Meson-Baryon s-wave Resonances with Strangeness -3

Starting from a consistent SU(6) extension of the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian (Phys. Rev. D74 (2006) 034025), we study the s-wave meson-baryon resonances in the strangeness S=-3 and negative parity sector. Those resonances are generated by solving the Bethe-Salpeter equation with the WT interaction used as kernel. The considered mesons are those of the 35-SU(6)-plet, which includes the pseudoscalar (PS) octet of pions and the vector (V) nonet of the rho meson. For baryons we consider the 56-SU(6)-plet, made of the 1/2+ octet of the nucleon and the 3/2+ decuplet of the Delta. Quantum numbers I(J^P)=0(3/2^-) are suggested for the experimental resonances Omega*(2250)- and Omega*(2380)-. Among other, resonances with I=1 are found, with minimal quark content sss\bar{l}l', being s the strange quark and l, l' any of the the light up or down quarks. A clear signal for such a pentaquark would be a baryonic resonance with strangeness -3 and electric charge of -2 or 0, in proton charge units. We suggest looking for K- Xi- resonances with masses around 2100 and 2240 MeV in the sector 1(1/2^-), and for pi Omega- and K- Xi*- resonances with masses around 2260 MeV in the sector 1(3/2^-).Comment: 3 pages, 1 Postscript figure, 7 table

SU(6)⊃\supsetSU(3)xSU(2) and SU(8)⊃\supsetSU(4)xSU(2) Clebsch-Gordan coefficients

Tables of scalar factors are presented for 63x63 and 120x63 in SU(8)$\supset$SU(4)xSU(2), and for 35x35 and 56x35 in SU(6)$\supset$SU(3)xSU(2). Related tables for SU(4)$\supset$SU(3)xU(1) and SU(3)$\supset$SU(2)xU(1) are also provided so that the Clebsch-Gordan coefficients can be completely reconstructed. These are suitable to study meson-meson and baryon-meson within a spin-flavor symmetric scheme.Comment: 30 pages, mostly table

Large Nc Weinberg-Tomozawa interaction and negative parity s--wave baryon resonances

It is shown that in the 70 and 700 SU(6) irreducible spaces, the SU(6) extension of the Weinberg-Tomozawa (WT) s-wave meson-baryon interaction incorporating vector mesons ({\it hep-ph/0505233}) scales as ${\cal O}(N_c^0)$, instead of the well known ${\cal O}(N_c^{-1})$ behavior for its SU(3) counterpart. However, the WT interaction behaves as order ${\cal O}(N_c^{-1})$ within the 56 and 1134 meson-baryon spaces. Explicit expressions for the WT couplings (eigenvalues) in the irreducible SU(2$N_F$) spaces, for arbitrary $N_F$ and $N_c$, are given. This extended interaction is used as a kernel of the Bethe-Salpeter equation, to study the large $N_c$ scaling of masses and widths of the lowest--lying negative parity s-wave baryon resonances. Analytical expressions are found in the $N_c\to \infty$ limit, from which it can be deduced that resonance widths and excitation energies $(M_R-M)$ behave as order ${\cal O} (N^0_c)$, in agreement with model independent arguments, and moreover they fall in the 70-plet, as expected in constituent quark models for an orbital excitation. For the 56 and 1134 spaces, excitation energies and widths grow ${\cal O} (N_c^{1/2})$ indicating that such resonances do not survive in the large $N_c$ limit. The relation of this latter $N_c$ behavior with the existence of exotic components in these resonances is discussed. The interaction comes out repulsive in the 700.Comment: 21 pages, 3 figures, requires wick.sty and young.sty. Subsection added. Conclusions revised. To appear in Physical Review

Non-localities and Fermi motion corrections in K−K^- atoms

We evaluate the p-wave $K^-N$ amplitudes from the chiral Lagrangians and from there construct the p-wave part of the $K^-$ nucleus optical potential plus a small s-wave part induced from the elementary p-wave amplitude and the nuclear Fermi motion. Simultaneously, the momentum and energy dependence of the s-wave optical potential, previously developed, are taken into account and shown to generate a small p-wave correction to the optical potential. All the corrections considered are small compared to the leading s-wave potential, and lead to changes in the shifts and widths which are smaller than the experimental errors. A thorough study of the threshold region and low densities is conducted, revealing mathematical problems for which a physical solution is given.Comment: revised version, 28 pages, Latex, 8 postscript figures. Submitted to Nucl. Phys.

The AMBRE Project: Stellar Parameterisation of the ESO:UVES archived spectra

The AMBRE Project is a collaboration between the European Southern Observatory (ESO) and the Observatoire de la Cote d'Azur (OCA) that has been established in order to carry out the determination of stellar atmospheric parameters for the archived spectra of four ESO spectrographs. The analysis of the UVES archived spectra for their stellar parameters has been completed in the third phase of the AMBRE Project. From the complete ESO:UVES archive dataset that was received covering the period 2000 to 2010, 51921 spectra for the six standard setups were analysed. The AMBRE analysis pipeline uses the stellar parameterisation algorithm MATISSE to obtain the stellar atmospheric parameters. The synthetic grid is currently constrained to FGKM stars only. Stellar atmospheric parameters are reported for 12,403 of the 51,921 UVES archived spectra analysed in AMBRE:UVES. This equates to ~23.9% of the sample and ~3,708 stars. Effective temperature, surface gravity, metallicity and alpha element to iron ratio abundances are provided for 10,212 spectra (~19.7%), while at least effective temperature is provided for the remaining 2,191 spectra. Radial velocities are reported for 36,881 (~71.0%) of the analysed archive spectra. Typical external errors of sigmaTeff~110dex, sigmalogg~0.18dex, sigma[M/H]~0.13dex, and sigma[alpha/Fe]~0.05dex with some reported variation between giants and dwarfs and between setups are reported. UVES is used to observe an extensive collection of stellar and non-stellar objects all of which have been included in the archived dataset provided to OCA by ESO. The AMBRE analysis extracts those objects which lie within the FGKM parameter space of the AMBRE slow rotating synthetic spectra grid. Thus by homogeneous blind analysis AMBRE has successfully extracted and parameterised the targeted FGK stars (23.9% of the analysed sample) from within the ESO:UVES archive.Comment: 19 pages, 16 figures, 11 table

Resonances and the Weinberg--Tomozawa 56-baryon --35-meson interaction

Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)--flavor WT results for the lowest-lying s--wave negative parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity $\frac32^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through $K^*$ decay. Neglecting d-wave KN decays, this state turns out to be quite narrow ($\Gamma \le 15$ MeV) and it might provide clear signals in reactions like $\gamma p \to \bar K^0 p K^+\pi^-$ by looking at the three body $p K^+\pi^-$ invariant mass.Comment: Talk given at the IVth International Conference on Quarks an Nuclear Physics, Madrid, June 5th-10th 2006. Minor correction

Quark-mass dependence of baryon resonances

We study the quark-mass dependence of J^P = \frac12^- s-wave and J^P = \frac32^- d-wave baryon resonances. Parameter-free results are obtained in terms of the leading order chiral Lagrangian. In the 'heavy' SU(3) limit with m_\pi =m_K \simeq 500 MeV the s-wave resonances turn into bound states forming two octets plus a singlet representations of the SU(3) group. Similarly the d-wave resonances turn into bound states forming an octet and a decuplet in this limit. A contrasted result is obtained in the 'light' SU(3) limit with m_\pi =m_K \simeq 140 MeV for which no resonances exist.Comment: 8 pages, three figures, talk presented at HYP200