Narrow multiquark baryons

We assume that two recently discovered narrow hypercharge zero states are composed of four quarks and an antiquark. Expected masses and decay modes of other multiquark baryons are predicted.     

Baryonium states in multiquark spectroscopy

The spectrum of qq$\text{qq}$ states, examined in a quark-gluon model combined with dual unitarization, yields two types of baryoniums both of which have narrow widths into mesons. One type has normal hadronic widths ～ 100 MeV into B$\text{B}$. The other is narrow, ～ 10 MeV, and goes into B$\text{B}$ only reluctantly, preferring, if possible, to decay by cascade, and, being a consequence only of hidden colour, is an important object to verify experimentally.     

Statistical model of coexisting multiquark clusters

A model for describing nuclear matter consisting of different multiquark clusters is constructed. Special attention is paid to the case when nucleons (3-quark clusters) coexist with 6-, 9- and 12-quark clusters. A detailed analysis of statistical properties for this mixture is presented over the whole density-temperature plane. The dependence of the results on the mass parametrization is also checked.     

Deuteron electrodisintegration reaction and multiquark configurations

We have obtained the cross sections d³ and d² for the ed e'pn reactions with allowance for the contribution of the six-quark state (6q) of the deuteron in its wave function. It is shown that the presence of a 6q component as an admixture of 5% can cause the cross section for deuteron electrodisintegration to increase by a factor of 1.5–2 under certain kinematical conditions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 45–50, July, 1985.In conclusion, we sincerely thank L. P. Kaptar', V. K. Luk'yanov, and A. I. Titov for numerous useful discussions and assistance in the work.     

The nucleus as a multiquark system

Model calculations for nuclear properties such as shell structure, magnetic moments and charge distributions are presented where quarks instead of nucleons are used as the fundamental nuclear constituents. It is shown that such a new picture is able to reproduce the gross properties of the classical theory. Nucleons and nuclearΔ-resonances show, however, a partial quark deconfinemement which leads to Pauli-blocking.     

Pair annihilation effects in multiquark spectroscopy

Pair annihilations in multiquark spectroscopy, in contrast to \(Q\bar Q\) mesons, is an effect of leading order in α _s and cannot be consistently neglected. Their observation in experiment would help to confirm QCD as a quantum field theory, identify the quantum numbers of the gluon, and give information on possible states with gluon constituents. These effects are studied here theoretically in some detail in expectation of experimental data which are beginning to be available.     

Identifying multiquark hadrons from heavy ion collisions

Identifying hadronic molecular states and/or hadrons with multiquark components either with or without exotic quantum numbers is a long-standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offers a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that, compared to the case of a nonexotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitude smaller when it is a compact multiquark state and a factor of 2 or more larger when it is a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured in these experiments.     

On the mass spectroscopy of charmed multiquark hadrons

The possible existence of charmed multiquark hadrons are investigated using phenomenologicalmit bag model and the SU(4) flavour symmetry. The masses of 6q, 9q and 15q systems having the same quantum numbers as the physically interesting ordinary nuclei, hypernuclei and supernuclei are estimated. We find that several new states with distinct signatures are predicted.     

Colour chemistry — A study of metastable multiquark molecules

We propose a framework for treating metastable multiquark states in general, borrowing some of the chemist's concepts and terminology. Lists of “ions” and “bonds” are compiled which allow one in principle to construct models of complex “molecules” and to predict their masses and decays.     

Calculations of multiquark functions in effective models of strong interaction

In this paper we present our results of the investigation of multiquark equations in the Nambu-Jona-Lasinio model with chiral symmetry of SU(2) group in the mean-field expansion. To formulate the mean-field expansion we have used an iteration scheme of solution of the Schwinger-Dyson equations with the fermion bilocal source. We have considered the equations for Green functions of the Nambu-Jona-Lasinio model up to third step for this iteration scheme. To calculate the high-order corrections to the mean-field approximation, we propose the method of the Legendre transformation with respect to the bilocal source, which allows effectively to take into account the symmetry constraints related with the chiral Ward identity. We discuss also the problem of calculating the multiquark functions in the mean-field expansion for Nambu-Jona-Lasinio-type models with other types of the multifermion sources.     

Λ(1405) as a multiquark state

In the QCD sum rule approach we predict the Λ (1405) mass by choosing the π⁰Σ⁰ multiquark interpolating field. It is found that the mass is about 1.419 GeV from Π₁ (q ²) sum rule which is more reliable than Π_q (q ²) sum rule, where Π_q (q ²) and Π₁ (q ²) are two invariant functions of the correlator Π (q ²). We also present the sum rules for the K ⁺ p and the π⁺Σ⁺ multiquark states, and compare to those for the π⁰Σ⁰ multiquark state. The mass of the Λ (1600) can be also reproduced in our approach. Received: 11 November 1997 / Revised version: 28 April 1998     

寻找多夸克新粒子态的实验进展

文章叙述了强子结构的夸克模型的成就和不足,详细介绍了寻找多夸克新粒子态的实验进展. 寻找多夸克新粒子态对中国粒子物理实验学家可能作出世界创新成果是一个良好机遇.     

On the existence of exotic and non-exotic multiquark meson states

To obtain an exact solution of a four-body system containing two quarks and two antiquarks interacting through two-body terms is a cumbersome task that has been tackled with more or less success during the last decades. We present an exact method for the study of four-quark systems based on the hyperspherical harmonics formalism that allows us to solve it without resorting to further approximations, like for instance the existence of diquark components. We apply it to systems containing two heavy and two light quarks using different quark-quark potentials. While $QQ{\bar n} {\bar n}$ states may be stable in nature, the stability of $Q\overline{Q}n {\bar n}$ states would imply the existence of quark correlations not taken into account by simple quark dynamical models.