
Aceti, F., Molina, R., & Oset, E. (2012). X(3872) > J/psi gamma decay in the D(D)overbar* molecular picture. Phys. Rev. D, 86(11), 113007–13pp.
Abstract: From a picture of the X(3872) where the resonance is a bound state of D (D) over bar* c.c., we evaluate the decay width into the J/psi gamma channel, which is sensitive to the internal structure of this state. For this purpose we evaluate the loops through which the X(3872) decays into its components, and the J/psi and the photon are radiated from these components. We use the local hidden gauge approach extrapolated to SU(4) with a particular SU(4) breaking. The radiative decay involves anomalous couplings, and we obtain acceptable values which are compared to experiments and results of other calculations. Simultaneously, we evaluate the decay rate for the X(3872) into J/psi omega and J/psi rho, and the results obtained for the ratio of these decay widths are compatible with the experiment. We also show that considering only the (D) over bar D0*(0) – c.c. component in the radiative decay reduces the partial decay width in more than three orders of magnitude, in large discrepancy with experiment.



Bayar, M., Martinez Torres, A., Khemchandani, K. P., Molina, R., & Oset, E. (2023). Exotic states with triple charm. Eur. Phys. J. C, 83(1), 46–9pp.
Abstract: In this work we investigate the possibility of the formation of states from the dynamics involved in the D* D* D* system by considering that two D*'s generate a JP = 1+ bound state, with isospin 0, which has been predicted in an earlier theoretical work. We solve the Faddeev equations for this system within the fixed center approximation and find the existence of J(P) = 0(), 1() and 2() states with charm 3, isospin 1/2, masses similar to 6000 MeV, which are manifestly exotic hadrons, i.e., with a multiquark inner structure.



Bayar, M., Molina, R., Oset, E., Liu, M. Z., & Geng, L. S. (2024). Subtleties in triangle loops for Ds+ → ρ+ η → π+ π0 η in a0(980) production. Phys. Rev. D, 109(7), 076027–7pp.
Abstract: We address a general problem in the evaluation of triangle loops stemming from the consideration of the range of the interaction involved in some of the vertices, as well as the energy dependence of the width of some unstable particles in the loop. We find sizeable corrections from both effects. We apply that to a loop relevant to the D + s > pi + pi 0 eta decay, and find reductions of about a factor of 4 in the mass distribution of invariant mass of the pi eta in the region of the a 0 ( 980 ) . The method used is based on the explicit analytical evaluation of the q 0 integration in the d 4 q loop integration, using Cauchy 's residues method, which at the same time offers an insight on the convergence of the integrals and the effect of form factors and cutoffs.



Branz, T., Molina, R., & Oset, E. (2011). Radiative decays of the Y(3940), Z(3930), and the X(4160) as dynamically generated resonances. Phys. Rev. D, 83(11), 114015–9pp.
Abstract: We study the radiative decay properties of the charmoniumlike X, Y, and Z mesons generated dynamically from vectormesonvectormeson interaction in the framework of a unitarized hiddengauge formalism. In the present work, we calculate the oneand twophoton decay widths of the hiddencharm Y(3940), Z(3930) [or X(3915)], and X(4160) mesons in the framework of the vectormeson dominance formalism. We obtain good agreement with the experiment in case of the twophoton width of the X(3915), which we associate to the 2(+) resonance that we find at 3922 MeV. However, in view of discrepancies with a different approach that also considers the resonances as molecular states, we urge independent calculations along the same lines to further clarify the issue.



Dai, L. R., Molina, R., & Oset, E. (2022). Prediction of new Tcc states of D* D* and Ds*D* molecular nature. Phys. Rev. D, 105(1), 016029–12pp.
Abstract: We extend the theoretical framework used to describe the Tcc state as a molecular state of D* D and make predictions for the D* D* and Ds(*) D) systems, finding that they lead to bound states only in the J(P) = 1+ channel. Using input needed to describe the Tcc state, basically one parameter to regularize the loops of the BetheSalpeter equation, we find bound states with bindings of the order of MeVand similar widths for the D*D* system, while the D*s D* system develops a strong cusp around the threshold.



Dai, L. R., Molina, R., & Oset, E. (2022). Looking for the exotic X0(2866) and its J(P)=1(+) partner in the (B)overbar(0) > D(*) + K K(*)0 reactions. Phys. Rev. D, 105(9), 096022–7pp.
Abstract: We propose two reactions, (B) over bar (0) > (KD+K)D0 and (B) over bar (0) > K*D0*K+(), which have been already measured at Belle, to look into the J(P) = 0(+), X0(2866) state and a 1(+) partner of molecular D*(K) over bar* nature by looking at the D+K and D*K+() invariant mass distributions, respectively. Very clear peaks over the background are predicted and the branching ratios for the production of these states are evaluated to facilitate the task of determining the needed statistics for their observation. We conclude that with the upgrade of Belle II clear peaks should be seen in both reactions for the two resonances discussed.



Dai, L. R., Molina, R., & Oset, E. (2022). The (B)overbar(0)> D*+ (D)overbar*K0() reaction to detect the I=0, J(P)=1+ partner of the X0(2866). Phys. Lett. B, 832, 137219–5pp.
Abstract: We have chosen the (B) over bar (0)> D*+ (D) over bar*K0 reaction in order to observe the I= 0, J(P)= 1(+)(R1) partner state of the X0(2866) stemming from the D*+ (K) over bar* molecular picture. The reaction proceeds via external emission in the most favored Cabibbo decay mode and one observes the R(1)state as a very strong peak versus the background in the D*+ K spectrum. The branching ratio for R1production in this reaction is estimated of the order of 4 x10(3). The method used, applied to the B+> D D+ K+ reaction, produces a ratio of signal to background in the D K+ spectrum in very good agreement with the LHCb experiment that observed the X0(2866).



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.



Feijoo, A., Molina, R., Dai, L. R., & Oset, E. (2022). Lambda(1405) mediated triangle singularity in the K()d > p Sigma() reaction. Eur. Phys. J. C, 82(11), 1028–16pp.
Abstract: We study for the first time the p Sigma() > K d and K d > p Sigma() reactions close to threshold and show that they are driven by a triangle mechanism, with the Lambda(1405), a proton and a neutron as intermediate states, which develops a triangle singularity close to the (K) over bard threshold. We find that a mechanism involving virtual pion exchange and the K p > pi(+)Sigma() amplitude dominates over another one involving kaon exchange and the K p > K p amplitude. Moreover, of the two Lambda(1405) states, the one with higher mass around 1420 MeV, gives the largest contribution to the process. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing (K) over barN observables above threshold, provide different extrapolations of the (K) over barN amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the (K) over barN amplitudes below threshold and to more accurate predictions of the Lambda(1405) state of lower mass.



Garzon, E. J., Molina, R., Hosaka, A., & Oset, E. (2014). Strategies for an accurate determination of the X(3872) energy from QCD lattice simulations. Phys. Rev. D, 89(1), 014504–9pp.
Abstract: We develop a method to determine accurately the binding energy of the X( 3872) from lattice data for the D (D) over bar* interaction. We show that, because of the small difference between the neutral and charged components of the X( 3872), it is necessary to differentiate them in the energy levels of the lattice spectrum if one wishes to have a precise determination of the the binding energy of the X( 3872). The analysis of the data requires the use of coupled channels. Depending on the number of levels available and the size of the box, we determine the precision needed in the lattice energies to finally obtain a desired accuracy in the binding energy.

