Narrow Results

A one-dimensional quantum mechanical model possessing mass-gap, a gapless excitation, and an approximate parity doubling of energy levels is constructed based on heuristic QCD-inspired arguments. The model may serve for illustrative purposes when considering the related dynamical phenomena in particle and nuclear physics.

The new potential model for pionic hydrogen, constructed with the employment of the two-body relativistic equation, is offered. The relativistic equation, based on the extension of the SL(2, C) group to the Sp(4, C) one, describes the effect of the proton spin and anomalous magnetic moment in accordance with the results of the quantum electrodynamics. Within this approach, using the experimental data on the strong energy level shift and width of the 1s state in pionic hydrogen as input, the pion–nucleon scattering lengths have been evaluated to be and

We apply color-spin and flavor-spin quark–quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this paper was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi–Breit (FB) and flavor-spin Glozman–Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially b quark mass). Another aim was to discern between the FB and GR HFI because our previous findings had indicated that both interactions were satisfactory. Our improved fitting procedure of constituent quark masses showed that on average color-spin (FB) HFI yields better fits. The method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.

A nonperturbative model for the QCD invariant charge, which contains no low-energy unphysical singularities and possesses an elevated higher-loop corrections stability, is developed in the framework of potential approach. The static quark–antiquark potential is constructed by making use of the proposed model for the strong running coupling. The obtained result coincides with the perturbative potential at small distances and agrees with relevant lattice simulation data in the nonperturbative physically-relevant region. The developed model yields a reasonable value of the QCD scale parameter, which is consistent with its previous estimations obtained within potential approach.

We review how quark models are able to describe the phenomenology of the charm meson sector. The spectroscopy and decays of charmonium and open charm mesons are described in a particular quark model and compared with the data and the results of other existing models in the literature. A quite reasonable global description of the heavy meson spectra is reached. A new assignment of the ψ(4415) resonance as a 3D state leaving aside the 4S state to the X(4360) is tested through the analysis of the resonance structure in e⁺e^- exclusive reactions around the ψ(4415) energy region. We make tentative assignments of some of the XYZ mesons. To elucidate the structure of the 1⁺cs states, i.e., D_s1(2460) and D_s1(2536), we study the strong decay properties of the D_s1(2536) meson. We also perform a calculation of the branching fractions for the semileptonic decays of B and B_s mesons into final states containing orbitally excited charmed and charmed-strange mesons, which have become a very important source of information about the structure of heavy mesons. Analysis of the nonleptonic B-meson decays into D^(*)D_sJ are also included.

In this paper, by applying the Pekeris approximation and in the frame of Supersymmetric Quantum Mechanics (SUSYQM), the semi-relativistic solutions of the two-body spinless Salpeter equation are obtained analytically. For an interaction of nuclear form, we obtain the approximate bound-state energy eigenvalues and the corresponding wave functions using the shape invariance concept. The solutions are reported for any l state and some energy eigenvalues are given. These results are useful in elementary-particle physics and nuclear physics to obtain the bound states spectra of relativistic systems such as fermion–antifermion systems.

We use a chiral constituent quark model to study possible molecular structures in the heavy baryon spectrum. We first analyze D*N states and we find a bound state in the J^P = 3/2^- sector with an small binding energy. This state can be identified with the Λ_c(2940)⁺. The decays of this state are compatible with the existent experimental data. As a by product a state is predicted in the bottom baryon spectrum as a state with a mass around 6250 MeV. Moreover we also analyze other DN, D*N, DΔ and D*Δ states and their analogs in the bottom baryon sector finding several bound states.

In this talk I summarize our current understanding of quarkonium states above deconfinement based on phenomenological and lattice QCD studies.