Search

The masses, the fine-structure splitting, and two-photon decay widths of the higher -charmonium states are calculated in the relativistic string model, reduced to the spinless Salpeter equation, where the static potential has no fitting parameters and the c-quark mass has the physical value. The resulting masses of , , , , are obtained in a good agreement with the experimental masses of the LHCb resonances: (4300), (4274), (4500), (4700), (4685). To test sensitivity of results to a chosen gluon-exchange (GE) potential, three types of are considered. In first case the non-screened GE potential with large vector coupling at asymptotic, , and the c-quark mass GeV are taken; in second case a screened and GeV are investigated, and in third case the GE potential is totally suppressed, , and GeV. The agreement with experiment is reached only if the same (universal) flattened confining potential, introduced in the analysis of the radial Regge trajectories of light mesons, is used. The unobserved , resonance with the mass GeV, near (1680) threshold, is predicted. Our analysis shows that the screening of the GE potential is possible but weakly affects the physical results obtained. The calculated two-photon decay widths weakly differ in the three cases but may become an important factor, which distinguishes and four-quark states. [ABSTRACT FROM AUTHOR]

Within the diquark–antidiquark model the masses of the 0 , resonances are calculated, using the expansion of the four-quark wave function in the set of the hyperspherical functions. The interaction is defined via a universal pairwise potential, which does not contain fitting parameters. The resulting masses are shown to be very sensitive to the value of -quark mass, chosen in relativistic string Hamiltonian, and , 1.30, 1.43 (in GeV) are considered. The choice of , equal to the current mass, GeV, yields three ( , 1, 2) states in a very good agreement with the masses of the (6550), (6900), (7280) resonances, if the gluon-exchange interaction is totally neglected. This fact indicates possible screening of the gluon-exchange interaction in the system. For GeV the ground state mass MeV is obtained in agreement with experiment only if is used, however, in this case the masses of the 2 , 3 radial excitations exceed the masses of (6900), (7280) by 100 MeV. [ABSTRACT FROM AUTHOR]

The scalar resonances X (3915) , X (3960) , X 0 (4140) are considered as exotic four-quark states: c q c ¯ q ¯ , c s c ¯ s ¯ , c s c ¯ s ¯ , while the X(3863) is proved to be the c c ¯ , 2 3 P 0 state. The masses and the widths of these resonances are calculated in the framework of the Extended Recoupling Model, where a four-quark system is formed inside the bag and has relatively small size ( ≲ 1.0 fm). Then the resonance X(3915) appears due to the transitions: J / ψ ω into D ∗ + D ∗ - (or D ∗ 0 D ¯ ∗ 0 ) and back, while the X(3960) is created due to the transitions D s + D s - into J / ψ ϕ and back, and the X 0 (4140) is formed in the transitions J / ψ ϕ into D s ∗ + D s ∗ - and back. The characteristic feature of the recoupling mechanism is that this type of resonances can be predominantly in the S-wave decay channels and has J P = 0 + . In two-channel case the resonance occurs to be just near the lower threshold, while due to coupling to third channel (like the c c ¯ channel) it is shifted up and lies by (20–30) MeV above the lower threshold. The following masses and widths are calculated: M (X (3915)) = 3920 MeV, Γ (X (3915)) = 20 MeV; M (X (3960)) = 3970 MeV, Γ (X (3960) = 45 (5) MeV, M (X 0 (4140)) = 4120 (20) MeV, Γ (X 0 (4140)) = 100 MeV, which are in good agreement with experiment. [ABSTRACT FROM AUTHOR]

Numerous resonances in the c c ¯ and 4q systems, containing c c ¯ plus s s ¯ quarks (or light q q ¯ ) were observed during last decades and recently the LHCb has found a remarkable narrow peak T cc (3875) in the D D ∗ system. Besides there are several highly excited charmonium-like resonances, which can be treated as the shifted standard charmonium states. We analyze all these groups of the resonances in the mass region (3900–4700) MeV, using relativistic strong coupling theory with possible channel coupling phenomena. For the shifted charmonium states conventional charmonium spectrum is presented, being calculated with the relativistic string Hamiltonian, which does not contain fitting parameters, while for high excitations the universal flattened confining potential is used. It is shown that X(4274), X(4500), X(4700) can be identified as 3 3 P 1 , 4 3 P 0 , 5 3 P 0 states. The group of exotic states are considered using the Extended Recoupling Model, where two mesons m 1 , m 2 transfer into another pair of mesons m 3 , m 4 and back (infinite number of times), creating the four-quark resonance. Within this approach the resonances – T cc (3875) , Z c (3900) , X (3915) , Z cs (3985) , X (4014) , and X(4140) – can be explained as the exotic four-quark states in the S-wave decay channels. [ABSTRACT FROM AUTHOR]

The masses of excited charmed mesons are shown to decrease by (50–150) MeV due to a flattening of the confining potential at large distances, which effectively takes into account open decay channels. The scale of the mass shifts is similar to that in charmonium for (4660) and (4700). The following masses of the first excitations: MeV, MeV, MeV, and MeV, and second excitations: MeV, MeV, MeV, and MeV, are predicted. The other states with , 1, 2 and have their masses in the region GeV. [ABSTRACT FROM AUTHOR]

The dielectron widths of Y( nS)( n = 1, ..., 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction. For Y( nS) ( n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580) and Y(11020) a good agreement with experiment is reached only if the 4 S-3 D mixing (with a mixing angle θ = 27°± 4°) and 6 S-5 D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, $$ \tilde \Upsilon $$( n3 D1) with n = 3, 4, 5 is discussed. In particular, $$ \tilde \Upsilon $$(≈11120), originating from the pure 53 D1 state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e+ e− experiments. On the contrary, the widths of pure D-wave states are very small, Γ ee( n3 D1)≤ 2 eV. [ABSTRACT FROM AUTHOR]

The vector and pseudoscalar decay constants are calculated in the framework of the Field Correlator Method. Di-electron widths: Γ ee( J/ψ) = 5.41 keV, Γ ee( ψ′(3686)) = 2.47 keV, Γ ee( ψ″(3770)) = 0.248 keV, in good agreement with experiment, are obtained with the same coupling, α s = 0.165, in the QCD radiative corrections. We show that the larger α s = 0.191 ± 0.004 is needed to reach agreement with experiment for Γ γγ( χ c) = 7.22 keV, Γ γγ( χ c(3 P0)) = 3.3 keV, Γ γγ χ c(3 P2)) = 0.54 keV, and also for Γ( J/ψ → 3 g) = 59.5 keV, Γ( J/ψ → γ2 g) = 5.7 keV. Meanwhile, even larger α s = 0.238 gives rise to good description of Γ( ψ′ → 3 g) = 52.7 keV, Γ( ψ′ → γ2 g) = 3.5 keV, and provides correct ratio of the branching fractions: $$ \frac{{\mathcal{B}({J \mathord{\left/ {\vphantom {J \psi }} \right. \kern-\nulldelimiterspace} \psi } \to light hadrons)}} {{\mathcal{B}(\psi ' \to light hadrons)}} = 0.24 $$. [ABSTRACT FROM AUTHOR]

The dielectron widths of ψ(4040), ψ(4160), and ψ(4415), and their ratios are shown to be in good agreement with experiment, if in all cases the S-D mixing with a large mixing angle θ ≅ 34° is taken. Arguments are presented why continuum states give small contributions to the wave functions at the origin. We find that the Y (4360) resonance, considered as a pure 3 3 D1 state, would have very small dielectron width, Γ ee( Y (4360)) = 0.060 keV. On the contrary, for large mixing between the 4 3 S1 and 3 3 D1 states with the mixing angle θ = 34.8°, Γ ee( ψ(4415)) = 0.57 keV coincides with the experimental number, while a second physical resonance, probably Y (4360), has also a rather large Γ ee( Y (∼4400)) = 0.61 keV. For the higher Y (4660) resonance, considered as a pure 5 3 S1 state, we predict the dielectron width Γ ee( Y (4660)) = 0.70 keV, but it becomes significantly smaller, namely 0.31 keV, if the mixing angle between the 5 3 S1 and 4 3 D1 states has the characteristic value θ = 34°. The mass and dielectron width of the 6 3 S1 charmonium state are calculated. [ABSTRACT FROM AUTHOR]

The vacuum gluonic correlation length is extracted from recent lattice data on spin-dependent interquark potentials in heavy quarkonia. It is shown that the data are consistent with extremely small values of the correlation length, T g ≲ 0.1 fm. [ABSTRACT FROM AUTHOR]

The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths. Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing is fixed by known G/ ψ−η c(1 S), ψ(2 S)− η c′(2 S) splittings, which appears to be small, r ss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed in bottomonium. For nS b $$\bar b$$ states ( n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3 S and 4 S charmonium states, the splittings 16(2) and 12(4) MeV are obtained. [ABSTRACT FROM AUTHOR]

The precision measurement of the hyperfine splitting, ΔHF(1 P, c-c) = M cog( xcJ) — M( h c), in the Fermilab-E835 and CLEO experiments allows one to determine the gluonic condensate G 2 with high accuracy if the gluonic correlation length T g is fixed. In our calculations, the negative value of ΔHF = −0.5 ± 0.4 MeV, as in the E835 experiment, is obtained only if the relatively small T g = 0.16 im and G 2 = 0.060(3) GeV4 are taken. For T g ≥ 0.2 fm, the hyperfine splitting is positive and grows for increasing T g. In particular, for T g = 0.2 fm and G 2 = 0.045(2) GeV4, the splitting ΔHF = 1.0(5) MeV is just in accordance with the recent CLEO result. The values of G 2 taken correspond to the “physical” string tension σ ≈ 0.18 GeV2. [ABSTRACT FROM AUTHOR]

The static force FB(r) and the strong coupling αF (r), which defines the gluon-exchange part of FB(r), are studied in QCD background perturbation theory (BPT). In the region r ∼< 0.6 fm, αF (r) turns out to be substantially smaller than the coupling αB(r) in the static potential. For the dimensionless function ΦB(r) = r2FB(r), the characteristic values ΦB(r1) = 1.0 and ΦB(r0) = 1.65 are shown to be reached at the following Q&Qmacr; separations: r1[This symbol cannot be presented in ASCII format]σ = 0.77 and r0[This symbol cannot be presented in ASCII format]σ = 1.09 in the quenched approximation and r1[This symbol cannot be presented in ASCII format]σ = 0.72 and r0[This symbol cannot be presented in ASCII format]σ = 1.04 for nf = 3. The numbers obtained appear to be only 8% smaller than those calculated in lattice QCD, while the values of the couplings αF (r1) and αF (r0) in BPT are ∼ 30% (nf = 3) and 50% (nf = 0) larger than the corresponding lattice couplings. With the use of BPT potential, a good description of the bottomonium spectrum is obtained. [ABSTRACT FROM AUTHOR]

From the fact that nonperturbative self-energy contribution CSE to the heavy-meson mass is small, CSE(b&bline;) = 0 and CSE(c&cline;) &approx; -40 MeV, strong restrictions on the pole masses mb and mc are obtained. The analysis of the b&bline; and the c&cline; spectra with the use of the relativistic (string) Hamiltonian gives mb(2-loop) = 4.78 ± 0.05 GeV and mc(2-loop) = 1.39 ± 0.06 GeV, which correspond to the &Msline; running masses &mline;b(&mline;b) = 4.19 ± 0.04 GeV and &mline;c(&mline;c) = 1.14 ± 0.05 GeV. [ABSTRACT FROM AUTHOR]

For a[sub 0](1450), considered as the q&qmacr; 1³P[sub 0] state, "experimental" tensor splitting, c[sub exp] = -150 ± 40 MeV, appears to be in contradiction with the conventional theory of fine structure. There is no such discrepancy if a[sub 0](980) belongs to the q&qmacr; 1³P[sub J] multiplet. The hadronic shift of a[sub 0](980) is shown to be greatly dependent on the value of strong coupling in spin-dependent interaction. [ABSTRACT FROM AUTHOR]

The coordinate space behavior of (vector) strong-coupling constant in the background field α[sub B](r) is compared with that in standard perturbation theory α[sub V](r). The numerically calculated two-loop coupling constant α[sub B](r) is shown to exceed α[sub V](r) by 1-5% at very small distances, r ... 0.02 fm, and to be in agreement with lattice measurements of the static potential. At large distances, α[sub B](r) approaches the freezing value at r ... 0.5 fm. An analytic form of α[sub B](r) is proposed that approximates α[sub B](r) with a precision ... 2% in the region r ... 0.5 fm. [ABSTRACT FROM AUTHOR]

It is shown that, in the relativistic case, the fine-structure splittings of the excited 2³P[sub J] and 3³P[sub J] states in charmonium are as large as those of the 1³P[sub J] state if the same value of α[sub s](μ) ≈ 0.36 is used. The predicted mass of M(2³P[sub 0]) = 3.84 GeV appears to be 120 MeV lower than the center of gravity of the 2³P[sub J] multiplet and lies below the D&Dmacr;[sup *] threshold. Our value of M(2³P[sub 0]) is nearly 80 MeV lower than that from the Godfrey and Isgur article [Phys. Rev. D 32, 189 (1985)], while the differences in other masses are not greater than 20 MeV. [ABSTRACT FROM AUTHOR]

It is shown that a 25(20)% difference between the decay constants $$f_{D_s } $$ ( $$f_{B_s } $$ ) and f D ( f B ) occurs due to large differences in the pole masses of the s and d( u) quarks. The values η D = $$f_{D_s } $$ / f D ∼ 1.23(15), recently observed in the CLEO experiment, and η B = $$f_{B_s } $$ / f B ∼ 1.20, obtained in unquenched lattice QCD, can be reached only if, in the relativistic Hamiltonian the running mass, m s at low scale is m s (∼0.5 GeV) = 170–200 MeV. Our results follow from the analytical expression for the pseudoscalar decay constant f P based on the path-integral representation of the meson Green’s function. [ABSTRACT FROM AUTHOR]

The spectrum of the s s ¯ mesons is studied performing a phenomenological analysis of the Regge trajectories defined for the excitation energies. For the ϕ (3 3 S 1) state the mass M (ϕ (3 S)) = 2100 (20) MeV and the leptonic width Γ ee (ϕ (3 S)) = 0.27 (2) keV are obtained, while the mass of the 2 3 D 1 state, M (ϕ (2 3 D 1)) = 2180 (5) MeV, appears to be in agreement with the mass of the ϕ (2170) resonance, and its leptonic width, Γ ee (2 3 D 1) = 0.20 ± 0.10 keV, has a large theoretical uncertainty, depending on the parameters of the flattened confining potential. [ABSTRACT FROM AUTHOR]

In this study, genetic structure and pathogenic diversity of Sclerotinia sclerotiorum, the causal agent of white cottony stem rot, were assessed through Mycelial Compatibility Groupings (MCGs) and comparison of isolate virulence. 65 isolates from six different hosts from three northern provinces of Iran (Golestan, Mazandaran and Gilan) were placed at 39 different mycelial compatibility groups. The observed MCGs differed within three regions. From all MCGs, 61.53% and 15.38% belonged to Mazandaran and Golestan and 10.25% and 12.82% were common between Mazandaran and Gillan and Mazandaran and Golestan, respectively. Shannon diversity index (Ho) of MCGs for the whole regions was 1.509 (Htot). Partition of total diversity (Htot) showed that 68% corresponded to a variation in diversity within S. sclerotiorum populations. Study on virulence was tested using a stem inoculation technique under greenhouse conditions. Evaluating of severity by two methods Stem Lesion Length and the Area Under Disease Progress Curve (AUDPC) showed that isolate virulence varied within the foue clade. Moreover, in most cases the differences in virulence of isolates within MCGs were significant. The data indicated that populations of S.sclerotiorum obtained from the studied regions were composed of a heterogeneous mix of MCGs, therefore the population structure of this pathogen as well as variations in virulence of isolates must be considered in disease management systems in these regions. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined the properties of a-Si:H films deposited by the flow plasma-chemical method with electron beam activation of gases. Methodology of the study; Results and discussion on the study.