1,644 research outputs found
Structure of the nuclear force in a chiral quark-diquark model
We discuss the structure of the nuclear force using a lagrangian derived from
hadronization of a chiral quark and diquark model. A generalized trace log
formula including meson and nucleon fields is expanded to the order in which
relevant terms emerge. It is shown that the nuclear force is composed of long
and medium range parts of chiral meson exchanges and short range parts of
quark-diquark exchanges. The ranges of the scalar and vector interactions
coincide well with those of sigma () and omega () meson
exchanges if the size of the nucleon core of a quark-diquark bound state is
adjusted appropriately.Comment: 12 pages, 9 figure
Structure of the Nucleon and Roper Resonance with Diquark Correlations
We investigate the electric form factors of the nucleon and Roper resonance
using a quark-diquark model. We find that the charge radii of the nucleon and
Roper resonance are almost the same in size.Comment: To appear in the proceedings of Chiral 07, Osaka, Japan, November
13-16, 2007. 4pages, 4figure
Nucleon axial couplings and [(1/2,0) + (0,1/2)]-[(1,1/2) + (1/2,1)] chiral multiplet mixing
Three-quark nucleon interpolating fields in QCD have well-defined SU_L(2) x
SU_R(2) and U_A(1) chiral transformation properties. Mixing of the [(1,1/2) +
(1/2,1)] chiral multiplet with one of [(1/2,0) + (0,1/2)] or [(0,1/2) +
(1/2,0)] representation can be used to fit the isovector axial coupling g_A(1)
and thus predict the isoscalar axial coupling g_A(0) of the nucleon, in
reasonable agreement with experiment. We also use a chiral meson-baryon
interaction to calculate the masses and one-pion-interaction terms of J=1/2
baryons belonging to the [(0,1/2) + (1/2,0)] and [(1,1/2) + (1/2,1)] chiral
multiplets and fit two of the diagonalized masses to the lowest-lying nucleon
resonances thus predicting the third J=1/2 resonance at 2030 MeV, not far from
the (one-star PDG) state Delta(2150).Comment: To appear in Modern Physics Letters
A Lagrangian for the Chiral (1/2,0) + (0,1/2) Quartet Nucleon Resonances
We study the nucleon and three N* resonances' properties in an effective
linear realization chiral SU_L(2) x SU_R(2) and U_A(1) symmetric Lagrangian. We
place the nucleon fields into the so-called "naive" (1/2,0) + (0, 1/2) and
"mirror" (0, 1/2) + (1/2,0) (fundamental) representations of SU_L(2) x SU_R(2),
two of each -distinguished by their U_A(1) chiral properties, as defined by an
explicit construction of the nucleon interpolating fields in terms of three
quark (Dirac) fields. We construct the most general one-meson-baryon chiral
interaction Lagrangian assuming various parities of these four nucleon fields.
We show that the observed masses of the four lowest lying nucleon states can be
well reproduced with the effective Lagrangian, after spontaneous symmetry
breakdown, without explicit breaking of U_A(1) symmetry. This does not mean
that explicit U_A(1) symmetry breaking does not occur in baryons, but rather
that it does not have a unique mass prediction signature that exists e.g. in
the case of spinless mesons. We also consider briefly the axial couplings with
chiral representation mixing.Comment: Published in International Journal of Modern Physics
A Method to Unambiguously Determine the Parity of the Theta+ Pentaquark
With the recent discovery of the pentaquark, the question of
its parity is paramount since this will constrain the correct description of
its internal structure. We show that the measurement of the spin singlet and
triplet cross sections for the reaction
will unambiguously determine the parity of the .Comment: 3 page
Exotic mesons with hidden charm and bottom near thresholds
We study heavy hadron spectroscopy near heavy meson thresholds. We employ
heavy pseudoscalar meson P and heavy vector meson P* as effective degrees of
freedom and consider meson exchange potentials between them. All possible
composite states which can be constructed from the P and P* mesons are studied
up to the total angular momentum J <= 2. We consider, as exotic states,
isosinglet states with exotic J^{PC} quantum numbers and isotriplet states. We
solve numerically the Schr\"odinger equation with channel-couplings for each
state. We found B(*)barB(*) molecule states for I^G(J^{PC}) = 1^+(1^{+-})
correspond to the masses of twin resonances Zb(10610) and Zb(10650). We predict
several possible B(*)barB(*) bound and/or resonant states in other channels. On
the other hand, there are no B(*)barB(*) bound and/or resonant states whose
quantum numbers are exotic.Comment: 10 pages, 1 figure, to appear in the proceedings of The 5th
International Workshop on Charm Physics (Charm 2012
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