Determination of radiative widths of scalar mesons from experimental results on \gamma\gamma\to\pi\pi

The scalar mesons in the 1 GeV region constitute the Higgs sector of the strong interactions. They are responsible for the masses of all light flavour hadrons. However, the composition of these scalar states is far from clear, despite decades of experimental effort. The two photon couplings of the 's are a guide to their structure. Two photon results from Mark II, Crystal Ball and CELLO prompt a new Amplitude Analysis of , cross-sections. Despite their currently limited angular coverage and lack of polarized photons, we use a methodology that provides the nearest one can presently achieve to a model-independent partial wave separation. We find two distinct classes of solutions. Both have very similar two photon couplings for the and . Hopefully these definitive results will be a spur to dynamical calculations that will bring us a better understanding of these important states. Received: 10 Decmeber 1998 / Published online: 27 April 1999     

The photon structure and exclusive production of vector mesons in \gamma\gamma collisions

The process of exclusive vector meson production, , is studied for almost real photons. This process may be reduced to the photoproduction of off the meson. We discuss the possibility of extracting the gluon distribution of and of the photon from such a measurement. Predictions are also given for the reaction for various cms energies typical for LEP and for the future linear colliders. Received: 13 December 2000 / Revised version: 6 January 2001/ Published online: 6 April 2001     

Model of scalar mesons

A model containing a nonet of scalar mesonsS, a nonet of pseudoscalar mesonsP, and a nonet of baryons is constructed where the mesons enter in the form of the matrixM=e^i(S+iP), Several Lagrangians are introduced such that the mesons get their physical masses, and the decay widths of the scalar mesons are calculated. The model satisfies generalized PCAC. It is found that the coupling constants of the mesonsε(700) andε′(1060) to pions and nucleons satisfy the relations: $$\frac{{|G_{\varepsilon NN} |}}{{|G_{\varepsilon \pi \pi } |}} = 1 \cdot 4,\frac{{|G_{\varepsilon 'NN} |}}{{|G_{\varepsilon '\pi \pi } |}} = 0 \cdot 89,\frac{{|G_{\varepsilon \pi \pi } G_{\varepsilon NN} |}}{{4\pi }} = 4 \cdot 9,{\text{and}}\frac{{|G_{\varepsilon '\pi \pi } G_{\varepsilon 'NN} |}}{{4\pi }} = 0 \cdot 34.$$      

Scalar mesons and scalar gluonium

We investigate the mixing of scalar mesons (S ^*, ?) with gluonium in the context of a potential model. We calculate the masses of the scalars and the branching ratios to ππ,KK, ηη and ηη′. The model can accomodate the stateG(1.59) and explain its peculiar rates. We also investigate other possibilities for gluonium mass and branching ratios and find that a gluonium state around 1 GeV may explain the unusual branching ratios in the scalar sector.     

Elementary scalar mesons and Regge poles

We show, for the annihilation amplitude of π⁺π^? → two vector mesons, that parity conservation and rotational symmetry demand the existence of a triplet of Regge singularities crossing at t = 0. In the usual scalar-vector field theory, calculations of the leading terms of this amplitude up to the eight order show that these singularities are moving Regge poles. Contrary to common belief, the elementary scalar meson lies on one of them.     

Light vector mesons

This article reviews the current status of experimental results obtained in the measurement of light vector mesons produced in proton-proton and heavy ion collisions at different energies. The review is focused on two phenomena related to the light vector mesons; the modification of the spectral shape in search of chiral symmetry restoration and suppression of the meson production in heavy ion collisions. The experimental results show that the spectral shape of light vector mesons are modified compared to the parameters measured in vacuum. The nature and the magnitude of the modification depends on the energy density of the media in which they are produced. The suppression patterns of light vector mesons are different from the measurements of other mesons and baryons. The mechanisms responsible for the suppression of the mesons are not yet understood. Systematic comparison of existing experimental results points to the missing data which may help to resolve the problem.     

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.     

KLOE results on scalar and pseudoscalar mesons

The data collected by the KLOE Collaboration at the Frascati φ-factory DAΦNE 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 ηγ 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.     

D decays into pseudoscalar and scalar mesons

Zeitschrift für Physik C Particles and Fields - In this paper, we study the pseudoscalar-scalar meson (PS) weak decays ofD-mesons in the non-relativistic quark model using factorization...     

Soliton bag model with scalar mesons

We propose a soliton bag model with scalar mesons which is a modification of the simple soliton bag model and the linear sigma model. Our model can give comparatively large quark mass, so that it is applicable to low energy scattering. We have solved the Euler-Lagrange equations in the mean-field approximation for the hedgehog baryon state. The static properties of the nucleon is calculated by a projection method. Our results are in reasonable agreement with the observed values.     

Production of vector and tensor mesons in proton-proton collisions at\sqrt s = 52.5 GeV

Inclusive production of ?⁰,f, andg ⁰ mesons and ofK _s ⁰ ,K ^*0 (892), ? andK ^*0(1430)mesons has been measured at <y>～2.6 and <p _T >～1.1 GeV/c in proton-proton interactions at \(\sqrt s = 52.5\) GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp _T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.