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.     

On the existence of KMS states

A necessary and sufficient condition for the existence of KMS states is formulated in terms of a certain left ideal in the algebraA ⁰ A.     

On exotic hybrid meson production in γ*γ collisions

We present a theoretical study of exotic hybrid meson (J^PC=1^- +) production in photon-photon collisions where one of the photons is deeply virtual, including twist two and twist three contributions. We calculate the cross section of this process, which turns out to be large enough to imply sizeable counting rates in the present high luminosity electron–positron colliders. We emphasize the importance of the πη decay channel for the detection of the hybrid meson candidate π₁(1400) and calculate the cross section and the angular distribution for π η pair production in the unpolarized case. This angular distribution is a useful tool for disentangling the hybrid meson signal from the background. Finally, we calculate the single spin asymmetry associated with one initial longitudinally polarized lepton.     

Search for exotic meson and hyperon final states in K-d interactions at 5.5 Gev/c

A search has been made for exotic states produced in K^?d interactions at 5.5 GeV/c. The reactions investigated were: K^?d→X^??pp, $\text{K}{}^{\mathrm{?}}\text{d}\text{→}\text{Y}{}^{\mathrm{1??}}\text{π}{}^{\mathrm{+}}\text{p}$ and K^?d→ M^??Σ⁺p. Upper limits are set for the production cross sections.     

Multiquark states and the mixing of scalar meson

In order to describe Kaon-Nucleon scattering data, the mixing of scalar meson σ_0 and σ_8 must be introduced in the chiral SU(3) quark model. Inspired by this, now the mixing of scalar meson is further considered to study some interesting dibaryons in the chiral SU(3) quark model. The results show that the mixing of scalar meson has different effects on these dibaryons.     

On the existence of stationary states during granular compaction

When submitted to gentle mechanical taps a granular packing slowly compacts until it reaches a stationary state that depends on the tap characteristics. The properties of such stationary states are experimentally investigated. The influence of the initial state, taps properties and tapping protocol are studied. The compactivity of the packings is determinated. Our results strongly support the idea that the stationary states are genuine thermodynamic states.     

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.     

On the existence conditions of localized states in linear chains

The existence conditions of localized states in linear chains with one or two impurities, are investigated in the tight-binding model. The influence of the coupling between impurity and its neighbour is stressed, in the cases of infinite and semi-infinite chains.     

On the possible existence of a vector meson ϱ' (1250)

By combining new results obtained at C.M. energies of 1.2 and 1.3 GeV with previous data obtained at lower energies from the e⁺e^? annihilation process e⁺e^? → π⁺π^?π^oπ^o, we get an indication in favour of the existence of a new vector meson of the ? type, ?' (1250), the first daughter of the ? in the predictions of the Veneziano model. Further results on the annihilation process e⁺e^? → π (1600) → π⁺π^?π⁺π^? are also presented.     

On the existence of equilibrium states in local quantum field theory

It is shown that any local quantum field theory admits thermodynamical equilibrium states (KMS-states) for all positive temperatures provided it satisfies a nuclearity condition, proposed by Wichmann and one of the authors, which restricts the admissible number of local degrees of freedom.Dedicated to E. H. Wichmann on the occasion of his 60th birthday     

神奇有趣的五夸克态

对今年国际上有关五夸克态的实验与理论研究现状作一个总体的评述 ,指出了有待解决的主要问题和相关的一些背景知识 ,并简单介绍了作者所在研究小组的有关研究工作 .     

Chiral corrections to the 1~(-+) exotic meson mass

We first construct the effective chiral Lagrangians tor the 1~(-+) exotic mesons.With the infrared regularization scheme,we derive the one-loop infrared singular chiral corrections to the π_1(1600) mass explicitly.We investigate the variation of the different chiral corrections with the pion mass under two schemes.Hopefully,the explicit non-analytical chiral structures will be helpful for the chiral extrapolation of lattice data from the dynamical lattice QCD simulation of either the exotic light hybrid meson or the tetraquark state.     

A possible interpretation of the \pi_1(1400) exotic meson

I will discuss the current theoretical and experimental status of exotic mesons and a possible interpretation of the light, exotic meson as a final state interaction effect.Received: 30 September 2002, Published online: 22 October 2003PACS: 12.39.Mk Glueball and nonstandard multi-quark/gluon states - 13.60.Le Meson productionA.P. Szczepaniak: Present address: Department of Physics, Indiana University, Bloomington, IN 47405, USA     

Mixing of meson, hybrid, and glueball states

An effective QCD Hamiltonian is constructed with the aid of the background perturbation theory and relativistic Feynman-Schwinger path integrals for Green's functions. The resulting spectrum displays mass gaps of about 1 GeV when an additional valence gluon is added to the bound state. The mixing of meson, hybrid, and glueball states is defined in two ways—through generalized Green's functions and through a modified Feynman diagram technique—giving similar answers. Results for mixing matrix elements are numerically not large (around 0.1 GeV) and agree with earlier analytic estimates and lattice simulations.     

Potential of quasielastic meson knockout from a nucleon by high-energy electrons and pions for studying the structure of exotic excited states of a final-state baryon

The possibility of studying q ⁴ \(\bar q\) exotic baryon states by means of N(e, e’M)B reactions proceeding via an extremely simple mechanism and involving the quasielastic knockout of various mesons from a nucleon by electrons of energy in the few-GeV region is considered as a development of the previous investigations of our group. A quark microscopic formalism based on the cluster model of q ⁴ \(\bar q\) states, which makes it possible to determine momentum distributions of mesons in various channels of B → N + M virtual decays (in principle, these distributions can be compared with experimental data), is expounded by considering the example of the pentaquark (B = Θ⁺). The decay widths of the q ⁴ \(\bar q\) baryon states being discussed are governed by the degree of separation of quark clusters (this is a parameter of the model used). The electroproduction cross sections prove to be small because of kinematical constraints requiring that physically admissible values of the momentum ‖k‖ of the virtual meson M lie in the region where relevant amplitudes are suppressed substantially by form factors in pentaquark vertices. In particular, N (e, e′π ^±)B reactions involving pion knockout furnish direct information about nonstrange components of baryon B; however, the expected cross sections for such reactions are an order of magnitude smaller than their counterparts for analogous reactions leading to the production of a pentaquark Θ⁺. Because of the smallness of the electroproduction cross sections, it is reasonable to consider the production of a pentaquark and other q ⁴ \(\bar q\) exotic states in reactions characterized by quasielastic kinematics and initiated by pions of energy in the range between about 1 and 5 GeV and in similar stripping and pickup nuclear reactions.