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Albaladejo, M., & Oset, E. (2013). Combined analysis of the pn -> d pi(+)pi(-) and pn -> pn pi(+)pi(-) cross sections and implications for the interpretation of the pn -> d pi(+)pi(-) data. Phys. Rev. C, 88(1), 014006–6pp.
Abstract: We use recent data that show a narrow peak around root s = 2.37 GeV in the pn -> d pi(+)pi(-) cross section, with about double strength at the peak than in the analogous pn -> d pi(0)pi(0) reaction, and, assuming that it is due to the excitation of a dibaryon resonance, we evaluate the cross section for the pn -> pn pi(+)pi(-) reaction, with the final pn unbound but with the same quantum numbers as the deuteron. We use accurate techniques to determine the final state interaction in the case of the pn forming a deuteron or a positive energy state, which allow us to get the pn -> pn pi(+)pi(-) cross section with pn in I = 0 and S = 1, that turns out to be quite close or saturates the experimental pn -> pn pi(+)pi(-) total cross section around root s = 2.37 GeV, depending on the angular momentum assumed. This poses problems to the assumption of the dibaryon hypothesis, which could be rendered more restrictive with future precise data on the pn -> pn pi(+)pi(-) reaction.
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Ozpineci, A., Xiao, C. W., & Oset, E. (2013). Hidden beauty molecules within the local hidden gauge approach and heavy quark spin symmetry. Phys. Rev. D, 88(3), 034018–14pp.
Abstract: Using a coupled channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-meson interaction with hidden beauty and obtain several new states. Both I = 0 and I = 1 states are analyzed, and it is shown that in the I = 1 sector, the interactions are too weak to create any bound states within our framework. In total, we predict with confidence the existence of six bound states and six more possible weakly bound states. The existence of these weakly bound states depends on the influence of the coupled channel effects.
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Jido, D., Oset, E., & Sekihara, T. (2013). The K(-)d -> pi Sigma n reaction revisited. Eur. Phys. J. A, 49(8), 95–11pp.
Abstract: The appearance of some papers dealing with the K(-)d -> pi Sigma n reaction, with some discrepancies in the results and a proposal to measure the reaction at forward n angles at J-PARC justifies to retake the theoretical study of this reaction. We do this in the present paper showing results using the Watson approach and the truncated Faddeev approach. We argue that the Watson approach is more suitable to study the reaction because it takes into account the potential energy of the nucleons forming the deuteron, which is neglected in the truncated Faddeev approach. The paper shows the strength and limitations of both approaches and we perform calculations using four different approximations. Comparison of the results shows that the truncated Faddeev approach produces a strong asymmetry between the energy of the two nucleons of the deuteron, while in the Watson approach this energy is equally shared. From the experimental point of view the results are very valuable since they show that the different approximations share the feature that the peak of the pi Sigma mass distribution is drastically shifted in the presence of the Lambda(1405). Additionally, we also show that in the angle-integrated cross section the threshold cusp effects are basically washed away and all approximations show a clear shape of the Lambda(1405). In this sense, measurements of all these magnitudes in different K- energies are bound to bring new information that sheds new light on the properties and nature of the Lambda(1405) resonance.
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Xiao, C. W., Nieves, J., & Oset, E. (2013). Combining heavy quark spin and local hidden gauge symmetries in the dynamical generation of hidden charm baryons. Phys. Rev. D, 88(5), 056012–20pp.
Abstract: We present a coupled channel unitary approach to obtain states dynamically generated from the meson-baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. As a basis of states, we use (D) over barB, (D) over bar *B states, with B baryon charmed states belonging to the 20 representations of SU(4) with J(P) = 1/2(+), 3/2(+). In addition we also include the eta N-c and J/psi N states. The inclusion of these coupled channels is demanded by heavy quark spin symmetry, since in the large m(Q) limit the D and D* states are degenerate and are obtained from each other by means of a spin rotation, under which QCD is invariant. The novelty in the work is that we use dynamics from the extrapolation of the local hidden gauge model to SU(4), and we show that this dynamics fully respects the constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we look for states dynamically generated and find four basic states that are bound, corresponding to (D) over bar Sigma(c), (D) over bar Sigma(c)*, (D) over bar*Sigma(c) and (D) over bar*Sigma*(c) decaying mostly into eta N-c and J/psi N. All the states appear in isospin I = 1/2, and we find no bound states or resonances in I = 3/2. The (D) over bar Sigma(c) state appears in J = 1/2 and the (D) over bar Sigma*(c) in J = 3/2; the (D) over bar*Sigma(c) appears nearly degenerate in J = 1/2, 3/2 and the (D) over bar*Sigma*(c) appears nearly degenerate in J = 1/2, 3/2, 5/2, with the peculiarity that in J = 5/2 the state has zero width in the space of states chosen. All the states are bound with about 50 MeV with respect to the corresponding (D) over barB thresholds, and the width, except for the J = 5/2 state, is also of the same order of magnitude. Finally, we discuss the uncertainties stemming from the expected breaking of SU(4) and the heavy quark spin symmetry.
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Martinez Torres, A., Khemchandani, K. P., Jido, D., Kanada-En'yo, Y., & Oset, E. (2013). Three-body hadron systems with strangeness. Nucl. Phys. A, 914, 280–288.
Abstract: Recently, many efforts are being put in studying three-hadron systems made of mesons and baryons and interesting results are being found. In this talk, we summarize the main features of the formalism used to study such three hadron systems with strangeness S = -1, 0 within a framework built on the basis of unitary chiral theories and solution of the Faddeev equations. In particular, we present the results obtained for the pi(K) over barN, K (K) over barN and KK (K) over bar systems and their respective coupled channels. In the first case, we find four Sigma's and two A's with spin-parity J(P) = 1/2(+), in the 1500-1800 MeV region, as two meson-one baryon s-wave resonances. In the second case, a 1/2(+) N* around 1900 MeV is found. For the last one a kaon close to 1420 MeV is formed, which can be identified with K(1460).
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Bayar, M., & Oset, E. (2013). The (K)over-barNN system revisited including absorption. Nucl. Phys. A, 914, 349–353.
Abstract: We present the Fixed Center Approximation (FCA) to the Faddeev equations for the (K) over bar NN system with S = 0, including the charge exchange mechanisms in the (K) over bar rescattering. The system appears bound by about 35 MeV and the width, omitting two body absorption, is about 50 MeV. We also evaluate the (K) over bar absorption width in the bound (K) over bar NN system by employing the FCA to account for (K) over bar rescattering on the NN cluster. The width of the states found previously for S = 0 and S = 1 is found now to increase by about 30 MeV due to the (K) over bar NN absorption, to a total value of about 80 MeV.
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Tolos, L., Cabrera, D., Garcia-Recio, C., Molina, R., Nieves, J., Oset, E., et al. (2013). Strangeness and charm in nuclear matter. Nucl. Phys. A, 914, 461–471.
Abstract: The properties of strange (K, (K) over bar and (K) over bar*) and open-charm (D, (D) over bar and D*) mesons in dense matter are studied using a unitary approach in coupled channels for meson-baryon scattering. In the strangeness sector, the interaction with nucleons always comes through vector-meson exchange, which is evaluated by chiral and hidden gauge Lagrangians. For the interaction of charmed mesons with nucleons we extend the SU(3) Weinberg-Tomozawa Lagrangian to incorporate spin-flavor symmetry and implement a suitable flavor symmetry breaking. The in-medium solution for the scattering amplitude accounts for Pauli blocking effects and meson self-energies. On one hand, we obtain the K, (K) over bar and (K) over bar* spectral functions in the nuclear medium and study their behaviour at finite density, temperature and momentum. We also make an estimate of the transparency ratio of the gamma A -> K+ K*(-) A' reaction, which we propose as a tool to detect in-medium modifications of the (K) over bar* meson. On the other hand, in the charm sector, several resonances with negative parity are generated dynamically by the s-wave interaction between pseudoscalar and vector meson multiplets with 1/2(+) and 3/2(+) baryons. The properties of these states in matter are analyzed and their influence on the open-charm meson spectral functions is studied. We finally discuss the possible formation of D-mesic nuclei at FAIR energies.
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Dote, A., Bayar, M., Xiao, C. W., Hyodo, T., Oka, M., & Oset, E. (2013). A narrow quasi-bound state of the DNN system. Nucl. Phys. A, 914, 499–504.
Abstract: We have investigated a charmed system of DNN (composed of two nucleons and a D meson) by a complementary study with a variational calculation and a Faddeev calculation with fixed-center approximation (Faddeev-FCA). In the present study, we employ a DN potential based on a vector-meson exchange picture in which a resonant A(c)(2595) is dynamically generated as a DN quasi-bound state, similarly to the A(1405) as a (K) over barN one in the strange sector. As a result of the study of variational calculation with an effective DN potential and three kinds of NN potentials, the DNN(J(pi) =0(-), I = 1/2) is found to be a narrow quasi-bound state below A(c)(2595)N threshold: total binding energy similar to 225 MeV and mesonic decay width similar to 25 MeV. On the other hand, the J(pi) =1(-) state is considered to be a scattering state of A(c)(2595) and a nucleon. These results are essentially supported by the Faddeev-FCA calculation. By the analysis of the variational wave function, we have found a unique structure in the DNN(J(pi) = 0, I = 1/2) such that the D meson stays around the center of the total system due to the heaviness of the D meson.
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Dai, L. R., & Oset, E. (2013). Tests on the molecular structure of f(2)(1270), f'(2) (1525) from psi(nS) and Upsilon(nS) decays. Eur. Phys. J. A, 49(10), 130–6pp.
Abstract: Based on previous studies that support the vector-vector molecular structure of the f(2)'(1270), f 2 (1525), K * 0 2 (1430), f0(1370) and f0(1710) resonances, we make predictions for the.(2S) decay into.(f) f2(1270),.(f) f 2 (1525), K* 0 (892) K * 0 2 (1430) and the radiative decay of.(1S),.(2S),.(2S) into.f2(1270),.f 2 (1525),.f0(1370),.f0(1710). Agreement with experimental data is found for three available ratios, without using free parameters, and predictions are done for other cases.
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Liang, W. H., Albaladejo, M., & Oset, E. (2013). Searching for a hidden charm h(1) state in the X(4660) -> eta h(1) and X(4660) -> eta D*(D)over-bar* decays. Phys. Rev. D, 88(7), 074027–7pp.
Abstract: We explore the possibility of experimentally detecting a predicted h(1) inverted right perpendicular I-G(J(PC)) = 0(-)(1(+-))inverted left perpendicular state of hidden charm made out from the D*(D) over bar* interaction. The method consists in measuring the decay of X(4660) into eta D*(D) over bar* and determining the binding energy with respect to the D*(D) over bar* threshold from the shape of the D*(D) over bar* invariant mass distribution. A complementary method consists in looking at the inclusive X(4660) -> eta X decay and searching for a peak in the X invariant mass distribution. We make calculations to determine the partial decay width of X(4660) -> eta h(1) from the measured X(4660) -> eta D*(D) over bar* distribution. This estimation should serve in an experiment to foresee the possibility of detecting the h(1) state on top of the background of inclusive events.
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