2,792 research outputs found
Generalized form factors and spin structures of the kaon
We investigate the spin structure of the kaon, based on the nonlocal chiral
quark model from the instanton vacuum. We first revisit the electromagnetic
form factors of the pion and kaon, improving the results for the kaon. We
evaluate the generalized tensor form factors of the kaon in order to determine
the probability density of transversely polarized quarks inside the kaon. We
consider the effects of flavor SU(3) symmetry breaking, so that the probability
density of the up and strange quarks are examined in detail. It is found that
the strange quark behaves differently inside the kaon in comparison with the up
quark.Comment: 9 pages, 7 figures, accepted for publication in Phys. Lett.
Pion properties at finite density
In this talk, we report our recent work on the pion weak decay constant
(F_pi) and pion mass (m_pi) using the nonlocal chiral quark model with the
finite quark-number chemical potential (mu) taken into account. Considering the
breakdown of Lorentz invariance at finite density, the time and space
components are computed separately, and the corresponding results turn out to
be: F^t_pi = 82.96 MeV and F^s_pi = 80.29 MeV at mu_c ~ 320 MeV, respectively.
Using the in-medium Gell-Mann Oakes-Renner (GOR) relation, we show that the
pion mass increases by about 15% at mu_c.Comment: 5 pages, 2 figures, Talk given at the 4th Asia-Pacific Conference on
Few-Body Problems in Physics 2008 (APFB08), 19 ~ 23 Aug 2008, Depok,
Indonesi
Twist-3 pion and kaon distribution amplitudes from the instanton vacuum with flavor SU(3) symmetry breaking
We investigate the twist-3 pion and kaon distribution amplitudes of the
pseudoscalar (phi^p_{pi,K}) and pseudotensor (phi^{sigma}_{pi,K}) types, based
on the effective chiral action from the instanton vacuum. Effects of flavor
SU(3) symmetry breaking are explicitly taken into account. The Gegenbauer
moments and the moments of the distribution amplitudes () are also
computed. Our results are summarized as follows: a^p_{2,pi} ~ 0.4, a^p_{1,K} ~
0.02 and a^p_{2,K} ~ 0.14, and a^{sigma}_{2,pi} ~ 0.02 and a^{sigma}_{1,K} ~
a^{sigma}_{2,K} ~ 0; ^p_{\pi} ~ ^p_K ~ 0.37 and ^p_K ~ 0, and
^{sigma}_{pi} ~ ^{sigma}_K ~ 0.20 and ^{sigma}_K ~ 0. We
compare our results with those from the QCD sum rules. We also discuss the
relevant Wilson coefficients which were analyzed recently in chiral
perturbation theory.Comment: 12 pages, 4 figures, accepted for publication in PR
Photon and nucleon induced production of Theta^+
We investigate Theta^+ production via photon and nucleon induced reactions.
We observe that the positive parity Theta^+ production provides about ten times
larger total cross sections than those of the negative parity one in both
photon and nucleon induced reactions due to P-wave enhancement of the K-N-Theta
vertex. We also consider the model independent method in the nucleon induced
reaction to determine the parity of Theta^+ and show clearly distinguishable
signals for the two parities.Comment: 4 pages, 8 figures, Talk given at International Workshop on
PENTAQUARK04, Spring-8, Hyogo, Japan, 20-23 Jul 200
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