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Now showing items 97 - 111 of 111

  • eta ' N scattering at low energies

    Oset, E.   Ramos, A.  

    We calculate the eta' amplitude at low energies considering chiral Lagrangians and eta eta' mixing, the coupling of eta'N to the vector-baryon channels and one Lagrangian allowed for singlet meson-baryon interaction. We obtain cross sections for elastic eta' scattering and transition of eta'N to the open channels pi N, eta N, eta'N, K Lambda and K Sigma,
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  • Study of the D* rho system using QCD sum rules

    Martinez Torres, A.   Khemchandani, K. P.   Nielsen, M.   Navarra, F. S.   Oset, E.  

    In this proceeding we present a study of the D* rho system made by using the method of QCD sum rules. Considering isospin and spin projectors, we investigate the different configurations and obtain three D* mesons with isospin I = 1/2, spin S = 0, 1, 2 and with masses 2500 +/- 67 MeV, 2523 +/- 60 MeV, and 2439 +/- 119 MeV, respectively. The last state can be related to D*(2) (2460) (spin 2) listed by the Particle Data Group, while one of the first two might be associated with D*(2640), whose spin-parity is unknown. In the case of I = 3/2 we also find evidences of three states with spin 0, 1 and 2, respectively, with masses 2467 +/- 82 MeV, 2420 +/- 128 MeV, and 2550 +/- 56 MeV.
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  • Triangle singularity enhancing isospin violation in (B)over-bar(s)(0)-> J/psi pi(0)f(0)(980)

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

    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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  • Nucleon resonances from three-hadron interactions

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

    Our study of meson-meson-baryon systems with total strangeness zero revealed that many nucleon resonances can be understood as dynamically generated states of three-hadrons. We considered pipiN,pietaN,piKLambda, and piKSigma as coupled channels and solved the Fadeev equations. To be precise, the study lead to dynamical generation of N*(1710), N*(2100), Delta(1910) along with a new isospin 1/2 resonance around 1920 MeV. In this manuscript I briefly review the formalism we use for three-body calculations and the results obtained for the nucleon resonances.
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  • Kaon-induced Lambda(1405) production on a deuteron target at DAFNE

    Jido, D.   Oset, E.   Sekihara, T.  

    The K(-)- induced production of.(1405) in the K(-)d -> pi Sigma n reaction is investigated having in mind the conditions of the DAFNE facility at Frascati where kaons are obtained from the decay of slow-moving phi mesons. We find that the K(-)d -> Lambda(1405)n process favors the production of Lambda(1405) initiated by the K(-)p channel, which gives largest weight to the higher mass Lambda(1405) appearing at 1420MeV in chiral theories. We find that the fastest kaons from the decay of the phi are well suited to see this resonance, particularly if one selects forward going neutrons in the center of mass, which reduce the contribution of single scattering and make the double scattering dominate where the signal of the resonance appears clearer.
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  • reaction

    Yu, Q. X.   Liang, W. H.   Bayar, M.   Oset, E.  

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  • The role of f 0(1710) in the phiomega threshold peak of J/psirarrgammaphiomega

    Martinez Torres, A.   Khemchandani, K.P.   Navarra, F.S.   Nielsen, M.   Oset, E.  

    We study the process J/Psirarrgammaphiomega, measured by the BES experiment, where a neat peak close to the phiomega threshold is observed and is associated to a scalar meson resonance around 1800 MeV. We make the observation that a scalar resonance coupling to phiomega unavoidably couples strongly to KK, but no trace of a peak is seen in the KK spectrum of the J/PsirarrgammaKK at this energy. This serves us to rule out the interpretation of the observed peak as a signal of a new resonance. After this is done, a thorough study is performed on the production of a pair of vector mesons and how its interaction leads necessarily to a peak in the J/Psirarrgammaphiomega reaction close to the phiomega threshold, due to the dynamical generation of the f0(1710) resonance by the vector-vector interaction. We then show that both the shape obtained for the phiomega mass distribution, as well as the strength are naturally reproduced by this mechanism. The work also explains why the phiomega peak is observed in the BES experiment and not in other reactions, like B+or-rarrK+or-phiomega of Belle. [All rights reserved Elsevier].
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  • Coherent and incoherent (mu -, e -) conversion in nuclei

    Chiang, H.C.   Oset, E.   Kosmas, T.S.   Faessler, A.   Vergados, J.D.  

    Coherent and incoherent (mu -, e -) conversion in nuclei is studied within the framework of several theories which violate flavour lepton number. A useful approach is followed which allows a factorization of the conversion widths into nuclear factors and other factors which depend only on the elementary process. The nuclear factors are evaluated in a wide range of nuclei allowing simple calculations of the conversion rates throughout the periodic table for a given theory with a minimum of work in the elementary sector. The coherent conversion is found to dominate the process. The results obtained modify appreciable previous results in the literature, particularly in the incoherent process
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  • Kaonic production of Lambda(1405) off deuteron target in chiral dynamics

    Jido, D.   Oset, E.   Sekihara, T.  

    The K(-)-induced production of Lambda(1405) is investigated in K(-)d -> pi Sigma n reactions based on coupled-channels chiral dynamics, in order to discuss the resonance position of the.(1405) in the (K) over barN channel. We find that the K(-)d -> Lambda(1405)(n) process favors the production of Lambda(1405) initiated by the (K) over barN channel. The present approach indicates that the Lambda(1405)-resonance position is 1420 MeV rather than 1405 MeV in the pi Sigma invariant-mass spectra of K(-)d -> pi Sigma n reactions. This is consistent with an observed spectrum of the K(-) d -> pi(+) Sigma(-)n with 686-844 MeV/c incident K(-) by bubble chamber experiments done in the 70s. Our model also reproduces the measured Lambda(1405) production cross-section.
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  • Conventional view versus FINUDA claims of a deeply bound K(-)pp state

    Ramos, A.   Magas, V. K.   Oset, E.   Toki, H.  

    We critically revise the recent claims of a deeply bound K(-)pp state associated to a peak seen in the Lambda p invaiiant-mass spectrum following nuclear K- absorption reactions measured by the FINUDA Collaboration. An explicit theoretical simulation shows that the peak is simply generated from a two-nucleon absorption process, like K(-)pp -> Lambda p, followed by final-state interactions of the produced particles with the residual nucleus.
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  • Chiral unitary approach to eta ' N scattering at low energies

    Oset, E.   Ramos, A.  

    We study the eta'N interaction within a chiral unitary approach which includes pi N, eta N and related pseudoscalar meson-baryon coupled channels. Since the SU(3) singlet does not contribute to the standard interaction and the eta' is mostly a singlet, the resulting scattering amplitude is very small and inconsistent with the experimental scattering length. The additional consideration of vector meson-baryon states into the coupled channel scheme, via normal and anomalous couplings of pseudoscalar to vector mesons, enhances substantially the eta'N amplitude. We also exploit the freedom of adding to the Lagrangian a new term, allowed by the symmetries of QCD, which couples baryons to the singlet meson of SU(3). Adjusting the unknown strength to the eta'N scattering length, we obtain predictions for the elastic eta'N -> eta'N and inelastic eta'N -> eta N, pi N, K Lambda, K Sigma cross sections at low eta' energies, and discuss their significance. (C) 2011 Elsevier B.V. All rights reserved.
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  • Charm and hidden charm scalar mesons in the nuclear medium

    Molina, R.   Gamermann, D.   Oset, E.   Tolos, L.  

    We study the renormalization of the properties of low-lying charm and hidden charm scalar mesons in a nuclear medium, concretely of the D(s0)(2317) and the theoretical hidden charm state X(3700). We find that for the D(s0)(2317), with negligible width at zero density, the width becomes about 100 MeV at normal nuclear-matter density, while in the case of the X(3700) the width becomes as large as 200 MeV. We discuss the origin of this new width and trace it to reactions occurring in the nucleus, while offering a guideline for future experiments testing these changes. We also show how those medium modifications will bring valuable information on the nature of the scalar resonances and the mechanisms of the interaction of D mesons with nucleons and nuclei.
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  • INTERACTION OF VECTOR MESONS WITH BARYONS AND NUCLEI

    Oset, E.   Ramos, A.   Garzon, E. J.   Molina, R.   Tolos, L.   Xiao, C. W.   Wu, J. J.   Zou, B. S.  

    After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper, we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector-baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the J/Psi N interaction. We also address the interaction of K* with nuclei and make suggestions to measure the predicted huge width in the medium by means of transparency ratio. The formalism is extended to study the phenomenon of J/psi suppression in nuclei via J/psi photo-production reactions.
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  • The rhoNN coupling with direct coupling and loops

    Jido, D.   Oset, E.   Palomar, J.E.  

    Starting from a gauge formalism of rho mesons, pions and baryons we evaluate the rho coupling to the nucleon, including the direct coupling provided by the Lagrangians, plus contributions from loops with the virtual pion cloud. We find a contribution to the magnetic rho coupling to the nucleon from pionic loops of the same size as the direct coupling, which is, however, still small compared to the empirical values. This finding goes in line with chiral formulations of the strong interaction of mesons at low energies where, unlike the scalar mesons which are mostly built of a pion (kaon) cloud, the rho meson stands as a genuine QCD state with intrinsic properties not tied to those of the pion cloud
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  • Hidden beauty baryon states in the local hidden gauge approach with heavy quark spin symmetry

    Xiao, C. W.   Oset, E.  

    Using a coupled-channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-baryon interaction with hidden beauty and obtain several new states of N around 11 GeV. We consider the basis of states eta (b) N, I'N, BI > (b) , BI pound (b) , B (*) I > (b) , B (*) I pound (b) , B (*) I pound (b) (*) and find four basic bound states which correspond to BI pound (b) , BI pound (b) (*) , B (*) I pound (b) and B (*) I pound (b) (*) , decaying mostly into eta (b) N and I'N and with a binding energy about 50-130 MeV with respect to the thresholds of the corresponding channel. All of them have isospin I = 1/2 , and we find no bound states or resonances in I = 3/2 . The BI pound (b) state appears in J = 1/2 , the BI pound (b) (*) in J = 3/2 , the B (*) I pound (b) appears nearly degenerate in J = 1/2 , 3/2 and the B (*) I pound (b) (*) appears nearly degenerate in J = 1/2 , 3/2, 5/2. These states have a width from 2-110 MeV, with conservative estimates of uncertainties, except for the one in J = 5/2 which has zero width since it cannot decay into any of the states of the basis chosen. We make generous estimates of the uncertainties and find that within very large margins these states appear bound.
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