arXiv subjects

Fu-Guang Cao

Publications and source records attributed to Fu-Guang Cao.

24 records · Page 2Linked to original sources

arXiv1998

Electromagnetic Transition Form Factor of Pseudoscalar Meson and $η-η'$ Mixing

The electromagnetic transition form factors of $η$ and $η'$ are calculated in the light-cone perturbation theory. We show that it is unreliable to determine the η-\etap'$ mixing angle without any additional normalization conditions other than their decay widthes to two photons. The possible intrinsic $c\bar{c}$ component in the flavor singlet is investigated. The heavy quark pair has distinct properties from the light ones in electromagnetic transition processes of pseudoscalar mesons. It is possible to explore the size of $c\bar{c}$ component and our numerical results disfavor a large portion of $c\bar{c}$ component.

hep-ph↗

arXiv1998

Twist-3 contribution to the pion electromagnetic form factor

Non-leading contribution to the pion electromagnetic form factor which comes from the pion twist-3 wave function is analyzed in the modified hard scattering approach (MHSA) proposed by Li and Sterman. This contribution is enhanced significantly due to bound state effect (the twist-3 wave function is independent of the fractional momentum carried by the parton and has a large factor $\sim m_π^2/m_0$ with $m_π$ being the pion meson mass and $m_0$ being the mean u- and d-quark masses). Consequently, although it is suppressed by the factor $1/Q^2$, the twist-3 contribution is comparable with and even larger than the leading twist (twist-2) contribution at intermediate energy region of $Q^2$ being $2 \sim 40 {GeV}^2$.

hep-ph↗

arXiv1997

Large corrections to asymptotic $F_{η_c γ}$ and $F_{η_b γ}$ in the light-cone perturbative QCD

The large-$Q^2$ behavior of $η_c$-$γ$ and $η_b$-$γ$ transition form factors, $F_{η_cγ}(Q^2)$ and $F_{η_bγ}(Q^2)$ are analyzed in the framework of light-cone perturbative QCD with the heavy quark ($c$ and $b$) mass effect, the parton's transverse momentum dependence and the higher helicity components in the light-cone wave function are respected. It is pointed out that the quark mass effect brings significant modifications to the asymptotic predictions of the transition form factors in a rather broad energy region, and this modification is much severer for $F_{η_bγ}(Q^2)$ than that for $F_{η_cγ}(Q^2)$ due to the $b$-quark being heavier than the $c$-quark. The parton's transverse momentum and the higher helicity components are another two factors which decrease the perturbative predictions. For the transition form factor $F_{η_cγ}(Q^2)$, they bring sizable corrections in the present experimentally accessible energy region ($Q^2 \leq 10 GeV^2$). For the transition form factor $F_{η_bγ}(Q^2)$, the corrections coming from these two factors are negligible since the $b$-quark mass is much larger than the parton's average transverse momentum. The coming $e^+ e^-$ collider (LEP2) will provide the opportunity to examine these theoretical predictions.

hep-ph↗

arXiv1996

Saturation properties and liquid-gas phase transition of nucleus

Saturation properties and liquid-gas phase transition of nucleus are analysed in the framework of Hatree-Fock theory. We modify Hill-Wheller formula with a finite-size-effect parameter by fitting the zero-temperature properties of nucleus. Employing Gogny effective interaction and phenomenological expression of Coulomb energy, we give the critical temperature of liquid-gas phase transition of nucleus being about 12 MeV, which agrees with the result extracted from heavy-ion collision experiments. It is pointed out that a phenomenological formula of surface energy of hot nucleus is not avaliable in the region where nucleon density is far away from the normal density.

nucl-th↗

arXiv1996

Transverse momentum dependence in the perturbative calculation of pion form factor

By reanalysing transverse momentum dependence in the perturbative calculation of pion form factor an improved expression of pion form factor which takes into account the transverse momentum dependenc in hard scattering amplitude and intrinsic transverse momentum dependence associated with pion wave functions is given to leading order, which is available for momentum transfers of the order of a few GeV as well as for $Q \to \infty$. Our scheme can be extended to evaluate the contributions to the pion form factor beyond leading order.

hep-ph↗

arXiv1996

The perturbative pion-photon transition form factors with transverse momentum corrections

We perform a perturbative QCD analysis of the quark transverse momentum effect on the pion-photon transition form factors $F_{πγ}$ and $F_{πγ^*}$ in the standard light-cone formalism, with two phenomenological models of wavefunction as the input of the non-perturbative aspect of the pion. We point out that the transverse momentum dependence in both the numerator and the denominator of the hard scattering amplitude is of the same importance and should be considered consistently. It is shown that after taking into account the quark transverse momentum corrections, the results obtained from different model wave function are consistent with the available experimental data at finite $Q^2$.

hep-ph↗