Xie, J. J., Liang, W. H., & Oset, E. (2018). Hidden charm pentaquark and Lambda(1405) in the Lambda(0)(b) -> eta K-c(-) p(pi Sigma) reaction. Phys. Lett. B, 777, 447–452.
Abstract: We have performed a study of the Lambda(0)(b) -> eta K-c(-) p and Lambda(0)(b) -> eta(c)pi Sigma reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the K- p produced only couples to Lambda* states, not Sigma* and that the pi Sigma state is only generated from final state interaction of (K) over barN and eta Lambda channels which are produced in a primary stage. This guarantees that the pi Sigma state is generated in isospin I=0 and we see that the invariant mass produces a clean signal for the Lambda(1405) of higher mass at 1420 MeV. We also study the eta(c)p final state interaction, which is driven by the excitation of a hidden charm resonance predicted before. We relate the strength of the different invariant mass distributions and find similar strengths that should be clearly visible in an ongoing LHCb experiment. In particular we predict that a clean peak should be seen for a hidden charm resonance that couples to the eta(c)p channel in the invariant eta(c)p mass distribution.
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Bayar, M., Pavao, R., Sakai, S., & Oset, E. (2018). Role of the triangle singularity in Lambda(1405) production in the pi(-) p -> K-0 pi Sigma and pp -> pK(+) pi Sigma processes. Phys. Rev. C, 97(3), 035203–12pp.
Abstract: We have investigated the cross section for the pi(-) p -> K-0 pi Sigma and pp -> pK(+) pi Sigma reactions, paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a N* to K* Sigma and the K* decay into pi K, and the pi Sigma finally merges into Lambda (1405). The mechanism is expected to produce a peak around 2140 MeV in the K Lambda (1405) invariant mass. We found that a clear peak appears around 2100 MeV in the K Lambda (1405) invariant mass, which is about 40 MeV lower than the expectation, and that is due to the resonance peak of a N* resonance which plays a crucial role in the K* Sigma production. The mechanism studied produces the peak of the Lambda (1405) around or below 1400 MeV, as is seen in the pp -> pK(+) pi Sigma HADES experiment.
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Dai, L. R., Dias, J. M., & Oset, E. (2018). Disclosing D* (D)over bar* molecular states in the B-c(-) -> pi(-) J/psi omega decay. Eur. Phys. J. C, 78(3), 210–7pp.
Abstract: We study the B-c(-) -> pi(-) J/omega and B-c(-) -> pi(-) D* (D) over bar* reactions and show that they are related by the presence of two resonances, the X(3940) and X(3930), that are of molecular nature and couple most strongly to D* (D) over bar*, but also to J/psi omega. Because of that, in the J/psi omega mass distribution we find a cusp with large strength at the D* (D) over bar* threshold and predict the ratio of strengths between the peak of the cusp and the maximum of the D* (D) over bar* distribution close to D* (D) over bar* threshold, which are distinct features of the molecular nature of these two resonances.
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Dias, J. M., Debastiani, V. R., Xie, J. J., & Oset, E. (2018). The radiative decay D-0 -> (K)over-bar*(0)gamma with vector meson dominance. Chin. Phys. C, 42(4), 043106–7pp.
Abstract: Motivated by the experimental measurements of D-0 radiative decay modes, we have proposed a model to study the D-0 -> (K) over bar*(0)gamma decay, by establishing a link with D-0 -> (K) over bar*(0) V (V = rho(0), omega) decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for V gamma conversion. As a result, we have found the branching ratio B[D-0 -> (K) over bar*(0)gamma]=(1.55-3.44)x10(-4), which is in fair agreement with the experimental values reported by the Belle and BaBar collaborations.
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Liang, W. H., Sakai, S., Xie, J. J., & Oset, E. (2018). Triangle singularity enhancing isospin violation in (B)over-bar(s)(0)-> J/psi pi(0)f(0)(980). Chin. Phys. C, 42(4), 044101–9pp.
Abstract: We perform calculations for the (B) over bar (0)(s)-> J/psi pi(0)f(0)(980) and (B) over bar (0)(s)-> J/psi pi(0)a(0)(980) reactions, showing that the first is isospin-suppressed while the second is isospin-allowed. The reaction proceeds via a triangle mechanism, with (B) over bar (0)(s)-> J/psi K*(K) over bar +c.c., followed by the decay K*-> K pi and a further fusion of K (K) over bar into the f(0)(980) or a(0)(980). We show that the mechanism develops a singularity around the pi(0)f(0)(980) or pi(0)a(0)(980) invariant mass of 1420 MeV, where the pi(0)f(0) and pi(0)a(0) decay modes are magnified and also the ratio of pi(0)f(0) to pi(0)a(0) production. Using experimental information for the (B) over bar (0)(s)-> J/psi K*(K) over bar +c.c. decay, we are able to obtain absolute values for the reactions studied which fall into the experimentally accessible range. The reactions proposed and the observables evaluated, when contrasted with actual experiments, should be very valuable to obtain information on the nature of the low lying scalar mesons.
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