Static structure factor of electrons around a heavy positively charged impurity in a one-component quantum rare plasma

An expression for the static structure factor,g ⁺⁻ (r), of electrons at a distancer from an infinitely heavy positively charged particle in a one component quantum rare plasma has been obtained in linear response theory using an appropriate quantum dielectric function of the rare plasma. The expression is a complicated function of the electron plasma frequency, Debye screening length andr, but reduces to that of classical plasma when quantum corrections are neglected. Forr<r _s (2r _s being the mean distance between two electrons), the temperature dependentg ⁺⁻ (r) has larger values in quantum case in comparison to that in classical situation and keeps increasing with decrease inr, more so at low temperatures when de-Broglie wavelength becomes larger and a considerable fraction ofr _s.     

Improved condition for the absence of bound states and converging analytic bounds to critical screening parameter

Converging lower bound to the critical screening parameterD _c associated with the ground state of a two-particle system interacting through a cut-off Coulomb potential is obtained analytically using an improved condition for the absence of bound states. The predicted numerical result for the lower bound is found to be within 10⁻³% of the exact result. On the other hand, a multi-parameter variational approach yields a tight upper bound, within 0.54% of the exact result. It is shown that the critical screening parameter for the exciteds-states can also be determined in an approximate way. We obtainD _c ^ms ≈ [0.764435n ⁻²+0.617737n ⁻³]⁻¹ wheren is the principal quantum number. The predictedD _c for various quantum states (n=1 to 8) are in good agreement with the values obtained numerically by Singh and Varshni.     

Possible molecular states of D*s[`(D)]*sD^{*}_{s}\bar{D}^{*}_{s} system and Y(4140)

The interpretation of Y(4140) as a D^*_s[`(D)]<sup>*</sup><sub>s</sub>D^{*}_{s}\bar{D}^{*}_{s} molecule is studied dynamically in the one boson exchange approach, where σ, η and φ exchange are included. Ten allowed D<sup>*</sup><sub>s</sub>[`(D)]^*_sD^{*}_{s}\bar{D}^{*}_{s} states with low spin parity are considered, and we find that the J ^PC =0⁺⁺, 1⁺⁻, 0⁻⁺, 2⁺⁺ and 1⁻⁻ D^*_s[`(D)]<sup>*</sup><sub>s</sub>D^{*}_{s}\bar{D}^{*}_{s} configurations are most tightly bound. We suggest that the most favorable quantum numbers are J <sup>PC</sup> =0<sup>++</sup> for Y(4140) as a D<sup>*</sup><sub>s</sub>[`(D)]^*_sD^{*}_{s}\bar{D}^{*}_{s} molecule; however, J ^PC =0⁻⁺ and 2⁺⁺ cannot be excluded. We propose to search for the 1⁺⁻ and 1⁻⁻ partners in the J/ψ η and J/ψ η′ final states, which is an important test of the molecular hypothesis of Y(4140) and the reasonability of our model. The 0⁺⁺ B^*_s[`(B)]^*_sB^{*}_{s}\bar{B}^{*}_{s} molecule should be deeply bound; experimental search in the ϒ(1S)φ channel at Tevatron and LHC is suggested.     

Progress in pion-decay channelling: Refractory bcc metals at high and low temperatures

By means of π⁺/μ⁺ channelling, positive pions (π⁺) implanted intoTa, Mo, andW are investigated up to high temperatures. A striking observation is that the channelling effect disappears in a rather narrow temperature interval centred at 0.26 (Ta) to 0.51 (W) of the melting temperature. From studies of π⁺ trapping by oxygen atoms inTa estimates for the low-temperature π⁺ diffusivity inTa [D _π(23K)=1.4·10^−10±0.3 m²s⁻¹,D _π(47K)=5.7·10^−10±0.3 m²s⁻¹] as well as for the binding enthalpy of π⁺ to 0 atoms (H _B=7·10⁻² eV) have been obtained. The diffusion data are in reasonable agreement with the theory of phonon-assisted tunnelling.     

Measurement of atomic parameters for the3 D 1 state of I–II

The decay rates of the³ D ₁ level of I–II and the 3s ₂ level of neon have been measured by the magnetic-field power dip method. The decay rate at the zero-pressure limit is found to be 7.1 MHz/2π for the³ D ₁ level. The collision cross-section for excited I ions with helium atoms equals 0.19×10⁻¹⁵ cm². This work was supported by project MR-1.5-1.05.     

Spectroscopic and structural proprieties of LiAr and LiAr<Subscript>2</Subscript> molecules

We determined and tried to understand the spectroscopic and structural properties of small LiAr and LiAr₂ molecules within a simple model considering LiAr as a result of interaction between a valence electron and a LiAr⁺ molecular ion. Potential energy curves, spectroscopic constants, and vibrational levels corresponding to the Li(2s, 2p, 3s, and 3p)+Ar dissociation are reported for the LiAr molecule. The depth of the potential well for the X ²Σ⁺ ground state is found to be 50 cm⁻¹ (the corresponding experimental value is (42.5±1.2) cm⁻1 [1]). R _e is determined to be 9.36 a.u. (the experimental value is 9.24 a.u.). For the first excited state A, R _e = 4.97 a.u. and D _e = 993cm ⁻¹ (the corresponding experimental values are 4.68 a.u. and (925−40) cm⁻¹, respectively [1]). The spacing between the vibrational levels for the ground and first excited states is in very good agreement with the experiment. For the ground state, the difference between our results and the data of the most recent experiment is about 1 cm⁻¹. The model has been extended to study the LiAr₂ molecule in two forms (linear and triangular). We have determined the potential energy surfaces of the states dissociating to Li(2s, 2p)+Ar₂ and thus found the triangular form to be more stable as compared to the linear one. We have also calculated the transition energy between the ground state and first excited states of this molecule. The emission spectrum of the Li(2s)+Ar₂→Li(2p)+Ar₂ transition in both forms redshifts as compared to the Li(2s)→Li(2p) atomic transition.     

Conservation laws for classical and relativistic collisions. II

On the basis of elementary symmetry arguments it is shown that (1) if in classical mechanics there exists a quantity λ+Σ_iμ_iυ_i+1/2νυ ² that is conserved, where λ,μ _i, andν are particle parameters, then theμ _i andν are all proportional to a single parameterμ and the quantityAμ+Σ_iB_iμυ_i+C(λ+ 1/2Dμυ ²), whereD ≡ν/μ, is conserved for all values ofA, B _i, andC; (2) if in relativistic mechanics there exists a quantity λ+Σ_iμ_iυ_i[1−(υ ²/c ²)]^−1/2+νc[1−(υ ²/c ²)]^−1/2 that is conserved, then theμ _i andν are all proportional to a single parameterμ and the quantityAλ+Σ_iB_iμν_i[1−(υ ²/c ²)]^−1/2+Cμc [1−(υ ²/c ²)]^−1/2 is conserved for all values ofA, B _i, andC.     

Perspectives for the measurement of Ds+ mesons via?the?Ds+ →K+K?π+ channel in the ALICE experiment

Heavy quarks, such as charm, are produced in hard scatterings in the early stages of high energy nucleus-nucleus collisions and are expected to be a powerful tool to investigate the properties of the quark gluon plasma (QGP). The tracking detectors of the ALICE apparatus will allow to track and identify particles in central rapidity range down to low P _t . Among D mesons it would be particularly interesting to measure D _s yield via an exclusive hadronic decay channel because it could help to disentangle different hadronization mechanisms. The possibility of reconstructing the D _s meson through its D _s ⁺→K ⁺ K ⁻ π ⁺ decay channel in the central barrel was studied. The problem considered is characterized by the comparatively low yield of the D _s mesons against the huge amount of combinatorial background. Different kinematic and topological cuts have been studied in order to increase the signal-to-background ratio and the statistical significance. In addition, D _s mesons preferentially decay through intermediate resonant states and this fact can improve the separation of signal from background. Results of cut parameters tuning and values of significance for an analysis performed on simulated data are presented.     

Detection of trielectronic recombination of In<Superscript>+</Superscript> ion

The trielectronic recombination of an In⁺ (4d ¹⁰5s ^{2 1} S ₀) ion in collisions with slow electrons, including the two-electron excitation of the 5s2 core of the ion with the simultaneous capture of the triply excited 5p ³ intermediate autoionizing state with its subsequent radiative stabilization 5p ³ → 5s5p ² + hν has been detected and experimentally examined for the first time. The maximum effective cross section of trielectronic recombination is 1.6 × 10⁻¹⁶ cm², which is comparable to the effective cross sections for both dielectronic recombination and electron excitation of the In⁺ ion.     

Screening effect of impurities in metals: a possible explanation of the process of cold nuclear fusion

Summary The screening length of the deuterium ion by surrounding electrons in a palladium metal lattice, as estimated using two approaches—viz. the Thomas-Fermi screening theory and the Debye screening theory for plasmas in metal—is found to be less than the interatomic separation of ordinary hydrogen molecules. This has important implications for the possibility of cold nuclear fusion at room temperature, since slight fluctuations in equilibrium conditions may drive the deuterons to fuse together. The relative magnitudes of screening length for the cold nuclear fusion regime and classical hot nuclear regimes (inertial and magnetic confinement) reveal that in the former a comparatively smaller amount of energy is needed to overcome the repulsive Coulomb barrier between two deuterium ions.     

Josephson and single-particle currents between partially dielectricized superconductors with charge-density waves

The amplitudes of the nonstationary Josephson current I ¹, the interference current I ², and the quasiparticle current J through symmetric and asymmetric tunnel junctions, including superconductors with charge density waves, are calculated. In the symmetric (s) case the dependence of the Josephson current I _s ¹ on the voltage V on the junction has a logarithmic singularity at |eV|=2Δ, Δ+D, and 2D, where , Δ and Σ are the superconducting and dielectric order parameters, and e is the unit charge. At temperatures T≠0 jumps appear in the current-voltage characteristics I _s ¹ (V) at |eV|=D−Δ. Jumps and singularities are observed in the currents I _s ² and J _s at the same voltages at which singularities and jumps appear in I _s ¹ , respectively. In the nonsymmetric (ns) junctions which include an ordinary superconductor, singularities and jumps occur at |eV|=D+Δ_BCS, Δ+Δ_BCS, and (for T≠0) |D−Δ_BCS| and |Δ−Δ_BCS|, where Δ_BCS is the order parameter of an ordinary superconductor. The quasiparticle current J _ns is an asymmetric function of the voltage V and does not depend on the sign of Σ. The results are compared with experiment. Fiz. Tverd. Tela (St. Petersburg) 39, 991–999 (June 1997)     

Theψ-particles in an SU4 scheme with anomalous currents

The recently discovered narrow peaks (theψ-particles) in e⁺e⁻ system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU₄ symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU₃ quantum numbers in the group SU₄. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can changeZ. The decays of theψ-particles are discussed. New enlarged SU₄ multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation of two rather broad resonances in e⁺ e⁻ collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays of theψ-particles. Important results concerning the recently observed phenomena in the process e⁺e⁻→hadrons follow in this scheme.     

Electromagnetic mass splittings of heavier hadrons in quantum chromodynamics

The electromagnetic mass splittings of heavier hadrons are estimated in the framework of gauge theory model where ligher quarks are taken to behave relativistically and the spatial wave functions are described by the spin-spin interaction affected relative distances between quarks. The predictions for (Ξ⁻-Ξ⁰), (Σ*⁰−Σ*⁺), (Ξ^*−-Ξ^*0), (D _c ⁺−D _c ⁰) and (D _c ^*+ −D _c ^*0 ) are in fair agreement with the experimental data available whereas those for (D _b ⁻ −D _b ⁰ ) and (D _b ^*− −D _b ^*0 ) are in qualitative agreement with other theoretical estimates.     

Search for <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">s</Emphasis></Subscript> → µµ<Emphasis Type="Italic">γ</Emphasis> at large hadron collider

The branching ratio for B _s → ℓ⁺ℓ⁻ γ mode is of the same order as B _s → ℓ⁺ℓ⁻, since there is no helicity suppression in the 3-body decay mode. New Physics beyond Standard Model may affect these rates favourably for experimental observation at LHC and simultaneous measurements of the modes B _s → μ⁺μ⁻ and B _s → μ⁺μ⁻ γ at LHC experiment will indicate the basic nature of the interaction at play. A simulation study has been performed to evaluate the potential of CMS detector to observe the more difficult mode of B _s → μ⁺μ⁻γ. An upper limit of 2.08 × 10⁻⁷ on the branching ratio is expected to be achieved corresponding to an integrated luminosity of 10 fb⁻¹.     

Observational constraint on generalized Chaplygin gas model

We investigate observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Union SNe Ia data, the observational Hubble data, the SDSS baryon acoustic peak and the five-year WMAP shift parameter. The result is obtained that the best-fit values of the GCG model parameters with their confidence level are A _s=0.73_−0.06^+0.06 (1σ) _−0.09^+0.09 (2σ), α=−0.09_−0.12^+0.15 (1σ) _−0.19^+0.26 (2σ). Furthermore, in this model, we can see that the evolution of equation of state (EOS) for dark energy is similar to quiessence, and its current best-fit value is w _0de=−0.96 with the 1σ confidence level −0.91≥w _0de≥−1.00.     

Deuterium-deuterium fusion by an activated precursor

Summary A general scheme is proposed for the interpretation of the phenomena involving low-energy hydrogen-isotope fusion. This scheme is especially developed for the interpretation of the fusion rate observed after the impact of heavy-water clusters (D₂O) _n , 25≲n≲1350, onto targets of titanium deuteride TiD. It is shown that 1) the impinging energy of large clusters or molecules is equiparted among a lot of target atoms which are brought in collective motion; 2) data can conveniently be represented in an Arrhenius plot; 3) this plot suggests that fusion is a thermally activated process from a metastable precursor; 4) the activation energy for the precursor formation isE ^*≃2E ₀ (E ₀ being the electron binding energy in the hydrogen atom), and 5) the activated precursor can reasonably be identified with the metastable binuclear heliumlike (D⁺D⁺)2e⁻ atom.     

Systematic trends in the line strengths of E1 transitions in the oxygen isoelectronic sequence

Line strengthsS for the dipole allowed transitions within then=2 complex of the oxygen isoelectronic sequence have been fitted in the formZ ² S=A+B/(Z −C), whereZ is the nuclear charge of a particular ion. The constantsA, B andC are determined by using a non-linear least square method. The data forS are taken from the configuration interaction calculations which included internal, semi-internal and all external type correlations for ions in the rangeZ=8 − 25. It is shown that the values ofA obtained from the fit for all the transitions are in excellent accord with the ab-initio values obtained in the hydrogenic limitZ → ∞ provided near degeneracy effects are included in the ground state multiplet 1s²2s²2p^{4 1}S.     

ESR study of exchange coupled pairs in copper diethyldithiocarbamate

ESR investigations on exchange coupled pairs of Cu ions in single crystals of Cu(dtc)₂, isomorphously diluted with the corresponding diamagnetic zinc salt, are reported. The spin Hamiltonian parameters for the coupled species (S=1) are:g _‖=2.1025,g ₊=2.031,A=75.1×10⁻⁴ cm⁻¹,B=14.8×10⁻⁴,D=276.0×10⁻⁴ cm⁻¹ andE=46.7×10⁻⁴ cm⁻¹. While theg andA tensors show tetragonal symmetry, the zeor-field splitting tensor is rhombic and has principal axes different from those of theg andA tensors. Intensity measurements made down to 4.2 K indicate that the exchange is ferromagnetic with |FFF| ∼ 10 cm⁻¹. Direct dipole-dipole interaction appears to be the major contribution to the zero-field splitting. A calculation on the distributed point dipole model shows that dipolar interaction is considerably modified by the high covalency of the Cu-S bond and accounts for the rhombic nature of the tensor. The possible exchange mechanisms in Cu(dtc)₂—direct exchange and superexchange through the bridging sulphurs—are discussed.     

Hydrogen diffusion constants in stainless steel and Pd60Ag40 alloy, and permeability of diaphragms made of these metals

Hydrogen permeability through diaphragms made of 12X18H12T stainless steel and Pd₆₀Ag₄₀ alloy under electrolytic hydrogen saturation has been studied with an electrolytic cell with a vacuum chamber. Hydrogen diffusion constants D _H = 3.86 × 10⁻¹⁰ cm² s⁻¹ for stainless steel and D _H = 4.36 × 10⁻⁸ cm² s⁻¹ for Pd₆₀Ag₄₀ alloy have been determined at a temperature of 40°C using the Berrer relations.     

Muons in type-II superconductors: μ+ diffusion in ultra-pure niobiumdiffusion in ultra-pure niobium

The diffusivityD _μ of positive muons (μ⁺) in the mixed state of superconducting high-purity, high-perfection niobium single crystals is investigated by measurements of the relaxation of the transverse muon spin polarization (μ⁺SR). The method makes use of the strong magnetic field gradients existing in the mixed state of Type-II superconductors and monitorsD _μ through the variation of the magnetic field felt by the μ⁺ during their diffusion through the crystals. For μ⁺ near the centres of the flux lines inNb it givesD _μ(4.6 K)=(8±2)·10⁻¹¹m²S⁻¹. The positive temperature coefficient ofD _μ indicates that at liquid-helium temperatures the diffusivity of μ⁺ inNb is mainly due to phonon-assisted tunnelling processes.