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Eef van Beveren

Publications and source records attributed to Eef van Beveren.

102 records · Page 6Linked to original sources
arXiv2002

Remarks on the f_0(400-1200) scalar meson as the dynamically generated chiral partner of the pion

The quark-level linear sigma model is revisited, in particular concerning the identification of the f_0(400-1200) (or σ(600)) scalar meson as the chiral partner of the pion. We demonstrate the predictive power of the linear sigma model through the pi-pi and pi-N s-wave scattering lengths, as well as several electromagnetic, weak, and strong decays of pseudoscalar and vector mesons. The ease with which the data for these observables are reproduced in the linear sigma model lends credit to the necessity to include the sigma as a fundamental q\bar{q} degree of freedom, to be contrasted with approaches like chiral perturbation theory or the confining NJL model of Shakin and Wang.

hep-ph↗
arXiv2002

Scalar Mesons within a model for all non-exotic mesons

We describe a four-parameter model for non-exotic meson-meson scattering, which accommodates all non-exotic mesons, hence also the light scalar mesons, as resonances and bound states characterised by complex singularities of the scattering amplitude as a function of the total invariant mass. The majority of the full $S$-matrix mesonic poles stem from an underlying confinement spectrum. However, the light scalar mesons K0*(830), a0(980), f0(400-1200), and f0(980) do not, but instead originate in 3P0-barrier semi-bound states. In the case of bound states, wave functions can be determined. For ccbar and bbbar, radiative transitions have been calculated. Here we compare the results to the data.

hep-ph↗
arXiv2001

Comment on Intrinsic and dynamically generated scalar meson states

The scalar-meson assignments of Shakin and Wang in a generalized Nambu--Jona-Lasinio model are contradicted by recent experimental information. Also the strict distinction made by these authors between ``intrinsic'' and ``dynamically generated'' states is contested, as well as a number of other statements.

hep-ph↗
arXiv2001

Modified Breit-Wigner formula for mesonic resonances describing OZI decays of confined $q\bar{q}$ states and the light scalar mesons

A general expression resembling Breit-Wigner formulae is derived for the description of resonances which appear in meson-meson scattering. Starting point is a unitarised meson model, but reduced to a simpler form and freed from the specific assumption about the confining force. The parameters of the resulting ``Resonance-Spectrum Expansion'' are directly related to the confinement spectrum and the mechanism of $^3P_0$ valence-quark-pair creation for OZI-allowed hadronic decay, and not to the central positions and widths of resonances. The method also provides a straightforward explanation for the origin of the light scalar mesons without requiring extra degrees of freedom.

hep-ex↗
arXiv2001

Identifying the quark content of the isoscalar scalar mesons f_0(980), f_0(1370), and f_0(1500) from weak and electromagnetic processes

The assignments of the isoscalar scalar mesons f0(980), f0(1370), and f0(1500) in terms of their qqbar substructure is still a matter of heated dispute. Here we employ the weak and electromagnetic decays D(s)(+) to f0+pi(+) and f0 two-photon decays, respectively, to identify the f0(980) and f0(1500) as mostly ssbar, and the f0(1370) as dominantly nonstrange, in agreement with previous work. The two-photon decays can be satisfactorily described with quark as well as with meson loops, though the latter ones provide a less model-dependent and more quantitative description.

hep-ph↗
arXiv2001

Why the f(0)(980) is mostly ssbar

We exploit the W-emission process to study the measured weak decay of the D(s,+)(1.9686) meson into f(0)(980) and a positively charged pion. We conclude that the scalar f(0)(980) meson contains mostly strange-antistrange flavors, which is supported by different model studies.

hep-ph↗
arXiv2001

The pionic width of the $ω(782)$ meson within a well-defined, unitary quantum field theory of (anti-)particles and (anti-)holes

We investigate the indirect generation of the partial width of the $ω(782)$ meson with respect to the reaction $ω(782) \to ρ(770) π\toπ^+π^-π^0$ within the context of a ``Unitary Effective Resonance Model'' (UERM), which has previously been applied to resonant fermionic field operators, here extended to scalar, pseudoscalar and vector bosonic fields. The $ω(782)$ meson is described by a (quasi-)real field, while the intermediate $ρ(770)$ meson is considered to be a resonant degree of freedom, which can be treated consistently within the UERM. In the limit of an infinitesimal width (imaginary part of self-energy), the UERM yields a consistent treatment of relativistic quantum field theory (QFT). Some aspects of the UERM of (anti-)particles and (anti-)holes are discussed.

hep-ph↗
arXiv2001

On the dominance of non-exotic meson-meson scattering by s-channel qqbar confinement states and the classification of the scalar mesons

Non-exotic scalar-meson resonances in S-wave meson-meson scattering are studied in the light of a unitarised Schroedinger model. The resulting poles in the scattering matrices, by analytical continuation into the complex-energy plane, are grouped into nonets of isoscalar, isodoublet, and isotriplet resonances. All singularities can be related to quark-antiquark confinement states, the light-quark nonet of which has ground states at 1.3 to 1.4 GeV and level spacings of some 300-400 MeV, except for a nonet of light scalar mesons below 1 GeV. All non-exotic S-wave resonances reported by experiment fit into this scheme.

hep-ph↗
arXiv1999

Scalar mesons as simple quark+antiquark states

The Nijmegen Unitarized Meson Model and its application to scalar mesons is briefly revisited. It is shown that all scalar states up to 1.5 GeV can be described as triplet-P-zero quark+antiquark states coupled to the OZI-allowed open and closed two-meson channels consisting of pseudoscalar and vector mesons. Crucial are the manifestation of a resonance-doubling phenomenon, typical for strong S-wave decay, and the employment of truly flavor-symmetric coupling constants. Also S-wave meson-meson scattering is thus reasonably well described, without any parameter fit.

hep-ph↗
arXiv1999

Comment on ``Understanding the scalar meson quark-antiquark nonet''

It is shown that the incomplete scalar meson nonets found by Toernqvist (T) and Toernqvist and Roos (TR), employing a new version of the Helsinki unitarised quark model, should in fact be complete, including an as yet unconfirmed light K*0 below 1 GeV (old kappa) and the established f0(1500). A detailed comparison is presented with the predictions of the Nijmegen unitarised meson model, in which two complete scalar nonets show up below 1.5 GeV. The reason for the flavour-nonet breaking found in T and TR we argue to originate in the use of coupling constants for the three-meson vertex which are not independent of flavour. Also some statements made by Toernqvist are critically reviewed.

hep-ph↗
arXiv1999

Flavour symmetry of mesonic decay couplings

We present flavour-symmetric results for the couplings of quark-antiquark systems to meson-meson channels in the harmonic-oscillator expansion. We tabulate their values for all possible open and closed decay channels of pseudo-scalar, vector and scalar mesons. We compare the predictions of a model that employs these flavour-symmetric couplings, both with the results of a model which uses explicitly flavour-dependent couplings, and with experiment.

hep-ph↗