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Search Results: 1 - 10 of 211664 matches for " L. Alvarez-Ruso "
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The role of the Roper resonance in n p --> d (pi pi)
L. Alvarez-Ruso
Physics , 1998, DOI: 10.1016/S0370-2693(99)00310-X
Abstract: In this work, a model for the n p --> d (pi pi) reaction is developed. It is shown that the structure of the deuteron momentum spectra for a neutron beam momentum of 1.46 GeV can be explained as a consequence of the interplay of two mechanisms involving the excitation of the N^*(1440) resonance and its subsequent decay into N (pi pi)^{T=0}_{S-wave} and Delta pi respectively. The relevance of the present analysis for the study of the Roper excitation and decay properties, as well as for the interpretation of other two-pion production experiments is discussed.
Two-pion decay modes of the N*(1440) in n p -> d pi pi
L. Alvarez-Ruso
Physics , 2000, DOI: 10.1016/S0375-9474(01)00500-0
Abstract: A simple model for the n p -> d pi pi reaction has been developed. It is shown that the deuteron momentum spectra measured at T_n = 795 MeV can be understood in terms of the Roper excitation and its N pi pi decay modes. A similar pattern, recently observed in p p -> p p pi+ pi-, can be explained in the same way.
On the nature of the Roper resonance
L. Alvarez-Ruso
Physics , 2010,
Abstract: The lightest N* state, N(1440) P11, also known as Roper resonance, has puzzled physicists for decades. A large variety of theoretical models aimed to understand its properties have been proposed. Some of them are briefly reviewed here, together with the hadronic processes where the Roper resonance is revealed or plays an important role.
Phi meson propagation in a hot hadronic gas
L. Alvarez-Ruso,V. Koch
Physics , 2002, DOI: 10.1103/PhysRevC.65.054901
Abstract: The Hidden Local Symmetry Lagrangian is used to study the interactions of phi mesons with other pseudoscalar and vector mesons in a hadronic gas at finite temperature. We have found a significantly small phi mean free path (less than 2.4 fm at T > 170 MeV) due to large collision rates with rho mesons, kaons and predominantly K* in spite of their heavy mass. This implies that phi mesons produced after hadronization in relativistic heavy ion collisions will not leave the hadronic system without scattering. The effect of these interactions on the time evolution of the phi density in the expanding hadronic fireball is investigated.
The influence of the nuclear medium on inclusive electron and neutrino scattering off nuclei
Buss, O.;Leitner, T.;Alvarez-Ruso, L.;Mosel, U.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevC.76.035502
Abstract: We present a model for inclusive electron and neutrino scattering off nuclei paying special attention to the influence of in-medium effects on the quasi-elastic scattering and pion-production mechanisms. Our results for electron scattering off Oxygen are compared to experimental data at beam energies ranging from 0.7-1.5 GeV. The good description of electron scattering serves as a benchmark for neutrino scattering.
Neutrino induced pion production at MiniBooNE and K2K
Leitner, T.;Buss, O.;Mosel, U.;Alvarez-Ruso, L.
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevC.79.038501
Abstract: We investigate charged and neutral current neutrino induced incoherent pion production off nuclei at MiniBooNE and K2K energies within the GiBUU model. We assume impulse approximation and treat the nucleus as a local Fermi gas of nucleons bound in a mean-field potential. In-medium spectral functions are also taken into account. The outcome of the initial neutrino nucleon reaction undergoes complex hadronic final state interactions. We present results for neutral current pi^0 and charged current pi^+ production and compare to MiniBooNE and K2K data.
Photon emission in neutral current interactions with nucleons and nuclei
Alvarez-Ruso, L.;Nieves, J.;Wang, E.
High Energy Physics - Phenomenology , 2013,
Abstract: We report on our study of photon emission induced by Enu ~ 1 GeV (anti)neutrino neutral current interactions with nucleons and nuclei. This process is an important background for nu_e appearance oscillation experiments. At the relevant energies, the reaction is dominated by the excitation of the Delta (1232) resonance but there are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. We have obtained differential and integrated cross section for the (anti)neutrino-nucleon scattering and compare them with previous results. Furthermore, we have extended the model to nuclear targets taking into account Fermi motion, Pauli blocking and the in-medium modifications of the Delta properties. This study is important in order to reduce systematic effects in neutrino oscillation experiments.
Neutrino scattering with nuclei - Theory of low energy nuclear effects and its applications
Leitner, T.;Buss, O.;Mosel, U.;Alvarez-Ruso, L.
High Energy Physics - Phenomenology , 2008,
Abstract: Current long baseline experiments aim at measuring neutrino oscillation parameters with a high precision. A critical quantity is the neutrino energy which can not be measured directly but has to be reconstructed from the observed hadrons. A good knowledge of neutrino-nucleus interactions is thus necessary to minimize the systematic uncertainties in neutrino fluxes, backgrounds and detector responses. In particular final-state interactions inside the target nucleus modify considerably the particle yields through rescattering, charge-exchange and absorption. Nuclear effects can be described with our coupled channel GiBUU transport model where the neutrino first interacts with a bound nucleon producing secondary particles which are then transported out of the nucleus. In this contribution, we give some examples for the application of our model focusing in particular on the MiniBooNE and K2K experiments.
Electron- and neutrino-nucleus scattering from the quasielastic to the resonance region
Leitner, T.;Buss, O.;Alvarez-Ruso, L.;Mosel, U.
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevC.79.034601
Abstract: We present a model for electron- and neutrino-scattering off nucleons and nuclei focussing on the quasielastic and resonance region. The lepton-nucleon reaction is described within a relativistic formalism that includes, besides quasielastic scattering, the excitation of 13 N* and Delta resonances and a non-resonant single-pion background. Recent electron-scattering data is used for the state-of-the-art parametrizations of the vector form factors; the axial couplings are determined via PCAC and, in the case of the Delta resonance, the axial form factor is refitted using neutrino-scattering data. Scattering off nuclei is treated within the GiBUU framework that takes into account various nuclear effects: the local density approximation for the nuclear ground state, mean-field potentials and in-medium spectral functions. Results for inclusive scattering off Oxygen are presented and, in the case of electron-induced reactions, compared to experimental data and other models.
Neutrino Interactions with Nuclei
Leitner, T.;Buss, O.;Mosel, U.;Alvarez-Ruso, L.
High Energy Physics - Phenomenology , 2007, DOI: 10.1063/1.2834476
Abstract: We investigate neutrino-nucleus collisions at intermediate energies incorporating quasi-elastic scattering and the excitation of 13 resonances as elementary processes, taking into account medium effects such as Fermi motion, Pauli blocking, mean-field potentials and in-medium spectral functions. A coupled-channel treatment of final state interactions is achieved with the GiBUU transport model. Results for inclusive reactions, neutrino- and electron-induced, as well as for pion production and nucleon knockout are presented.
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