Dynamically generated resonances from the vector octet-baryon decuplet interaction and their radiative decays into γ-baryon decuplet

The dynamically generated resonances from vector meson-baryon decuplet are studied using La-grangians of the hidden gauge theory for vector interactions. One shows that some of the generated states can be associated with some known baryon resonances in the PDG data, while others are predictions for new states. Furthermore, we calculate the radiative decay widths of these resonances into a photon and a baryon decuplet.     

Baryon resonance as fluctuations of the skyrme soliton

Normal modes of fluctuations around the static Skyrme soliton solution are investigated. They carry an unconventional quantum number I, which is the sum of orbital angular momentum and isospin of the asymptotic pion field and which serves well as a label for experimentally observed resonances. From the calculated phase-shift positions and widths of corresponding baryon resonances are extracted.     

Few-body Decay and Recombination in Nuclear Astrophysics

Three-body continuum problems are investigated for light nuclei of astrophysical relevance. We focus on three-body decays of resonances or recombination via resonances or the continuum background. The concepts of widths, decay mechanisms and dynamic evolution are discussed. We also discuss results for the triple ?? decay in connection with 2⁺ resonances and density and temperature dependence rates of recombination into light nuclei from ??-particles and neutrons.     

An su (6)w fit to the negative parity baryon decay rates

We present a least squares fit to the experimental data on decays of negative parity baryon resonances into a pseudoscalar meson and either a J^P = 1/2⁺ stable baryon or a J^P = 3/2⁺ decuplet member. We find that the s-waves and d-waves are separately in good agreement with the predictions of SU (6)_w ⊗ O(2)_Lz. Predictions are given regarding several as yet unobserved decay processes, and for those which concern hitherto undetected resonances, their possible detection is discussed.     

Electromagnetic radiation from hot and dense hadronic matter

The modifications of hadronic masses and decay widths at finite temperature and baryon density are investigated using a phenomenological model of hadronic interactions in the Relativistic Hartree Approximation. We consider an exhaustive set of hadronic reactions and vector meson decays to estimate the photon emission from hot and dense hadronic matter. The reduction in the vector meson masses and decay widths is seen to cause an enhancement in the photon production. It is observed that the effect of p-decay width on photon spectra is negligible. The effects on dilepton production from pion annihilation are also indicated.     

Hadronic decays of N and Δ resonances in a chiral quark model

π and η decay modes of light baryon resonances are investigated within a chiral quark model whose hyperfine interaction is based on Goldstone-boson exchange. For the decay mechanism a modified version of the ³ P ₀ model is employed. Our primary aim is to provide a further test of the recently proposed Goldstone-boson exchange constituent quark model. We compare the predictions for π and η decay widths with experiment and also with results from a traditional one-gluon exchange constituent quark model. The differences between nonrelativistic and semirelativistic versions of the constituent quark models are outlined. We also discuss the sensitivity of the results on the parameterization of the meson wave function entering the ³ P ₀ model. Received: 11 May 2001 / Accepted: 17 September 2001     

Analog resonances with J π = 3/2− in the 40Ar(pγ)41 K reaction

γ decay of isobaric analog 2p _3/2 resonances in the ⁴¹K nucleus, observed in the ⁴⁰Ar(pγ)⁴¹K reaction at E _p = 1102, 1839, 1842, 1859, 1875, and 1896 keV, has been experimentally investigated. The decay schemes of these resonances are constructed, the angular distributions of γ rays are measured, and the partial γ widths are determined for the first time. The intensities of single-particle M1 transitions are compared with the results of the calculations within the shell model with surface δ interaction.     

Thermal hadron production in high energy heavy ion collisions

We provide a method to test if hadrons produced in high energy heavy ion collisions were emitted at freeze-out from an equilibrium hadron gas. Our considerations are based on an ideal gas at fixed temperatureT _f , baryon number densityn _B , and vanishing total strangeness. The constituents of this gas are all hadron resonances up to a mass of 2 GeV; they are taken to decay according to the experimentally observed branching ratios. The ratios of the various resulting hadron production rates are tabulated as functions ofT _f andn _B . These tables can be used for the equilibration analysis of any heavy ion data; we illustrate this for some specific cases.     

Partial decay widths of baryons in the spin-momentum operator expansion method

The cross-sections for photo- and pion-induced production of baryon resonances and their partial decay widths to the two-body and multi-body final states are calculated in the framework of the operator expansion method. The approach is fully relativistic invariant, and it allows us to perform combined analyses of different reactions imposing directly the analyticity and unitarity constraints. All formulae are given explicitly in the form used by the Crystal Barrel Collaboration in the partial-wave analysis.     

Non-strange four quark systems

Using a Coulombic one gluon exchange interaction, and a generalisation of a linear confining potential to multiquark systems, the four body Schrodinger equation is solved, using potential parameters and effective quark masses obtained from a previous fit to the baryon spectrum. Masses of non-strange four states are predicted, and their decay properties considered. Good agreement is obtained between the predicted properties ofT-diquonium states and observed resonances coupled toB B channels, but it is found thatM-diquonia have a strong tendency to decay into multimeson final states. Alternative possibilities for narrow four quark states are considered.     

Heavy baryon decay widths in the large $$N_c$$ limit in chiral theory

We propose large \(N_c\) generalizations for the “diquark” representations of \(\hbox {SU}(3)_\mathrm{flav}\) relevant for positive parity heavy baryons, including putative exotic states. Next, within the framework of the Chiral Quark Soliton Model, we calculate heavy baryon masses and decay widths. We show that in the limit of \(N_c \rightarrow \infty \) all decay widths vanish, including the widths of exotica. This result is in fact more general than the model itself, as it relies only on the underlying symmetries: i.e. \(\hbox {SU}(3)_\mathrm{flav}\) and hedgehog symmetry. Furthermore, using explicit model formulae for the decay constants in the non-realtivistic limit, we show that there is a hierarchy of the decay couplings, which may explain observed pattern of experimental widths.     

Photoexcitation of baryon resonances

The study of baryon resonances via meson photoproduction reactions on the free proton, nucleons bound in light nuclei, and in the nuclear medium is discussed. Special emphasis is laid on the production of neutral mesons which due to the suppression of non-resonant backgrounds are particularly well suited for the study of excited states of the nucleon. Experiments carried out during the last ten years with the TAPS-detector at the Mainz MAMI accelerator have contributed very significantly to the detailed investigation of the four lowest lying baryon resonances the P₃₃ (1232), the P₁₁ (1440), the D₁₃(1520) and the S₁₁(1535). Future experiments with TAPS at the ELSA accelerator have a large potential for the investigation of higher lying resonances via many different decay channels.     

Multipole analysis of resonance photoproduction

The single-quark-transition language of the Melosh transformation is used to extract reduced multipole matrix elements from three recent sets of photocouplings for nonstrange baryon resonances. Magnetic dipole excitation of 56, L = 2 resonances is found to be suppressed, a result to be expected if spin-orbit effects are weak. Suggestions are made for further reduction of uncertainties in the data.     

Dual properties of inclusive spectra

The dual properties of the inclusive reaction π^?p → pX are studied over a wide energy range by exploiting the scaling behaviour. Semi-local duality is found to be well satisfied. An energy-dependent triple-Regge analysis reveals a strong triple-pomeron coupling. There is some evidence of an abnormal component in which diffractively produced resonances are dual to pomeron exchange. Combining duality with factorization leads to relations between production cross sections of meson and baryon resonances in πp and pp collisions, which are compatible with existing experimental data.     

Sextet string tension,mock baryonia and theU(3.1) resonance

We investigate the potential between static color sextet sources, a topic of central importance in connection with the existence or non-existence of mock-baryonia. The result is that these states should exist. We derive an effective potential for diquarks and discuss features ofT- andM-baryonia which may help to clarify the nature of theU(3.1) in forthcoming experiments. The suggested decay mechanism predicts that decays into Λ \(\bar p\) plus pions prefer to proceed via the negative parity baryon resonances.     

Study of J/Ψ three-body decays involving baryons and a pseudoscalar meson in the diquark model

The J/Ψ decay into a baryon pair and a pseudoscalar meson is computed, for some channels, in lowest order in perturbative QCD, modeling the baryon with a quark-diquark system. We use a set of parameters that has been proposed by some authors in order to fit the proton magnetic form factor G _M ^P, the angular distribution of protons in the processes γγ → pp?, γp → γp and the width of η_c → γγ.