Molina, R., Doring, M., & Oset, E. (2016). Determination of the compositeness of resonances from decays: The case of the B-s(0) -> J/Psi f(1)(1285). Phys. Rev. D, 93(11), 114004–10pp.
Abstract: We develop a method to measure the amount of compositeness of a resonance, mostly made as a bound state of two hadrons, by simultaneously measuring the rate of production of the resonance and the mass distribution of the two hadrons close to threshold. By using different methods of analysis we conclude that the method allows one to extract the value of 1-Z with about 0.1 of uncertainty. The method is applied to the case of the (B) over bar (0)(s) -> J/Psi f(1)(1285) decay, by looking at the resonance production and the mass distribution of K (K) over bar*.
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Chen, H. X., Geng, L. S., Liang, W. H., Oset, E., Wang, E., & Xie, J. J. (2016). Looking for a hidden-charm pentaquark state with strangeness S =-1 from Xi(-)(b) decay into J/Psi K- Lambda. Phys. Rev. C, 93(6), 065203–9pp.
Abstract: Assuming that the recently observed hidden-charm pentaquark state, P-c(4450), is of molecular nature as predicted in the unitary approach, we propose to study the decay of Xi(-)(b) -> J/psi K-Lambda to search for the strangeness counterpart of the P-c(4450). There are three ingredients in the decay mechanism: the weak decay mechanism, the hadronization mechanism, and the final state interactions in the meson-baryon system of strangeness S = -2 and isospin I = 1/2 and of the J/psi Lambda. All these have been tested extensively. As a result, we provide a genuine prediction of the invariant mass distributions where a strangeness hidden-charm pentaquark state, the counterpart of the P-c(4450), can be clearly seen. The decay rate is estimated to be of similarmagnitude as the Lambda(0)(b) -> J/psi K(-)p measured by the LHCb Collaboration.
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Kamiya, Y., Miyahara, K., Ohnishi, S., Ikeda, Y., Hyodo, T., Oset, E., et al. (2016). Antikaon-nucleon interaction and Lambda(1405) in chiral SU(3) dynamics. Nucl. Phys. A, 954, 41–57.
Abstract: The properties of the Lambda(1405) resonance are key ingredients for determining the antikaon-nucleon interaction in strangeness nuclear physics, and the novel internal structure of the Lambda(1405) is of great interest in hadron physics, as a prototype case of a baryon that does not fit into the simple three-quark picture. We show that a quantitative description of the antikaon-nucleon interaction with the Lambda(1405) is achieved in the framework of chiral SU(3) dynamics, with the help of recent experimental progress. Further constraints on the (K) over barN subthreshold interaction are provided by analyzing pi Sigma spectra in various processes, such as the K(-)d -> pi Sigma n reaction and the Lambda(c) -> pi pi Sigma decay. The structure of the Lambda(1405) is found to be dominated by an antikaon-nucleon molecular configuration, based on its wavefunction derived from a realistic (K) over barN potential and the compositeness criteria from a model-independent weak-binding relation.
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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 K-0 Lambda and Xi(-)(b) -> J/psi K-Lambda, 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.
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Albaladejo, M., Nieves, J., Oset, E., & Jido, D. (2016). Ds0*(2317) and DK scattering in B decays from BaBar and LHCb data. Eur. Phys. J. C, 76(6), 300–8pp.
Abstract: We study the experimental DK invariant mass spectra of the reactions B+ -> (D) over bar (DK+)-D-0-K-0, B-0 -> D-(DK+)-K-0 (measured by the BaBar collaboration) and B-s -> pi(+DK-)-K-0 measured by the LHCb collaboration), where an enhancement right above the threshold is seen. We show that this enhancement is due to the presence of D-s0*(2317), which is a D K bound state in the I (J(P)) = 0(0(+)) sector. We employ a unitarized amplitude with an interaction potential fixed by heavy meson chiral perturbation theory. We obtain a mass M-Ds0* = 2315(-17) (+12 +10)(-5) MeV, and we also show, by means of theWeinberg compositeness condition, that the DK component in the wave function of this state is P-DK = 70(-6 -8)(+4 +4) %, where the first (second) error is statistical (systematic).
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Dias, J. M., Navarra, F. S., Nielsen, M., & Oset, E. (2016). f(0)(980) production in D-s(+)-> pi(+) pi(+) pi(-) and D-s(+) -> pi(+) K+ K- decays. Phys. Rev. D, 94(9), 096002–8pp.
Abstract: We study the D-s(+)-> pi(+) pi(+) pi(-) and D-s(+) -> pi(+) K+ K- decays adopting a mechanism in which the D-s(+) meson decays weakly into a pi+ and a q (q) over bar component, which hadronizes into two pseudoscalar mesons. The final state interaction between these two pseudoscalar mesons is taken into account by using the chiral unitary approach in coupled channels, which gives rise to the f(0)(980) resonance. Hence, we obtain the invariant mass distributions of the pairs pi(+) pi(-) and K+ K- after the decay of that resonance and compare our theoretical amplitudes with those available from the experimental data. Our results are in a fair agreement with the shape of these data, within large experimental uncertainty, and a f(0)(980) signal is seen in both the pi(+) pi(-) and K+ K- distributions. Predictions for the relative size of pi(+) pi(-) and K+ K- distributions are made.
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Bayar, M., Aceti, F., Guo, F. K., & Oset, E. (2016). Discussion on triangle singularities in the Lambda(b) -> J/psi K(-)p reaction. Phys. Rev. D, 94(7), 074039–10pp.
Abstract: We have analyzed the singularities of a triangle loop integral in detail and derived a formula for an easy evaluation of the triangle singularity on the physical boundary. It is applied to the Lambda(b) -> J/psi K(-)p process via Lambda*-charmonium-proton intermediate states. Although the evaluation of absolute rates is not possible, we identify the chi(c1) and the psi(2S)as the relatively most relevant states among all possible charmonia up to the psi(2S). The Lambda(1890)chi(c1)p loop is very special, as its normal threshold and triangle singularities merge at about 4.45 GeV, generating a narrow and prominent peak in the amplitude in the case that the chi(c1)p is in an S wave. We also see that loops with the same charmonium and other Lambda* hyperons produce less dramatic peaks from the threshold singularity alone. For the case of chi(c1)p -> J/psi p and quantum numbers 3/2(-) or 5/2(+), one needs P and D waves, respectively, in the chi(c1)p, which drastically reduce the strength of the contribution and smooth the threshold peak. In this case, we conclude that the singularities cannot account for the observed narrow peak. In the case of 1/2(+), 3/2(-) quantum numbers, where chi(c1)p -> J/psi p can proceed in an S wave, the Lambda(1890)chi(c1)p triangle diagram could play an important role, though neither can assert their strength without further input from experiments and lattice QCD calculations.
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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.
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Sekihara, T., Oset, E., & Ramos, A. (2016). On the structure observed in the in-flight He-3(K-, Lambda p)n reaction at J-PARC. Prog. Theor. Exp. Phys., 2016(12), 123D03–27pp.
Abstract: A theoretical investigation is done to clarify the origin of the peak structure observed near the K-pp threshold in the in-flight He-3(K-, Lambda p)n reaction of the J-PARC E15 experiment, which could be a signal of the lightest kaonic nuclei, i.e., the (K) over bar NN (I = 1/2) state. For the investigation, we evaluate the Lambda p invariant mass spectrum assuming two possible scenarios to interpret the experimental peak. One assumes that the Lambda (1405) resonance is generated after the emission of an energetic neutron from the absorption of the initial K-, not forming a bound state with the remaining proton. This uncorrelated Lambda (1405)p system subsequently decays into the final Lambda p. The other scenario implies that, after the emission of the energetic neutron, a (K) over bar NN bound state is formed, decaying eventually into a Lambda p pair. Our results show that the experimental signal observed in the in-flight He-3(K-, Lambda p)n reaction at J-PARC is qualitatively well reproduced by the assumption that a (K) over bar NN bound state is generated in the reaction, definitely discarding the interpretation in terms of an uncorrelated Lambda (1405)p s tate.
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Feijoo, A., Magas, V. K., Ramos, A., & Oset, E. (2016). A hidden-charm S =-1 pentaquark from the decay Lambda(b) into J/psi eta Lambda states. Eur. Phys. J. C, 76(8), 446–12pp.
Abstract: The hidden-charm pentaquark P-c(4450) observed recently by the LHCb collaboration may be of molecular nature, as advocated by some unitary approaches that also predict pentaquark partners in the strangeness S = -1 sector. In this work we argue that a hidden-charm strange pentaquark could be seen from the decay of the Lambda b, just as in the case of the non-strange P-c(4450), but looking into the J/psi eta Lambda decay mode and forming the invariant mass spectrum of J/psi Lambda pairs. In the model presented here, which assumes a standard weak decay topology and incorporates the hadronization process and final-state interaction effects, we find the J/psi eta Lambda final states to be populated with similar strength as the J/psi K- p states employed for the observation of the non-strange pentaquark. This makes the Lambda b -> J/psi eta Lambda decay to be an interesting process to observe a possible strange partner of the P-c(4450). We study the dependence of the J/psi Lambda mass spectra on various model ingredients and on the unknown properties of the strange pentaquark.
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