
Oset, E., Chen, H. X., Feijoo, A., Geng, L. S., Liang, W. H., Li, D. M., et al. (2016). Study of reactions disclosing hidden charm pentaquarks with or without strangeness. Nucl. Phys. A, 954, 371–392.
Abstract: We present results for five reactions, Lambda(b) > J/psi K()p, Lambda(b) > J/psi eta Lambda, Lambda(b) > J/psi pi()p, Lambda(b) > J/psi K0 Lambda and Xi()(b) > J/psi KLambda, where combining information from the meson baryon interaction, using the chiral unitary approach, and predictions made for molecular states of hidden charm, with or without strangeness, we can evaluate invariant mass distributions for the light meson baryon states, and for those of J/psi p or J/psi Lambda. We show that with the present available information, in all of these reactions one finds peaks where the pentaquark states show up. In the Lambda(b) > J/psi K()p, and Lambda(b) > J/psi pi()p reactions we show that the results obtained from our study are compatible with present experimental observations.



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.



Oset, E., & Roca, L. (2018). Triangle mechanism in tau > f(1)(1285)pi nu(tau) decay. Phys. Lett. B, 782, 332–338.
Abstract: We show that the tau() decay into f(1)(1285) pi()nu(tau) is dominated by a triangle loop mechanism with K*, (K) over bar* and K( or (K) over bar) as internal lines, which manifests a strong enhancement reminiscent of a nearby singularity present in the narrow K* limit and the near (K) over bar* K* threshold of the internal K* propagators. The f1(1285) is then produced by its coupling to the K* (K) over bar and (K) over bar* K which is obtained from a previous model where this resonance was dynamically generated as a molecular K* (K) over bar (or (K) over bar* K) state using the techniques of the chiral unitary approach. We make predictions for the f(1)pi mass distribution which significantly deviates from the phasespace shape, due to the distortion caused by the triangle mechanism and the K* (K) over bar threshold. We find a good agreement with the experimental value within uncertainties for the integrated partial decay width, which is a clear indication of the importance of the triangle mechanism in this decay and supports the dynamical origin of the f(1)(1285) as a K* (K) over bar and (K) over bar* K molecular state.



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.



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., & 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.



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.



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.



Dai, L. R., Roca, L., & Oset, E. (2019). tau decay into a pseudoscalar and an axialvector meson. Phys. Rev. D, 99(9), 096003–14pp.
Abstract: We study theoretically the decay tau() > nu(tau)P()A, with P a pi() or K and A an axialvector resonance b(1)(1235), h(1) (1170), h(1) (1380), a(1) (1260), f(1) (1285) or any of the two poles of the K1 (1270). The process proceeds through a triangle mechanism where a vector meson pair is first produced from the weak current and then one of the vectors produces two pseudoscalars, one of which reinteracts with the other vector to produce the axial resonance. For the initial weak hadronic production we use a recent formalism to account for the hadronization after the initial quarkantiquark pair produced from the weak current, which explicitly filters Gparity states and obtain easy analytic formulas after working out the angular momentum algebra. The model also takes advantage of the chiral unitary theories to evaluate the vectorpseudoscalar (VP) amplitudes, where the axialvector resonances were obtained as dynamically generated from the vectorpseudoscalar interaction. We make predictions for invariant mass distribution and branching ratios for the channels considered.



Dias, J. M., Roca, L., & Sakai, S. (2018). Prediction of new states from D(*)B(*)(B)overbar(*) threebody interactions. Phys. Rev. D, 97(5), 056019–8pp.
Abstract: We study threebody systems composed of D(*), B(*), and (B) over bar(*) in order to look for possible bound states or resonances. In order to solve the threebody problem, we use the fixed center approach for the Faddeev equations considering that the B*(B) over bar*(B (B) over bar) are clusterized systems, generated dynamically, which interact with a third particle D((D) over bar) whose mass is much smaller than the twobody bound states forming the cluster. In the DB*(B) over bar*, D*B*(B) over bar*, DB (B) over bar, and D*B (B) over bar systems with I = 1/2, we found clear bound state peaks with binding energies typically a few tens MeV and more uncertain broad resonant states about ten MeV above the threshold with widths of a few tens MeV.

