1,795 research outputs found
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)SU(3)xSU(2) and SU(8)SU(4)xSU(2) Clebsch-Gordan coefficients
Tables of scalar factors are presented for 63x63 and 120x63 in
SU(8)SU(4)xSU(2), and for 35x35 and 56x35 in
SU(6)SU(3)xSU(2). Related tables for SU(4)SU(3)xU(1) and
SU(3)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
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 bound
state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through
decay. Neglecting d-wave KN decays, this state turns out to be quite narrow
( MeV) and it might provide clear signals in reactions like
by looking at the three body
invariant mass.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics, Madrid, June 5th-10th 2006. Minor correction
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 ,
instead of the well known behavior for its SU(3)
counterpart. However, the WT interaction behaves as order
within the 56 and 1134 meson-baryon spaces. Explicit expressions for the WT
couplings (eigenvalues) in the irreducible SU(2) spaces, for arbitrary
and , are given. This extended interaction is used as a kernel of
the Bethe-Salpeter equation, to study the large scaling of masses and
widths of the lowest--lying negative parity s-wave baryon resonances.
Analytical expressions are found in the limit, from which it
can be deduced that resonance widths and excitation energies behave
as order , 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 indicating that such resonances do not
survive in the large limit. The relation of this latter 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
Exotic dynamically generated baryons with C1
We follow a model based on the SU(8) symmetry for the interaction of mesons
with baryons. The model treats on an equal footing the pseudo-scalars and the
vector mesons, as required by heavy quark symmetry. The T-matrix calculated
within an unitary scheme in coupled channels has poles which are interpreted as
baryonic resonances.Comment: 5 pages. Proceedings for Chiral10 workshop, Valencia, June 21-24 201
Large Weinberg-Tomozawa interaction and spin-flavor symmetry
The construction of an extended version of the Weinberg-Tomozawa Lagrangian,
in which baryons and mesons form spin-flavor multiplets, is reviewed and some
of its properties discussed, for an arbitrary number of colors and flavors. The
coefficient tables of spin-flavor irreducible representations related by
crossing between the -, - and -channels are explicitly constructed.Comment: 3 pages, no figures. Presented at the IVth International Conference
on Quarks and Nuclear Physics, Madrid, June 5th-10th 200
Odd Parity Light Baryon Resonances
We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian
within a coupled channel unitary approach in order to calculate the T-matrix
for meson-baryon scattering in s-wave. The building blocks of the scheme are
the pion and nucleon octets, the rho nonet and the Delta decuplet. We identify
poles in this unitary T-matrix and interpret them as resonances. We study here
the non exotic sectors with strangeness S=0,-1,-2,-3 and spin J=1/2, 3/2 and
5/2. Many of the poles generated can be associated with known N, Delta, Sigma,
Lambda and Xi resonances with negative parity. We show that most of the
low-lying three and four star odd parity baryon resonances with spin 1/2 and
3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This
study allows us to predict the spin-parity of the Xi(1620), Xi(1690), Xi(1950),
Xi(2250), Omega(2250) and Omega(2380) resonances, which have not been
determined experimentally yet.Comment: New appendix and references adde
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