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Now showing items 113 - 128 of 187

  • Unitarized Chiral Perturbation Theory in a finite volume: Scalar meson sector

    Doering, M.   Meissner, U. -G.   Oset, E.   Rusetsky, A.  

    We develop a scheme for the extraction of the properties of the scalar mesons f(0)(600), f(0)(980), and a(0)(980) from lattice QCD data. This scheme is based on a two-channel chiral unitary approach with fully relativistic propagators in a finite volume. In order to discuss the feasibility of finding the mass and width of the scalar resonances, we analyze synthetic lattice data with a fixed error assigned, and show that the framework can be indeed used for an accurate determination of resonance pole positions in the multichannel scattering.
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  • Predictions for the X(YZ) and X(YZ) with X(4160), Y(3940), Z(3930)

    Liang, Wei-Hong   Molina, R.   Xie, Ju-Jun   Doering, M.   Oset, E.  

    We investigate the decay of and with R being the , , resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of , well within the present measurable range. In order to further test the dynamical nature of these resonances we study the and decays close to the and thresholds and make predictions for the ratio of the mass distributions in these decays and the decay widths. The measurement of these decays rates can help unravel the nature of these resonances.
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  • Three-body hadronic structure of low-lying 1/2(+) Sigma and Lambda resonances

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

    We discuss the dynamical generation of some low-lying 1/2(+) Sigma and Lambda's in two-meson one-baryon systems. These systems have been constructed by adding a pion in the S-wave to the (K) over barN pair and its coupled channels, where the 1/2(-) Lambda(1405) -resonance gets dynamically generated. We solve Faddeev equations in the coupled-channel approach to calculate the T-matrix for these systems as a function of the total energy and the invariant mass of one of the meson-baryon pairs. This squared T-matrix shows peaks at the energies very close to the masses of the strangeness -1 , 1/2(+) resonances listed in the particle data book.
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  • Deeply bound pionic atoms with resonant Compton scattering

    Nieves, J.   Oset, E.   Carrasco, R.C.  

    We study the contribution to ordinary Compton nuclear scattering of the resonant channel gamma+Ararr(A'pi -)rarrgamma+A with thepi - bound in the nucleus. We show that the interference of this resonant channel with background amplitudes produces significant peaks in the elastic backward differential cross section as a function of the incoming photon energy for light and medium-size nuclei. We also find that for light nuclei the signals in forward Compton scattering or in the total photonuclear cross section are big enough to be observed, provided there is a good resolution in the photon beam. The reaction is particularly suited to find deeply bound pionic states in medium-size nuclei, or ordinary levels in unstable light nuclei
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  • Hadronic particles made of multi-rho(770) mesons

    Roca, L.   Oset, E.   Yamagata-Sekihara, J.  

    We summarize the work [1] where we studied the few body system made of several rho(770) mesons. Based on the very strong interaction of two rho(770) vector mesons in spin 2 and isospin 0, we show that the resonances rho(3)(1690) (3(--)), f(4)(2050) (4(++)), rho(5)(2350) (5(--)) and f(6)(2510) (6(++)) can be interpreted as few body systems made of an increasing number of rho(770) particles. The fixed center approximation of the Faddeev equations is used in order to write the multi-body interaction in terms of the elementary two-body scattering amplitudes. Very good agreement with the experimental masses is found. An extension of the model to include also the interaction with K*(895) is discussed.
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  • Recent developments on hadron interaction and dynamically generated resonances

    Oset, E.   Albaladejo, M.   Xie, Ju-Jun   Ramos, A.  

    In this talk I report on the recent developments in the subject of dynamically generated resonances. In particular I discuss the gamma p -> K-0 Sigma+ and gamma n -> K-0 Sigma(0) reactions, with a peculiar behavior around the K*(0)Lambda threshold, due to a 1/2(-) resonance around 2035 MeV. Similarly, I discuss a BES experiment, J/psi -> eta K*(0) (K) over bar*(0) decay, which provides evidence for a new h(1) resonance around 1830 MeV that was predicted from the vector-vector interaction. A short discussion is then made about recent advances in the charm and beauty sectors.
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  • Study of the f(2)(1270) , f(2)'(1525) , f(0)(1370) and f(0)(1710) in the J/psi radiative decays RID C-6441-2009 RID F-5325-2010

    Geng, L. S.   Guo, F. K.   Hanhart, C.   Molina, R.   Oset, E.   Zou, B. S.  

    In this paper we present an approach to study the radiative decay modes of the J/psi into a photon and one of the tensor mesons f (2)(1270) , f' (2)(1525) , as well as the scalar ones f (0)(1370) and f (0)(1710) . Especially, we compare predictions that emerge from a scheme where the states appear dynamically in the solution of vector meson-vector meson scattering amplitudes to those from a (admittedly naive) quark model. We provide evidence that it might be possible to distinguish amongst the two scenarios, once improved data are available.
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  • Baryonic resonances from baryon decuplet-meson octet interaction (vol 750, pg 294, 2005)

    Sarkar, Sourav   Oset, E.   Vicente-Vacas, M. J.  

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  • Two, three, many body systems involving mesons

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

    In this talk we show recent developments on few body systems involving mesons. We report on an approach to Faddeev equations using chiral unitary dynamics, where an explicit cancellation of the two body off shell amplitude with three body forces stemming from the same chiral Lagrangians takes place. This removal of the unphysical off shell part of the amplitudes is most welcome and renders the approach unambiguous, showing that only on shell two body amplitudes need to be used. Within this approach, systems of two mesons and one baryon are studied, reproducing properties of the low lying 1/2(+) states. On the other hand we also report on multirho and K* multirho states which can be associated to known meson resonances of high spin. (C) 2012 Elsevier B.V. All rights reserved.
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  • Vector meson-baryon dynamics in photoproduction reactions around 2 GeV

    Ramos, A.   Oset, E.  

    We investigate the role of vector mesons and coupled-channel unitarization on photoproduction reactions off the proton at energies around 2 GeV. We explain the sudden drop on the gamma p -> K-0 Sigma(+) cross section, observed recently by the CBELSA/TAPS collaboration, by a delicate interference between amplitudes having K*Lambda and K*Sigma intermediate states modulated by the presence of a nearby N* resonance produced by our model, a feature that we have employed to predict its properties. We also show the importance of coupled-channel unitarization in the gamma p -> K*(0)Sigma(+) reaction, measured recently by CBELSA/TAPS and CLAS with conflicting results.
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  • Searching for exotic states in the N pi K system

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

    We study the N pi K system in order to investigate the possibility of existence of strangeness +1 resonance(s). The formalism consists of solving the Faddeev equations with the N pi, pi K and KN t-matrices obtained from chiral dynamics. The same formalism, which leads to the finding of several 1/2(+) resonances in the corresponding three-body S = -1 channels in the 1400-2000 MeV energy region, results into only one broad bump around 1700 MeV with isospin 0. The amplitudes in isospin 1 and 2 configuration do not have any resonant structure. (C) 2009 Published by Elsevier B.V.
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  • The f 0(1370), f 0(1710), f 2(1270), f 2'(1525), and K 2*(1430) as dynamically generated states from vector meson-vector meson interaction

    Geng, L.S.   Oset, E.   Molina, R.   Torres, A.M.   Branz, T.   Guo, F.K.   Dai, L.R.   Sun, B.X.  

    We report on some recent developments in understanding the nature of the low-lying mesonic resonances f 0(1370), f 0(1710), f 2(1270), f 2'(1525), and K 2*(1430). In particular we show that these five resonances can be dynamically generated from vector meson-vector meson interaction in a coupled-channel unitary approach, which utilizes the phenomenologically very successful hidden-gauge Lagrangians to produce the interaction kernel between two vector mesons, which is then unitarized by the Bethe-Salpeter-equation method. The data on the strong decay branching ratios, total decay widths, and radiative decay widths of these five states, and on related J/psi decay processes can all be well described by such an approach. We also make predictions, compare them with the results of earlier studies, and highlight observables that if measured can be used to distinguish different pictures of these resonances.
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  • (B)over-bar(0),B- and (B)over-bar(S)(0) decays into J/psi and K (K)over-bar or pi eta

    Liang, Wei-Hong   Xie, Ju-Jun   Oset, E.  

    We study the (B) over bar (0)(S) -> J/psi K+ K-, (B) over bar (0) -> J/psi K+ K, B- -> J/psi K+ K-, (B) over bar (0) -> J/psi pi(0)eta(-), decays and compare their mass distributions with those obtained for the (B) over bar (0)(S) -> J/psi pi(+) pi(-) and (B) over bar (0)(S) -> J/psi pi(+)pi(-). The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial CabibboKobayashi- Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part of the theory and thus, up to a global normalization factor, all the invariant mass distributions are predicted with no free parameters. Comparison is made with the limited experimental information available. Further comparison of these results with coming LHCb measurements will be very valuable to make progress in our understanding of the meson- meson interaction and the nature of the low lying scalar meson resonances, f(0)(500), f(0)( 980) and a(0)(980).
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  • Theoretical study of incoherent phi photoproduction on a deuteron target

    Sekihara, T.   Torres, A. Martinez   Jido, D.   Oset, E.  

    We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross-section from bound protons to the free ones. For this purpose we take into account Fermi motion in single scattering and rescattering of phi to account for phi absorption on a second nucleon as well as the rescattering of the proton on the neutron. We find that the contribution of the double scattering for phi is much smaller than the typical cross-section of gamma p -> phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross-section of gamma p -> phi p in free space, and leads to a moderate reduction of the phi photoproduction cross-section on a deuteron at forward angles if the LEPS set-up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase-space in the free case. In particular, we find that for momentum transfer squared close to the maximum value, the Fermi motion changes drastically the shape of d sigma/dt, to the point that the ratio of this cross-section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem to be the most indicated to find effects of a possible phi absorption in the deuteron. This reaction is studied theoretically as a function of t and the results are contrasted with recent experiments at LEPS and Jefferson Lab. The effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction.
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  • Unitary chiral dynamics of two hadrons in a finite volume: the KD, eta Ds system and the Ds*0(2317) resonance

    Torres, A. Martinez   Dai, L. R.   Koren, C.   Jido, D.   Oset, E.  

    We investigate the KD and eta D-s system in a finite volume and study the properties of the D-s*0(2317) resonance, which is generated in this coupled channel system. We calculate the energy levels in a cubic box and considering them as synthetic lattice data we solve the inverse problem of determining the bound states and phase shifts in the infinite volume. We observe that it is possible to obtain accurate KD phase shifts and the position of the D-s*0(2317) state from the synthetic lattice data considered and that a careful analysis of the finite volume data can shed some light on the nature of the D-s*0(2317) resonance as a KD molecule or otherwise.
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  • [AIP HADRON SPECTROSCOPY: Tenth International Conference on Hadron Spectroscopy - Aschaffenburg (Germany) (31 August-6 Septembe)] AIP Conference Proceedings - η → π0γγ decay within a chiral unitary approach

    Oset, E.  

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