Strange mesonic transition form factor in the chiral constituent quark model

Abstract

The form factor g (S) ρπ (Q 2 ) of the strange vector current transition matrix element ρ|sγ µ s|π is calculated within the chiral quark model. A strange vector current of the constituent U -and D-quarks is induced by kaon radiative corrections and this mechanism yields the nonvanishing values of g (S)ρπ (0). The numerical result at the photon point is consistent with the one given by the φ-meson dominance model, but the fall-off in the Q 2 -dependence is faster than the monopole form factor. Mesonic radiative corrections are also examined for the electromagnetic ρ-to-π and K * -to-K transition amplitudes.

The strange quark contribution to the proton's magnetic moment

“…More generally, one-loop computations using a hadronic basis represent a perturbative approximation to the full dispersion theoretic treatment. Such loop calculations entail truncation of an expansion in the strong hadronic coupling g at second order and, therefore, tend to be subject to a substantial degree of model-dependent ambiguities [37,40]. In particular, the one-loop amplitudes rely on a unitarity violating approximation to pseudoscalar meson-nucleon scattering amplitudes, the omission of higher-order (in g) rescattering contributions that restore unitarity and generate the physically important resonant behavior of the spectral functions, and use of unphysical, point-like pseudoscalar vector current form factors [46,47].…”

“…( 5) and the dispersion theoretic studies, play an important role in the dynamics of G s M . In general, the systematic, model-independent treatment of hadronic loop effects in χPT does not yield predictions that are independent of the G s M measurements since the operator sγ µ s contains an SU(3)-singlet component [40]. Apart from the SAMPLE result for G s M itself, there exists no other experimental information on the SU(3)-singlet component of the nucleon vector current that would allow one to determine the LEC's relevant to strange magnetism.…”

Strange meson–nucleon states in the quark potential model

“…The puzzle of (1405) came from the obvious discrepancy between the downward shift of the 1S level of the kaonic hydrogen atom which was determined from the measurement of atomic x-rays [10][11][12] and the upward shift measured from lowenergy KN scattering [13]. Although the discrepancy itself has been resolved recently by elaborate measurement of x-rays from the atom with an upward shift of the 1S level [14,15], how to understand the nature of the state has not reached its last word yet. The state seems to be able to be interpreted as an elementary baryon, i.e., a three-quark state belongs to the 70 − multiplet, a meson-baryon composite being a KN bound state or a π resonance, or a five-quark bound state.…”