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Now showing items 65 - 80 of 187

  • Recent Developments in Chiral Unitary Theory and Triangle Singularities Involving Baryons

    Oset, E.   Bayar, M.   Aceti, F.   Guo, F. K.   Debastiani, V. R.   Sakai, S.   Wang, E.   Xie, J. J.   Liang, W. H.   Roca, L.   Samart, D.  

    We report on several reactions involving baryons that develop triangle singularities. The combination of elements of chiral unitary theory with the triangle mechanisms explain different features of reactions and shed light on some decay modes of several resonances. We address the role of a triangle singularity in the contribution to , another singularity, producing a peak in the reaction which was previously unexplained, the role of a singularity in the decay of the N(1700), and also discuss the resonance from this perspective.
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  • The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction

    Molina, R.   Oset, E.  

    We study the vector-vector interaction within the framework of the hidden gauge formalism for the sector with quantum numbers charm C = 0 and strangeness S = 0 in the region around 4000 MeV. We get five poles, three of which could be identified with the Y(3940), Z(3930) and X(4160). These poles appear with quantum numbers I = 0 and J(PC) = 0(++), 2(++) and 2(++), respectively, and can be considered as hadronic molecules made of D*(D) over bar*, D(s)*(D) over bar (s)*.
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  • Selected topics on Hadrons in Nuclei

    Oset, E.   Kaskulov, M.   Hernandez, E.   Ramos, A.   Magas, V. K.   Yamagata-Sekihara, J.   Hirenzaki, S.   Gamermann, D.   Molina, R.   Tolos, L.   Roca, L.  

    In this talk we report on selected topics on hadrons in nuclei. The first topic is the renormalization of the width of the A(1520) in a nuclear medium. This is followed by a short update of the situation of the omega in the medium. The investigation of the properties of (K) over bar in the nuclear medium from the study of the (K-flight, p) reaction is also addressed, as well as properties of X,Y,Z charmed and hidden charm resonances in a nuclear medium. Finally we address the novel issue of multimeson states.
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  • Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances

    Liang, W. H.   Molina, R.   Oset, E.  

    We determine the radiative decay amplitudes for the decay into D* and (D) over bar gamma, or (D) over bar gamma(s)* and s. of some of the charmonium- like states classified as X, Y, Z resonances, plus some other hidden charm states which are dynamically generated from the interaction of vector mesons with charm. The mass distributions as a function of the (D) over bar gamma or (D) over bar (s)gamma. invariant mass show a peculiar behavior as a consequence of the D* (D) over bar gamma* nature of these states. The experimental search of these magnitudes can shed light on the nature of these states.
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  • Three Body Systems with Strangeness and Exotic Systems

    Oset, E.   Torres, A. Martinez   Khemchandani, K. P.   Roca, L.  

    We report on four Sigma's and three Lambda's, in the 1500-1800 MeV region, as two meson-one baryon S-wave (1/2)(+) resonances found by solving the Faddeev equations in the coupled channel approach, which can be associated to the existing S = -1, J (P) = 1/2(+) low lying baryon resonances. On the other hand we also report on a new, hidden strangeness N (*) state, mostly made of K (K) over bar N, with mass around 1920MeV, which we think could be responsible for the peak seen in the gamma p -> K(+)Lambda around this energy. Finally we address a very novel topic in which we show how few body systems of several rho mesons can be produced, with their spins aligned up to J = 6, and how these states found theoretically can be associated to several known mesons with spins J = 2, 3, 4, 5, 6.
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  • [AIP HADRON SPECTROSCOPY: Eleventh International Conference on Hadron Spectroscopy - Rio de Janeiro (Brazil) (21-26 August 2005)] AIP Conference Proceedings - Evidence for two Λ(1405) resonance states

    Oset, E.  

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  • Reanalysis of lattice QCD spectra leading to the Ds0*(2317) and Ds1*(2460)

    Martinez Torres, A.   Oset, E.   Prelovsek, S.   Ramos, A.  

    We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of KD and KD* are induced and identified with the narrow D-s0*(2317) and D-s1*(2460) resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis KD(*()), and a two-channel basis KD(*()), eta D-s(()*()). By means of an extended Luscher method we determine poles of the continuum t-matrix, bound by about 40 MeV with respect to the KD and KD* thresholds, which we identify with the D-s0*(2317) and D-s1*(2460) resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state D-s0*(2317) contains a KD component in an amount of about 70%, while the state D-s1*(2460) contains a similar amount of KD*. We argue that the present lattice simulation results do not still allow us to determine which are the missing channels in the bound state wave functions and we discuss the necessary information that can lead to answer this question.
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  • S =-1 resonances in two meson-one baryon systems

    Khemchandani, K. P.   Martinez Torres, A.   Oset, E.  

    We study the two meson-one baryon systems by solving Faddeev equations, using chiral dynamics. The calculations, carried out for the pi(K) over barN system and its coupled channels for the case of strangeness = -1, in the S-wave, lead to a dynamical generation of many strangeness = -1 resonances in the 1500-1800 MeV region. While building the formalism, we found important cancellations between different sources of three-body forces.
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  • Study of the J/psi -> phi(omega) f(2)(1270), J/psi -> phi(omega) f '(2)(1525) and J/psi -> K*(0)(892) (K)over-bar(2)*(0)(1430) decays RID C-6441-2009

    Martinez Torres, A.   Geng, L. S.   Dai, L. R.   Sun, Bao Xi   Oset, E.   Zou, B. S.  

    We present an approach to Study the decay modes of the J/psi into a vector meson and a tensor meson, taking into account the nature of the f(2)(1270), f'(2)(1525). (K) over bar (2)*(0)(1430) resonances as dynamically generated states from the vector meson-vector meson interaction. We evaluate four ratios of partial decay widths in terms of a flavor dependent OZI breaking parameter and the results obtained compare favorably with experiment, although the experimental uncertainties are still large. Further refinements of the data Would provide a more stringent test on the theoretical approach. The fit to the data is possible due to the particular strength and sign of the couplings of the resonances to pairs of vector mesons given by the theory. (C) 2009 Elsevier B.V. All rights reserved.
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  • Radiative decay into gamma-baryon of dynamically generated resonances from the vector-baryon interaction

    Garzon, E. J.   Sun, Bao-Xi   Oset, E.  

    We study the radiative decay into gamma and a baryon of the SU(3) octet and decuplet of nine and ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the octet and the decuplet respectively. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances. For the case of baryons of the octet we determine the helicity amplitudes and compare them with experimental data when available.
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  • Latest Results for the Antikaon-Nucleon Optical Potential

    Magas, V. K.   Yamagata-Sekihara, J.   Hirenzaki, S.   Oset, E.   Ramos, A.  

    The key question of this letter is whether the K (-)-nucleus optical potential is deep, as it is prefered by the phenomenological fits to kaonic atoms data, or shallow, as it comes out from unitary chiral model calculations. The current experimental situation is reviewed.
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  • The rho(omega) B*(B) interaction and states of J=3D0, 1, 2

    Fernandez-Soler, P.   Sun, Zhi-Feng   Nieves, J.   Oset, E.  

    In this work, we study systems composed of a rho/omega and B* meson pair. We find three bound states in isospin, spin-parity channels (1/2, 0(+)), (1/2, 1(+)), and (1/2, 2(+)). The state with J =3D 2 can be a good candidate for the B-2*(5747). We also study the rho B system, and a bound state with mass 5728 MeV and width around 20 MeV is obtained, which can be identified with the B-1(5721) resonance. In the case of I =3D 3/2, one obtains repulsion and, thus, no exotic (molecular) mesons in this sector are generated in the approach.
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  • The nature of Lambda(1405) hyperon resonance in chiral dynamics

    Jido, D.   Sekihara, T.   Ikeda, Y.   Hyodo, T.   Kanada-En'yo, Y.   Oset, E.  

    The nature of the Lambda(1405) is discussed based on the unitarised coupled-channels approach with chiral dynamics (chiral unitary model). This approach describes the (K) over barN scattering cross sections and the Lambda(1405) spectra phenomenologically very well. With this successful description of Lambda(1405), it is found that the Lambda(1405) is composed by two resonance states having different coupling nature to the meson-baryon states. As a consequence, the resonance position in the pi Sigma invariant mass spectrum depends on the initial channel of the Lambda(1405) production. To observe the Lambda(1405) initiated by the (K) over barN channel, K(-)d -> Lambda(1405)n is one of the most favorable reactions. Hadronic molecule states with kaons are also discussed by emphasizing an important role of Lambda(1405) as a quasibound state of (K) over barN
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  • The (K -, p) reaction on nuclei with in-flight kaons

    Ramos, A.   Magas, V.K.   Yamagata-Sekihara, J.   Hirenzaki, S.   Oset, E.  

    We perform a theoretical study of the spectrum of protons with kinetic energies of around 600 MeV, emitted following the interaction of 1 GeV/c kaons with nuclei. A recent experimental analysis of this (K -, p) reaction on 12C, based on the dominant quasielastic process, has suggested a deeply attractive kaon nucleus potential. Our Monte Carlo simulation considers, in addition, the one-and two-nucleon K - absorption processes producing hyperons that decay into piN pairs. We find that this kaon in-flight reaction is not well suited to determine the kaon optical potential due, essentially, to the limited sensitivity of the cross section to its strength, and also to unavoidable uncertainties from the coincidence requirement applied in the experiment. A shallow kaon nucleus optical potential obtained in chiral models is perfectly compatible with the observed spectrum. [All rights reserved Elsevier].
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  • Quantum loops in radiative decays of the a 1 and b 1 axial-vector mesons

    Roca, L.   Hosaka, A.   Oset, E.  

    A previous model where the low-lying axial-vector mesons are dynamically generated, implementing unitarity in coupled channels in the vector-pseudoscalar (VP) meson interaction, is applied to evaluate the decay widths of the a 1(1260) and b 1(1235) axial-vector mesons into pigamma. Unlike the case of the a 1, the b 1 radiative decay is systematically underestimated at tree level. In this work we evaluate for the first time the loop contribution coming from an initial VP vertex. Despite the large superficial divergence of the loops, the convergence of the relevant loops can be established by using arguments of gauge invariance. The partial decay widths obtained agree with the experimental values within uncertainties, and we show that the loop contribution is crucial in the b 1 case and also important for the a 1 case. [All rights reserved Elsevier].
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  • Baryon states with open charm in the extended local hidden gauge approach

    Liang, W. H.   Uchino, T.   Xiao, C. W.   Oset, E.  

    In this paper we examine the interaction of DN and D* N states, together with their coupled channels, by using an extension of the local hidden gauge formalism from the light meson sector, which is based on heavy quark spin symmetry. The scheme is based on the use of the impulse approximation at the quark level, with the heavy quarks acting as spectators, which occurs for the dominant terms where there is the exchange of a light meson. The pion exchange and the Weinberg-Tomozawa interactions are generalized and with this dynamics we look for states generated from the interaction, with a unitary coupled channels approach that mixes the pseudoscalar-baryon and vector-baryon states. We find two states with nearly zero width, which are associated to the I > (c) (2595) and I > (c) (2625). The lower state, with J (P) =3D 1/2(-), couples to DN and D* N, and the second one, with J (P) =3D 3/2(-), to D* N. In addition to these two I > (c) states, we find four more states with I =3D 0, one of them nearly degenerate in two states of J (P) =3D 1/2, 3/2. Furthermore we find three states in I =3D 1, two of them degenerate in J =3D 1/2, 3/2.
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