
Roca, L., Song, J., & Oset, E. (2024). Molecular pentaquarks with hidden charm and double strangeness. Phys. Rev. D, 109(9), 094005–8pp.
Abstract: We analyze theoretically the coupledchannel mesonbaryon interaction with global flavor c<overline>cssn and c<overline>csss, where mesons are pseudoscalars or vectors, and baryons have JP = 1/2+ or 3/2+. The aim is to explore whether the nonlinear dynamics inherent in the unitarization process within coupled channels can dynamically generate double and triplestrange pentaquarktype states (Pcss and Pcsss, respectively), for which there is no experimental evidence to date. We evaluate the swave scattering matrix by implementing unitarity in coupled channels, using potential kernels obtained from tchannel vector meson exchange. The required PPV and VVV vertices are obtained from Lagrangians derived through appropriate extensions of the local hidden gauge symmetry approach to the charm sector, while capitalizing on the symmetry of the spin and flavor wave function to evaluate the BBV vertex. We find four different poles in the double strange sector, some of them degenerate in spin. For the triplestrange channel, we find the mesonbaryon interaction insufficient to generate a bound or resonance state through the unitary coupledchannel dynamics.



Oset, E., & Roca, L. (2022). Exotic molecular meson states of B(*) K(*) nature. Eur. Phys. J. C, 82(10), 882–9pp.
Abstract: We evaluate theoretically the interaction of the open bottom and strange systems (B) over bar (K) over bar, (B) over bar * (K) over bar, (B) over bar (K) over bar * and (B) over bar* (K) over bar* to look for possible bound states which could correspond to exotic nonquarkantiquark mesons since they would contain at least one b and one s quarks. The swave scattering matrix is evaluated implementing unitarity by means of the BetheSalpeter equation, with the potential kernels obtained from contact and vector meson exchange mechanisms. The vertices needed are supplied from Lagrangians derived from suitable extensions of the hidden gauge symmetry approach to the bottom sector. We find poles below the respective thresholds for isospin 0 interaction and evaluate the widths of the different obtained states by including the main sources of imaginary part, which are the B *> B gamma decay in the (B) over bar * (K) over bar channels, the K *> K pi in the channels involving a K *, plus the box diagrams with (B) over bar (K) over bar and (B) over bar * (K) over bar intermediate states for the (B) over bar * (K) over bar * channels.



Dai, L. R., Oset, E., Feijoo, A., Molina, R., Roca, L., Martinez Torres, A., et al. (2022). Masses and widths of the exotic molecular B(s)(()*B)((s))(*()) states. Phys. Rev. D, 105(7), 074017–11pp.
Abstract: We study the interaction of the doubly bottom systems BB, B*B, BsB, Bs*B, B*B*, B*BS, B*Bs*, BsBs, BsBs*, Bs*Bs* by means of vector meson exchange with Lagrangians from an extension of the local hidden gauge approach. The full swave scattering matrix is obtained implementing unitarity in coupled channels by means of the BetheSalpeter equation. We find poles below the channel thresholds for the attractively interacting channels B*B in I = 0, Bs*B – B*Bs in I = 1/2, B* B* in I = 0, and Bs*B* in I = 1/2, all of them with J(P) = 1(+). For these cases the widths are evaluated identifying the dominant source of imaginary part. We find binding energies of the order of 1020 MeV, and the widths vary much from one system to the other: of the order of 10100 eV for the B* B system and Bs*B – B* Bs, about 6 MeV for the B*B* system and of the order of 0.5 MeV for the Bs*B* system.



Roca, L., Liang, W. H., & Oset, E. (2022). Inconsistency of the data on the K1(1270) > pi K0*(1430) decay width. Phys. Lett. B, 824, 136827–3pp.
Abstract: We show, using the same Lagrangian for the K1(1270) > pi K0*(1430) and K0*(1430) > K1 (1270)pi decays, that the present PDG data on the partial decay width of K1 (1270) > pi K0*(1430) implies a width for K0*(1430) > K1 (1270)pi decay which is about one order of magnitude larger than the total K0*(1430) width. A discussion on this inconsistency is done, stressing its relationship to the existence of two K1(1270) states obtained with the chiral unitary theory, which are not considered in the experimental analyses of K pi pi data.



Dias, J. M., Toledo, G., Roca, L., & Oset, E. (2021). Unveiling the K1(1270) doublepole structure in the (B)overbar > J/psi rho(K)overbar and (B)overbar > J/psi(K)overbar*pi decays. Phys. Rev. D, 103(11), 116019–13pp.
Abstract: By looking at the pseudoscalarvector meson spectra in the (B) over bar > J/psi rho(K) over bar and (B) over bar > J/psi(K) over bar*pi weak decays, we theoretically investigate the doublepole structure of the K1 (1270) resonance by using the chiral unitary approach to account for the finalstate interactions between the pseudoscalar (P) and vector (V) mesons. The K1 (1270) resonance is dynamically generated through these interactions in coupled channels and influences the shape of the invariant mass distributions under consideration. We show how these shapes are affected by the K1 (1270) doublepole structure to confront the results from our model with future experiments that might investigate the PV spectra in these decays.



Roca, L., & Oset, E. (2021). Scalar resonances in the D+ > KK+K+ decay. Phys. Rev. D, 103(3), 034020–9pp.
Abstract: We study theoretically the resonant structure of the double Cabibbo suppressed D+ > KK+K+ decay. We start from an elementary production diagram, considered subleading in previous approaches, which cannot produce a final KK+ pair at the tree level but which we show to be able to provide the strength of the decay through final mesonmeson state interaction. The different mesonmeson elementary productions are related through SU(3), and the final rescattering is implemented from a suitable implementation of unitary extensions of chiral perturbation theory, which generate dynamically the scalar resonances1 f(0)(980) and a(0)(980). We obtain a good agreement with recent experimental data from the LHCb Collaboration with a minimal freedom in the fit and show the dominance of the a(0)(980) contribution close to the threshold of the KK+ spectrum.



Martinez Torres, A., Khemchandani, K. P., Roca, L., & Oset, E. (2020). Fewbody systems consisting of mesons. FewBody Syst., 61(4), 35–16pp.
Abstract: We present a work which is meant to inspire the fewbody practitioners to venture into the study of new, more exotic, systems and to hadron physicists, working mostly on twobody problems, to move in the direction of studying related fewbody systems. For this purpose we devote the discussions in the introduction to show how the input twobody amplitudes can be easily obtained using techniques of the chiral unitary theory, or its extensions to the heavy quark sector. We then briefly explain how these amplitudes can be used to solve the Faddeev equations or a simpler version obtained by treating the threebody scattering as that of a particle on a fixed center. Further, we give some examples of the results obtained by studying systems involving mesons. We have also addressed the field of many meson systems, which is currently almost unexplored, but for which we envisage a bright future. Finally, we give a complete list of works dealing with unconventional fewbody systems involving one or several mesons, summarizing in this way the findings on the topic, and providing a motivation for those willing to investigate such systems.



Dai, L. R., Roca, L., & Oset, E. (2020). Tau decay into tau(t) and a(1)(1260), b(1)(1235), and two K1(1270). Eur. Phys. J. C, 80(7), 673–9pp.
Abstract: We study the tau > nu(tau). A decay, with A an axialvector meson. We produce the a(1) (1260) and b(1) (1235) resonances in the Cabibbo favored mode and two K1 (1270) states in the Cabibbo suppressed mode. We take advantage of previous chiral unitary approach results where these resonances appear dynamically from the vector and pseudoscalar meson interaction in swave. Actually two different poles were obtained associated to the K1(1270) quantum numbers. We find that the unmeasured rates for b(1)(1235) production are similar to those of the a(1)(1260) and for the two K1 states we suggest to separate the present information on the (K) over bar pi pi invariant masses into (K) over bar*pi and rho K modes, the channels to which these two resonances couple most strongly, predicting that thesemodes peak at different energies and have different widths. These measurements should shed light on the existence of these two K1 states. In addition, we have gone one step further making a comparison with experimental results of three meson decay channels, letting the vector mesons of our approach decay into pseudoscalars, and we find an overall good agreement with experiment.



Wang, G. Y., Roca, L., Wang, E., Liang, W. H., & Oset, E. (2020). Signatures of the two K1(1270) poles in D – plus ve plus V P decay. Eur. Phys. J. C, 80(5), 388–7pp.
Abstract: We analyze theoretically the D+ ye+ pK and D+ pe+ K*7 decays to see the feasibility to check the double pole nature of the axial vector resonance Kt(1270) predicted by the unitary extensions of chiral perturbation theory (UChPT). Indeed, within UChPT the K1(1270) is dynamically generated from the interaction of a vector and a pseudoscalar meson, and two poles are obtained for the quantum numbers of this resonance. The lower mass pole couples dominantly to 10 and the higher mass pole to pK, therefore we can expect that different reactions weighing differently these channels in the production mechanisms enhance one or the other pole. We show that the different final V P channels in D pe+ V P weigh differently both poles, and this is reflected in the shape of the final vectorpseudoscalar invariant mass distributions. Therefore, we conclude that these decays are suitable to distinguish experimentally the predicted double pole of the Kt(1270) resonance.



Wang, G. Y., Roca, L., & Oset, E. (2019). Discerning the two K1 (1270) poles in D0 > pi(+) VP decay. Phys. Rev. D, 100(7), 074018–10pp.
Abstract: Within the chiral unitary approach, the axialvector resonance K1 (1270) has been predicted to manifest a twopole nature. The lowest pole has a mass of 1195 MeV and a width of 246 MeV and couples mostly to K*pi, and the highest pole has a mass of 1284 MeV and a width of 146 MeV and couples mostly to rho K. We analyze theoretically how this doublepole structure can show up in D0 > pi+VP decays by looking at the vectorpseudoscalar (VP) invariant mass distribution for different VP channels, exploiting the fact that each pole couples differently to different VP pairs. We find that the final (K) over bar*pi and rho(K) over tilde channels are sensible to the different poles of the K1 (1270) resonance and hence are suitable reactions to analyze experimentally the doublepole nature of this resonance.

