)$ in terms of the underlying dynamics, use it to determine the invariant mass distribution of the $D^*π$ system, and compare the results with the experimental data. We also determine the $D^*π$ scattering length, for which different values are available from different sources, leading to a controversy. To our knowledge, this is the first attempt to reproduce the mentioned data using model calculations. Our formalism relies on the hadronization of different mesons through a weak decay, allowing for the final-state (strong) interactions among the relevant constituents. We benefit from our previous work when obtaining the amplitudes corresponding to the strong interactions. We hope that our findings can be useful in further investigations of the properties of $D_1(2420)$.

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arXiv2025

Production of the $ X(3872)$ state via the $B^0 \to K^{\ast 0} X(3872)$ decay

In this work the production of the state $X(3872)$ is estimated via the reaction $B^0 \to K^{\ast 0} X(3872)$ through triangle mechanisms described by the sequence $B^0 \to D_s^{(*)+} (\to K^{\ast 0} D^{(*)+} ) \ D^{(*)-} \to K^{\ast 0} \ ( D^{(*)+} D^{(*)-} ) \to K^{\ast 0} X(3872) $. The molecular configuration $(D\bar D^* - c.c. )$ of the $X(3872)$ is considered. By means of the effective Lagrangian approach, the branching ratio $\mathcal{B}(B^0 \to K^{\ast 0} X(3872))$ is calculated as a function of the strength of the coupling of the charged components $(D^+\bar D^{*-} - c.c. )$ to the $X(3872)$ and compared with experimental data. Besides, employing the decay $B^0 \to K^{\ast 0} ψ(2S)$ as a normalization channel, the ratio of branching fractions $R = \frac{\mathcal{B}( B^0 \to K^{\ast 0} X(3872) )}{\mathcal{B}( B^0 \to K^{\ast 0} ψ(2S) )}\times \frac{\mathcal{B}( X(3872) \to J/ψπ^{+} π^{-} )}{\mathcal{B}( ψ(2S) \to J/ψπ^{+} π^{-} )} $ is also estimated. The findings provide another concrete example for the vital role of charged components in achieving a quantitatively correct description of the $X(3872)$.

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arXiv2025

Fully-heavy tetraquarks in the vacuum and in a hot environment

We study the thermal behavior of quarkonia and fully-heavy tetraquark states associated to the charmonium, bottomonium and bottom-charmonium mass spectra. The starting point is the Schrödinger formalism with a vacuum Cornell-like potential. The spin-spin, spin-orbit and tensor contributions are also considered to describe the structure of the vacuum quarkonia $Q\bar Q$ spectra ($Q$ denoting $c,b$ quarks). The parameters of the model are fixed using the experimental data of the $Q\bar Q$ states. After that, this formalism is extended to the fully-heavy tetraquark states within the $1^3 S_1$ axial diquark--$1^3 S_1$ axial antidiquark configuration $[QQ] [\bar Q \bar Q]$, and their vacuum mass spectra are obtained and compared to the experimental data recently obtained. Our predictions support the interpretation of the $X(6600)$ (or $X(6552)$), $X(6900)$ and $X(7200)$ states as the radially-excited $T_{4c}(n^1S_0)$ configurations with $n=2,3,4$. In the sequence, we evaluate the mass spectra behavior in a thermal medium, by introducing a modified temperature-dependent Cornell potential. As a consequence, this formalism enables us to get some insight into the dissociation mechanism of $[QQ] [\bar Q \bar Q]$ states caused by a thermal medium, and into the temperature range at which the tetraquark states might be formed. We find that these structures cannot be formed in the thermal medium when the system has a temperature higher than about twice the critical temperature. These findings may be useful to better understand the features of the exotics in heavy-ion collisions. [NOTE: version with inclusion of an Addendum incorporating the $2^{++}$ state predictions, motivated by the new CMS results [arXiv:2506.07944].]

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arXiv2025

Correlation functions for $n\,\bar{D}_{s1}(2460)$ and $n\,\bar{D}_{s1}(2536)$

We study the interaction of the $n \bar {D}_{s1}(2460)$ and $n \bar {D}_{s1}(2536)$ systems from the perspective that the $D_{s1}(2460)$ and $D_{s1}(2536)$ states are molecular states of $K D^*$ and $K^*D$, respectively. We use an improved version of the fixed center approximation to the Faddeev equations which fulfills exact elastic unitarity at the threshold of the systems. We predict the existence of resonant states below threshold and also determine the scattering length, effective range and correlation functions of these systems, showing that the results contain important information to test the assumed molecular nature of the two $D_{s1}$ states.

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arXiv2025

Searching for femtoscopic signatures of the $D \bar D (I=0) \ [X(3700)]$ bound state

The femtoscopic $D \bar D $ correlations correlation functions are investigated to predict the signature of the not-yet-established $X(3700)$ state. Here it is interpreted as a bound state generated by solving the coupled-channel Bethe-Salpeter equations with the local hidden-gauge formalism. We prospect how the relevant properties and observables characterizing this state -- like the pole position, scattering lengths and compositeness -- might be affected by the variation of the parameters of the model. The amplitudes are then used as input into the momentum correlation functions of the $D^0 \bar D^0$ and $D^+ D^- $ pairs. We discuss how their behaviors encode the features of the $X(3700)$ state.

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arXiv2024

Studying the nature of the lightest charmed axial mesons via femtoscopy

In this work we discuss how femtoscopic analysis can shed light on the nature of the two lightest axial charmed mesons, denominated as $D_1(2430)$ and $D_1(2420)$, whose masses are similar but widths are different. Their properties are reasonably described taking into account meson-meson coupled channel dynamics and a bare quark-model pole constituting the lowest-order amplitudes. Two different bare quark-model states are used in order to accommodate the different scattering lengths coming from the lattice QCD calculations for the $Dπ$ and $D^*π$ systems and the data from the ALICE Collaboration on the $Dπ$ system. The amplitudes are employed as inputs to determine the correlation functions for the $D^{*}π$ and $Dρ$ channels and identify the signatures associated with the lowest-lying axial charmed mesons.

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arXiv2024

A study of the $ϕN$ correlation function

The femtoscopic $ϕN$ correlation function is studied within a hadronic effective Lagrangian approach with coupled channels, based on hidden local symmetry. The results are compared with the data recently reported by the ALICE collaboration. We find that the correlation function has very different features for the $ϕN$ system in the spin 1/2 and 3/2 configurations, with the spin-averaged combination matching well with the experimental data. A strong attraction, leading to the formation of a $ϕN$ bound state or a very prominent cusp is found in the spin 3/2 case. The correlation function for spin 1/2, on the other hand, is strongly impacted by the negative parity $N^*(1895)$ nucleon resonance.

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arXiv2024

Can femtoscopic correlation function shed light on the nature of the lightest, charm, axial mesons?

We present a coupled channel treatment of meson-meson dynamics, for systems with spin-parity $1^+$, and determine the corresponding amplitudes by solving the Bethe-Salpeter equations, which lead to the generation of two axial resonances when mesons are considered as the degrees of freedom in the model. One of them is narrow and has properties in good agreement with those of $D_1(2420)$. The other pole is wider, but its real and imaginary parts do not match well with the mass and width of $D_1(2430)$. The situation improves when a bare quark-model state is included, indicating that the dynamics at the quark level as well as among hadrons can describe the two states simultaneously. Further, we discuss that there exists a divergence in the value of the $D^*π$ scattering length determined through data coming from lattice QCD calculations and from heavy ion collisions. Such different values can be accommodated in the model by making small changes in the parameters while producing two poles having properties compatible with the two lightest $D_1$ states. With these results, we proceed to calculate the correlation function for the $D^{*+(0)}π^{0(+)}$ system for different sizes of the source. We discuss which scenarios can be useful to shed some light on the issue.

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arXiv2024

Production of $ B \bar{B}$ bound state via $Υ(4S)$ radiative decays

Motivated by recent theoretical predictions about the existence of a $ B \bar{B}$ bound state (also denoted as $ X(10550) $), in this work we estimate the production of the $S$-wave $ B^+ B^-$ molecule via $Υ(4S)$ radiative decays. In particular, we make use of effective Lagrangian approach and the compositeness condition to calculate the $ X(10550) $ production rate via $Υ(4S)\rightarrow γX(10550)$ decays employing triangle diagrams. Our results show that the partial decay width of this reaction is of the order of $0.5 - 192 \ \keV $ for a respective binding energy of $1 - 100 $ MeV, corresponding to a branching fraction of $ 10^{-5} - 10^{-3}$. These findings suggest that the existence of the $ X(10550) $ might be checked via the analysis of the mentioned decay in present and future experiments.

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arXiv2024

A note on the tensor and vector exchange contributions to $K \bar K \to K \bar K, D \bar D \to D \bar D $ and $π^+ π^-\to π^+ π^-$ reactions

In this note we study the tensor and vector exchange contributions to the elastic reactions involving the pseudoscalars mesons $π^+ π^-$, $K^{+}K^{-}$ and $D^{+}D^{-}$. In the case of the tensor-exchange contributions we assume that an intermediate tensor $f_2(1270)$ is dynamically generated from the interaction of two virtual $ρ$ mesons, with the use of a pole approximation. The calculation of the two-loop amplitude is facilitated since the triangle loops can be factorized and computed separately. The results show very small contributions coming from the tensor-exchange mechanisms when compared with those from the vector-exchange processes. We compare our results for $ππ$ and $K\bar{K}$ scattering with those obtained in other works where the $f_2(1270)$ is considered as an ordinary $q\bar{q}$ meson. Our picture provides a smaller contribution but of similar order of magnitude for pion scattering and stabilizes the results in the case of $K\bar{K}$, allowing us to make estimates for $D\bar{D}$ scattering.

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arXiv2023

Inverse magnetic catalysis and size-dependent effects on the chiral symmetry restoration

We investigate the combined finite-size and thermo-magnetic effects on the properties of the quark matter, in the context of the two-flavored Nambu--Jona-Lasinio model. In particular, by using the mean-field approximation and the Schwinger proper time method in a toroidal topology with periodic or antiperiodic conditions, we evaluate the chiral phase transition, the constituent quark mass and the thermal and spatial susceptibilities under the change of the size, temperature and strength of external magnetic field. To take into account the inverse magnetic catalysis phenomenon, we make use of a recently proposed magnetized coupling constant. The findings suggest that the observables are strongly affected by the variation of the variables and also by the periodicity of the boundary conditions, with the final outcomes depending on the balance of these competing phenomena.

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