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We investigate the K1--> K pi pi strong interaction decays. Using the 3P0 quark-pair-creation model to derive the basic parametrization, we discuss in detail how to obtain the various partial wave amplitudes into the possible quasi-two-body decay channels as well as their relative phases from the currently available experimental data. We obtain the K1 mixing angle to be thetaK1= 60 deg, in agreement with previous works. Our study can be applied to extract the information needed for the photon polarization determination of the radiative B--> K1 gamma decay.
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Constituent quark models provide a reasonable description of the baryon mass spectra. However, even in the light- and strange-flavor sectors several intriguing shortcomings remain. Especially with regard to strong decays of baryon resonances no consistent picture has so far emerged, and the existing experimental data cannot be explained in a satisfactory manner. Recently first covariant calculations with modern constituent quark models have become available for all pi, eta, and K decay modes of the low-lying light and strange baryons. They generally produced a remarkable underestimation of the experimental data for partial decay widths. We summarize the main results and discuss their impact on the classification of baryon resonances into flavor multiplets. These findings are of particular relevance for future efforts in the experimental investigation of baryon resonances.
We present a new approach to coherent parton showers in the decays of coloured resonances, based on the notion of resonance-final (RF) QCD antennae. A full set of mass- and helicity-dependent $2to 3$ antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in $2to N$ hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorisations are different. The consequent radiation patterns respect QCD coherence (at leading colour) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorisation is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the VINCIA antenna-shower plug-in to the PYTHIA 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using POWHEG, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.
There has been important experimental progress in the sector of heavy baryons in the past several years. We study the strong decays of the S-wave, P-wave, D-wave and radially excited charmed baryons using the $^3P_0$ model. After comparing the calcul
ated decay pattern and total width with the available data, we discuss the possible internal structure and quantum numbers of those charmed baryons observed recently.
Although the spectra of heavy quarkonium systems has been successfully explained by certain QCD motivated potential models, their strong decays are difficult to deal with. We perform a microscopic calculation of charmonium strong decays using the same constituent quark model which successfully describes the $cbar{c}$ meson spectrum. We compare the numerical results with the $^{3}P_{0}$ and the experimental data. Comparison with other predictions from similar models are included.
Strong two- and three-body decays of the new excited hyperon $Omega^*(2012)$ are discussed in the hadronic molecular approach. The $Omega^*(2012)$ state is considered to contain the mixed $Xi bar K$ and $Omega eta$ hadronic components. In our calculations we use a phenomenological hadronic Lagrangian describing the coupling of the bound states to its constituents and of the constituents to other hadrons occurring in the final state. Our results show that the decay widths of the two-body decay modes $Omega^*(2012) to Xi bar K$ lie in the few MeV region and are compatible with or dominate over the rates of the three-body modes $Omega^*(2012) to Xi pi bar K$. The sum of two- and three-body decay widths is consistent with a width of the $Omega^*(2012)$ originally measured by the Belle Collaboration. A possible scenario for the suppression of the three-body decay rate recently noticed by the Belle Collaboration is due to the dominant admixture of the $Omega eta$ hadronic component in the $Omega^*(2012)$ state.
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