KLOE results on scalar and pseudoscalar mesons

The data collected by the KLOE Collaboration at the Frascati φ-factory DAФNE from 2001 to 2006 have been used for extensive studies in meson spectroscopy. The decays of the scalar mesons a0（980） and f0（980） into two pseudoscalar mesons have been exploited to measure the relevant parameters of those resonances. The radiative decays φ →ηγ and η＇γ have been used for the determination of the pseudoscalar mixing angle and to search for a possible gluonium content in the η＇. The dynamics of the η → 3π decay has been studied and the Dalitz Plot parameters have been measured. The large amount of η mesons produced allowed also to study interesting rare η decays.

Leptonic Decays of Heavy Vector and Pseudoscalar Mesons

Pure leptonic decays of D~*0)(B_^(*s),B_d~*)→l^+l^- and D^(±*)(D_s~*,B^(*+),B_c~*)→lν_l are investigated.The hadronic contributions such as D^0→D^(*0)γ→μ^+μ^- are also explored.We then obtain the updated branching fractions of the pseudoscalar mesons to lepton pairs are modified by a factor of few percentages.Specifically,the Br(B+→e^+ν_e)is reduced by a factor 13%.

Study on the Effects of the Light CP-odd Higgs via the Leptonic Decays of Pseudoscalar Mesons

To explain the anomALously large decay rate of ∑＋→p＋μ＋μ-, it was proposed that a new mechanism where a light CP-odd pseudoscaJar boson of mAo = 214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π0→e＋e- and γ→γA10 in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of ∑＋→p＋μ＋μ- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π0→e＋e-;η（η′）→μ＋μ-;ηc→μ＋μ-;ηb→τ＋τ- within the same framework. It is noted that for π0→ e＋ e-, the standard model （SM） prediction is smaller than the data, whereas the experimental central value of η→μ＋μ- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would cheek if we can obtain a univers mass for A10 which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible conclude that the phenomenology does not favor such a to have such a mass with the same coupling｜gt｜. Therefore we light A10, even though a small window is still open.

Light axion-like particles and the pseudoscalar mesonic decays M→M′vv

The axion-like particle(ALP)is one kind of the best-motivated new particles.We consider its production from the pseudoscalar mesonic decays M→M′a,with M being a pseudoscalar meson B or K.The upper limits on the flavor-conserving ALP–quark coupling parameter guare obtained by assuming the ALP to be an invisible particle.We find that the most severe constraint on gucomes from the decay K^(+)→π^(+)vv for 0.05 Ge V≤M_(a)≤0.35 Ge V,while the decays B^(+,0)→K^(+,0)vvand B^(+,0)→π^(+,0)υvcan also generate significant constraints.

Measurements of the γγ＊ → π^0 and γγ＊ → ηc transition form factors at BABAR

We present measurements of the γγ＊ → π^0 transition form factor for the momentum transfer range Q^2=4-40 GeV^2 and the γγ＊ → ηc transition form factor for the range Q^2=2-50 GeV^2. The current status of measurements of the meson-photon transition form factors for the η and η＇ mesons is discussed. The results of the measurement of the ηc mass, total and two-photon widths are also presented.

Radial excitation states of η and η′ in the chiral quark model

A chiral quark model is applied to calculate the spectra of pseudoscalar mesons η and η . By analyzing the obtained spectra, we find that the mesons η （2 1 S 0 ）, η（4 1 S 0 ）, η （3 1 S 0 ） and η （4 1 S 0 ） are the possible candidates of η（1760）, X（1835）, X（2120） and X（2370）. The strong decay widths of these pseudoscalars to all the possible two-body decay channels are calculated within the framework of the 3 P 0 model. Although the total width of η （21S0 ） is compatible with the BES Collaboration＇s experimental value for η（1760）, the partial decay width to ωω is too small, which is not consistent with the BES result. If X（1835） is interpreted as η（4 1 S 0 ）, the total decay width is compatible with the experimental data, and the main decay modes will be πa 0 （980） and πa 0 （1450）, which needs to be checked experimentally. The assignment of X（2120） and X（2370） to η （31S0 ） and η （41S0 ） is disfavored in the present calculation because of the incompatibility of the decay widths.

γγ interactions with KLOE

Studies of γγ interactions are performed with the KLOE detector, without tagging of the outgoing e^＋e^-. The data sample is from an integrated luminosity of 240 pb^-1. It was collected at the φ-factory DAONE with e^＋e^- beams colliding at √s ≌1 GeV, below the φ resonance peak. We present preliminary results concerning the observation of the γγ→η process and the evidence for γγ→π^0π^0 production at low π^0π^0 invariant masses.

Glueball spectrum from Nf=2 lattice QCD study on anisotropic lattices

The lowest-lying glueballs are investigated in lattice QCD using Nf = 2 clover Wilson fermions on anisotropic lattices. We simulate at two different and relatively heavy quark masses, corresponding to physical pion masses of mπ～938 MeV and 650 MeV. The quark mass dependence of the glueball masses has not been investigated in the present study. Only the gluonic operators built from Wilson loops are utilized in calculating the corresponding correlation functions. In the tensor channel, we obtain the ground state mass to be 2.363（39） GeV and 2.384（67）GeV at mπ～938 MeV and 650 MeV, respectively. In the pseudoscalar channel, when using the gluonic operator whose continuum limit has the form of ∈_ijkTrB_iD_jB_k, we obtain the ground state mass to be 2.573（55） GeV and 2.585（65） GeV at the two pion masses. These results are compatible with the corresponding results in the quenched approximation. In contrast, if we use the topological charge density as field operators for the pseudoscalar, the masses of the lowest state are much lighter（around 1 GeV） and compatible with the expected masses of the flavor singlet qq meson. This indicates that the operator ∈ijk TrBiDjBk and the topological charge density couple rather differently to the glueball states and qq mesons. The observation of the light flavor singlet pseudoscalar meson can be viewed as the manifestation of effects of dynamical quarks. In the scalar channel, the ground state masses extracted from the correlation functions of gluonic operators are determined to be around 1.4-1.5 GeV, which is close to the ground state masses from the correlation functions of the quark bilinear operators. In all cases, the mixing between glueballs and conventional mesons remains to be further clarified in the future.