arXiv subjects

Eef van Beveren

Publications and source records attributed to Eef van Beveren.

At least 91 records · Page 5Linked to original sources

arXiv2005

Complex Meson Spectroscopy

We do meson spectroscopy by studying the behavior of S-matrix poles in the complex-energy plane, as a function of the coupling strength for triplet-P-zero quark-pair creation. Thereto, a general formula for non-exotic hadron-hadron scattering involving arbitrary quark confinement is used, which can be applied to all flavors. We find two distinct types of poles, which we call "confinement" and "continuum" poles, respectively. Together, they suffice to understand the experimental meson spectrum.

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arXiv2005

From the Kappa via the Ds0*(2317) to the chi_c0: connecting light and heavy scalar mesons

Pole trajectories connecting light and heavy scalar mesons, both broad resonances and quasi-bound states, are computed employing a simple coupled-channel model. Instead of varying the coupling constant as in previous work, quark and meson masses are continuously changed, so as to have one scalar meson evolve smoothly into another with different flavor(s). In particular, it is shown, among several other cases, how the still controversial K0*(800) turns into the established chi_c0, via the disputed D_s(2317). Moreover, a chi'_c0(3946) is predicted, which may correspond to the recently observed Y(3943) resonance. These results lend further support to our unified dynamical picture of all scalar mesons, as unitarized q-qbar states with important two-meson components.

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arXiv2004

Scalar mesons and Adler zeros

A simple unitarized quark-meson model, recently applied with success to light and charmed scalar mesons, is shown to encompass Adler-type zeros in the amplitude, due to the use of relativistic kinematics in the scattering sector. These zeros turn out to be crucial for the description of the $K_0^*$(800) resonance, as well as the new charmed scalar mesons $D_{s0}^*$(2317) and $D_0^*$(2300). ~

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arXiv2004

CP Violation and $ΔI=1/2$ Enhancement for $K \to ππ$, $K \to ππγ$ Weak Decays

Data indicate that $ΔI=1/2$ transitions account for 4.5-4.7% of both CP conserving and CP violating $K \to 2π$ decays, as well as CP conserving radiative $K \to ππγ$ processes. Observed $K \to ππγ/ππ$ branching ratios are shown to scale near $α/π$ or $α/2π$. The $K_L$-$K_S$ mixing angle $ϕ$ and the semileptonic weak-rate asymmetry $δ$ are reviewed, and theory is shown to be consistent with data. Also, $K \to 2π$ $ΔI=1/2$ dominance is studied in the context of the chiral constituent quark model, displaying again excellent agreement with data. Finally, indirect and direct kaon CP violation are successfully described in the framework of photon-mediated loop graphs. This suggests that kaon CPV can be understood via second-order weak transitions, radiatively corrected.

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arXiv2004

Multichannel calculation for Ds* vector states and the Ds(2632) resonance

We study bound states below threshold and resonances above threshold in the D0-K+ and Ds-eta systems, using a many-coupled-channel model for non-exotic meson-meson scattering applied to states with the quantum numbers of c-sbar quark-antiquark vector mesons. We fit the ground state at 2.112 GeV, whence the lowest resonances in D0-K+ come out at 2.61, 2.72, 3.03, and 3.08 GeV. The resonance at 2.61 GeV acquires a width of about 8 MeV, while its partial P-wave cross section is up to six times larger in Ds-eta than in D0-K+, provided a mechanism accounting for Okubo-Zweig-Iizuka--forbidden decays is included. The latter finding is in agreement with the observations of the SELEX collaboration with respect to the recently reported DsJ(2632) resonance. Therefore, we conclude that the DsJ(2632) is most probably the first recurrence excitation of the Ds*(2112) meson.

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arXiv2004

Classification of the scalar mesons: a strange pole expedition into charm and beauty territory

The classification of scalar and vector mesons is reviewed within the framework of the Resonance-Spectrum Expansion (RSE). This method allows a simple and straightforward description of non-exotic meson-meson scattering, incorporating the effects of quark confinement and OZI-allowed decay in a fully nonperturbative way. Results for resonances and bound states are compared to experiment, on the basis of computed pole positions and cross sections. New predictions for open-charm and -bottom scalar mesons are presented. Concretely, observed vector states for u-ubar/d-dbar, s-sbar, c-cbar, and b-bbar are reproduced, and others are predicted. In the light scalar sector, the now established two nonets, one below 1 GeV and one in the region 1.3 - 1.5 GeV, are easily described, through the appearance of extra poles in the scattering matrix. The recently found Ds0*(2317) meson is accurately reproduced by the same mechanism, as a quasi-bound state in the coupled c-sbar/DK system. In S-wave D-pion and B-pion scattering, new resonances are foreseen close to threshold, i.e., a D0* at 2.16(+-0.05) GeV some 250 MeV wide, and a B0* at 5.47(+-0.05) GeV with a width of about 50 MeV. Additional predictions concern the existence of b-sbar and b-cbar scalar mesons, stable with respect to OZI-allowed decay to BK and BD, respectively, namely at 5.61(+-0.05) GeV resp. 6.64(+-0.05) GeV.

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arXiv2003

Nonperturbative scalar-meson resonances with open charm and beauty

We predict several new bound states and resonances for B-pion, B-Kaon, and B-D S-wave elastic scattering, within the same model which was recently employed to explain the D*sJ(2317)+ meson. In the charm-nonstrange sector we find a (virtual ?) bound state close to the B-pion threshold, and moreover two nearby resonances of comparable width in the range 5.9 to 6.1 GeV. We obtain bound states B*s0(5570) in b-sbar and B*c0(6490) in bbar-c, as well as resonances at higher energies. No JP=0+ states are found at 5.6 GeV (in bbar-u/d), at 5.7 GeV (in b-sbar), or at 6.1 GeV (in bbar-c), where they are predicted from pure confinement.

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arXiv2003

Ground-State Scalar $\bar{q}q$ Nonet: SU(3) Mass Splittings and Strong, Electromagnetic, and Weak Decay Rates

By comparing SU(3)-breaking scales of linear mass formulae, it is shown that the lowest vector and scalar mesons all have a $\bar{q}q$ configuration, while the ground-state octet and decuplet baryons are $qqq$. Also, the quark-level linear $σ$ model is employed to predict similar $\bar{q}q$ and $qqq$ states. Furthermore, the approximate mass degeneracy of the scalar $a_0$(985) and $f_0$(980) mesons is demonstrated to be accidental. Finally, it is shown that various strong, electromagnetic, and weak mesonic decay rates are successfully explained within the framework of the quark-level linear $σ$ model.

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arXiv2003

W-boson unitarity effects and oscillations in the neutral Kaon system

We study the effects on oscillations in the neutral-Kaon system from lepton and hadron self-energy loops in the W-boson propagators. The corresponding W box diagrams are evaluated by attaching the external quark lines to covariant vertex functions for the composite Kaons, integrating over all off-shell momenta. We find that the ratio of the imaginary and real parts of the amplitude is of the same size as with the experimental value of the modulus of the CP-violating parameter epsilon.

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arXiv2003

Continuum bound states K-long, D_{1}(2420), D_{s1}(2536) and their partners K-short, D_{1}(2400), D*_{sJ}(2463)

The very recently observed $D^{\ast}_{sJ}(2463)$ meson is described as a $J^{P}=1^{+}$ $c\bar{s}$ bound state in a unitarised meson model, owing its existence to the strong OZI-allowed $^{3}P_{0}$ coupling to the nearby $S$-wave $D^{\ast}K$ threshold. By the same non-perturbative mechanism, the narrow axial-vector $D_{s1}(2536)$ resonance shows up as a quasi-bound-state partner embedded in the $D^{\ast}K$ continuum. With the same model and parameters, it is also shown that the preliminary broad $1^{+}$ $D_{1}(2400)$ resonance and the established narrow $1^{+}$ $D_{1}(2420)$ may be similar $c\bar{n}$ partners, as a result of the strong OZI-allowed $^{3}P_{0}$ coupling to the nearby $S$-wave $D^{\ast}π$ threshold. The continuum bound states $D_{1}$(2420) and $D_{s1}(2536)$ are found to be mixtures of 33% $^{3}P_{1}$ and 67% $^{1}P_{1}$, whereas their partners $D_{1}(2400)$ and $D^{\ast}_{sJ}(2463)$ have more or less the opposite $^{2S+1}P_1$-state content, but additionally with some $D^{\ast}π$ or $D^{\ast}K$ admixture, respectively. The employed mechanism also reproduces the ratio of the $K_{L}$-$K_{S}$ mass difference and the $K_{S}$ width, by describing $K_{L}$ as a bound state embedded in the $ππ$ continuum. The model's results for $J^{P}=1^{+}$ states containing one $b$ quark are also discussed.

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arXiv2003

Observed D_s(2317) and tentative D(2100-2300) as the charmed cousins of the light scalar nonet

The very recently observed D^*_{sJ}(2317)^+ meson is described as a quasi-bound scalar c\bar{s} state in a unitarized meson model, owing its existence to the strong ^3P_0 OZI-allowed coupling to the nearby S-wave DK threshold. By the same mechanism, a scalar D_0(2100-2300) resonance is predicted slightly above the Dπthreshold. These scalars are the charmed cousins of the light scalar nonet f_0(600), f_0(980), K^*_0(800), and a_0(980), reproduced by the same model. The standard c\bar{n} and c\bar{s} charmed scalars D_{0} and D_{s0}, cousins of the scalar nonet f_0(1370), f_0(1500), K_0^*(1430), and a_0(1450), are predicted to lie at about 2.64 and 2.79 GeV, respectively, both with a width of some 200 MeV.

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arXiv2003

Threshold behavior of scattering poles

The results of a model for meson-meson scattering are studied. The model is shown to be capable of on the one hand reproducing the scattering data, while on the other hand a quark-antiquark confinement spectrum can be determined. It is concluded that adopting the model's formulation of the transition matrix elements for data analysis, it may serve as a link between experiment and quenched lattice calculations.

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arXiv2003

Explaining the Ds(2317)

The recently observed Ds(2317) meson is explained as a scalar c+anti-s system which appears as a bound state pole, below threshold, in the DK scattering amplitude. The standard c+anti-s charmed scalar D_{s0} is found at about 2.9 GeV, with a width of some 150 MeV. For the scattering length of DK in S wave we predict 5+-1 1/GeV.

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arXiv2003

Reconciling the Light Scalar Mesons with Breit-Wigner Resonances as well as the Quark Model

Resonances appearing in hadronic scattering processes are described by a two-phase model. In the one phase, scattering products are observed, whereas the other phase describes confinement. A so-called ``Resonance-Spectrum Expansion'' is derived, containing expressions that resemble Breit-Wigner formulae. This method also provides a straightforward explanation for the origin of the light scalar mesons without requiring extra degrees of freedom.

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arXiv2002

Relativistic Unitarized Quark/Meson Model in Momentum Space

An outline is given how to formulate a relativistic unitarized constituent quark model of mesons in momentum space, employing harmonic quark confinement. As a first step, the momentum-space harmonic-oscillator potential is solved in a relativistically covariant, three-dimensional quasipotential framework for scalar particles, using the spline technique. Then, an illustrative toy model with the same dynamical equations but now one $q\bar{q}$ and one meson-meson channel, coupled to one another through quark exchange describing the $^3P_0$ mechanism, is solved in closed form on a spline basis. Conclusions are presented on how to generalize the latter to a realistic multichannel quark/meson model.

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arXiv2002

The light scalar mesons within quark models

Low-energy meson-meson scattering data are a powerful testing ground for quark models. Here, we describe the behaviour at threshold of S-wave scattering-matrix singularities. The majority of the full scattering-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. We show that the behaviour of the corresponding poles is identical at threshold. In passing, the light-meson sector is given a firm basis.

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arXiv2002

Meson Form Factors and the Quark-Level Linear Sigma Model

The quark-level linear sigma model is employed to compute a variety of electromagnetic and weak observables of light mesons, including pion and kaon form factors and charge radii, charged-pion polarizabilities, semileptonic weak $K_{\ell3}$ decay, semileptonic weak radiative pion and kaon form factors, radiative decays of vector mesons, and nonleptonic weak $K_{2π}$ decay. The agreement of all these predicted observables with experiment is striking. In passing, the tight link between the linear sigma model and vector-meson dominance is shown. Some conclusions are drawn on the linear sigma model in connection with lattice and renormalization-group approaches to QCD.

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arXiv2002

Behaviour of S-Wave poles Near Threshold and the Scalar Meson Nonet Below 1 GeV

We describe the behaviour at threshold of S-wave poles of the scattering matrix within a four-parameter model for non-exotic meson-meson scattering. This model 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. We show that the behaviour of the corresponding poles is identical at threshold.

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