arXiv subjects

M. Ericson

Publications and source records attributed to M. Ericson.

At least 37 records · Page 2Linked to original sources

arXiv2009

Neutrino interactions with nuclei

We present a model for neutrino-nucleus scattering in the energy region relevant for present and forthcoming neutrino-oscillation experiments. The model is based on the RPA treatment of the nuclear responses in the quasi-elastic and Delta-resonance region. It includes also in a phenomenological way nucleon knock-out. It aims at the description, within a single framework, of several final state channels i.e. quasi-elastic, incoherent and coherent one-pion production and two- or several-nucleon knock-out.

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arXiv2009

Relativistic Chiral Theory of Nuclear Matter and QCD Constraints

We present a relativistic chiral theory of nuclear matter which includes the effect of confinement. Nuclear binding is obtained with a chiral invariant scalar background field associated with the radial fluctuations of the chiral condensate Nuclear matter stability is ensured once the scalar response of the nucleon depending on the quark confinement mechanism is properly incorporated. All the parameters are fixed or constrained by hadron phenomenology and lattice data. A good description of nuclear saturation is reached, which includes the effect of in-medium pion loops. Asymmetry properties of nuclear matter are also well described once the full rho meson exchange and Fock terms are included.

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arXiv2008

Scalar field and QCD constraints in Nuclear Physics

Relativistic theories of nuclear matter are discussed in a new pespective. First the chiral character of the scalar nuclear field is introduced in the framework of the linear sigma model. With the assumption that the nucleon mass originates in part from the coupling to the quark condensate it is possible to relate the optical potential for the propagation of the scalar field to the QCD scalar susceptibility of the nucleon, on which indications exist from the lattice evolution of the nucleon mass with the quark mass. Constraining the parameters of the nuclear scalar potential by the lattice expansion parameters a successful description of the nuclear saturation properties can be reached.

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arXiv2007

Constraints on nuclear matter properties from QCD susceptibilities

We establish the interrelation between the QCD scalar response of the nuclear medium and its response to a scalar probe coupled to nucleons, such as the scalar meson responsible for the nuclear binding. The relation that we derive applies at the nucleonic as well as at the nuclear levels. Non trivial consequences follow. In particular it opens the possibility of relating medium effects in the scalar meson exchange or three-body forces of nuclear physics to QCD lattice studies of the nucleon mass

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arXiv2007

Interplay between QCD and nuclear responses

We establish the interrelation between the QCD scalar response of the nuclear medium and its response to a scalar probe coupled to nucleons, such as the scalar meson responsible for the nuclear binding. The relation that we derive applies at the nucleonic as well as at the nuclear levels. Non trivial consequences follow. One concerns the scalar QCD susceptibility of the nucleon. The other opens the possibility of relating medium effects in the scalar meson exchange of nuclear physics to QCD lattice studies of the nucleon mass.

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arXiv2007

From QCD to nuclear matter saturation

We discuss a relativistic chiral theory of nuclear matter with $σ$ and $ω$ exchange using a formulation of the $σ$ model in which all the chiral constraints are automatically fulfilled. We establish a relation between the nuclear response to the scalar field and the QCD one which includes the nucleonic parts. It allows a comparison between nuclear and QCD information. Going beyond the mean field approach we introduce the effects of the pion loops supplemented by the short-range interaction. The corresponding Landau-Migdal parameters are taken from spin-isospin physics results. The parameters linked to the scalar meson exchange are extracted from lattice QCD results. These inputs lead to a reasonable description of the saturation properties, illustrating the link between QCD and nuclear physics. We also derive from the corresponding equation of state the density dependence of the quark condensate and of the QCD susceptibilities.

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arXiv2006

QCD susceptibilities and nuclear matter saturation in a chiral theory: inclusion of pion loops

We derive the equation of state of symmetric nuclear matter in a relativistic theory with $σ$ and $ω$ exchange. We take a chiral version of this model which insures all the chiral constraints. Going beyond the mean field approach we introduce the effects of the pion loops. For the parameters of the model, in order to fix those linked to pion exchange, we exploit the most recent information on the short-range part of the spin-isospin interaction. For those linked to the scalar meson exchange we make use of an analysis of lattice results on the nucleon mass evolution with the quark mass. With these inputs we are able reach a correct description of the saturation properties. From the equation of state of symmetric nuclear matter we alsoderive the density dependence of the quark condensate and of the QCD susceptibilities.

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arXiv2005

Two-pion production processes, chiral symmetry and NN interaction in the medium

We study the two-pion propagator in the nuclear medium. This quantity appears in the $π-π$ T-matrix and we show that it also enters the QCD scalar susceptibility. The medium effects on this propagator are due to the influence of the individual nucleon response to a scalar field through their pion clouds. This response is appreciably increased by the nuclear environment. It produces an important convergence effect between the scalar and pseudoscalar susceptibilities, reflecting the reshaping of the scalar strengh observed in $2π$ production experiments. While a large modification of the $σ$ propagator follows, due to its coupling to two pion states, we show that the NN potential remains instead unaffected.

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arXiv2004

Nuclear matter saturation in a relativistic chiral theory and QCD susceptibilities

We study a chiral relativistic theory of nuclear matter aimed at the desciption of both the binding and saturation properties and the QCD properties, quark condensate and QCD susceptibilities. For this purpose the nucleon scalar response of the quark-meson coupling model is introduced in the linear sigma model. The consequences for the nuclear and the QCD scalar susceptibilities are discussed.

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arXiv2003

Scalar susceptibility and chiral symmetry restoration in nuclei

We study the nuclear modification of the scalar QCD susceptibility, calculated as the derivative of the quark condensate with respect to the quark mass. We show that it has two origins. One is the low lying nuclear excitations. At normal nuclear density this part is constrained by the nuclear incompressibility. The other part arises from the individual nucleon response and it is dominated by the pion cloud contribution. Numerically the first contribution dominates. The resulting increase in magnitude of the scalar susceptibility at normal density is such that it becomes close to the pseudoscalar susceptibility, while it is quite different in the vacuum. We interpret it as a consequence of chiral symmetry restoration in nuclei.

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arXiv2002

Fluctuations of the quark densities in nuclei

We study the static scalar susceptibility of the nuclear medium, i.e., the change of the quark condensate for a small modification of the quark mass. In the linear sigma model it is linked to the in-medium sigma propagator. At ordinary nuclear densities, when chiral symmetry is spontaneously broken, the scalar susceptibility is distinct from the pseudoscalar one, which is linked to the fluctuations of the quark pseudoscalar density. We show that the pseudoscalar one, which is large in the vacuum, owing to the smallness of the pion mass, follows the density evolution of the quark condensate and thus decreases. The scalar one instead increases due to the mixing with the softer modes of the nucleon-hole excitations. At normal nuclear matter density the two susceptibilities become much closer, a partial chiral symmetry restoration effect as they become equal when the full restoration is achieved.

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arXiv2002

Nuclear modification of transverse-longitudinal structure function ratio

We investigate the nuclear effects on the transverse and longitudinal responses in the deep inelastic region due to the nuclear binding and nucleon Fermi motion. We display the role of the transverse-longitudinal admixture due to the transverse nucleon momentum. The mixing effect is appreciable at small Q^2 values, and gradually disappears at large Q^2 values. The nuclear modification is then dominated by the binding and Fermi-motion effects which are contained in the spectral function.

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arXiv2002

In-medium modification of the isovector pion-nucleon amplitude

We study the in-medium modification of the isovector pi N amplitude using a non-linear representation of the sigma model but keeping the scalar degree of freedom. We check that our result does not depend on the representation. We discuss the connection with other approaches based on chiral perturbation theory.

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arXiv2000

Chiral symmetry and quantum hadro-dynamics

Using the linear sigma model, we study the evolutions of the quark condensate and of the nucleon mass in the nuclear medium. Our formulation of the model allows the inclusion of both pion and scalar-isoscalar degrees of freedom. It guarantees that the low energy theorems and the constrains of chiral perturbation theory are respected. We show how this formalism incorporates quantum hadro-dynamics improved by the pion loops effects.

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arXiv2000

Quark Condensate in the Deuteron

We study the changes produced by the deuteron on the QCD quark condensate by means the Feynman-Hellmann theorem and find that the pion mass dependence of the pion-nucleon coupling could play an important role. We also discuss the relation between the many body effect of the condensate and the meson exchange currents, as seen by photons and pions. For pion probes, the many-body term in the physical amplitude differs significantly from that of soft pions, the one linked to the condensate. Thus no information about the many-body term of the condensate can be extracted from the pion-deuteron scattering length. On the other hand, in the Compton amplitude, the relationship with the condensate is a more direct one.

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arXiv1999

Pion Scalar Density and Chiral Symmetry Restoration at Finite Temperature and Density

This paper is devoted to the evaluation of the pionic scalar density at finite temperature and baryonic density. We express the latter effect in terms of the nuclear response evaluated in the random phase approxima- tion. We discuss the density and temperature evolution of the pionic density which governs the quark condensate evolution. Numerical evalua- tions are performed.

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arXiv1999

Neutrino-Oxygen interactions: role of nuclear physics in the atmospheric neutrino anomaly

The apparent anomaly in the ratio of muon to electron atmospheric neutrinos first observed by Kamiokande and IMB has been confirmed by Super-Kamiokande and Soudan-2. The experimental analysis, including the asymmetry in the zenithal distributions of the $ μ-\mathrm{type} $ events in Super-Kamiokande gives a strong support to the neutrino oscillation hypothesis to solve the anomaly. In this work we are interested by the role of nuclear physics in the neutrino-oxygen reactions used to detect the atmospheric neutrinos. We point out that multi-nucleon excitations of np-nh type and that nuclear correlations could modify an experimental analysis à la Super-Kamiokande because they lead to a substantial enhancement of the number of 1 Čerenkov ring retained events.

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arXiv1999

Correlator mixing and mass reduction as signals of chiral symmetry restoration

Chiral symmetry restoration in a dense medium is to some extent a consequence of the nuclear pion cloud. These pions induce a mixing of the axial and vector current contributions in the axial and vector correlators. We discuss their influence on hadron masses and investigate the signal produced by the remaining contribution associated with chiral symmetry restoration. Using the quark-meson coupling model we find that the latter is associated with the reduction of hadron masses.

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