We estimate the valence quark contributions for the gamma* Y -> Lambda* (Y=Lambda, Sigma0) electromagnetic transition form factors. We focus particularly on the case Lambda*=Lambda(1670) as an analog reaction with gamma* N -> N(1535). The results are compared with those obtained from chiral unitary model, where the Lambda* resonance is dynamically generated and thus the electromagnetic structure comes directly from the meson cloud excitation of the baryon ground states. The form factors for the case Y=Sigma0 in particular, depend crucially on the two real phase (sign) combination, a phase between the Lambda and Lambda* states, and the other, the phase between the Lambda and Sigma0 radial wave functions. Depending on the combination of these two phases, the form factors for the gamma* Sigma0 -> Lambda* reaction can be enhanced or suppressed. Therefore, there is a possibility to determine the phase combination by experiments.
Valence quark and meson cloud contributions to the $γ^\ast N \to N^\ast(1520)$ form factors
将协变旁观夸克模型应用于$γ^\ast N \to N^\ast(1520)$反应。利用大平方动量转移$Q^2$的实验数据标定了$N^\ast(1520)$波函数的协变结构，估算了价夸克对电磁形状因子和螺旋度跃迁振幅的贡献.模型结果和实验数据之间的差异，然后使用参数化的低$Q^2$的行为，介子云效应被假定为占主导地位。这种参数化对于今后的反应研究以及将过渡形状因子扩展到类时区域是非常有用的。
A local coupled-channels Kbar N-pi Sigma-pi Lambda potential is constructed, equivalently reproducing the scattering amplitude in chiral SU(3) dynamics. By analyzing the wave function of the Lambda(1405), we show the Kbar N dominance of the upper pole within the two-pole structure of the Lambda(1405). The resulting potential will be useful for investigating Kbar few-nucleon systems including their coupled channels.
In order to investigate the tomographical structure of light pseudoscalar mesons, particularly, pion and kaon, we study the valence quark distribution function (PDF) and the generalized parton distributions (GPDs) using light-cone quark model (LCQM).
This is the first study on the double-gluon hybrid, which consists of one valence quark and one valence antiquark together with two valence gluons. We concentrate on the one with the exotic quantum number $J^{PC} = 2^{+-}$ that conventional $\bar q q$ mesons can not reach. We apply QCD sum rule method to evaluate its mass to be $2.26^{+0.20}_{-0.25}$ GeV, and study its possible decay patterns. Especially, its three-meson decay patterns are generally not suppressed severely compared to two-meson decay patterns, so the $S$-wave three-meson decay channels $f_1ωπ/f_1ρπ$ can be useful in identifyin…
We use light-front Holography to estimate the valence quark and the meson cloud contributions to the nucleon axial form factor. The free couplings of the holographic model are determined by the empirical data and by the information extracted from lattice QCD. The holographic model provides a good description of the empirical data when we consider a meson cloud mixture of about 30\% in the physical nucleon state. The estimate of the valence quark contribution to the nucleon axial form factor compares well with the lattice QCD data for small pion masses. Our estimate of the meson cloud contribut…
The structure of the nucleon and the first radial excitation of the nucleon, the Roper, $N(1440)$, is studied within the formalism of Light-Front holography. The nucleon elastic form factors and $γ^\ast N \to N(1440)$ transition form factors are calculated under the assumption of the dominance of the valence quark degrees of freedom. Contrary to the previous studies, the bare parameters of the model associated with the valence quark are fixed by the empirical data for large momentum transfer ($Q^2$) assuming that the corrections to the three-quark picture (meson cloud contributions) are suppre…
We study the influence of non-valence quark-pair contributions in weak transition form factors of heavy-light mesons. Form factors are first calculated for spacelike momentum transfers in a reference frame where such contributions are suppressed. Analytic continuation to the timelike region and a comparison with the direct decay calculation, done with pure valence degrees of freedom, provides an estimate of the role that quark-pair contributions may play. We use the point form of relativistic quantum mechanics, which is particularly useful when treating heavy-light systems.
In-medium valence-quark distributions of $π^+$ and $K^+$ mesons in symmetric nuclear matter are studied by combining the Nambu--Jona-Lasinio model and the quark-meson coupling model. The in-medium properties of the current quarks, which are used as inputs for studying the in-medium pion and kaon properties in the Nambu--Jona-Lasinio model, are calculated within the quark-meson coupling model. The light-quark condensates, light-quark dynamical masses, pion and kaon decay constants, and pion- and kaon-quark coupling constants are found to decrease as nuclear density increases. The obtained valen…
We study the leading-twist time-reversal even transverse momentum dependent parton distribution functions (TMDs) of light and heavy vector mesons, i.e., the $ρ$, $J/ψ$ and $Υ$. We employ the leading Fock-state light front wave functions (LF-LFWFs) of $ρ$ and $J/ψ$ from our recent study, and supplement with $Υ$'s LF-LFWFs. These LF-LFWFs are extracted from dynamically solved Bethe-Salpeter wave functions. The vector meson TMDs are then studied with the light front overlap representation at leading Fock-state. All the obtained TMDs are non-vanishing and evolve with current quark mass, in particu…
We study the mechanism of the weak decay process of Xi_b^0 into D^0 with a meson-baryon pair. It is shown that the dominant component of the prompt weak decay produces the meson-baryon pair with the spectator strange quark being transferred to the baryon, so that the Kbar N channel is absent. Subsequent final state interaction then reflects the pi Sigma originated Lambda(1405) formation amplitude, which has been difficult to access in previous experimental studies. We predict the line shapes of the pi Sigma invariant mass distribution using a realistic chiral meson-baryon amplitude for the fin…
Neutrino induced meson productions in forward limit
将PCAC假设应用到我们的动力学耦合通道模型中，研究了中微子诱导的介子产生。DCC模型合理地描述了共振区域中的π N，γ N -> π N，η N，K λ，K σ数据。我们给出了nu N -> pi N，pi pi N，eta N，K λ，K σ反应截面的预测.我们比较我们的结果与那些从Rein-Sehgal模型，并找到一个显着的差异。
Neutrino-induced meson productions off nucleon at forward limit in nucleon resonance region
研究了共振区中微子诱导的介子前向产生。我们的计算是基于一个动态耦合通道（DCC）模型，合理地描述了π（γ）N -> π N，η N，K λ，K σ数据的共振区。我们将PCAC假设应用到DCC模型中，将π N反应振幅与前向中微子反应振幅联系起来。用这种方法，我们给出了nu N -> pi N，pi pi N，eta N，K λ，K σ反应截面的预测.预测的nu N -> pi pi N，eta N，K λ，K σ截面，第一次，根据广泛的数据测试模型。我们比较了我们的结果与那些从Rein-Sehgal模型，已非常经常地使用在现有的Monte Carlo模拟器的中微子实验。我们发现它们之间存在显著差异。
Hadron masses are subject to few MeV corrections arising from QED interactions, almost entirely arising from the electric charge of the valence quarks. The QED effects include both self-energy contributions and interactions between the valence quarks/anti-quarks. By combining results from different signs of the valence quark electric charge we are able to isolate the interaction term which is dominated by the Coulomb piece, $\langle α_{\mathrm{QED}}e_{q_1}e_{\overline{q}_2}/r \rangle$, in the nonrelativistic limit. We study this for $D_s$, $η_c$ and $J/ψ$ mesons, working in lattice QCD plus qu…
We present our analysis on the valence quark distribution functions of the $K^{+}$ meson, $v^{K (u)} (x, Q^2)$ and $v^{K (\bar{s})} (x, Q^2)$, taking into account the meson cloud effects in the framework of the chiral constituent quark model. Assuming appropriate bare quark distribution functions at the initial scale, evaluating the Goldstone boson dressing corrections with the model, and performing the QCD evolution, one can obtain the realistic dressed distributions at a certain scale. The phenomenologically satisfactory valence quark distribution of the pion was obtained in the previous stu…
The Bethe-Salpeter equation is solved in the framework of unitary coupled-channel approximation by using the pseudoscalar meson-baryon octet interaction. The loop function of the intermediate meson and baryon is deduced in a dimensional regularization scheme, where the relativistic kinetic effect and off-shell corrections are taken into account. According to the experimental data at the $K^- p$ threshold, the subtraction constants in the loop function are determined. The squared amplitude is suppressed strongly and only one $Λ(1405)$ state is generated dynamically in the strangeness $S=-1$ and…
