arXiv subjects
Publications and source records attributed to P. Gonzalez.
In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.
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We present the results of the first calculations involving the interaction of vector mesons with baryons, by means of which one generates a large amount of dynamically generated resonances, many of which can be associated to known resonances, while others represent predictions for new states.
The CHASE project started in 2007 with the aim of providing young southern supernovae (SNe) to the Carnegie Supernova Project (CSP) and Millennium Center for Supernova Studies (MCSS) follow-up programs. So far CHASE has discovered 33 SNe with an average of more than 2.5 SNe per month in 2008. In addition to the search we are carrying out a follow-up program targeting bright SNe. Our fully automated data reduction allows us to follow the evolution on the light curve in real time, triggering further observations if something potentially interesting is detected
We use the $ρΔ$ interaction in the hidden gauge formalism to dynamically generate $N^{\ast}$ and $Δ^{\ast}$ resonances. We show, through a comparison of the results from this analysis and from a quark model study with data, that the $Δ_{5/2^{-}}(1930),$ $Δ_{3/2^{-}}(1940)$ and $Δ_{1/2^{-}}(1900)$ resonances can be assigned to $ρΔ$ bound states. More precisely the $Δ_{5/2^{-}}(1930)$ can be interpreted as a $ρΔ$ bound state whereas the $Δ_{3/2^{-}}(1940)$ and $Δ_{1/2^{-}}(1900)$ may contain an important $ρΔ$ component. This interpretation allows for a solution of a long-standing puzzle concerning the description of these resonances in constituent quark models. In addition we also obtain degenerate $J^{P}=1/2^{-},3/2^{-},5/2^{-}$ $N^{*}$ states but their assignment to experimental resonances is more uncertain.
We show that a static central potential may provide a precise description of highly excited light unflavoured mesons. Due to string breaking this potential becomes of chromoelectric type at sufficiently large quark-antiquark distances giving rise to a coulombian spectrum. The same conclusion can be inferred for any other meson sector through a straightforward extension of our analysis.
We discuss recent results on heavy and light baryon spectroscopy
We argue that selected $S$ wave meson-baryon channels may play a key role to match poor baryon mass predictions from quark models with data. The identification of these channels with effective inelastic channels in data analysis allows to derive a prescription which could improve the extraction and identification of baryon resonances.
From an SU(2)$\otimes $SU(2) chiral quark potential model incorporating spontaneous chiral symmetry breaking the asymptotic $π$ and $σ$ exchange pieces of the $NN$ potential are generated. From them the $πNN$ and $σNN$ coupling constants can be extracted. The generalization to SU(3)$\otimes $SU(3) allows for a determination of $πB_{8}B_{8}$ and $% σB_{8}B_{8}$ coupling constants according to exact SU(3) hadron symmetry. The implementation of the values of the couplings at $Q^{2}=0$ provided by QCD sum rules and/or phenomenology makes also feasible the extraction of the meson-baryon-baryon form factors. In this manner a quite complete knowledge of the couplings may be attained.
We present a study of the baryon spectra for all flavor sectors within a constituent quark model. We address some of the outstanding problems in baryon spectroscopy, as for example the spin splitting evolution for te different flavor sectors, the flavor independence of confinement and the missing state problem.
We review some selected recent results on hadron spectroscopy and related theoretical studies based on constituent quark models.
We revise the role played by symmetry in the study of the low-lying baryon spectrum and comment on the difficulties when trying to generalize the symmetry pattern to higher energy states. We show that for the $(N,Δ)$ part such a generalization is plausible allowing the identification of spectral regularities and the prediction of until now non-identified resonances.
We show that nonstrange baryon resonances can be classified according to multiplets of $SU(4)\otimes O(3)$. We identify spectral regularities and degeneracies that allow us to predict the high spin spectrum from 2 to 3 GeV.
We extract, from a quark model potential that reproduces the number and ordering of nonstrange baryonic resonances up to 2.3 GeV, the quantum numbers for the dominant configurations in the ground and first non-radial excited states. From the pattern of quantum numbers we identify, from data, spectral regularities that allow us to predict the expected high spin low-lying spectrum from 2.3 to 3.0 GeV. $N-Δ$ degeneracies and $N$ parity doublets showing up can be interpreted in terms of a simple dynamics.
We use two-body potentials derived from a constituent quark cluster model to analyze the bound-state problem of the $ΣNN$ system. The observables of the two-body subsystems, $NN$ and $ΣN$, are well reproduced. We do not find $ΣNN$ bound states, but there are two attractive channels with a resonance close above the three-body threshold. These channels are the $(I,J)=(1,1/2)$ and $(0,1/2)$, their quantum numbers, widths and energy ordering consistent with the recently measured strange tribaryons from the $^{4}{\rm He}(K_{\rm stopped}^{-},N)$ reactions in the KEK PS E471 experiment.
We derive a $ΛΛ$ potential from a chiral constituent quark model that has been successful in describing one, two and three nonstrange baryon systems. The resulting interaction at low energy is attractive at all distances due to the $σ$ exchange term. The attraction allows for a slightly bound state just below the $ΛΛ$ threshold. No short-range repulsive core is found. We extract the diquark-diquark contribution that turns out to be the most attractive and probable at small distances. At large distances the asymptotic behavior of the $ΛΛ$ interaction provides a prediction for the $σΛΛ$ coupling constant.
We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the NN, N$Δ$, $ΔΔ$ and NN$^*(1440)$ systems, and also for the binding energies of three non-strange baryon systems. We make emphasis on observable effects related to quark antisymmetry and its interplay with quark dynamics.
Recent lattice QCD calculations suggest a rather abrupt transition in the confinig potential from a linear to a constant behavior. We analyze the effects of such a fast deconfinement in the simplest non-relativistic system, bottomonium.