Pole analysis on unitarized SU (3) × SU (3) one loop χPT amplitudes (3) chiral perturbation theory. By fitting phase shift and inelasticity data, we determine pole positions in different channels (f 0 (980), a 0 (980),f 0 (600), K * 0 (800), K * (892), ρ(770)) and trace their N c trajectories. We stress that a couple channel Breit-Wigner resonance should exhibit two poles on different Riemann sheets that reach the same position on the real axis when N c = ∞. Poles are hence classified using this criteria and we conclude that K * (892) and ρ(770) are unambiguous Breit-Wigner resonances. For scalars the situation is much less clear. We find that f 0 (980) is a molecular state rather than a Breit-Wigner resonance, while a 0 (980), though behaves oddly when varying N c , does maintain a twin pole structure.

We study the property of X(4260) resonance by re-analyzing all experimental data available, especially the e + e − → J/ψ π + π − , ωχc0 cross section data. The final state interactions of the ππ, KK couple channel system are also taken into account. A sizable coupling between the X(4260) and ωχc0 is found. The inclusion of the ωχc0 data indicates a small value of Γ e + e − = 23.30 ± 3.55eV. * 0 molecule [16-18], non-resonant explanation [19,20], etc.. Besides, the tetraquark state explanation is also very intersting [21-26], especially when two resonances, Z c (3900) and Z c (4025), are recently found in J/ψπ and D ( * )D( * ) channels in e + e − annihilation near 4.26GeV by BESIII Collaboration [27], and confirmed by Belle [28] and CLEO [29] Collaborations. However the open charm channels such asDD * , DD * , D * D * are not found in the final states of X(4260) decays [30][31][32], making the property of X(4260) to be more mysterious.The present authors have also studied the X(4260) issue in the previous edition of the present paper (Preprint arXiv:1206.6911v2, herewith denoted as V1). Through a careful analysis to experimental data available, it is found that the X(4260) has a sizable coupling to ωχ c0 channel, but not to other (nearby) channels. Inspired by our result, a recent experimental analysis [33,34] shows that there is indeed a sizable ωχ c0 final state signal in e + e − collision at around 4.26GeV,

We study, at leading order in the large number of colours expansion and within the Resonance Chiral Theory framework, the odd-intrinsic-parity e + e − → π + π − (π 0 , η) crosssections in the energy regime populated by hadron resonances, namely 3 m π < ∼ E < ∼ 2 GeV. In addition we implement our results in the Monte Carlo generator PHOKHARA 7.0 and we simulate hadron production through the radiative return method.

Amplitude Analysis of two photon production of $\pi\pi$ and ${\overline K}K$, using S-matrix constraints and fitting all available data, including the latest precision results from Belle, yields a single partial wave solution up to 1.4 GeV. The two photon couplings of the $\sigma/f_0(500)$, $f_0(980)$ and $f_2(1270)$ are determined from the residues of the resonance poles.Comment: 11 pages, 3 figures, extended for detail

We study the Sivers asymmetry in semi-inclusive hadron production in deep inelastic scattering. We concentrate on the contribution from the photon-gluon fusion channel at O(α 2 em αs), where threegluon correlation functions play a major role within the twist-3 collinear factorization formalism. We establish the correspondence between such a formalism with three-gluon correlation functions and the usual transverse momentum dependent (TMD) factorization formalism at moderate hadron transverse momenta. We derive the coefficient functions used in the usual TMD evolution formalism related to the quark Sivers function expansion in terms of the three-gluon correlation functions. We further perform the next-to-leading order calculation for the transverse-momentum-weighted spindependent differential cross section, and identify the off-diagonal contribution from the three-gluon correlation functions to the QCD collinear evolution of the twist-3 Qiu-Sterman function.