Recent progress on the chiral unitary approach to meson meson and meson baryon interactions

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and K⁻ atoms.     

Correlations between the baryon and meson mass spectra

A qualitative and quantitative picture of the hadron mass spectrum in the sector with zero orbital momentum, obtained from the application of both exact inequalities and the 1/d-expansion to the zeroth-order non-relativistic hadron Hamiltonians, is presented and tested by using the available experimental data on meson and baryon masses.     

Two-channel description of the rho meson and delta baryon

We describe the ? meson and Δ baryon in a coupled-channel formalism in which these hadrons are bound quark states in a closed channel and hadron scattering states in an open channel. We obtain good agreement with the known properties of the ? and Δ. Furthermore, we find that the coupling between channels produces substantial shifts in the calculated masses of the ? and Δ.     

Observation of meson central production in baryon exchange processes

The central production of ⁰,f ₂ and ₃ ⁰ mesons is observed for the first time in processes which are originated by ⁺ p reactions proceeding via baryon exchange mechanism. The data come from the CERN WA56 experiment designed to separate the baryon exchange reactions in ⁺ p-collisions at 20 GeV/c. We report on the measured integral and differential cross sections and also give the density matrix elements of the meson resonances observed.     

Radiative corrections in monopole catalysis of baryon number violation

We propose an improved framework for discussing the monopole catalysis of proton decay. Instead of discarding higher partial waves from the outset we integrate over them and obtain the s-wave effective action. We present a detailed calculation to confirm that the effects of higher partial waves through one-loop radiative corrections neither spoil nor modify the conventional treatment of monopole catalysis of proton decay.     

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.     

Measurement of inclusive baryon production inB meson decays

Using the ARGUS detector at thee ⁺ e ^– storage ring DORIS II, we have studied nine decay modes of theD ⁰ meson. In addition to a higher-precision determination of the branching ratios for these modes, several new channels, the decays , and , have been observed for the first time.Supported in part by the Institute of Physics, University of Lund, Sweden     

Oscillations of the static meson fields at finite baryon density

The spatial dependence of static meson correlation functions at finite baryon density is studied in the Nambu-Jona-Lasinio model. In contrast to the finite-temperature case, we find that the correlation functions at finite density are not screened but exhibit long-range oscillations. The observed phenomenon is analogous to the Friedel oscillations in a degenerate electron gas.     

Geometrodynamics for quarks and hadrons: The baryon states

In the geometrodynamical approach, baryons turn out to exist only in configuration where the quark coordinates are spatially aligned. As a consequence, the spectrum of [SU(6), L^P] multiplets follows the pattern: (56, 0⁺), (70, 1^?; (56, 2⁺), (70, 2⁺); (70, 3^?);… with their radial recurrences. This appears to solve an old quark-model puzzle.     

A non-perturbative calculation of meson and baryon masses with a one-parameter potential

Using a non-perturbative method and a Hamiltonian with only one parameter which is fitted from charmonium, we calculate the masses of all mesons and the baryon ground state masses. In addition we calculate the ratios of the leptonic width of the 1^{? ?} heavy quark bound states. Some general theorems are checked and the accuracy of the method used to solve the Schrödinger equation is discussed. The over-all agreement of the results with experiment is very good.     

Possible hidden-charm molecular baryons composed of an anti-charmed meson and a charmed baryon

Using the one-boson-exchange model, we studied the possible existence of very loosely bound hidden-charm molecular baryons composed of an anti-charmed meson and a charmed baryon. Our numerical results indicate that the Σ_cD^* and Σ_cD states exist, but that the Λ_cD and Λ_cD^* molecular states do not.     

磁单极与磁洛伦兹力

概述了磁单极概念的历史发展,从洛伦兹变换出发,利用电磁场张量和四维力的协变性以及电荷相对论不变,直接证明了运动磁单极受磁洛伦兹力,建议了一个磁洛伦兹力的验证方案,并用磁洛伦兹力公式导出狄拉克电荷量子化条件．证明了磁洛伦兹力公式具有与库仑定律相同的精确度．     

Towards a complete QFT treatment of monopole induced baryon number violating transitions

By showing that the radially reduced QCD of s-wave fermions outside the core of a GUT monopole can be treated in a way analogous to 't Hofft's QCD₂ in the large N_climit, we are able to give a complete QFT treatment of all the relevant long-range gauge fields outside the monopole core. We prove that the original cluster argument for the existence of baryon number violating fermion “condensates” around the core, gives in fact, the correct result, despite the neglect of QCD strong interactions, which prevent the propagation of isolated quarks. We discuss briefly how a complete computational framework for a monopole induced hadron-lepton transition might be derived.     

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.     

The influence of different anomalous terms in effective meson lagrangians on baryon resonances

Anomalous actions are responsible for the coupling of ω-mesons in effective meson theories. The influence of two different choices for the anomalous terms on baryon resonances is investigated. It is shown that pion-nucleon scattering does not provide a criterion to prefer one of these two terms.