arXiv subjects
Publications and source records attributed to A. Martínez Torres.
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
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.
We investigate whether photon-induced production in ultraperipheral heavy-ion collisions and at the EIC can provide a new environment to search for the scalar $D \bar{D}$ molecular candidate usually denoted as $X(3700)$. We calculate the tree-level amplitudes for $γγ\to D^+ D^-$ and $γγ\to D^0 \bar{D^0}$, dress the outgoing pair with a coupled-channel Bethe-Salpeter interaction in the $(D^+ D^- , D^0 \bar{D^0})$ basis, and convolute the resulting subprocess cross sections with equivalent-photon spectra. In the adopted two-channel scenario the analytic continuation of the $T$-matrix gives a bound state at $M_X=3.7162$~GeV, which is below the $D^0 \bar{D^0}$ threshold. As a consequence of this, the observed signal in the continuum is not simply an isolated narrow peak, and a characteristic near-threshold line-shape distortion is produced: around $3.70 \leq W \leq 3.85$~GeV the integrated dressed-to-bare ratios are $(13.71,0.35)$ in Pb-Pb UPCs and $(13.74,0.35)$ in $e$-Au collisions for $(D^+D^-,D^0 \bar{D^0})$. Using the BABAR-fitted central normalization $K_{\rm dressed}=0.382$, the corresponding dressed cross sections are $(24.6,14.6)~μ{\rm b}$ in Pb-Pb UPCs and $(2.41,1.43)~\rm nb$ at the EIC. The charged-to-neutral ratios are directly accessible observables, whereas the dressed-to-bare ratios provide theoretical diagnostics of the final-state interaction. The near-threshold features are controlled by the common $γγ\to D\bar{D}$ dynamics and are rather independent of the external photon source.
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 $D_1(2420)$.
In view of the recent discovery of $T_{cc}$, which can be described as a $DD^*$ molecular state, we perform a study of the $KDD^*$ system, and its extension to studying $KD^*D^*$, where $D^*D^*$ is bound as a spin 1 $T_{cc}$-like state, to search for the possible existence of exotic mesons with the open flavors $ccs$ being part of their quark configuration. Considering the additional attractive interactions present in the $KD$ and $KD^*$ subsystems, where the states $D^*_{s0}(2317)$ and $D_{s1}(2460)$ are generated, we solve the Faddeev equations considering the fixed-center approximation for the mentioned three-body systems and find the existence of two doubly charmed $K^*$-like mesons, $K_{cc}^*(4309)$ and $K_{cc}^*(4449)$, with quantum numbers $I(J^P)=1/2\,(1^-)$. Considering the respective three-body thresholds of the two systems, both $K_{cc}$-states are bound by around $60$ MeV. An experimental confirmation will bring evidence for the existence of a degree of exoticity beyond charm +2.
Leading $Λ$ (LL) production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account the nonlinear QCD effects. In particular, the impact of the absorptive effects on the LL spectra are estimated considering the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). Our results indicate that the LL spectrum is strongly suppressed at small photon virtualities. These results suggest that absorptive effects are not negligible and should be taken into account in order to extract the kaon structure function from data on leading $Λ$ production.
In this talk I review the findings of our recent works where we have studied the decay of $N^*(1895)$ and the implications of such properties on the photoproduction of light hyperons. I discuss that meson-baryon interactions play an essential role in describing the nature of $N^*(1895)$ and report the details of our investigation of its decays to different meson-baryon systems and to final states involving $Λ(1405)$ and a proposed $Σ(1400)$. We find that the width of $N^*(1895)$ gets important contributions from the decay to light hyperon resonances. Such an information can be used to look for alternative processes to study $N^*(1895)$ in experimental data.
We study the interaction of the doubly bottom systems $BB$, $B^* B$, $B_s B$, $B_s^* B$, $B^* B^*$, $B^* B_s$, $B^*B_s^*$, $B_s B_s$, $B_s B_s^*$, $B_s^* B_s^*$ by means of vector meson exchange with Lagrangians from an extension of the local hidden gauge approach. The full s-wave scattering matrix is obtained implementing unitarity in coupled channels by means of the Bethe-Salpeter equation. We find poles below the channel thresholds for the attractively interacting channels $B^* B$ in $I=0$, $B^*_s B-B^*B_s$ in $I=\frac{1}{2}$, $B^* B^*$ in $I=0$, and $B^*_s B^*$ in $I=\frac{1}{2}$, all of them with $J^P=1^+$. For these cases the widths are evaluated identifyng the dominant source of imaginary part. We find binding energies of the order of $10-20$ MeV, and the widths vary much from one system to the other: of the order of 10-100 eV for the $B^* B$ system and $B^*_s B-B^*B_s$, about $6$ MeV for the $B^* B^*$ system and of the order of $0.5$ MeV for the $B^*_s B^*$ system.
In this talk we discuss the formation of exotic hadrons with hidden charm arising from three-body interactions. To be more specific, in the strangeness sector, we predict the existence of a mesonic state, $K^*(4307)$, which is dynamically generated from the three-body interactions of the $KD\bar{D}^*$ system, has mass around $4307$ MeV and quantum numbers $I(J^P) = 1/2\,(1^-)$. In the baryonic sector, we predict the existence of $N^*$ states, which are generated from the three-body interactions of the $ND\bar{D}^*$ system, with masses around $4400\sim 4600$ MeV, widths of $2\sim 20$ MeV and positive parity.
In this talk we show our recent results on the decay widths of $ϕ(2170)$ to final states formed by an anti-Kaon and a Kaonic resonance, in particular, $K(1460)$, $K_1(1270)$ and $K_1(1400)$, considering a molecular description for $ϕ(2170)$. Branching fraction ratios are obtained and compared with the recent results found by the BESIII collaboration, finding compatible results.
Nowadays, it is generally accepted that the $DK$ interaction in isospin zero is strongly attractive and the $D_{s0}^*(2317)$ can be described as a $DK$ molecular state. Recent studies show that the three-body $DDK$ system binds as well with a binding energy about 60$\sim$70 MeV. The $DDK$ bound state has isospin $1/2$ and spin-parity $0^-$. If discovered either experimentally or in lattice QCD, it will not only provide further support on the molecular nature of the $D_{s0}^*(2317)$, but also provide a way to understand other exotic hadrons expected to be of molecular nature. In the present work, we study its two-body strong decay widths via triangle diagrams. We find that the partial decay width into $DD_sπ$ is at the order of $2\sim3$ MeV, which seems to be within the reach of the current experiments such as BelleII. As a result, we strongly recommend this decay channel of the $DDK$ bound state to be searched for experimentally.
We study hyperon resonances by solving coupled channel scattering equations. The coupled systems include pseudoscalar- and vector-baryon channels. The parameters of the model are restricted by making a $χ^2$-fit to the cross section data on processes: $K^- p \to K^- p$, $K^- p \to \bar K^0 n$, $K^- p \to ηΛ$, $K^- p \to π^0 Λ$, $K^- p \to π^0 Σ^0$, $K^- p \to π^\pm Σ^\mp$. Data on the energy level shift and width of the $1s$ state of the kaonic hydrogen, as well as some cross-section ratios near the threshold are also considered in the fit. Two types of fits are found as a result. In both cases, the properties of $Λ(1405)$ are well reproduced. In addition to this, a $Σ$ state is also found with mass around 1400 MeV. Cross sections, obtained with one of the two fits, are found to stay close to the data at energies away from the thresholds too, and as a result resonances with higher masses have also been studied.
In relativistic heavy ion collisions, after the quark gluon plasma (QGP) phase there is a hadron gas (HG) phase. In both phases $J/ψ$ may be formed and destroyed. In this note we study the $J/ψ$ interactions with other mesons in the hadron gas phase. Making use of effective field Lagrangians we obtain the cross sections for the production and absorption processes. With respect to the existing calculations, the improvements introduced here are the inclusion of $K$ and $K^*$'s in the effective Lagrangian approach and the inclusion of processes involving the new exotic charmonium states $Z_c(3900)$ and $Z_c(4025)$. We conclude that the interactions between $J/ψ$ and all the considered mesons reduce the original $J/ψ$ abundance ( determined at the end of the quark gluon plasma phase ) by 20 \% and 24 \% in RHIC and LHC collisions respectively. Consequently, any really significant change in the $J/ψ$ abundance comes from dissociation and regeneration processes in the QGP phase.
The $Ξ$ baryons are expected to be naturally narrower as compared to their nonstrange and strange counterparts since they have only one light quark and, thus, their decay involves producing either a light meson and doubly strange baryon or both meson and baryon with strangeness which involves, relatively, more energy. In fact, some $Ξ$'s have full widths of the order of even 10-20 MeV when, in principle, they have a large phase space to decay to some open channels. Such is the case of $Ξ(1690)$, for which the width has been found to be of the order of 10 MeV in the latest {\it BABAR} and BELLE data. In this manuscript we study why some $Ξ$'s are so narrow. Based on a coupled channel calculation of the pseudoscalar meson-baryon and vector meson-baryon systems with chiral and hidden local symmetry Lagrangians, we find that the answer lies in the intricate hadron dynamics. We find that the known mass, width, spin-parity and branching ratios of $Ξ(1690)$ can be naturally explained in terms of coupled channel meson-baryon dynamics. We find another narrow resonance which can be related to $Ξ(2120)$. We also look for exotic states $Ξ^{+}$ and $Ξ^{--}$ but find none. In addition we provide the cross sections for $ \bar K Λ, \bar K Σ\rightarrow πΞ$ which can be useful for understanding the enhanced yield of $Ξ$ reported in recent studies of heavy ion collisions.
In this manuscript we discuss the results of our recent study on $Ξ$ resonances. We have studied meson-baryon interaction with strangeness $-2$ by solving scattering equations in a coupled channel approach and found that the dynamics gives rise to the development of two poles in the complex plane close to the real axis. The corresponding narrow states have isospin half and spin half in one case and spin 3/2 in the other case. We find that the properties of the isospin and spin 1/2 state are strikingly similar to $Ξ(1690)$, while the state with spin 3/2 can be related to $Ξ(2120)$. We find that our results on $Ξ(1690)$ are in good agreement with the data available from the BELLE and BABAR Collaborations. Our formalism consists of treating pseudoscalar-baryon and vector-baryon channels on an equal footing. Since the thresholds of such channels are distributed over a relatively larger energy range, we obtain all interaction kernels needed to solve the Bethe-Salpeter equation without resorting to any nonrelativistic approximation even though the amplitudes are calculated at low energies.
In heavy ion collisions after the quark-gluon plasma there is a hadronic gas phase. Using effective Lagrangians we study the interactions of charmed mesons which lead to $J/ψ$ production and absorption in this gas. We update and extend previous calculations introducing strange meson interactions and also including the interactions mediated by the recently measured exotic charmonium resonances $Z(3900)$ and $Z(4025)$. These resonances open new reaction channels for the $J/ψ$, which could potentially lead to changes in its multiplicity. We compute the $J/ψ$ production cross section in processes such as $D_{(s)}^{(*)} + \bar{D}^{(*)} \to J/ψ+ (π, ρ, K, K^{\ast})$ and also the $J/ψ$ absorption cross section in the corresponding inverse processes. Using the obtained cross sections as input to solve the rate equation, we conclude that the interactions in the hadron gas phase do not significantly affect the $J/Ψ$ abundance. In other words, there is neither a charmonium suppression nor charmonium regeneration from light mesons in the hadronic phase.
Motivated by the experimental findings of some new exotic states decaying into channels like $J/ψϕ$, we investigate the formation of resonances/bound states in the $D^*_s\bar D^*_s$ system using QCD sum rules. To do this we start with a current of the type vector times vector and use spin projectors to separate the spin 0, 1 and 2 contributions to the correlation function. We find three states with isospin 0, nearly spin degenerate, with a mass around 4.1 GeV. We have also investigated the decay of these states to $J/ψϕ$ and provide the corresponding partial widths. Such information should be useful for experimental studies in future.
We investigate the production and absorption of $Z_b (10610)$ and $Z_b ^{\prime}(10650)$ states in a hadronic medium, via the processes $\bar{B}^{(*)} B^{(*)} \rightarrow πZ_b ^{(\prime)} $ and the corresponding inverses reactions. We use effective field Lagrangians based on an $SU(4)$-extension of the hidden gauge formalism to account for the couplings between light and heavy mesons, and a phenomenological Lagrangian involving the $ B^{\ast} B^{(\ast)} Z_b ^{(\prime)}$ vertices. The absorption cross sections are found to be much larger than the production ones.