A study of hadronic decays of the ϒ′

We present a detailed study of the decays ?′ → π⁺π^?? and ?′ → π⁰π⁰?, where the ? decays subsequently to e⁺e^? or μ⁺μ^?. The results are obtained from a sample of 146 000 ?′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ?′ → π′π^?? and (10.3 ± 2.3)% for ?′ → π⁰π⁰?, and determined partial widths for these decays. Invariant mass and angular distributions of both the π⁺π^? and π⁰π⁰ systems are presented. We also set a limit on the branching fraction for ?′ → η? of less than 0.2% at the 90% confidence level.     

Optimal Hamiltonian of internal motion of an atomic-molecular system in a magnetic field

The effect of a uniform magnetic field on the state of an atomic-molecular system considered as a united system of N particles (without separation of the motion of acoelightac and particles) is analyzed. It is shown that the Hamiltonian of the internal motion of the system in the magnetic field contains (N-1)(N-2)/2 arbitrary parameters corresponding to the coefficients of the gauge transformation of the vector potential. A method of calculation of the optimal values of these coefficients based on the requirement for the minimum diamagnetic correction to the energy is proposed. New formulas for the diamagnetic susceptibility of atomic-molecular systems are obtained that take into account the simultaneous perturbing effect of the magnetic field on the motion of all particles. The theory is applied for calculation of the diamagnetic susceptibilities of the H, He, Li, and Be atoms; the muonic analogues of helium atoms ^∞He²⁺µ^? e ^?,⁴He²⁺µ^? e ^?, and ³He²⁺µ^? e ^?; and the positron-containing systems t ⁺ e ⁺ e ^? e ^?, d ⁺ e ⁺ e ^? e ^?, p ⁺ e ⁺ e ^? e ^?, µ⁺ e ⁺ e ^? e ^?, and e ⁺ e ⁺ e ^? e ^?, with regard for the motion of all particles.     

Analysis of the spectra of In XII–XIV and Sn XIII–XV in the far-VUV region

The 4p ⁶4d?(4p ⁶5p + 4p ⁶4f + 4p ⁵4d ²) transitions in the spectra of In XIII-Sn XIV and the 4p ⁶4d ²?(4p ⁶4d5p + 4p ⁶4d4f + 4p ⁵4d ³) transitions in the spectra of In XII-Sn XIII are investigated. About 150 spectral lines in the wavelength range 120–160 Å, which is important for projection vacuum UV lithography, have been classified for the first time. The fine structure intervals of the ground state 4p ⁶4d ² D and the energies of eight levels of the 4p ⁶5p, 4p ⁶4f, and 4p ⁵4d ² configurations are measured in each spectrum of In XIII and Sn XIV. The energies of all levels of the ground configuration 4p ⁶4d ² and the energies of 35 levels of the interacting configurations (4p ⁶5p + 4p ⁶4f + 4p ⁵4d ³) are determined in the spectra of In XII and Sn XIII. The resonant transitions 4p ^{6 1} S ₀?4p ⁵4d ¹ P ₁ in the spectra of In XIV and Sn XV are also identified. The semiempirical parameters of the configurations under study determined by mean-square fitting of measured level energies are in agreement along both isoelectronic and isonuclear sequences of the spectra.     

A measurement of the electromagnetic form factor of the eta meson and of the branching ratio for the eta Dalitz decay

In an optical spark chamber experiment we have obtained a sample of 80 eta Dalitz decays (η → e⁺e^?γ) and have measured the eta electromagnetic form factor to be F(X) = 1.0?(0.22 ±0.45)X, where X=M_ee²/M_η², and the branching ratio (η→e⁺e^?γ/(η→π⁺π^?π⁰)= (0.0082 ± 0.0020).     

Rotational distribution in simultaneously excited electronic states of CH

A²Δ, B²Σ^? and C²Σ⁺ states of CH were excited in discharges through flowing C₂H₂ and C₂H₄ and in flames of C₂H₂. The rotational distributions in these states were determined from the measured integrated intensities of rotational lines for bands of A²Δ → X²Π, B²Σ^? → X²Π and C²Σ⁺ → X²Π. The A²Δ state exhibits a non-Maxwellian distribution while the B²Σ^? and C²Σ⁺ states show Maxwellian distributions. The non-Maxwellian distribution of the A²Δ state and the different rotational distributions in the three states are discussed.     

Theoretical study of the spectroscopy of niobium nitride

State-averaged (SA) complete-active-space self-consistent-field (CASSCF) multireference configuration-interaction (MRCI) calculations are reported for the singlet and triplet states of NbN below about 20 000 cm⁻¹ and the quintet states below about 30 000 cm⁻¹. The theoretical spectroscopic constants for the four lowest triplet states, X³Δ, A³Σ⁻, B³Φ, and C³Π, are in excellent agreement with experiment. The calculations predict the ordering of states in the singlet manifold to be a¹Δ, b¹Σ⁺, c¹Γ, d¹Σ⁺, and e¹Π. These states have all been experimentally observed, except for the d¹Σ⁺ state near 13 000 cm⁻¹. The lowest quintet state, ⁵Π, is predicted to lie above 17 000 cm⁻¹. The calculations confirm the experimental conjecture, based on hyperfine splittings, that the X³Δ state is of predominantly 4dδ¹5s¹ character. Although the NbN molecule is very ionic, the ground-state dipole moment of 3.68 D is only moderately large, because of the polarization of the 5s electron away from nitrogen atom. Electronic transition moments are computed for all of the dipole-allowed transitions in the singlet and triplet manifolds. The radiative lifetimes for the v′ = 0 level are computed to be 37 ns, 35 ns, 1 μs, and 64 ns for the B³Φ, C³Π, d¹Σ⁺, and e¹Π states, respectively. For small v′, the largest Einstein coefficients all involve transitions with v′ = v″, because the transitions in NbN are nearly vertical. We constrast our results for NbN with similar calculations for the isoelectronic ZrO molecule. The considerable differences between the spectroscopy of ZrO and that of NbN are a result of the greater stability of the d orbitals for Nb, and the fact that Nb has a 4dⁿ⁺¹5s¹ ground state, whereas Zr has a 4dⁿ5s² ground state.     

The stability boundary of four-particle mesomolecules

Multiparametric variational calculations of the ground-state energy of symmetric four-particle mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^? as a function of masses M and m of particles X and Y are carried out. A basis consisting of 3200 Gaussian functions depending on all six interparticle distances is used. Calculations are carried out with the optimization of 1200 nonlinear parameters of the first 200 basis functions. As opposed to mesomolecules of the type X ⁺ X ⁺ Y ^? Y ^?, which are stable for all values of masses M and m in X ⁺ Y ⁺ X ^? Y ^? systems, are stable with respect to dissociation if the ratio of the masses of particles X and Y in them satisfies the condition 0.472≤M/m≤2.12. Hence it follows that four symmetric mesomolecules of the type considered (π⁺μ ⁺π^?μ^?, t ⁺ d ⁺ t ^? d ^?, p ⁺ K ⁺ p ^? K ^?, and d ⁺ p ⁺ d ^? p ^?) and 84 various asymmetric mesomolecules of the type X ⁺ Y ⁺ Z ^? T ^? are knowingly stable with respect to dissociation. For mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^?, which are stable with respect to dissociation, mathematical expectations of their physical quantities depending on interparticle distances that specify averaged geometrical structures of these systems are calculated and their dependence on the masses of particles M and m is studied.     

Lepton charge and model of weak interactions with μ-e transitions

The gauge model of weak interactions is proposed and μ^±?e^? transitions predicted by the model are discussed. Estimates are given for μ^±→e^? transitions on hadrons like K⁺→π^?μ⁺e⁺ with Γ (K⁺→π^?μ⁺e⁺) ? 10^?11Γ(K⁺ and μ^? capture on nuclei with W(μ^?→e⁺) ? 10^?12W(μ^? → ν). Single μ^± production in e^? beams with a cross section δ ～ 10^?42?10^?41 cm² is predicted.     

Investigation of theβ +-decay of105,106,109In and of100,102Ag

Isomers in the nuclei¹⁰⁰Ag (I=5⁺),¹⁰²Ag (I=5⁺),¹⁰⁵In (I=9/2⁺),¹⁰⁶In (I=6⁺),¹⁰⁸In (I=6⁺) were selectively populated by the reactions⁹⁰Zr(¹⁹F,xnγ),⁹²Mo(¹⁹F, 2pnγ),⁹²Mo(¹²C,pxnγ),⁹⁰Zr(¹⁹F,α3nγ) atE _lab=72 and 66MeV, and their (β ⁺+EC)-decay was studied with an Anticomptonγ-spectrometer. Spins of the beta-decaying isomers are determined. The results obtained for the beta strength functions are discussed as well as new information on the structure of the neutron-deficient even-even daughter nuclei nearZ=50.     

First observation of the production and decay of the Σc+

An event with the decay chain Σ_c⁺ → Λ_c⁺ + π⁰, Λ_c⁺ → K^? + p + π⁺, has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = ?ΔQ reaction v + p → μ^? + p + K^? + π⁺ + π⁺ + π⁰ with both gammas from the π⁰ decay detected. The proton and other final state particles are identified. The masses are M(Λ_c⁺) = 2290 ± 3 MeV/c², M(Σ_c⁺) = 2457 ± 4 MeV/c² and M(Σ_c⁺) ? M(Λ_c⁺) = 168 ± 3 MeV/c². Including other data one obtains M (Σ_c⁺⁺) ? M(Σ_c⁺) = 0 ± 4 MeV/c².     

Phenomenology of Σ+→pℓ+ℓ− and the structure of the weak non-leptonic Hamiltonian

The problem of the radiative non-leptonic weak baryon decays is reviewed in light of the new experimental findings. With the aim of exploring the structure of the weak non-leptonic Hamiltonian, we present a detailed phenomenological analysis of Σ⁺→p?⁺?^? transitions. Lower and upper limits for rates derivable with standard physics are determined as Γ(Σ⁺→pe ⁺ e ^?)/Σ⁺→pγ)≧7.2×10^?3 and 1/1210? Γ(Σ⁺→pe ⁺ e ⁺)/Γ(Σ⁺→pe ⁺ e ^?)?1/120. From existing data on Σ⁺→pe ⁺ e ^? we obtain limits on the values of the charge radius form factors |c ₁/b ₁|?5;|c ₂/b ₁|? 10, where the magnetic form factor is given by the Σ⁺→dγ, decay asb ₁(0)= 6.9±0.9 MeV. The short distance contribution of the QCD corrected single quarks→dλ transition is shown not to play a dominant role in these decays.     

Hyperfine anomaly in the spectrum of the osmium atom. effect of the spatial distribution of nuclear charge

Contributions of the superposition of configurations ns ²5d ⁸+ns5d ⁸ n′s (n=1–5, n′=6–10) and ns ²5d ⁶+ns5d ⁶ n′s (n=1–6, n′=7–10) to parameters a _5d ⁰¹ , a _5d ¹² , and a _5d ¹⁰ of the hyperfine structure in the spectrum of the osmium atom OsI are calculated. It is shown that the nonzero contribution is made only to a _5d ¹⁰ . The effect of the spatial distribution of nuclear charge on the parameters of the hyperfine structure in the spectra of ¹⁸⁷Os and ¹⁸⁹Os isotopes and on the hyperfine anomaly for the 5d ⁷6s levels in the spectrum of these isotopes is estimated.     

Possible mechanisms of fragmentation of 16O nuclei with a momentum of 4.5 GeV/c per nucleon in track emulsions

The angular distributions of doubly charged fragments of ¹⁶O nuclei having a momentum of 4.5 GeV/c per nucleon and interacting with track-emulsion nuclei were studied. The experimental angular distributions of doubly charged fragments of a ¹⁶O nucleus are not described by the statistical model of the fragmentation of nuclei. The possible channels of fragmentation of ¹⁶O nuclei may include ¹⁶O → 2⁸Be → 4α, ¹⁶O → ⁸Be +⁸ Be* → 4α, ¹⁶O → 2⁸Be* → 4α, ¹⁶O → α+¹²C, ¹⁶O → α +¹²C* → α + 3α, ¹⁶O → α +¹²C* → α + pα ⁷Li, ¹⁶O → α +¹²C* → α + 2⁶Li, ¹⁶O → α +¹²C* → α + pt2α, ¹⁶O → Li + B, and ¹⁶O → Li* + B*.     

Measurement of pp annihilation cross sections into charged particles in the momentum range 374–680 MeV/c

$\text{p}\text{p}$ annihilation cross sections into 2-, 4- and 6-prong topologies, and the exclusive annihilation cross sections for the π⁺π^?, K⁺K^?, π⁺π^?π⁰, π⁺π⁺π^?π^?, π⁺π⁺π^?π^?π⁰, π⁺π⁺π⁺π^?π^?π^?, and π⁺π⁺π⁺π^?π^?π^?π⁰ channels in the momentum range 374–680 MeV/c were measured. No prominent structure was observed in the momentum dependence of any of the above cross sections, but a small enhancement in the cross section was observed at 490 MeV/c corresponding to the S meson mass in the topological, and π⁺π^?π⁰ and π⁺π⁺π^?π^?π⁰ cross sections. If the extensive of the S meson with a mass and width of 1935.5 and 2.8 MeV/c² is assumed, our measurement gives a total resonant annihilation cross section into charged particles of 10.0±3.0 mb.     

High precision measurements of the hyperfine structure of seven metastable atomic states of57Fe by laser-Rf double-resonance

The hyperfine structure of the metastable atomic states (3d ⁷4s)⁵ F _2,3,4,5 and (3d ⁷ 4s)³ F _2,3,4 of⁵⁷Fe has been measured using theABMR- LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). From these measurements the following hfs constantsA of the magnetic dipole interaction have been obtained (corrected for second order effects):A(⁵ F ₂)=55.994(7) MHzA(⁵ F ₃)=69.632(5) MHzA(⁵ F ₄)=78.435(4) MHzA(⁵ F ₅)=87.246(3) MHzA(³ F ₂)=143.328(4) MHzA(³ F ₃)=50.602(10) MHzA(³ F ₄)=13.456(5) MHz     

Analysis of the 2ν3 band of 12CD3F at 5.06 μm recorded under high resolution

The 2ν₃(A₁) band of ¹²CD₃F near 5.06 μm has been recorded with a resolution of 20–24 × 10^?3 cm^?1. The value of the parameter (α^B ? α^A) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν₀ = 1977.178(3) cm^?1, B″ = 0.68216(9) cm^?1, D″_J = 1.10(30) × 10^?6 cm^?1, α^B = (B″ ? B′) = 3.086(7) × 10^?3 cm^?1, and β^J = (D″_J ? D′_J) = ?3.24(11) × 10^?7 cm^?1. A value of α^A = (A″ ? A′) = 2.90(5) × 10^?3 cm^?1 has been obtained through band contour simulations of the R(J) and P(J) multiplets.     

Fourier transform spectroscopy of NbS

Emission bands attributed to the NbS radical have been observed in the near infrared and visible regions with FTS techniques using an electrodeless 2450 MHz discharge as a source. Transitions within the doublet and quartet manifolds were recorded at high resolution. The present paper gives the first rotational analysis of this molecule. Numerous bands within the doublet and quartet manifolds have been analyzed, resulting in the characterization of seven different electronic states, three in the doublet and four in the quartet manifold. The states have been labeled in analogy with NbO. The analyzed electronic states are: X⁴Σ⁻, C⁴Σ⁻, A′⁴Φ, D⁴Δ, a²Δ, c²Π, and e²Φ. Four additional substates in the doublet manifold have also been analyzed. In all, 27 vibrational sublevels have been included in the analysis, the total number of rotational lines being about 18 000. The positions of the analyzed transitions are: C⁴Σ⁻ → X⁴Σ⁻ near 15 670 cm⁻¹, D⁴Δ → A′⁴Φ near 7740 cm⁻¹, c²Π → a²Δ near 5850 cm⁻¹ and e²Φ → a²Δ near 8500 cm⁻¹. The overall picture is consistent with the corresponding analysis of NbO. However, three energy separations could not be derived from the experimental data in the case of NbS, i.e., the a²Δ− X⁴Σ⁻, A′⁴Φ− X⁴Σ⁻ and a²Δ_5/2-a²Δ_3/2 splittings. These were set to 4992, 5490, and 992 cm⁻¹, respectively, from preliminary ab initio calculations. In this way, a tentative energy level scheme could be drawn. The first order spin-orbit parameter of the A′⁴Φ state was indeterminable from the experimental data and was set to the value 170 cm⁻¹, derived from the same calculations.     

Hyperfine structure of the atomic osmium spectrum: Superposition of configurations and the effect of nucleus volume

The contributions of the superposition of configurations ns ²5d ⁷6s+ns5d ⁷6sn′s+ns5d ⁷6s ² (n=1–5, n′=7–10) to the parameters of the hyperfine structure a _5d ⁰¹ , a _5d ¹² , a _5d ¹⁰ , a _6s ¹⁰ in the spectrum of the osmium atom Os I are calculated. Nonzero contributions are shown to be made only to the parameters a _5d ¹⁰ and a _6s ¹⁰ . This fact justifies the inclusion of the parameter a _5d ¹⁰ in the semiempirical analysis of experimental values of magnetic dipole constants of the hyperfine structure of the 5d ⁷ s configuration in the spectrum of the osmium atom. The effect of nucleus volume on the parameters of the hyperfine structure in the spectra of osmium isotopes ¹⁸⁷Os and ¹⁸⁹Os is estimated.     

Experimental determination of isotope shifts in Mg I

The isotope shift in the Mg l transitionsλλ 5167, 5172 and 5183Å (3s3p ³ P-3s4s ³ S) andλ 5528 Å (3s3p ¹ P 3s4d ¹ D) has been measured for the isotopes²⁴Mg,²⁵Mg and²⁶Mg. The hyperfine structure of theλ 5167 Å line has been studied and theA andB factors for the 3s4s ³ S ¹ level in²⁵Mg determined. The measurements were made with separated isotopes using a scanning Fabry-Perot interferometer.