arXiv subjects

A. Martínez Torres

Publications and source records attributed to A. Martínez Torres.

57 records · Page 4Linked to original sources

arXiv2008

Three-body hadronic structure of low-lying $1/2^+$ $Σ$ and $Λ$ resonances

We discuss the dynamical generation of some low-lying $1/2^+$ $Σ$'s and $Λ$'s in two-meson one-baryon systems. These systems have been constructed by adding a pion in $S$-wave to the $\bar{K} N$ pair and its coupled channels, where the $1/2^-$ $Λ$(1405)-resonance gets dynamically generated. We solve Faddeev equations in the coupled-channel approach to calculate the $T$-matrix for these systems as a function of the total energy and the invariant mass of one of the meson-baryon pairs. This squared $T$-matrix shows peaks at the energies very close to the masses of the strangeness -1, $1/2^+$ resonances listed in the particle data book.

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arXiv2008

The $σK$ coupling in the chiral unitary approach and the isoscalar $\bar{K}N$, $\bar{K}A$ interaction

We evaluate the "$σ$" exchange contribution to the $\bar{K}N\to\bar{K}N$ scattering within a chiral unitary approach. We show that the chiral transition potentials for $ππ\to K \bar{K}$ in the $t$-channel lead to a "$σ$" contribution that vanishes in the $\bar{K}$ forward direction and, hence, would produce a null "$σ$" exchange contribution to the $K^-$ optical potential in nuclear matter in a simple impulse approximation. This is a consequence of the fact that the leading order chiral Lagrangian gives an I=0 $ππ\to K\bar{K}$ amplitude proportional to the squared momentum transfer, $q^2$. This finding poses questions on the meaning or the origin of "$σ$" exchange potentials used in relativistic mean field approaches to the $K^-$ nuclear selfenergy. This elementary "$σ$" exchange potential in $\bar{K}N\to\bar{K}N$ is compared to the Weinberg-Tomozawa term and is found to be smaller than present theoretical uncertainties but will be relevant in the future when aiming at fitting increasingly more accurate data.

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arXiv2008

The $N^*(1710)$ as a resonance in the $ππN$ system

We study the $ππN$ system by solving the Faddeev equations, for which the input two-body $t$-matrices are obtained by solving the Bethe-Salpeter equation in the coupled channel formalism. The potentials for the $ππ$, $πN$ sub-systems and their coupled channels are obtained from chiral Lagrangians, which have been earlier used to study resonances in these systems successfully. In this work, we find a resonance in the $ππN$ system with a mass of $1704 - i 375/2$ MeV and with quantum numbers $I=1/2$, $J^π=1/2^+$. We identify this state with the $N^*(1710)$. This peak is found where the energies of the $ππ$ sub-system fall in the region of the $σ$ resonance. We do not find evidence for the Roper resonance in our study indicating a more complex structure for this resonance, nor for any state with total isospin $I=3/2$ or $5/2$.

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