Coupling vector and pseudoscalar mesons to study baryon resonances

A study of meson-baryon systems with total strangeness -1 is made within a framework based on the chiral and hidden local symmetries. These systems consist of octet baryons, pseudoscalar and vector mesons. The pseudoscalar meson-baryon (PB) dynamics has been earlier found determinant for the existence of some strangeness -1 resonances, for example, $\Lambda(1405)$, $\Lambda(1670)$, etc. The motivation of the present work is to study the effect of coupling the closed vector meson-baryon (VB) channels to these resonances. To do this, we obtain the $PB \rightarrow PB$ and $VB \rightarrow VB$ amplitudes from the t-channel diagrams and the $PB \leftrightarrow VB$ amplitudes are calculated using the Kroll-Ruddermann term where, considering the vector meson dominance phenomena, the photon is replaced by a vector meson. The calculations done within this formalism reveal a very strong coupling of the VB channels to the $\Lambda(1405)$ and $\Lambda(1670)$. In the isospin 1 case, we find an evidence for a double pole structure of the $\Sigma (1480)$ which, like the isospin 0 resonances, is also found to couple strongly to the VB channels. The strong coupling of these low-lying resonances to the VB channels can have important implications on certain reactions producing them.Comment: Minor typos corrected (in Eq.(22) and axis-labels of some figures

Plausible explanation of the Δ5/2+(2000)\Delta_{5/2^{+}}(2000) puzzle

From a Faddeev calculation for the $\pi-(\Delta\rho)_{N_{5/2^{-}}(1675)}$ system we show the plausible existence of three dynamically generated $I(J^{P})=3/2 (5/2^{+})$ baryon states below 2.3 GeV whereas only two resonances, $\Delta_{5/2^{+}}(1905)(\ast\ast\ast\ast)$ and $\Delta_{5/2^{+}}(2000)(\ast\ast),$ are cataloged in the Particle Data Book Review. Our results give theoretical support to data analyses extracting two distinctive resonances, $\Delta_{5/2^{+}}(\sim1740)$ and $\Delta_{5/2^{+}}(\sim2200),$ from which the mass of $\Delta_{5/2^{+}}(2000)(\ast\ast)$ is estimated. We propose that these two resonances should be cataloged instead of $\Delta_{5/2^{+}}(2000).$ This proposal gets further support from the possible assignment of the other baryon states found in the approach in the $I=1/2,3/2$ with $J^{P}=1/2^{+},3/2^{+},5/2^+$ sectors to known baryonic resonances. In particular, $\Delta_{1/2^{+}}(1750)(\ast)$ is naturally interpreted as a $\pi N_{1/2^{-}}(1650)$ bound state.Comment: 13 pages, 7 figure

Mass-radius relation for magnetized strange quark stars

We review the stability of magnetized strange quark matter (MSQM) within the phenomenological MIT bag model, taking into account the variation of the relevant input parameters, namely, the strange quark mass, baryon density, magnetic field and bag parameter. A comparison with magnetized asymmetric quark matter in $\beta$-equilibrium as well as with strange quark matter (SQM) is presented. We obtain that the energy per baryon for MSQM decreases as the magnetic field increases, and its minimum value at vanishing pressure is lower than the value found for SQM, which implies that MSQM is more stable than non-magnetized SQM. The mass-radius relation for magnetized strange quark stars is also obtained in this framework.Comment: 7 pages, 6 figures. To be published in the Proceedings of 4th International Workshop on Relativistic Astrophysical and Astronomy IWARA0