Peláez Sagredo, José Ramón

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First Name
José Ramón
Last Name
Peláez Sagredo
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Física Teórica
Física Teórica
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Now showing 1 - 10 of 124
  • Publication
    The non-ordinary Regge behavior of the K_(0)^(*)(800) or κ-meson versus the ordinary K_(0)^(*) (1430)
    (Springer, 2017-06-28) Peláez Sagredo, José Ramón; Rodas Bilbao, Arkaitz
    The Regge trajectory of an elastic resonance can be calculated from dispersion theory, instead of fitted phenomenologically, using only its pole parameters as input. This also provides a correct treatment of resonance widths in Regge trajectories, essential for very wide resonances. In this work we first calculate the K_(0)^(*)(1430) Regge trajectory, finding the ordinary almost real and linear behavior, typical of q (q) over bar resonances. In contrast, for the K_(0)^(*)(800) meson, the resulting Regge trajectory is non-linear and has a much smaller slope than ordinary resonances, being remarkably similar to that of the f_(0)(500) or σ meson. The slope of these unusual Regge trajectories seems to scale with themeson masses rather than with scales typical of quark degrees of freedom. We also calculate the range of the interaction responsible for the formation of these resonances. Our results strongly support a non- ordinary, predominantly meson-meson- like, interpretation for the lightest strange and non-strange resonances.
  • Publication
    Dispersive πK → πK and ππ → KK amplitudes from scattering data, threshold parameters, and the lightest strange resonance κ or K0∗ (700)
    (Elsevier Science Bv, 2022-07-26) Peláez Sagredo, José Ramón; Rodas, Arkaitz
    We discuss the simultaneous dispersive analyses of nK -> nK and nn -> KK over bar scattering data and the K/K0*(700) resonance. The unprecedented statistics of present and future hadron experiments, modern lattice QCD calculations, and the wealth of new states and decays require such precise and model-independent analyses to describe final state interactions. We review the existing and often conflicting data and explain in detail the derivation of the relevant dispersion relations, maximizing their applicability range. Next, we review and extend the caveats on some data, showing their inconsistency with dispersion relations. Our main result is the derivation and compilation of precise amplitude parameterizations constrained by several nK -> nK and nn -> KK over bar dispersion relations. These constrained parameterizations are easily implementable and provide the rigor and accuracy needed for modern experimental and phenomenological hadron physics. As applications, after reviewing their status and interest, we will provide new precise threshold and subthreshold parameters and review our dispersive determination of the controversial K/K0*(700) resonance and other light-strange resonances.
  • Publication
    M_(π) and N_c dependence of resonances form Unitarized Chiral Perturbation Theory
    (Amer Inst Physics, 2011) Rios, G.; Hanhart, Christoph; Peláez Sagredo, José Ramón
    We review our studies on the ρ and σ resonances properties derived from the Inverse Amplitude Method. In particular, we study the leading 1/N_c behavior of the resonances masses and widths and their evolution with changing m_(π). The 1/N_c expansion gives a clear definition of q̅ q states, which is neatly satisfied by the ρ but not by the σ, showing that its dominant component is not q̅q. The m_(π) dependence of the resonance properties is relevant to connect with lattice studies. We show that our predictions compare well with some lattice results and we find that the rho π πcoupling constant is m_π independent, in contrast with the σ π π coupling, that shows a strong m_π dependence.
  • Publication
    Improved unitarized Heavy Baryon Chiral Perturbation Theory for π N scattering
    (Elsevier science, 2000-07-27) Gómez Nicola, Ángel; Nieves, J.; Peláez Sagredo, José Ramón; Ruiz Arriola, E.
    We show how the unitarized description of pion nucleon scattering within Heavy Baryon Chiral Perturbation Theory can be considerably improved, by a suitable reordering of the expansion over the nucleon mass. Within this framework, the ∆ resonance and its associated pole can be recovered from the chiral parameters obtained from low-energy determinations. In addition, we can obtain a good description of the six S and P wave phase shifts in terms of chiral parameters with a natural size and compatible with the Resonance Saturation Hypothesis.
  • Publication
    Dispersive chiral approach to meson-meson dynamics: Spectroscopy results for light scalars and precision studies
    (Amer Inst Physics, 2007) Peláez Sagredo, José Ramón
    Dispersive approaches provide model independent description of meson-meson scattering. We first review here the use of dispersion relations to obtain a model independent unitarization of Chiral Perturbation Theory amplitudes, that establish the existence of light scalar mesons and whose leading 1/N_c behavior suggest they ahve a non q q̅ dominant component. We also review the forward dispersion relation checks on conflicting experimental data and the resulting very precise pi pi scattering scattering amplitudes.
  • Publication
    Nonordinary light meson couplings and the 1/N_c expansion
    (American Physical Society, 2014-08-14) Cohen, Thomas; Llanes Estrada, Felipe José; Peláez Sagredo, José Ramón; Ruiz de Elvira Carrascal, Jacobo
    We study the large N_c behavior of couplings among light meson states with different compositions in terms of quarks and gluons. We shortly review the most common compositions of mesons, which are of interest for the understanding of low-lying meson resonances, namely, the ordinary quark-antiquark states as well as the nonordinary glueball, tetraquark, and other states. We dedicate special attention to Jaffe's generalization of the tetraquark with N_c - 1 q -q over bar q pairs, which is the only type of state we have identified whose width does not necessarily vanish with N_c, though it does decouple exponentially with N_c from the ππ channel, so that it is weakly coupled to the meson-meson system.
  • Publication
    Strange and nonstrange quark mass dependence of elastic light resonances from SU(3) unitarized chiral perturbation theory to one loop
    (Amer Physical Soc, 2010-02-01) Nebreda Manjón, Jenifer; Peláez Sagredo, José Ramón
    We study the light quark mass dependence of the f_0(600), к(800), ρ(770), and K*(892) resonance parameters generated from elastic meson-meson scattering using unitarized one-loop chiral perturbation theory. First, we show that it is possible to fit simultaneously all experimental scattering data up to 0.8-1 GeV together with lattice results on decay constants and scattering lengths up to a pion mass of 400 MeV, using chiral parameters compatible with existing determinations. Then, the strange and nonstrange quark masses are varied from the chiral limit up to values of interest for lattice studies. In these amplitudes, the mass and width of the ρ(770) and K*(892) present a similar and smooth quark mass dependence. In contrast, both scalars present a similar nonanalyticity at high quark masses. Nevertheless, the f_0(600) dependence on the nonstrange quark mass is stronger than for the κ(800) and the vectors. We also confirm the lattice assumption of quark mass independence of the vector two-meson coupling that, in contrast, is violated for scalars. As a consequence, vector widths are very well approximated by the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin relation, and their masses are shown to scale like their corresponding meson decay constants.
  • Publication
    Thermal evolution of the chiral condensate in SU(2) and SU(3) Chiral Perturbation Theory.
    (Elsevier Science Bv, 2003-06) Peláez Sagredo, José Ramón
    The temperature evolution of the chiral condensates in a gas made of pions, kaons and etas is studied within the framework of SU(2) and SU(3) Chiral Perturbation Theory. We describe the temperature dependence of the quark condensates by using the meson meson scattering phase shifts in a second order virial expansion. We find that the SU(3) formalism yields an extrapolated melting temperature for the non-strange condensates which is lower by about 0-30 MeV than within SU(2). In addition our results show that the strange condensate melting is slower than that of the non-strange, due to the different strange and non-strange quark masses.
  • Publication
    Fast CP violation
    (American Physical Society, 1998-11-01) Grossman, Y; Peláez Sagredo, José Ramón; Worah, M. P.
    B flavor tagging will be extensively studied at the asymmetric B factories due to its importance in CP asymmetry measurements. The primary tagging modes are the semileptonic decays of the b (lepton tag), or the hadronic b → c(→ s) decays (kaon tag). We suggest that looking for time dependent CP asymmetries in events where one B is tagged leptonically and the other one is tagged with a kaon could result in an early detection of CP violation. Although in the standard model these asymmetries are expected to be small, 1%, they could be measured with about the same amount of data as in the "gold-plated" decay B_d→ψ K_s. In the presence of physics beyond the standard model, these asymmetries could be as large as 5%, and the first CP violation signal in the B system may show up in these events. We give explicit examples of new physics scenarios where this occurs. [S0556-2821(98)09321-7]
  • Publication
    f(0)(1370) Controversy from dispersive meson-meson scattering data analyses
    (American Physical Society, 2023-02-03) Peláez Sagredo, José Ramón; Rodas, A.; Ruiz de Elvira Carrascal, Jacobo
    We establish the existence of the long-debated f(0)(1370) resonance in the dispersive analyses of meson-meson scattering data. For this, we present a novel approach using forward dispersion relations, valid for generic inelastic resonances. We find its pole at (1245 +/- 40) - i(300(-70)(+30)) MeV in pi pi scattering. We also provide the couplings as well as further checks extrapolating partial-wave dispersion relations or with other continuation methods. A pole at (1380(-60)(+70)) - i(220(-70)(+80)) MeV also appears in the pi pi -> K (K) over bar over bar data analysis with partial-wave dispersion relations. Despite settling its existence, our model-independent dispersive and analytic methods still show a lingering tension between pole parameters from the pi pi and K (K) over bar channels that should be attributed to data.