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Now showing items 81 - 96 of 187

  • Recent developments in chiral unitary theory of mesons and baryons RID C-6441-2009

    Oset, E.   Gamermann, D.   Khemchandani, K.   Martinez, A.   Geng, L. S.   Napsuciale, A.  

    In this talk I summarize recent findings around the description of axial vector mesons as dynamically generated states from the interaction of pseudoscalar mesons and vector mesons, dedicating some attention to the two K(1)(1270) states. Then I review the generation of open and hidden charm scalar and axial states, and how some recent experiment supports the existence of the new hidden charm scalar state predicted. I present recent results showing that the low lying 1/2(+) baryon resonances for S=-1 can be obtained as bound states or resonances of two mesons and one baryon in coupled channels. Then show the differences with the S=0 case, where the N*(1710) appears also dynamically generated from the two pion one nucleon system, but the N*(1440) does not appear, indicating a more complex structure of the Roper resonance. Finally I shall show how the state X(2175), recently discovered at BABAR and BES, appears naturally as a resonance of the phi K (K) over bar system.
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  • Meson baryon components in the states of the baryon decuplet

    Aceti, F.   Oset, E.   Dai, L.R.   Zhang, Y.   Geng, L.S.  

    We extend the Weinberg compositeness condition to partial waves of L = 1 and resonant states to determine the weight of meson-baryon component in the J P = 3/ 2 + baryon 2 decuplet. We obtain an appreciable weight of piN in the Delta(1232) wave function, of the order of 60 % and we also show that, as we go to higher energies in the members of the decuplet, the weights of meson-baryon component decrease and they already show a dominant part for a genuine component in the wave function. We interpret the meaning of the Weinberg sum-rule extended to complex energies.
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  • Polarization amplitudes in VP decay beyond the Standard Model

    Dai, L. R.   Oset, E.  

    We study the amplitudes of the -VP decay for the different polarizations of the vector meson V, using a formalism where the mapping from the quark degrees of freedom to the meson ones is done with the P-3(0) model. We extend the formalism to a case, with the operator -5, that can account for different models beyond the Standard Model and study in detail the -K*0K- reaction for the different polarizations of the K*0. The results are shown in terms of the parameter that differs for each model. We find that is very different for each of the third components of the vector spin, M=3D+/- 1,0, and in particular the magnitude |M=3D-1 is very sensitive to the parameter, which makes the investigation of this magnitude very useful to test different models beyond the Standard Model.
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  • Delta rho pi Interaction Leading to N* and Delta* Resonances

    Xie, Ju-Jun   Torres, A. Martinez   Oset, E.   Gonzalez, P.  

    We have performed a calculation for the three-body Delta rho IEuro system by using the fixed center approximation to Faddeev equations, taking the interaction between Delta and rho, Delta and pi, and rho and pi from the chiral unitary approach. We find several peaks in the modulus squared of the three-body scattering amplitude, indicating the existence of resonances, which can be associated to known I = 1/2, 3/2 and J (P) = 1/2(+), 3/2(+) and 5/2(+) baryon states.
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  • Improved fixed center approximation of the Faddeev equations for the (K)over-bar N N system with S=0

    Bayar, M.   Oset, E.  

    We extend the Fixed Center Approximation (FCA) to the Faddeev equations for the (K) over bar N N system with S = 0, including the charge exchange mechanisms in the (K) over bar rescattering which have been ignored in former works within the FCA. We obtain similar results to those found before, but the binding is reduced by 6 MeV. At the same time we also evaluate the explicit contribution the pi N Sigma intermediate state in the three body system and find that it produces and additional small decrease in the binding of about 3 MeV. The system appears bound by about 35 MeV and the width omitting two body absorption, is about 50 MeV. (C) 2012 Elsevier B.V. All rights reserved.
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  • Scalar, axial-vector and tensor resonances from the rhoD*, omegaD* interaction in the hidden gauge formalism

    Molina, R.   Nagahiro, H.   Hosaka, A.   Oset, E.  

    We apply a unitary approach together with a set of hidden-gauge Lagrangians to study the vector-vector interaction. We study the case of the rho(omega)D* interaction within the model. In I = 1/2 we get strong enough attraction to bind the system. Concretely, we get one resonance for each spin J =0,1,2. For J = 1 and 2 these resonances can be easily identified with the D*(2460) and D*(2640). Whereas the state for J = 0 with mass M~2600 MeV is a prediction of the model. In I = 3/2 we get a repulsive interaction and hence no exotic dynamically generated states.
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  • Dynamically generated hadron resonances

    Oset, E.   Garzon, E. J.   Xie, Ju Jun   Gonzalez, P.   Ramos, A.   Torres, A. Martinez  

    As an example of dynamically generated resonances we mention the interaction of vector mesons with baryons within the local hidden gauge formalism which gives rise to a large amount of such states, many of which can be associated to known resonances, while others represent predictions for new resonances. The width of these states coming from decay into pseudoscalar baryon is also addressed. We also mention recent states coming from Delta rho pi interaction obtained with Faddeev equations.
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  • Helicity amplitudes in B -> D*(nu)over-barl decay

    Dai, L. R.   Oset, E.  

    We use a recent formalism of the weak hadronic reactions that maps the transition matrix elements at the quark level into hadronic matrix elements, evaluated with an elaborate angular momentum algebra that allows finally to write the weak matrix elements in terms of easy analytical formulas. In particular they appear explicitly for the different spin third components of the vector mesons involved. We extend the formalism to a general case, with the operator parameter, which suggest to use this magnitude to test different models beyond the standard model. We show that our formalism implies the heavy quark limit and compare our results with calculations that include higher order corrections in heavy quark effective theory. We find very similar results for both approaches in normalized distributions, which are practically identical at the end point of M-inv((nu l)) =3D m(B) - m(D)*
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  • Interpreting the peak structures around 1800 MeV in the BES data on J/psi -> phi pi(+)pi (-), J/psi -> gamma omega phi

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

    In this talk we present an interpretation for the experimental data available on two different processes, namely, J/psi -> phi pi(+)pi (-), J/psi -> gamma omega phi, which seem to indicate existence of two new resonances with the same quantum numbers (J(pi c) = 0(++), I = 0) and very similar mass (1800 MeV) but with very different decay properties. However, our studies show that the peak structure found in the w f invariant mass, in J/psi -> gamma omega phi, is a manifestation of the well known f(0)(1710) while the cross section enhancement found in J/psi -> phi pi(+)pi (-) is indeed a new f(0) resonance with mass near 1800 MeV. We present an explanation for the different decay properties of these two scalar resonances.
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    In this talk we report on the use of a chiral unitary approach for the interaction of the octets of meson and baryon and the octet of mesons with the decuplet of baryons. Two octets of J(pi) = 1/2(-) baryon states and a singlet are generated dynamically in the first case, resulting in the case of strangeness S = -1 in two poles of the scattering matrix close to the nominal A(1405) resonance. In the second case many resonances are also generated, among them an exotic baryon with S = I corresponding to a Delta K resonance. We make suggestions of experiments which could show evidence for the existence of these states.
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  • New aspect of hadron resonances

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

    In this talk we show our recent results for the study of three-hadron systems. The systems which we discuss here are made of two mesons and a baryon to give total strangeness -1, 0 and 1. The motivation for these studies comes from the data on many baryon resonances, especially the ones with J(pi) = 1/2+, which show a large branching ratio to two meson-one baryon decay channels. On solving the Faddeev equations with the input two body interactions obtained from the chiral Lagrangians, we find that many resonances couple strongly to three-hadron systems.
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  • The (K)over-barNN system revisited including absorption

    Bayar, M.   Oset, E.  

    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. (C) 2013 Elsevier B.V. All rights reserved.
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  • Signature of an h(1) state from J/psi -> eta K*(0)(K)over-bar*(0) and theoretical description of the Z(c)(3900) and Z(c)(4020) as D(D)over-bar and D*(D)over-bar* molecular states

    Oset, E.   Xie, Ju Jun   Albaladejo, M.   Aceti, F.   Bayar, M.   Dias, J. M.   Torres, A. Martinez   Khemchandani, K.   Nielsen, M.   Navarra, F.   Ren, X. L.   Geng, L. S.   Meng, Jie   Liang, W. H.  

    In this talk we address two topics: The first one is an empirical explanation in terms of a new state h(1) of the peak in the K*(0)(K) over bar*(0) invariant mass distribution close to threshold of this channel in the J/psi -> eta K*(0)(K) over bar*(0) decay. The second one is a theoretical description of the isospin I = 1 Z(c)(3900) and Z(c)(4020) states in terms of molecular states of D (D) over bar* + cc and D*(D) over bar*.
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  • Virtual versus real nuclear Compton scattering in the Delta(1232) region

    Gil, A.   Gomez Tejedor, J.A.   Oset, E.  

    In this paper we calculate the cross section for virtual Compton scattering off nuclei in the delta resonance region. We also calculate the background for the process from coherent bremsstrahlung in nuclei and explore the regions where the virtual Compton scattering cross section dominates. The study also shows that it is possible to extract the cross section for real Compton scattering from the virtual Compton one in a wide range of scattering angles
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    Molina, R.   Tolos, L.   Oset, E.   Ramos, A.  

    In this talk were view the properties of (K) over bar* mesons in nuclear matter. A unitary approach in coupled channels within the framework of the local hidden gauge formalism is used to account for the interaction of the antikaon with the nucleons and the (K) over bar pi decay channel is incorporated in matter. The in-medium (K) over bar* N interaction accounts for Pauli blocking effects and the inclusion of the (K) over bar* self-energy in a self-consistent manner. At normal nuclear matter density, the (K) over bar* meson feels a moderately attractive potential while the K* width increases enormously becoming up to five times larger than in free space. We also perform the transparency ratio for the gamma A -> K(+)K*(-) A` reaction, which can be a feasible scenario in experimental facilities.
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  • Three methods to detect the predicted D(D)over-bar scalar meson X(3700)

    Xiao, C. W.   Oset, E.  

    In analogy to the f(0)(500), which appears as a pi pi resonance in chiral unitary theory, and the f(0)(980), which appears as a quasibound K (K) over bar state, the extension of this approach to the charm sector also predicts a quasibound D (D) over bar state with mass around 3720 MeV, named as X(3700), for which some experimental support is seen in the e(+)e(-) -> J/psi D (D) over bar reaction close to the D (D) over bar threshold. In the present work we propose three different experiments to observe it as a clear peak. The first one is the radiative decay of the psi(3770), psi(3770) -> gamma X(3700) -> gamma eta eta'. The second one proposes the analogous reaction psi(4040) -> gamma X(3700) -> gamma eta eta' and the third reaction is the e(+)e(-) -> J/psi X(3700) -> J/psi eta eta'. Neat peaks are predicted for all the reactions and the calculated rates are found within measurable range in present facilities.
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