Selected problems of baryon spectroscopy: Chiral soliton versus quark models
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UCLEI, PARTICLES, FIELDS, GRAVITATION, AND ASTROPHYSICS
Selected Problems of Baryon Spectroscopy: Chiral Soliton Versus Quark Models1 V. B. Kopeliovich Institute for Nuclear Research, Russian Academy of Sciences, Moscow, 117312 Russia email: [email protected] Received December 30, 2008
Abstract—The inconsistency between the rigid rotator and bound state models at an arbitrary number of col ors, the rigid rotator—soft rotator dilemma, and some other problems of baryon spectroscopy are discussed in the framework of the chiral soliton approach (CSA). Consequences of the comparison of CSA results with simple quark models are considered and the 1/Nc expansion for the effective strange antiquark mass is pre sented, as it follows from the CSA. Strong dependence of the effective strange antiquark mass on the SU(3) multiplet is required to fit the CSA predictions. The difference between “good” and “bad” diquark masses, which is about 100 MeV, is in reasonable agreement with other estimates. Multibaryons (hypernuclei) with strangeness are described and some states of interest are also predicted within the CSA. PACS numbers: 12.39.Dc, 14.20.c, 14.65.q, 14.20.Pt DOI: 10.1134/S1063776109050069 1
1. INTRODUCTION
In spite of (or possibly due to) recent dramatic events with the (non)observation of narrow pen taquark states, the studies of baryon spectra (non strange, strange, and with heavy flavors) preserve their relevance for accelerator physics. A discovery of baryon states besides wellestablished ones (e.g., octet, decuplet, and certain resonances) could help to achieve progress in understanding the structure of hadrons. In the absence of the complete theory of strong interactions, there are different approaches and mod els of hadron structure; each has some advantages and certain drawbacks. Interpretation of hadron spectra in terms of quark models is widely accepted; quark mod els are the “most successful tool for the classification and interpretation” (R. Jaffe) of hadron spectra. These models are so widely accepted because they probably correspond to our intuitive ideas of how a bigger object—a baryon, for example,—can be made of smaller ones, quarks. However, our intuition, based on the macroscopic experience, may be totally mislead ing in the world of elementary particles. Quark models are to a large extent phenomenolog ical because there are no regular methods of solving the relativistic manybody problem. In a true relativis tic theory, the number of constituents (e.g., additional qq pairs) and their weight should not be fixed as a starting condition, but should be obtained by means of 1 The article is published in the original.
solving relevant relativistic equations (and the quark confinement should be obtained in this way as well). In view of this global unresolved problem, alterna tive approaches are of interest. In particular, the chiral soliton approach (CSA) based on few principles repre sented by the model Lagrangian, has certain advan tages. Baryons and baryonic systems are considered on equal f
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