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M. Lutz

Publications and source records attributed to M. Lutz.

7 recordsLinked to original sources
arXiv2001

Gradient Terms in the Microscopic Description of K-Atoms

We analyze the spectra of kaonic atoms using optical potentials withnon-local (gradient) terms. The magnitude of the non-local termsfollows from a self consistent many-body calculation of the kaon selfenergy in nuclear matter, which is based on s-wave kaon nucleoninteractions. The optical potentials exhibit strong non-linearitiesin the nucleon density and sizeable non-local terms. We find that thenon-local terms are quantitatively important in the analysis of thespectra and that a phenomenologically successful description can be obtained for p-wave like optical potentials. It is suggested that themicroscopic form of the non-local interaction terms is obtainedsystematically by means of a semi-classical expansion of the nucleusstructure. The resulting optical potential leads to less pronounced non-local effects.

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arXiv2000

Effective chiral theory of kaon-nucleon scattering

We apply the relativistic chiral SU(3) Lagrangian density to kaon-nucleon scattering imposing constraints from the pion-nucleon s- and p-wave threshold parameters at chiral order $Q^2$. The s and u channel decouplet baryon exchange is included explicitly and is found to play a crucial role in understanding the empirical s- and p-wave nuclear kaon dynamics quantitatively.

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arXiv2000

From meson-nucleon scattering to vector mesons in nuclear matter

We employ meson-nucleon scattering data to deduce the properties of the low-mass vector mesons in nuclear matter, and present results for the $ρ$ and $ω$ in-medium spectral functions. The corresponding thermal emission rate for lepton pairs is also discussed.

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arXiv1999

Effective chiral theory of nucleon-nucleon scattering

We present a new chiral expansion scheme for the nucleon-nucleon scattering amplitude which preserves unitarity exactly. Our effective field theory builds on the power counting rules for 2-nucleon reducible diagrams proposed in \cite{lutz}. We evaluate the leading order terms of the isospin one scattering amplitude and elaborate in detail on the $^1S_0$ phase shift. Our chiral description of the $^1S_0$-phase shift does compete in quality with modern phenomenological nucleon-nucleon potentials. We describe elastic and inelastic scattering quantitatively up to laboratory energies of $E_{\rm lab} \simeq 600$ MeV.

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arXiv1999

Saturation from nuclear pion dynamics

We construct an equation-of-state for nuclear matter based on the chiral Lagrangian. The relevant scales are discussed and an effective chiral power expansion scheme, which is constructed to work around the nuclear saturation density, is presented. A realistic equation-of-state is obtained by adjusting one free parameter, when the leading and subleading terms in the expansion are included. The saturation mechanism is due to correlations induced by the one-pion-exchange interaction. Furthermore, we find a substantial deviation from the Fermi-gas estimate of the quark condensate in nuclear matter already at the saturation density.

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arXiv1998

Masses of hadrons in nuclei

We emphasize the central role played by the spectral function in the description of hadrons in matter and discuss the applicability of the quasiparticle concept to the propagation of hadrons in dense nuclear matter. Theoretical and experimental results relevant for the in medium properties of vector mesons and kaons are briefly reviewed. We also present novel results for the $ρ$ and $ω$ spectral functions in nuclear matter, deduced from a coupled channel analysis of pion-nucleon scattering data.

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