Higher-order radiative corrections to the electron anomaly in QED: A remark on asymptotic behaviour of vacuum polarization insertions and explicit analytic values at the first six ladder graphs

We show that the series of multiple lowest-order vacuum polarization insertions in the lowest vertex graph is convergent for finite Pauli-Villars regularizing mass, and becomes divergent in the limit of infinite regularizing mass. We then evaluate, analytically, the contributions due to the first twelve vacuum polarization insertions. We consider also the contributions to the electron anomaly due to the vertex ladder graphs. They are all positive and growing fast; the ratio between two successive ones is also growing, up to 2.95 for the last two we evaluate.     

The definition of B(3)=B(0)k: A reply to e. comay

The recent claim by Comay that the B⁽³⁾ field has non-zero divergence for dipole radiation is shown to be incorrect.     

NNLO corrections to \bar{B}\to X_{u}\ell \bar{\nu}_{\ell} and the determination of |V ub |

We study the impact of next-to-next-to-leading order (NNLO) QCD corrections on partial decay rates in $\bar{B}\to X_{u}\ell \bar{\nu}_{\ell}$ decays, at leading-order in the 1/m _b expansion for shape-function kinematics. These corrections are implemented within a modified form of the BLNP framework, which allows for arbitrary variations of the jet scale μ _i ～1.5 GeV. Our analysis includes a detailed comparison between resummed and fixed-order perturbation theory, and between the complete NNLO results and those obtained in the large-β ₀ approximation. For the default choice μ _i =1.5 GeV used in current extractions of |V _ub | within the BLNP framework, the NNLO corrections induce significant downward shifts in the central values of partial decay rates with cuts on the hadronic variable P ₊, the hadronic invariant mass, and the lepton energy. At the same time, perturbative uncertainties are reduced, especially those at the jet scale, which are the dominant ones at next-to-leading order (NLO). For higher values of μ _i and in fixed-order perturbation theory, the shifts between NLO and NNLO are more moderate. We combine our new results with known power-suppressed terms in order to illustrate the implications of our analysis on the determination of |V _ub | from inclusive decays.     

The reactions 6, 7Li, 9Be, 10B(e,e′p) at 700 MeV and DWIA analysis

The proton spectral functions of ⁶Li, ⁷Li, ⁹Be and ¹⁰B obtained from the (e, e′p) reactions at 700 MeV are presented. The results were analyzed in the distorted-wave impulse approximation, using the shell-model single-particle wave functions consistent with the elastic electron scattering results. The observed Ip proton momentum distributions for the nuclei ⁶Li, ⁷Li and ⁹Be show significant disagreement with the shell-model momentum distributions. The occupation probabilities of the proton single-particle states are around 0.7, with a few exceptions.     

A green's function analysis of atomic and molecular (e, 2e) reactions

Investigation of Atomic and molecular (e, 2e) spectra will be discussed in terms of a Green's function approach. The energy, intensity and momentum distribution of energy levels observed by electron coincidence ionization spectroscopy, are directly related to the poles, pole strengths and generalized overlap amplitude of the one particle propagator or Green's function. The theoretical calculation of these observable quantities via the Green's function technique will be discussed. In particular, the position and intensity of satellite (or “shakeup”) lines, relative to the main lines, will be analysed in some detail.     

A Local (Perturbative) Construction of Observables in Gauge Theories: The Example of QED

Interacting fields can be constructed as formal power series in the framework of causal perturbation theory. The local field algebra is obtained without performing the adiabatic limit; the (usually bad) infrared behavior plays no role. To construct the observables in gauge theories we use the Kugo–Ojima formalism; we define the BRST-transformation as a graded derivation on the algebra of interacting fields and use the implementation of by the Kugo–Ojima operator Q _int. Since our treatment is local, the operator Q _int differs from the corresponding operator Q of the free theory. We prove that the Hilbert space structure present in the free case is stable under perturbations. All assumptions are shown to be satisfied in QED. Received: 5 August 1998 / Accepted: 20 November 1998     

The Semileptonic Decay Modes {\bar{B} \rightarrow D\ell \bar{\nu}} and {\bar{B}_{s} \rightarrow D_{s} \ell \bar{\nu}}: A New Analysis in Potential Model

We consider the Schrödinger equation with a combination of Deng–Fan-type and harmonic terms. To solve the corresponding differential equation, we split the equation to two parts: the parent and the perturbation terms. We use the Nikiforov–Uvarov technique to solve the parent part. For the perturbation part, we apply the series expansion method. Next, using the calculated wave function, we investigate some bottom and charm mesons within the Isgur–Wise function formalism. We present especially semileptonic \({\bar{B} \rightarrow D\ell \bar{\nu}}\) and \({\bar{B}_{s} \rightarrow D_s \ell \bar{\nu }}\) decay widths, branching ratios and \({|V_{cb}|}\) (element of the CKM matrix). Masses of some pseudoscalar mesons are also indicated. Comparisons of our results with experimental values and other approaches are included.     

Improved radiative corrections for (e, e'p) experiments: Beyond the peaking approximation and implications of the soft-photon approximation

Analyzing (e, e'p) experimental data involves corrections for radiative effects which change the interaction kinematics and which have to be carefully considered in order to obtain the desired accuracy. Missing momentum and energy due to bremsstrahlung have so far often been incorporated into the simulations and the experimental analyses using the peaking approximation. It assumes that all bremsstrahlung is emitted in the direction of the radiating particle. In this article we introduce a full angular Monte Carlo simulation method which overcomes this approximation. As a test, the angular distribution of the bremsstrahlung photons is reconstructed from H(e, e'p) data. Its width is found to be underestimated by the peaking approximation and described much better by the approach developed in this work. The impact of the soft-photon approximation on the photon angular distribution is found to be minor as compared to the impact of the peaking approximation.     

Noble gas halides: The B → X and D → X systems of 136Xe35Cl

The B → X (2870–3100 Å) and D → X (2250–2370 Å) band systems of ¹³⁶Xe³⁵Cl are photographed and vibrationally analyzed. A simultaneous least-squares fit of 41 band-heads in the B-X system and 35 in D-X yields, in part, the following constants (in cm^?1): T_eB = 32 405.8, T_eD = 42 347.9, ω_eB = 194.75, ω_eD = 204.34, ω_eX = 26.22. The ground state dissociation energy ($\text{D}$″_e) is estimated to be 281 ± 10 cm^?1. Potential curves are derived for all three states through Franck-Condon calculations. From these curves the D-state internuclear distance is 0.09 ± .02 Å smaller than the B-state distance.     

Proton polarization in the p(e,e′p)π0 reaction and the measurement of quadrupole components in the N to Δ transition

The recoil proton polarization in the π⁰ production off the proton with longitudinally polarized electron beam has been studied as a means to measure quadrupole components in the N to Δ transition. On top of the Δ resonance a high sensitivity to a possible Coulomb quadrupole excitation is found in parallel kinematics. The ratio of S ₁₊/M ₁₊ multipole amplitudes can be determined from the ratio of the two in-scattering-plane recoil proton polarization components. Avoiding the absolute measurement of the polarizations, such a ratio allows small experimental uncertainties. Furthermore, the electron helicity independent proton polarization component enables the characterization of resonant and non-resonant pieces. Received: 3 November 1997     

The investigation of short-range 3He, 3H and deuteron spin structure via the measurement of the angular distributions of the analyzing power in the \vec dd \to {}^3Hen and \vec dd \to Hp reactions at 140, 200 and 270 MeV

The results on the vector A _y and tensor A _yy , A _xx and A _xz analyzing powers of the $\vec dd \to {}^3Hen$ and $\vec dd \to {}^3Hp$ reactions obtained at intermediate energies at RARF(RIKEN, Japan) are presented. The high precision experimental data are compared with the theoretical calculation within the one nucleon exchange model by using standard ³He, ³H and deuteron wave functions. The data demonstrate the sensitivity to the short-range ³He, ³H and deuteron spin structure.     

Finite-field calculations of molecular polarizabilities using field-induced polarization functions: second- and third-order perturbation correlation corrections to the coupled Hartree-Fock polarizability of H2O

Ordinary Rayleigh-Schrödinger perturbation theory with Møller-Plesset (RSMP) partitioning is used to calculate second- and third-order correlation corrections to the CHF polarizability and dipole moment of the water molecule by a finite-field procedure. [2/1] Padé approximants are found to be useful in accelerating the convergence of the property perturbation expansions. Field-induced polarization functions suitable for polarizability calculations are determined. The average polarizability calculated, neglecting vibrational averaging, with Dunning's (9s5p/4s-4s2p/2s) contracted GTO basis set augmented by field-induced 1s1p2d/1p polarization functions is within 3 per cent of the experimental result. Correlation corrections to the dipole moment and polarizability of the water molecule calculated by the finite-field RSMP and single + double excitation CI(SDCI) methods for the same basis set are found to be in close agreement. The RSMP approach has the advantages of being size-consistent and of being capable of greater efficiency than the SCDI method. Comparative calculations carried out using Epstein-Nesbet partitioning show that through third order RSEN correlation perturbation expansions for the dipole moment and polarizability are less rapidly convergent than RSMP expansions. However, reasonable accord with RSMP results can be achieved by using [2/1] Padé approximants to accelerate the convergence of RSEN energy perturbation expansions. The convergence of RSMP property correlation expansions based on the zeroth-order uncoupled-Hartree-Fock (UCHF) and coupled-Hartree-Fock (CHF) approximations are compared through third order. Whereas the CHF + RSMP expansions are for practical purposes fully converged, the UCHF + RSMP expansions are not adequately converged.     

Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

The recently reported coexistence of an oscillatory magnetic order with wave vector Q = 0.241⁻¹ and superconductivity in TmNi₂B₂C is analyzed theoretically. It is shown that the oscillatory magnetic order and superconductivity interact predominantly via the exchange interaction between localized moments (LMs) and conduction electrons, while the electromagnetic interaction between them is negligible. In the coexistence phase of the clean TmNi₂B₂C the quasiparticle spectrum should have a line of zeros at the Fermi surface, giving rise to the power-law behavior of thermodynamic and transport properties. Two scenarios of the origin of the oscillatory magnetic order in TmNi₂B₂C are analyzed: (a) due to superconductivity and (b) independently of superconductivity. Experiments in a magnetic field are proposed in order to choose between them.