
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.



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.



YamagataSekihara, J., Roca, L., & Oset, E. (2010). Nature of the K2*(1430), K3*(1780), K4*(2045), K5*(2380), and K6* as K*multirho states. Phys. Rev. D, 82(9), 094017–8pp.
Abstract: We show that the K2*(1430), K3*(1780), K4*(2045), K5*(2380), and a notyetdiscovered K6* resonance are basically molecules made of an increasing number of rho(770) and one K*(892) mesons. The idea relies on the fact that the vectorvector interaction in the s wave with spins aligned is very strong for both rho rho and K*rho. We extend a recent work, where several resonances showed up as multirho(770) molecules, to the strange sector including the K*(892) into the system. The resonant structures show up in the multibody scattering amplitudes, which are evaluated in terms of the unitary twobody vectorvector scattering amplitudes by using the fixed center approximation to the Faddeev equations.



Dias, J. M., Debastiani, V. R., Roca, L., Sakai, S., & Oset, E. (2017). Binding of the BD(D)overbar and BDD systems. Phys. Rev. D, 96(9), 094007–6pp.
Abstract: We study theoretically the BD (D) over bar and BDD systems to see if they allow for possible bound or resonant states. The threebody interaction is evaluated implementing the fixed center approximation to the Faddeev equations which considers the interaction of a D or (D) over bar particle with the components of a BD cluster, previously proved to form a bound state. We find an I(J(P)) = 1/2(0()) bound state for the BD (D) over bar system at an energy around 89258985 MeV within uncertainties, which would correspond to a bottom hiddencharm meson. In contrast, for the BDD system, which would be bottom doublecharm and hence manifestly exotic, we have found hints of a bound state in the energy region 89358985 MeV, but the results are not stable under the uncertainties of the model, and we cannot assure, nor rule out, the possibility of a BDD threebody 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.



Roca, L., Nieves, J., & Oset, E. (2015). LHCb pentaquark as a (D)overbar*Sigma(c) – (D)overbar*Sigma(c)* molecular state. Phys. Rev. D, 92(9), 094003–6pp.
Abstract: We perform a theoretical analysis of the Lambda(b) > J/psi K()p reaction from where a recent LHCb experiment extracts a Lambda(1405) contribution in the K()p spectrum close to threshold and two baryon states of hidden charm in the J/psi p spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and J(P) of the experiment; concretely some states built up from the J/psi N, (D) over bar*Lambda(c), (D) over bar*Sigma(c), (D) over bar Sigma(c)* and (D) over bar*Sigma(c)* coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the K()p mass distribution close to threshold and the peak of the J/psi p distribution, with values of the J/psi p coupling to the resonance in line with the theoretical ones. The nontrivial matching of many properties gives support to a J(P) = 3/2() assignment to this state and to its nature as a molecular state mostly made of (D) over bar*Sigma(c) and (D) over bar*Sigma(c)*.



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., 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. (2017). Role of a triangle singularity in the pi Delta decay of N(1700)(3/2()). Phys. Rev. C, 95(6), 065211–8pp.
Abstract: We show the important role played by the pi Delta(1232) channel in the build up of the N(1700)(3/2()) resonance due to the nontrivial enhancement produced by a singularity of a triangular loop. The N(1700) is one of the dynamically generated resonances produced by the coupledchannel vectorbaryon interaction. The pi Delta channel was neglected in previous works but we show that it has to be incorporated into the coupledchannel formalism due to an enhancement produced by a singularity in the triangular loop with., nucleon, and p as internal loop lines and pi and Delta as external ones. The enhancement is of nonresonant origin but it contributes to the dynamical generation of the N(1700) resonance due to the nonlinear dynamics involved in the coupledchannel mechanisms. We obtain an important increase of the total width of the N(1700) resonance when the pi Delta channel is included and provide predictions for the partial widths of the N(1700) decays into VB and pi Delta.

