Measurement of mass and lifetime of hadronically produced charmed F mesons

We have observed three unique decays of F mesons into KKπ and five unique decays of D mesons into KKπ using the NA11 spectrometer together with a telescope of high-resolution silicon microstrip detectors. The mass value obtained for the F meson is (1975 ± 4) MeV, the lifetime (3.2±_1.3^3..0)×10^?13 s.     

Decay constant ratios ƒ ηc/ƒ J/ψ and ƒ ηb/ƒ ψ

We calculate the decay constant ratios ? _ηc/? _J/ψ and ? _ηb/? _ψ. In the calculation we take into account the mock meson structures of the mesons, as well as the difference of the wave functions at origin of the vector and pseudoscalar mesons studied by Ahmady and Mendel. We find that the different spin structures of the mesons much affect the ratios. We incorporate our results in the prediction of the branching ratios of B → K η _c.     

Q1(1290) and Q2 (1400) decay rates and their SU(3) implications

We summarize and combine the known information on the decay rates of the strangeness-one axial vector mesons, Q₁ and Q₂. From this information and the rate for B→ωπ, we determine the Q_A?Q_B mixing angle and the S-wave, symmetric and antisymmetric octet couplings for vector-pseudoscalar decays of axial vector mesons. If we assume the D(1285) and the E(1420) belong to the J^PC=1⁺⁺ nonet, we find the A₁ to have a mass of ～1.47 GeV and a large (>0.3 GeV) width.     

Open flavour charmed mesons in a quantum chromodynamics potential model

We modify the mesonic wave function by using a short distance scale r ₀ in analogy with hydrogen atom and estimate the values of masses and decay constants of the open flavour charm mesons D, D _s and B _c within the framework of a QCD potential model. We also calculate leptonic decay widths of these mesons to study branching ratios and lifetime. The results are in good agreement with experimental and other theoretical values.     

Mass breaking in a relativistic quark model for mesons

We study symmetry breaking via quark mass differences in a relativistic quark model where mesons are built from heavy (m > 3 GeV) spin $\text{1}\text{2}$) quarks and antiquarks. The meson (squared-)mass differences are linearly related to the number of strange, charmed, etc. quarks in the mesons. We show that the previously assumed SU_n symmetry of the mesonic couplings holds, i.e., quark mass differences only show up in the masses of the external particles, not in the three meson vertex itself.     

Analysis of the QCD spectrum and chiral symmetry breaking with varying quark masses

The meson spectrum of QCD is studied in the framework of nonperturbative QCD as a function of varying quark masses m _q . It is shown that the total spectrum consists of two branches: 1) the standard one, which may be called the flux-tube spectrum, depending approximately linearly on m _q , and 2) the chiral symmetry breaking (CSB) spectrum for pseudoscalar (PS) flavor nonsinglet mesons with mass dependence √m _q . The formalism for PS mesons is derived from the QCD Lagrangian with m _q corrections, and a unified form of the PS propagator was derived. It is shown that the CSB branch of PS mesons joins to the flux-tube branch at around m _q = 200 MeV. All these results are in close correspondence with recent numerical data on large lattices.     

Flavor correlations in B s -and B c -meson production at hadron colliders

We present a comparative analysis of three different theoretical approaches to the production of B _s and B _c mesons in high-energy hadron collisions. Our attention focuses on the azimuthal and pseudorapidity correlations between B _s or B _c mesons and accompanying strange or charmed particles. The corresponding kinematical distributions are found to exhibit a high sensitivity to details of the production mechanism and can therefore serve as indicators of interaction dynamics.     

Azimuthal Distributions of K + Mesons in Heavy-Ion Collisions

Strange mesons are considered to be sensitive to in-medium modifications. Theory predicts a repulsive K ⁺ N potential and an attractive K ^? N potential in dense matter. A repulsive K ⁺ N potential would repel the K ⁺ mesons from the bulk of the nucleons and therefore cause a preferred out-of-plane emission of K ⁺ mesons at midrapidity and a directed flow opposite to the nucleons at target and projectile rapidity. One of observables to probe in-medium effects is the azimuthal emission pattern of K ⁺ mesons in heavy ion collisions. KaoS collaboration has measured the azimuthal distributions of K ⁺ mesons in Au + Au reactions at 1.5 A GeV and Ni + Ni reactions at 1.93 A GeV. Data show that K ⁺ mesons exhibit a pronounced enhancement at ${\phi = {90}^\circ}$ , i.e. perpendicular to the reaction plane. The data have also been fitted using the first two components of a Fourier series to get the directed flow v ₁ and elliptic flow v ₂. We used the quantum molecular dynamics model based on the covariant kaon dynamics to simulate the Au + Au collisions at 1.5 A GeV and the Ni + Ni collisions at 1.93 A GeV, to analyze the azimuthal distributions of K ⁺ mesons, and to calculate v ₁ and v ₂ of K ⁺ mesons. Calculated results with a repulsive in-medium K ⁺ N potential can reasonably describe the features of KaoS data. This indicates that the azimuthal distribution is one of sensitive probes to extract information on in-medium properties at high densities.     

Meson properties from a bag model compared to lattice theory and heavy ion experiments

A bag at temperature (T) with pressureB(T)=B(0)[1?(T/T _c )⁴] is shown to be consistent with recent lattice data on the π and the ρ mesons. The limiting temperature,T _l , of the pion bag from the Bekenstein entropy bound is lower than that of other mesons. This agrees with the thermal distribution of π,K and the ρ in heavy ion collisions, which (unlike proton-nucleus or pp data) show a marked difference inT of pion and other mesons in the mid-rapidity region.     

Nonfactorizable contributions to charm meson (D→ PP) decays

Two-body weak decays of charm mesons into two pseudoscalar mesons are examined employing SU(3) flavor symmetry for the non-factorizable matrix elements. Using certain measured Cabibbo-favored modes, we fix the reduced matrix elements and predict the branching ratios of the Cabibbo-angle suppressed and doubly-suppressed decays of D and D _s mesons.     

Predictions on the couplings of f- and ϱ- trajectories to mesons from chiral symmetry

We employ a chiral saturation scheme involving 15, $\text{L = 0,}\text{and}\text{15}\text{, L = 1}$ mesons in a classification according to SU(4) ? O(3) (i.e. the mesonns π, ?, ω, A₁, A₂, f, A₀ (δ), B, D and σ) and calculate all f and ? Regge couplings between these mesons via a matrix version of finite-energy sum rules. In addition the size of exotic exchanges is evaluated and found to be small. The results are compared with experimental numbers and other models as far as available.     

Semileptonic and Nonleptonic Decays of B s Mesons

We investigate the semileptonic and nonleptonic decays of B _s mesons. We work within the context of nonrelativistic constituent quark models. We calculate the different form factors that parameterize the hadron matrix elements.     

The molecular systems composed of the charmed mesons in the H\bar{S}+h.c. doublet

We study the possible heavy molecular states composed of a pair of charm mesons in the H and S doublets. Since the P-wave charm-strange mesons D _s0(2317) and D _s1(2460) are extremely narrow, the future experimental observation of the possible heavy molecular states composed of $D_{s}/D_{s}^{\ast}$ and D _s0(2317)/D _s1(2460) may be feasible if they really exist. Especially the possible J ^PC =1^?? states may be searched for via the initial state radiation technique.     

Two photon decay of the glueball and scalar isoscalar mesons in a scaled NJL model

We use a modified version of the Nambu-Jona-Lasinio (NJL) model which implements the QCD trace anomaly to calculate the two photon decay width of the glueball (f₀(1500)) and of the two scalar mesons (f₀(1370), f_J=0(1710)) to which it is mixed. We investigate the effect of the mixing over the coupling constants of the f₀ states to the quarks and over the widths. We show that mass and phase space effects are crucial, at least in the NJL model, in determining the relative strength of the 2γ widths.     

CP-Violation parameters in the two Higgs doublets model

The perturbative unitarity constraints on the CP-violation parameters in the neutral scalar mesons sector are examined for the standard model extension involving two scalar Higgs doublets. The top- and bottom-quark condensates approach is employed, but we also use the alternative renormalization group approach based on the assumption that the coupling constants of the hard Yukawa and self-coupling scalar mesons interactions reach approximate infrared fixed points at the electroweak scale. The perturbative unification scale,F _X , the charged Higgs bosons mass, the complex CP-violation phase and eventually the ratio of vacuum expectation values of the neutral scalar fields constitute the sole free parameters. We evaluate numerically the CP-violation parameters, Imz _i , representing the mixing of scalar and pseudoscalar mesons as a function of these parameters. The allowed ranges for Imz _i are found to lie far below the unitarity bounds obtained by Weinberg.     

Nuclear bound states of ω mesons

Models based on chiral SU(3)_l ⊗ SU(3)_r symmetry and vector meson dominance suggest an attractive potential for the ω meson in a nuclear medium. We discuss the feasibility of producing nuclear bound states of ω mesons using (d, ³He) and pion induced reactions on selected nuclear targets.     

Mass of the up quark and chiral symmetry at infinite momentum

We find here that a very low mass for the X⁰ meson (m_X0=305.5 MeV) is predicted from a study of the pseudoscalar mesons in the framework of chiral symmetry at infinite momentum when the up quark mass vanishes (as an alternative to axion).     

Color dipole phenomenology of diffractive electroproduction of light vector mesons at HERA

We develop the color dipole phenomenology of diffractive photo- and electroproduction γ* N → V(V′)N of light vector mesons (V(1S) = ?⁰, ω⁰, ρ⁰) and their radial excitations (V′(2S) ?′, ω′, ρ′). The node of the radial wave function of the 2S states in conjunction with the energy dependence of the color dipole cross section is shown to lead to a strikingly different Q ² and ν dependence of diffractive production of the V(1S) and V′(2S) vector mesons. We discuss the restoration of flavor symmetry and universality properties of production of different vector mesons as a function of Q ² + m _V ² . The color dipole model predictions for the ρ ⁰ and ? ⁰ production are in good agreement with the experimental data from the EMC, NMC, ZEUS and H1 collaborations. We present the first direct evaluation of the dipole cross section from these data.     

Features of carbon-carbon interactions at a momentum of 4.2 GeV/c per nucleon that are accompanied by the production of Λ hyperons and K S 0 mesons versus the degree of nuclei collision centrality

Experiemntal data obtained by using the 2-m propane bubble chamber of the Joint Institute for Nuclear Research (JINR, Dubna) are used to study the effect collision centrality on the spectra of Λ hyperons and K _S ⁰ mesons produced in carbon-carbon interactions at 4.2 A GeV/c. The multiplicity of participant protons having momenta in excess of 300 MeV/c is taken to be a measure of collision centrality. The features of pions and protons accompanying strange-particle production are also presented. The experimental data in question are compared with the prediction of a modified version of the FRITIOF model. It is shown that strange particles are predominantly produced in central and semicentral collisions. The average kinematical features of K _S ⁰ mesons are found to be indepedent of collision centrality. At the same time, the average transverse momentum of Λ hyperons and the average value of their emission angle increase slowly with increasing degree of collision centrality. The anisotropy of the angular distributions of both Λ hypersons and K _S/0 mesons in the c.m. frame of nucleon-nucleon collisions decreases with increasing collision centrality. The average transverse momentum of K _S ⁰ mesons is approximately 1.6 times higher than the average transverse momentum of π ^? mesons.