Hadrogenesis Conjecture Research Articles

On light vector mesons and chiral SU(3) extrapolations

A chiral extrapolation of the light vector meson masses in the up, down and strange quark masses of QCD is presented. We apply an effective chiral Lagrangian based on the hadrogenesis conjecture to QCD lattice ensembles of PACS-CS, QCDSF-UKQCD and HSC in the strict isospin limit. The leading orders low-energy constants are determined upon a global fit to the lattice data set. We use the pion and kaon masses as well as the size of the finite volume as lattice ensemble parameters only. The quark mass ratio on the various ensembles are then predicted in terms of our set of low-energy constants. An accurate reproduction of the vector meson masses and quark-mass ratios as provided by the lattice collaborations and the Particle Data Group (PDG) is achieved. Particular attention is paid to the ω−ϕ mixing phenomenon, which is demonstrated to show a strong quark mass dependence.

On the chiral expansion of vector meson masses

We study the chiral expansion of meson masses and decay constants using a chiral Lagrangian that was constructed previously based on the hadrogenesis conjecture. The one-loop self energies of the Goldstone bosons and vector mesons are evaluated. It is illustrated that a renormalizeable effective field theory arises once specific conditions on the low-energy constants are imposed. For the case where the hadrogenesis mass gap scale Lambda_{HG} is substantially larger than the chiral symmetry breaking scale Lambda_chi a partial summation scheme is required. All terms proportional to (M/\Lambda_\chi)^n can be summed by a suitable renormalization, where M is the chiral and large-N_c limit of the vector meson masses in QCD. The size of loop effects from vector meson degrees of freedom is illustrated for physical quarks masses. Naturally sized effects are observed that have significant impact on the chiral structure of low-energy QCD with three light flavours.

On kinematical constraints in the hadrogenesis conjecture for the baryon resonance spectrum

We consider the reaction dynamics of bosons with negative parity and spin $0$ or $1$ and fermions with positive parity and spin $\frac{1}{2}$ or $\frac{3}{2}$. Such systems are of central importance for the computation of the baryon resonance spectrum in the hadrogenesis conjecture. Based on a chiral Lagrangian the coupled-channel partial-wave scattering amplitudes have to be computed. We study the generic properties of such amplitudes. A decomposition of the various scattering amplitudes into suitable sets of invariant functions expected to satisfy Mandelstam's dispersion-integral representation is presented. Sets are identified that are free from kinematical constraints and that can be computed efficiently in terms of a novel projection algebra. From such a representation one can deduce the analytic structure of the partial-wave amplitudes. The helicity and the conventional angular-momentum partial-wave amplitudes are kinematically constrained at the Kibble conditions. Therefore an application of a dispersion-integral representation is prohibitively cumbersome. We derive covariant partial-wave amplitudes that are free from kinematical constraints at the Kibble conditions. They correspond to specific polynomials in the 4-momenta and Dirac matrices that solve the various Bethe-Salpeter equations in the presence of short-range interactions analytically.

Photon-fusion reactions from the chiral Lagrangian with dynamical light vector mesons

We study the reactions γγ→π 0 π 0, π + π −, $K^{0}\bar{K}^{0}$ , K + K −, ηη and π 0 η based on a chiral Lagrangian with dynamical light vector mesons as formulated within the hadrogenesis conjecture. At present our chiral Lagrangian contains five unknown parameters that are relevant for the photon-fusion reactions. They parameterize the strength of interaction terms involving two vector meson fields. These parameters are fitted to photon-fusion data γγ→π 0 π 0, π + π −,π 0 η and to the decay η→π 0 γγ. In order to derive gauge invariant reaction amplitudes in the resonance region constraints from maximal analyticity and exact coupled-channel unitarity are used. Our results are in good agreement with the existing experimental data from threshold up to about 0.9 GeV for the two-pion final states. The a 0 meson in the π 0 η channel is dynamically generated and an accurate reproduction of the γγ→π 0 η data is achieved up to 1.2 GeV. Based on our parameter sets we predict the γγ→ $K^{0}\bar{K}^{0}$ , K + K −, ηη cross sections.

Dynamics of strong and radiative decays of Ds-mesons in the hadrogenesis conjecture

The positive parity scalar D*s0(2317) and axial-vector D*s1(2460) charmed strange mesons are generated by coupled-channel dynamics through the s-wave scattering of Goldstone bosons off the pseudoscalar and vector D(Ds)-meson ground states. The specific masses of these states are obtained as a consequence of the attraction arising from the Weinberg–Tomozawa interaction in the chiral Lagrangian. Chiral corrections to order Q2χ are calculated and found to be small. The D*s0(2317) and D*s1(2460) mesons decay either strongly into the isospin-violating π0Ds and π0D*s channels or electromagnetically. We show that the π0-η and (K0D+-K+D0) mixings act constructively to generate strong widths of the order of 140 keV and emphasize the sensitivity of this value to the KD component of the states. The one-loop contribution to the radiative decay amplitudes of scalar and axial-vector states is calculated using the electromagnetic Lagrangian to chiral order Q2χ. We show the importance of taking into account processes involving light vector mesons explicitly in the dynamics of electromagnetic decays. The radiative width are sensitive to both ηDs and KD components, hence providing information complementary to the strong widths on the positive parity Ds-meson structure.

Hadronic three-body decays of light vector mesons

The decays of light vector mesons into three pseudoscalar mesons are calculated to leading order in the recently proposed counting scheme that is based on the hadrogenesis conjecture. Fully differential as well as integrated decay widths are presented. Since the required parameters have been fixed by other processes, the considered three-body decays are predictions of the presented approach. The decay width of the omega meson into three pions agrees very well with the experiment. The partial decay widths of the K* into its three K $ \pi$ $ \pi$ channels are predicted.

On the radiative decays of light vector and axial-vector mesons

We study the light vector and axial-vector mesons. According to the hadrogenesis conjecture the nature of the two types of states is distinct. The axial-vector mesons are generated dynamically by coupled-channel interactions based on the chiral Lagrangian written down in terms of the Goldstone bosons and the light vector mesons. We propose a novel counting scheme that arises if the chiral Lagrangian is supplemented by constraints from large- N c QCD in the hadrogenesis conjecture. The counting scheme is successfully tested by a systematic study of the properties of vector mesons. The spectrum of light axial-vector mesons is derived relying on the leading order interaction of the Goldstone bosons with the vector mesons supplemented by phenomenological correction terms. The f 1 ( 1282 ) , b 1 ( 1230 ) , h 1 ( 1386 ) , a 1 ( 1230 ) and K 1 ( 1272 ) mesons are recovered as molecular states. Based on those results the one-loop contributions to the electromagnetic decay amplitudes of axial-vector molecules into pseudo-scalar or vector mesons are evaluated systematically. In order to arrive at gauge invariant results in a transparent manner we choose to represent the vector particles by anti-symmetric tensor fields. At present we restrict ourselves to loops where a vector and a pseudo-scalar meson couple to the axial-vector molecule. We argue that final and predictive results require further computations involving intermediate states with two vector mesons. The relevance of the latter is predicted by our counting rules.

Radiative and isospin-violating decays of [formula omitted]-mesons in the hadrogenesis conjecture

The masses and decays of the scalar D s 0 ∗ (2317) and axial-vector D s 1 ∗ ( 2460 ) charmed strange mesons are calculated consistently in the hadrogenesis conjecture. These mesons decay either strongly into the isospin-violating π 0 D s and π 0 D s ∗ channels or electromagnetically. They are generated by coupled-channel dynamics based on the leading order chiral Lagrangian. The effect of chiral corrections to chiral order Q χ 2 is investigated. We show that taking into account large- N c relations to determine the strength of these correction terms implies a measurable signal for an exotic axial-vector state in the η D ∗ invariant mass distribution. The one-loop contribution to the electromagnetic decay amplitudes of scalar and axial-vector states is calculated. The Lagrangian describing electromagnetic interactions is obtained by gauging the chiral Lagrangian for hadronic interactions and adding gauge-invariant correction terms to chiral order Q χ 2 . In addition the role of light vector meson degrees of freedom is explored. We confront our results with measured branching ratios. Once the light vector mesons are included, a natural explanation of all radiative decay parameters is achieved.

Open-charm meson systems in the hadrogenesis conjecture

We study the spectrum and isospin-violating strong decays of charmed mesons with strangeness. The scalar D s 0 ∗ ( 2317 ) ± and the axial-vector D s 1 ∗ ( 2460 ) ± states are generated by coupled-channel dynamics based on the leading order chiral Lagrangian. The effect of chiral corrections is investigated. We show that taking into account large- N c relations implies a measurable signal for an exotic axial-vector state in the η D ∗ invariant mass distribution. The hadronic decay widths of the scalar D s 0 ∗ ( 2317 ) ± and the axial-vector D s 1 ∗ ( 2460 ) ± are predicted to be 140 keV.