Aceti, F., Bayar, M., Dias, J. M., & Oset, E. (2014). Prediction of a Z(c)(4000) state and relationship with the claimed Z(c)(4025). Eur. Phys. J. A, 50(6), 103–13pp.
Abstract: After discussing the OZI suppression of one light meson exchange in the interaction of with isospin I = 1 , we study the contribution of the two-pion exchange to the interaction and the exchange of heavy vectors, J/psi for diagonal transitions and D-* for transitions of to J/psi rho. We find these latter mechanisms to be weak, but enough to barely bind the system in J = 2 with a mass around 4000 MeV, while the effect of the two-pion exchange is a net attraction, though weaker than that from heavy-vector exchange. We discuss this state and try to relate it to the Z (c) (4025) state, above the threshold, claimed in an experiment at BES from an enhancement of the distribution close to threshold. Together with the results from a recent reanalysis of the BES experiment showing that it is compatible with a J = 2 state below threshold around 3990 MeV, we conclude that the BES experiment could show the existence of the state that we find in our approach.
|
Aceti, F., Bayar, M., Oset, E., Martinez Torres, A., Khemchandani, K. P., Dias, J. M., et al. (2014). Prediction of an I=1 D(D)over-bar* state and relationship to the claimed Z(c)(3900), Z(c)(3885). Phys. Rev. D, 90(1), 016003–13pp.
Abstract: We study here the interaction of D (D) over bar* in the isospin I = 1 channel in light of recent theoretical advances that allow us to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light q (q) over bar is Okubo-Zweig-Iizuka (OZI) suppressed and thus we concentrate on the exchange of heavy vectors and of two pion exchange. The latter is found to be small compared to the exchange of heavy vectors, which then determines the strength of the interaction. A barely D (D) over bar* bound state decaying into eta(c)rho and pi J/psi is found. At the same time we reanalyze the data of the BESIII experiment on e(+)e(-) -> pi(+/-)(D (D) over bar*)(-/+), from where a Z(c)(3885) state was claimed, associated to a peak in the (D (D) over bar*)(-/+) invariant mass distribution close to threshold, and we find the data compatible with a resonance with mass around 3875 MeV and width around 30 MeV. We discuss the possibility that this and the Z(c)(3900) state found at BESIII, reconfirmed at 3894 MeV at Belle, or 3885 MeV at CLEO, could all be the same state and correspond to the one that we find theoretically.
|
Aceti, F., Dai, L. R., Geng, L. S., Oset, E., & Zhang, Y. (2014). Meson-baryon components in the states of the baryon decuplet. Eur. Phys. J. A, 50(3), 57–11pp.
Abstract: We apply an extension of the Weinberg compositeness condition on partial waves of L = 1 and resonant states to determine the weight of the meson-baryon component in the Delta(1232) resonance and the other members of the baryon decuplet. We obtain an appreciable weight of pi N in the Delta(1232) wave function, of the order of 60%, which looks more natural when one recalls that experiments on deep inelastic and Drell Yan give a fraction of pi N component of 34% for the nucleon. We also show that, as we go to higher energies in the members of the decuplet, the weights of the meson-baryon component decrease and they already show a dominant part for a genuine, non-meson-baryon, component in the wave function. We write a section to interpret the meaning of the Weinberg sum rule when it is extended to complex energies and another one for the case of an energy-dependent potential.
|
Aceti, F., Dai, L. R., & Oset, E. (2016). a(1)(1420) peak as the pi f(0)(980) decay mode of the a(1)(1260). Phys. Rev. D, 94(9), 096015–9pp.
Abstract: We study the decay mode of the a(1)(1260) into a pi(+) in p wave and the f(0)(980) that decays into pi(+)pi(-) in s wave. The mechanism proceeds via a triangular mechanism where the a(1)(1260) decays into K*K-, the K* decays to an external pi(+) and an internal K that fuses with the (K) over bar producing the f(0)(980) resonance. The mechanism develops a singularity at a mass of the a(1)(1260) around 1420 MeV, producing a peak in the cross section of the pp reaction, used to generate the mesonic final state, which provides a natural explanation of all the features observed in the COMPASS experiment, where a peak observed at this energy is tentatively associated to a new resonance called a(1)(1420). On the other hand, the triangular singularity studied here gives rise to a remarkable feature, where a peak is seen for a certain decay channel of a resonance at an energy about 200 MeV higher than its nominal mass.
|
Aceti, F., Dias, J. M., & Oset, E. (2015). f(1)(1285) decays into a(0)(980) pi(0), f(0)(980) pi(0) and isospin breaking. Eur. Phys. J. A, 51(4), 48–8pp.
Abstract: We evaluate the decay width for the processes f1(1285). p 0 a0(980) and f1(1285). p 0 f0(980) taking into account that all three resonances are dynamically generated from the meson- meson interaction, the f1(1285) from K* K – c. c. and the a0(980), f0(980) from p., K K and pp, K _ K, respectively. We use a triangular mechanism similar to that of.(1405). pp., which provides a decay width for f1(1285). p 0 a0(980) with a branching fraction of the order of 30%, in agreement with experiment. At the same time we evaluate the decay width for the isospin- forbidden f1(1285). p 0 f0(980), which appears when we consider different masses for the charged and neutral kaons, and show that it is much more suppressed than in the.(1405). pp. case, but gives rise to a narrow shape of the p + p- distribution similar to the one found in the eta(1405) -> pi pi eta decay.
|
Aceti, F., Liang, W. H., Oset, E., Wu, J. J., & Zou, B. S. (2012). Isospin breaking and f(0)(980)-a(0)(980) mixing in the eta(1405) -> pi(0)f(0)(980) reaction. Phys. Rev. D, 86(11), 114007–11pp.
Abstract: We make a theoretical study of the eta(1405) -> pi(0)f(0)(980) and eta(1405) -> pi(0)a(0)(980) reactions with an aim to determine the isospin violation and the mixing of the f(0)(980) and a(0)(980) resonances. We make use of the chiral unitary approach where these two resonances appear as composite states of two mesons, dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the f(0)(980) production in agreement with a BES experiment. As to the amount of isospin violation, or f(0)(980) and a(0)(980) mixing, assuming constant vertices for the primary eta(1405) -> pi K-0 (K) over bar and eta(1405) -> pi(0)pi(0)eta production, we find results which are much smaller than found in the recent experimental BES paper, but consistent with results found in two other related BES experiments. We have tried to understand this anomaly by assuming an I = 1 mixture in the eta(1405) wave function, but this leads to a much bigger width of the f(0)(980) mass distribution than observed experimentally. The problem is solved by using the primary production driven by eta' -> K*(K) over bar followed by K* -> K pi, which induces an extra singularity in the loop functions needed to produce the f(0)(980) and a(0)(980) resonances. Improving upon earlier work along the same lines, and using the chiral unitary approach, we can now predict absolute values for the ratio Gamma(pi(0), pi(+)pi(-))/Gamma(pi(0), pi(0)eta) which are in fair agreement with experiment. We also show that the same results hold if we had the eta(1475) resonance or a mixture of these two states, as seems to be the case in the BES experiment.
|
Aceti, F., Molina, R., & Oset, E. (2012). X(3872) -> J/psi gamma decay in the D(D)over-bar* 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 D-0*(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.
|
Aceti, F., & Oset, E. (2012). Wave functions of composite hadron states and relationship to couplings of scattering amplitudes for general partial waves. Phys. Rev. D, 86(1), 014012–12pp.
Abstract: In this paper we present the connection between scattering amplitudes in momentum space and wave functions in coordinate space, generalizing previous work done for s-waves to any partial wave. The relationship to the wave function of the residues of the scattering amplitudes at the pole of bound states or resonances is investigated in detail. A sum rule obtained for the couplings provides a generalization to coupled channels, any partial wave and bound or resonance states, of Weinberg's compositeness condition, which was only valid for weakly bound states in one channel and s-wave. An example, requiring only experimental data, is shown for the rho meson indicating that it is not a composite particle of pi pi and K (K) over bar but something else.
|
Aceti, F., Oset, E., & Roca, L. (2014). Composite nature of the Lambda (1520) resonance. Phys. Rev. C, 90(2), 025208–8pp.
Abstract: Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the Lambda (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave pi Sigma* and K Xi* and the d-wave (K) over bar N and pi Sigma channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of components in its wave function.
|
Aceti, F., Xie, J. J., & Oset, E. (2015). The K(K)over-bar pi decay of the f(1) (1285) and its nature as a K*(K)over-bar – cc molecule. Phys. Lett. B, 750, 609–614.
Abstract: We investigate the decay of f(1) (1285) > pi K (K) over bar with the assumption that the f(1) (1285) is dynamically generated from the K*(K) over bar – cc interaction. In addition to the tree level diagrams that proceed via f(1)(1285) -> K*(K) over bar – cc -> pi K (K) over bar, we take into account also the final state interactions of K (K) over bar -> K (K) over bar and pi K -> pi K. The partial decay width and mass distributions of f(1) (1285) -> pi K (K) over bar are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space and tied to the K*(K) over bar – cc nature of the f(1) (1285) state.
|
