An interpretation of the energy-momentum tensor of the dirac field with anomalous magnetic moment

The ground state radiative widths of the 1.56 MeV (3/2⁺) and the 1.35 MeV (5/2^?) levels in¹⁹F were determined by inelastic electron scattering. The measured cross sections have been analysed using DWBA calculations. The resultsΓ _y ⁰ (5/2^?→1/2^?,E3)=(8.1±1.7)·10^?10eV andΓ _y ⁰ (3/2⁺→1/2⁺,E2=(1.76±0.15)·10^?4eV are in agreement with, but more accurate than, former measurements.     

Critical scattering and pionic instabilities in heavy ion collisions

We investigate the effect of collective instabilities in heavy ion collisions. The focus is on critical scattering phenomena associated with pionic instabilities. The decay rate Γ of excited many-body systems is calculated in RPA. Γ is shown to give the rate of spontaneous “phonon” pair production. We express Γ as a sum of a collective, Γ_col, and a scattering, Γ_scat, rate. Γ_col is the pair production rate of phonons in unstable states. In the case of pionic instabilities, Γ_col is the condensation rate of π⁺π^? and π⁰π⁰ pairs into unstable states. Γ_scat is the pair production rate of phonons in the particle-hole excitation region and gives the two-body scattering rate in the medium. An effective (density-dependent) two-body cross section is obtained. The difference between critical scattering of external particles in a system near equilibrium and that of constituents of systems far from equilibrium is investigated. A model calculation suggests the existence of pionic instabilities in heavy ion collisions. Growth rates of unstable modes and the effective cross sections displaying critical scattering are calculated. Finally, we estimate Γ_scat and Γ_col.     

Asymptotic restrictions and ππ scattering lengths in non-linear chiral SU(2) × SU(2) dynamics

The most general effective lagrangian for ππ scattering, that takes into account the exchange of scalar (0⁺), tensor (2⁺) and ? mesons, is constructed within the framework of non-linear chiral SU(2) × SU(2) dynamics. Asymptotic restrictions proposed by Weinberg are imposed on the amplitude of ππ scattering. These restrictions allow one to obtain four independent sum rules containing particle masses, coupling constants and the coefficient A₂ in an expansion of the symmetry-breaking term in a power series of π². The use of only the f⁰ meson in the obtained sum rules leads to the following values of the ππ scattering lengths, the width of ?(700) → 2π decay, and the parameter A₂: α₀⁰ = 0.92m_π^?1, α₀² = 0.27 m_π^?1, α₁¹ = 0.033 m_π^?3, Γ[ε(700) → 2π] = 390 MeV, A₂ = + 1.6. It is shown that the inclusion of heavier mesons results in some increase of the ππ scattering lengths and the parameter A₂, but a decrease of the value of Γ(? → 2π). The field-algebra requirements lead to negligible changes in the results. Analysis of the sum rules shows the incompatability of the asymptotic restrictions with a symmetry breaking which has the transformation properties of the fourth component of a chiral vector.     

Measurement of the branching ratios for Kμ2+, Kπ2+, Ke3+ and Ke3+ decays using a magnetic spectrometer with streamer chambers

The momenta of ～30 000 charged particles from K⁺ decays were measured using a magnetic spectrometer with streamer chambers. The ratio R = Γ(K_π2⁺)/Γ(K_μ2⁺) = 0.3355 ± 0.0057 was obtained. Our values for the branching ratios are: (63.18±0.43)% for K_μ2⁺, (21.18±0.33)% for K_π2⁺, (3.33±0.51)% for K_μ3⁺, (4.99±0.54)% for K_e3⁺.     

Reaction dependence of nuclear decay linewidths

Various light- and heavy-ion reactions, 20 < E < 100 MeV, have been used to study the reaction dependence of α-decay widths for ⁸Be¹(2 ⁺ , 2.9 MeV) and ¹⁶O¹(1^?, 9.6 MeV). Although slight differences (< 20 %) are found for the observed line shapes (Γ), the resonance widths inferred (Γ_R) are self-consistent and indicate little if any reaction dependence (< 10 %). Near a decay threshold one may expect Γ < Γ_R by 20 % or more, however, and thus care must be taken in comparing decay widths inferred from nuclear reactions with those from scattering resonances. Reduced formal α-decay widths of γ_λ² = 680 ± 100 keV (s = 4.8 fm) and γ_λ² = 350 ± 50 keV(s = 5.4 fm), corresponding to θ_λ² = 0.50 and θ_λ² = 0.49 are deduced for ⁸Be¹(2 ⁺ , 2.9 MeV) and ¹⁶O¹(1^?, 9.6 MeV) using the nuclear-reaction Γ_R values and a particular set of α-nucleus potentials.     

The 1P shape resonance in electron-hydrogen scattering

The shape resonance in the ¹P channel in electron-hydrogen scattering which occurs just above the n = 2 threshold has been studied by variational calculations employing a pseudostate basis. Its parameters are E_R = 0.7512 (Ry), Γ = 0.0015 (Ry).     

Measurement of the alpha particle decay width of the first 0+, T = 2 state in 40Ca

The alpha decay width and total width of the first 0⁺, T = 2 state in ⁴⁰Ca have been measured by the elastic scattering of α-particles from ³⁶Ar. The results are Γ_α0 = 80 ± 10 eV and Γ = 81 ± 10 eV.     

Hyperfeinstrukturuntersuchung des 6p 2 P 3/2-Terms im Au I-Spektrum durch Resonanzstreuung von Licht

From about 6×10⁶ stoppingK ^?-meson reactions in the Saclay 80 cm hydrogen bubble chamber 70Σ ^?→Λe^?¯ν and 11Σ⁺→Λe⁺ν decays have been identified. The ratio of the vector to axial vector coupling constant has been determined,f ₁/g ₁=?0.22±0.28, consistent with the predictionf ₁=0 of the CVC-theory. The branching ratios for the two decay modes are,Γ(Σ ^?→Λe^?ν)/Γ(Σ^?→ all modes)=(0.69±0.12). 10^?4,Γ(Σ⁺→Λe⁺ν)/Γ(Σ⁺→ all modes)=(0.29±0.10). 10^?4. The ratio, Γ(Σ⁺→Λe⁺)/Γ(Σ^?→Λe^?v)=0.69±0.18, agrees with the phase space ratio, 0.61, therefore a theory that includes no second class currents is consistent with the data.     

Laser phase fluctuations in a four-level atomic system in N-configuration

We discuss here the effect of laser phase fluctuations on coherent spectroscopy of four-level N-system interacting with a trichromatic radiation field of frequencies Ω _i , (i = 1?3). The laser phase variables are described by the Wiener-Levy diffusion process to specify the bandwidths (Γ _i ) and cross-correlations (Γ _ij ) that may exist between pairs of laser fields. A general formalism based on the master equation and theory of multiplicative stochastic processes is developed and used to study three-photon and (2+1)-photon absorptive resonances in model N-system of ⁴⁰Ca⁺ ion. It is observed that the resonances are suppressed or broadened by all Γ _i ,(i = 1?3), while their revival is dependent only on Γ ₁₂ and Γ ₂₃, and yet the revival is only partial even when the relevant fields are critically correlated. In contrast Γ ₁₃ is observed to deteriorate the absorptive resonances. The distinctive features of the steady state and time dependent behavior of the system under three-photon and (2 + 1)-photon resonance conditions and for fluctuating fields are discussed.     

Nonfactorization and the decaysD s +→φπ +,φρ + andφl + ν l

Using the experimentally measured values ofx=A ₂(0)/A ₁(0) andy=V(0)/A ₁(0) and the measured ratiosR _st=Γ(D _s ⁺ →φl ⁺ ν _l)/Γ(D _ins ⁺ →φπ ⁺) andR _h=Γ(D _s ⁺ →φρ ⁺)/Γ(D _s ⁺ →φπ ⁺), we present evidence for significant nonfactorization contribution in the decay amplitude forD _s ⁺ →φπ ⁺. We analyze the role of nonfactorization inD _s ⁺ →φρ ⁺ and conclude that present data onR _h are consistent with factorization inD _s ⁺ →φρ ⁺. A measurement of polarization inD _s ⁺ →φρ ⁺ would greatly assist our analysis.     

Multihadronic decays and partial widths of the J/Ψ (3100) resonance produced in e+e− annihilation at adone

The reactions e⁺e^?→ hadrons and e⁺e⁺e^?→e⁺e^? have been studied at the J/gY (3100) resonance). The relative weights of the topological cross sections for fixed charged multiplicity are σ₂=(32±5)%, σ₄=(49±8)%, σ₆=(18±3)%, and σ₈=(1±0.6)%. The average pion multiplicities are 〈n_ch〉=3.8±0.3 and 〈n_{π^o〉=3.1±0.8}. The decay widths are Γ_e=(4.6±0.8) keV, Γ_h=(59±24) keV, and Γ=(68±26) keV.     

On the natural width of the hypersatellite lines

The natural width of a hypersatellite line (K ^?2→K ^?1 L ^?1 transition) has been measured for the first time. In the case of Cu (Z=29) this width has been found equal toΓ = 5 eV, i.e. much larger than that of the diagram (K ^?1→L ^?1) line. This result follows a proposed empirical law assuming this width to be equal to 3Γ _K+Γ_L.     

Unelastische Elektronenstreuung an14N für Anregungsenergien zwischen 8,5 und 11,5 MeV

¹⁴N was investigated by inelastic scattering of 35... 58 MeV electrons (scattering angles 117 to 165°). For theM1-transitions to the 2⁺,T=1 levels at 9.17 and 10.43 MeV, ground state radiation widths of (7.7±0.9) eV, and (12.1±1.5) eV, respectively, were obtained. The ratio of these two widths is 1.57±0.07. The 3^?,T=1 level at 8.90 MeV is excited by anM2-transition withΓ _γ ⁰ =(6.6±2.2) · 10^?3 eV. An excitation of a level at (11.01±0.07) MeV is observed.     

Measurement ofR ine + e − annihilation for\sqrt s between 7.4 and 9.4 GeV

The rationR=σ(e ⁺ e ^?→hadrons)/σ(e ⁺ e ^?→ µ⁺ µ^?) was measured with the LENA detector at DORIS in a scan between 7.40 and 7.48 GeV and between 8.67 and 9.43 GeV center of mass energies. Corrected for QED radiative effects,R is found to be constant with an average value ofR=3.37 ±0.06_stat±0.23_syst. No narrow resonances withΓ _ee (Γ _had/Γ _tot)?0.30 keV (95% C.L.) and no steps have been observed. Based on this value ofR, revised values for υ(1S) resonance parameters are presented.     

Disorder-induced Raman scattering of In1−xGaxP in the transverse acoustic phonon region

Raman scattering measurements have been performed on In_1?xGa_xP (0.62?x?1) over the entire frequency range of first and second order scattering. Besides the already known disorder activated band between the LO(Γ) and TO(Γ) modes a new disorder activated band is found in the region of transverse acoustic phonons around 87 cm^-1. The position of the new band shifts only slightly with composition while its strength and line-shape change.     

The Jπ = 3− doublet at Ex = 6241 keV in 18F: Isospin mixing

The resonance previously observed at E_x = 6241 keV in the reactions ¹⁷O(p, γ)¹⁸F and ¹⁴N(α, γ)¹⁸F has been found to be a closely separated doublet (ΔE_x = 2.09±0.04 keV). Resonance strengths in ¹⁷O(p, γ)¹⁸F, ¹⁷O(p, α)¹⁴N and ¹⁴N(α, γ)¹⁸ have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means of the ⁴He(¹⁴N, α)¹⁴N reaction using the differentially pumped gas target at CRNL. Analysis of these data using R-matrix theory yielded J^π = 3^? for both states and more precise values of the α-particle widths (Γ_α(lower) = 133 ±4 eV; Γ_α(upper) = 137 ±4 eV). The reduced α-particle widths and the E1 and M1 transition strengths indicate that the doublet arises from the nearly complete mixing of T = 0 and T = 1 eigenstates which in the absence of an isospin breaking interaction would have been separated by less than 40 eV. The α-particle scattering experiments included the J^π = 1⁺ resonance at E_x = 6257 keV and yielded the new values of Γ_α = 580±12 eV and Γ_p = 25⁺³⁵_?25 eV.     

Matthiessen's rule and its variation for cyclotron resonance width in two and three dimensions

Based on the proper connected diagram expansion, we calculated cyclotron resonance widths Γ_n associated with neighboring Landau states (n, n +1) for free electrons in interaction with more than one kind of impurities. In 3D usual Matthiessen's rule Γ_n=Γ⁽¹⁾_n+Γ⁽²⁾_n+…where Γ⁽ⁱ⁾_n represent widths calculated separately for each kind, is obtained. In 2D a new rule: is obtained.     

Resonances at collisions of slow electrons with cadmium atoms and ions

Using the crossed-beam method and a hypocycloidal electron spectrometer, the energy dependence of the ionization cross section for the cadmium atom has been studied in the near-threshold region and the elastic scattering of slow electrons at an angle close to 180° by Cd⁺ ions was studied for the first time. Within the region under study (0–7 eV above the first atomic ionization potential), a resonance structure determined by the contribution of atomic autoionization states is revealed in both the ionization curve and differential cross section of elastic scattering. The structure in the measured curves has been analyzed with the use of data on the ejected-electron spectra obtained under the excitation of autoionization states of Cd atoms, as well as the data on the optical excitation functions for the atomic spectral lines at λ=430.7 nm (5¹ P ₁-8¹ S ₀), 515.5 nm (5¹ P ₁-7¹ S ₀), 298.0 nm (5³ P ₂-6³ D _j ), and 361.0 nm (5³ P ₂-5³ D _j ).     

Luminescence of Tl<Superscript>+</Superscript> ions in a KZnF<Subscript>3</Subscript> crystal

The luminescence spectra of a KZnF₃: Tl⁺ crystal are investigated in the energy range from 4.75 to 5.9 eV at temperatures of 10–300 K upon excitation into the A absorption band (5.7–6.3 eV). At T=300 K, the luminescence spectra exhibit an intense band with a maximum at 5.45 eV, which is attributed to single Tl⁺ ions substituted for K⁺ ions. The 5.723-eV intense narrow band observed at T<20 K is assigned to the ³Γ_1u-¹Γ_1g zero-phonon transition, which is weakly allowed by the hyperfine interaction. The luminescence decay is studied as a function of temperature. The main characteristics of the luminescence spectra are adequately described in terms of the semiclassical theory based on the Franck-Condon principle and the Jahn-Teller effect for an excited sp configuration of the Tl⁺ ion with the use of the parameters obtained earlier from analyzing the absorption spectra of the system under investigation.     

Energy levels of O between 10.0 and 17.1 MeV excitation

A phase-shift analysis has been performed on ¹²C(α, α₀)¹²C cross sections which were measured over a broad angular range from 4.0 to 13.3 MeV in 15 to 50 keV increments. In addition to confirming the presence and determining the J, π, Γ, Γ_α, of the levels at 10.36, 11.50, 11.60, 12.47, 13.10, 13.11, 13.13, 13.25, 13.89, 14.07, 14.6, 14.82, 14.87, 15.47 and 16.30 MeV excitation in the ¹⁶O compound system, the results include the observation of a new 0⁺ level at 15.17 MeV. Definite J^π values of 4⁺, 5⁻ and 3⁻ have been assigned for the levels at 14.6, 14.82 and 15.47 MeV respectively. Refined level parameters are given for the 0⁺ (14.07 MeV) and 6⁺ (14.87 MeV) levels.