Feijoo, A., Magas, V. K., Ramos, A., & Oset, E. (2015). Lambda(b) -> J/psi K Xi decay and the higher order chiral terms of the meson baryon interaction. Phys. Rev. D, 92(7), 076015–10pp.
Abstract: We study the weak decay of the Lambda(b) into J/psi K Xi. and J/psi eta Lambda states, and relate these processes to the Lambda(b) -> J/psi(K) over barN decay mode. The elementary weak transition at the quark level proceeds via the creation of a J/psi meson and an excited sud system with I = 0, which upon hadronization leads to (K) over barN or eta Lambda pairs. These states undergo final-state interaction in coupled channels and produce a final meson-baryon pair. The K. state only occurs via rescattering, hence making the Lambda(b) -> J/psi K Xi process very sensitive to the details of the meson-baryon interaction in strangeness S = -1 and isospin I = 0. We show that the corresponding invariant mass distribution is dominated by the next-to-leading-order terms of the chiral interaction. The I = 0 selectivity of this decay, and its large sensitivity to the higher-order terms, makes its measurement very useful and complementary to the K- p -> K Xi cross section data. The rates of the Lambda(b) -> J/psi K Xi and Lambda(b) -> J/psi eta Lambda invariant mass distributions are sizable compared to those of the Lambda(b) -> J/psi(K) over barN decay, which is measured experimentally, and thus, we provide arguments for an experimental determination of these decay modes that will help us understand better the chiral dynamics at higher energies.
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Roca, L., Nieves, J., & Oset, E. (2015). LHCb pentaquark as a (D)over-bar*Sigma(c) – (D)over-bar*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)*.
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Miyahara, K., Hyodo, T., & Oset, E. (2015). Weak decay of Lambda(+)(c) for the study of Lambda(1405) and Lambda(1670). Phys. Rev. C, 92(5), 055204–8pp.
Abstract: We study the Lambda(c) decay process to pi(+) and the meson-baryon final state for the analysis of Lambda resonances. Considering the Cabibbo-Kobayashi-Maskawamatrix, color suppression, diquark correlation, and the kinematical condition, we show that the final meson-baryon state should be in a pure I = 0 combination, when the meson-baryon invariantmass is small. Because the I = 1 contamination usually makes it difficult to analyze Lambda resonances directly from experiments, the Lambda(c) decay is an ideal process to study Lambda resonances. Calculating the final-state interaction by chiral unitary approaches, we find that the pi Sigma invariant mass distributions have the same peak structure in the all charge combination of the pi Sigma states related to the higher pole of the two poles of the Lambda(1405). Furthermore, we obtain a clear Lambda(1670) peak structure in the (K) over bar N and eta Lambda spectra.
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Ikeno, N., & Oset, E. (2016). Semileptonic Lambda(c) decay to nu l(+) and Lambda(1405). Phys. Rev. D, 93(1), 014021–7pp.
Abstract: We study the semileptonic decay of Lambda(c) to nu l(+) and Lambda(1405), where the Lambda(1405) is seen in the invariant mass distribution of pi Sigma. We perform the hadronization of the quarks produced in the reaction in order to have a meson baryon pair in the final state and then let these hadron pairs undergo final state interaction from where the Lambda(1405) is dynamically generated. The reaction is particularly suited to study this resonance, because we show that it filters I = 0. It is also free of tree-level pi Sigma production, which leads to a clean signal of the resonance with no background. This same feature has as a consequence that one populates the state of the Lambda(1405) with higher mass around 1420 MeV, predicted by the chiral unitary approach. We make absolute predictions for the invariant mass distributions and find them within the measurable range in present facilities. The implementation of this reaction would allow us to gain insight into the existence of the predicted two Lambda(1405) states and their nature as molecular states.
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Xie, J. J., Oset, E., & Geng, L. S. (2016). Photoproduction of the f(2)'(1525), a(2)(1320), and K-2(*) (1430). Phys. Rev. C, 93(2), 025202–8pp.
Abstract: Assuming that the f(2)'(1525), a(2)(1320), and K-2(*) (1430) resonances are dynamically generated states from vector-meson-vector-meson interactions in the s-wave with spin S = 2, we study the gamma p -> f(2)'(1525)p, gamma p -> a(2)(0)(1320)p, and gamma p -> K-2(*)(1430)Lambda(Sigma) reactions. These reactions proceed in the following way: the incoming photon first mutates into a rho(0), omega, or phi meson via vector-meson dominance, which then interacts with the rho(0), omega, or K* emitted by the incoming proton to form the tensor mesons f(2)(')(1525), a(2)(1320), and K-2(*)(1430). The picture is simple and has no free parameters, as all the parameters of the mechanism have been fixed in previous studies. We predict the differential and total cross sections of these reactions. The results can be tested in future experiments and therefore offer new clues about the nature of these tensor states.
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Sun, Z. F., Bayar, M., Fernandez-Soler, P., & Oset, E. (2016). Ds0*(2317)(+) in the decay of Bc into J/Psi DK. Phys. Rev. D, 93(5), 054028–9pp.
Abstract: In this paper we study the relationship between the D-s0*(2317)(+) resonance and the decay of the B-c meson into J/Psi DK. In this process, the B-c meson decays first into J/Psi and the quark pair c (s) over bar, and then the quark pair hadronizes into DK or D-s eta components, which undergo final state interaction. This final state interaction, generating the D-s0*(2317)(+) resonance, is described by the chiral unitary approach. With the parameters which allow us to match the pole position of the D-s0*(2317)(+), we obtain the DK invariant mass distribution of the decay B-c -> J/Psi DK, and also the rate for B-c -> J/Psi D-s0*(2317). The ratio of these two magnitudes is then predicted.
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Geng, L. S., & Oset, E. (2016). Novel nonperturbative approach for radiative (B)over-bar(0)((B)over-bar(s)(0)) -> J/psi gamma decays. Phys. Rev. D, 94(1), 014018–11pp.
Abstract: Radiative (B) over bar (0)((B) over bar (0)(s)) -> J/psi gamma decays provide an interesting case to test our understanding of ( non) perturbative QCD and eventually to probe physics beyond the standard model. Recently, the LHCb Collaboration reported an upper bound, updating the results of the BABAR Collaboration. Previous theoretical predictions based on QCD factorization or perturbative QCD have shown large variations due to different treatment of nonfactorizable contributions and meson-photon transitions. In this paper, we report on a novel approach to estimate the decay rates, which is based on a recently proposed model for B decays and the vector meson dominance hypothesis, widely tested in the relevant energy regions. The predicted branching ratios are Br[(B) over bar (0) -> J/psi gamma] = (3.50 +/- 0.34(-0.63)(+1.12)) x 10(-8) and Br[(B) over bar (0)(s) -> J/psi gamma] = (7.20 +/- 0.68(-1.30)(+2.31)) x 10(-7). The first uncertainty is systematic and the second is statistical, originating from the experimental (B) over bar (0)(s) -> J/psi gamma branching ratio.
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Xie, J. J., Liang, W. H., & Oset, E. (2016). (K)over-bar-induced formation of the f(0)(980) and a(0)(980) resonances on proton targets. Phys. Rev. C, 93(3), 035206–8pp.
Abstract: We perform a calculation of the cross section for nine reactions induced by (K) over bar scattering on protons. The reactions studied are K- p -> Lambda pi(+)pi(-), K- p -> Sigma(0)pi(+)pi(-), K- p -> Lambda pi(0)eta, K- p -> Sigma(0)pi(0)eta, K- p -> Sigma(+)pi(-)eta, (K) over bar (0) p -> Lambda pi(+)eta, (K) over bar (0) p -> Sigma(0)pi(+)eta, (K) over bar (0) p -> Sigma(+)pi(+)pi(-), and (K) over bar (0) p -> Sigma+pi(0)eta. We find that in the reactions producing pi(+)pi(-), a clear peak for the f(0)(980) resonance is found, while no trace of f(0)(500) appears. Similarly, in the cases of p. production, a strong peak is found for the a(0)(980) resonance, with the characteristic strong cusp shape. Cross sections and invariant mass distributions are evaluated which should serve, by comparing them with future data, to test the dynamics of the chiral unitary approach used for the evaluations and the nature of these resonances.
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Wang, E., Chen, H. X., Geng, L. S., Li, D. M., & Oset, E. (2016). Hidden-charm pentaquark state in Lambda(0)(b) -> J/psi p pi(-) decay. Phys. Rev. D, 93(9), 094001–10pp.
Abstract: We study here the A(b)(0) -> J/psi p pi(-) reaction in analogy to the A(b)(0) -> J/psi pK(-) one, and we note that in both decays there is a sharp structure (dip or peak) in the J/psi p mass distribution around 4450 MeV, which is associated in the A(b)(0) -> J/psi pK(-) experiment to an exotic pentaquark baryonic state, although in J/psi p pi(-) it shows up with relatively low statistics. We analyze the A(b)(0) -> J/psi p pi(-) interaction along the same lines as the A(b)(0) -> J/psi pK(-) one, with the main difference stemming from the reduced Cabibbo strength in the former and the consideration of the pi(-)p final state interaction instead of the K(-)p one. We find that with a minimal input, introducing the pi(-)p and J/psi p interaction in S-wave with realistic interactions, and the empirical P-wave and D-wave contributions, one can accomplish a qualitative description of the pi(-)p and J/psi p mass distributions. More importantly, the peak structure followed by a dip of the experimental J/psi p mass distribution is reproduced with the same input as used to describe the data of A(b)(0) -> J/psi pK(-) reaction. The repercussion for the triangular singularity mechanism, invoked in some works to explain the pentaquark peak, is discussed.
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Lu, J. X., Wang, E., Xie, J. J., Geng, L. S., & Oset, E. (2016). Lambda(b) -> J/psi K-0 Lambda reaction and a hidden-charm pentaquark state with strangeness. Phys. Rev. D, 93(9), 094009–11pp.
Abstract: We study the Lambda(b) -> J/psi K-0 Lambda reaction considering both the K-0 Lambda interaction with its coupled channels and the J/psi Lambda interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to J/psi Lambda By using the coupling of the resonance to J/psi Lambda from these predictions, we show that a neat peak can be observed in the J/psi Lambda invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the J/psi Lambda spectrum.
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