Production of excited electrons ine + e − interactions

We present a complete lowest order calculation of the processe ⁺ e ^?→(e ^*)→e ⁺ e ^? ρ based on a phenomenological Lagrangian where interference with “standard” amplitudes and spin correlation effects are considered. The calculation has been implemented in a Monte Carlo generator of unweighted events and can be used to study interactions with polarized beams as well as the effects of other excited fermions.     

Generator-coordinate study of inelastic α + 12C scattering

A multi-channel calculation performed with the generator coordinate method is presented for α + ¹²C scattering. The inelastic channel α + ¹²C(2⁺) is included. Bound-state and resonance energies are determined for J^π = 0⁺ up to 6⁺. For the negative parity levels, the results are very similar to those obtained with a single-channel calculation. The positive parity resonances are more numerous and in better qualitative agreement with experiment in the multi-channel calculation. However, an incorrect value for the threshold energy α + ¹²C(2⁺) channel prevents one from obtaining a quantitative agreement with experiment.     

Production of neutral MSSM Higgs bosons ine + e − collisions: a complete 1-loop calculation

We present the first complete 1-loop diagrammatic calculation of the cross sections for the neutral Higgs production processese ⁺ e ^?→Z ⁰ h ⁰ ande ⁺ e ^?→A ⁰ h ⁰ in the minimal supersymmetric standard model. We compare the results from the diagrammatic calculation with the corresponding ones of the simpler and compact effective potential approximation and discuss the typical size of the differences.     

Efficient field-free orientation of CO molecules using a three-step excitation scheme

We report results from detailed state selective photo-recombination study along with the doubly excited autoionizing resonances in Be-like C²⁺ and Al⁹⁺ ions. In the present investigation, the primary focus is on detailed energy profiles of the individual photo-recombination cross sections. The calculation was carried out for the excited Rydberg states of type 1s ²2sns(¹S^e) which interact with the odd-parity continua up to the C³⁺ and Al¹⁰⁺ 2p threshold limit. The numerical evaluation has been performed at a fine energy mesh across all the autoionizing Rydberg series of resonances 1s ²2pns(¹P⁰) converging to Li-like ion 2p threshold. The method of calculation keeps the essential ingredients of the Feshbach projection operator approximation. The photo-ionization cross sections have been evaluated with and without relativistic effects included into the R-matrix numerical procedures, while the allowance for both quantum interference between dielectronic and radiative recombination, and overlapping resonances has been done utilizing results from the earlier R-matrix Floquet calculation. We discuss all these results with respect to the effect of quantum interference term on the energy dependence profile of photo-recombination cross section for studied transitions.     

Asymmetry in charmed-particle production in a Σ− beam

We present a calculation of the inclusive x _F distributions of charmed hadrons produced in a high-energy Σ^? beam. The calculation is based on the modified mechanism of charmed-quark fragmentation, as well as on the mechanism of c-quark recombination with the valence quarks from initial hadrons. We predict additional asymmetry in the production of charmed hadrons due to different distributions of the valence s and d quarks in a Σ^? beam.     

Production of neutral MSSM Higgs bosons ine + e ? collisions: a complete 1-loop calculation

We present the first complete 1-loop diagrammatic calculation of the cross sections for the neutral Higgs production processese ⁺ e ^???Z ⁰ h ⁰ ande ⁺ e ^???A ⁰ h ⁰ in the minimal supersymmetric standard model. We compare the results from the diagrammatic calculation with the corresponding ones of the simpler and compact effective potential approximation and discuss the typical size of the differences.     

Effects of ground-state correlations on 2νββ decay rates and limitations of the QRPA approach

Half-lives of the 2νββ decay are calculated in the proton-neutron QRPA for⁷⁶Ge,⁸²Se,¹⁰⁰Mo,^128,130Te,¹³⁶Xe and¹⁵⁰Nd. The strength of the particle-particle interaction, which plays a decisive role for a reliable evaluation of the half-lives, is determined from a QRPA calculation of singleβ ⁺ decays. The 2ν decay rates calculated with the interaction strength fitted in this way are strongly suppressed and found to be consistent with the existing experimental data. Effects of the ground-state correlations on the suppression are investigated. On the other hand, the present calculation indicates limitations of the QRPA approach.     

Projected Hartree-Fock calculation in intermediate coupling for11B

An intermediate coupling calculation has been carried out for¹¹B using the deformed functions obtained from a Projected Hartree-Fock calculation as a basis. The resulting wave functions give an important improvement for the energy spectrum of the low-lying nonnormal parity levels. TheE2 matrix elements are enhanced with respect to the conventional shell model. Nuclear structure¹¹B; calculated levelsJ, π, B(M1),B(E2). Projected Hartree-Fock method, intermediate coupling.     

Compton profiles of multiply ionized oxygen atoms

We have calculated Compton profiles of multiply ionized oxygen atoms with electronic configurations 1s^m2sⁿ2p^q, m=1−2,n=0−2,q=0−4. The values of the Compton profiles from the present calculation can be used to determine the doubly differential electron production cross sections in recent ion-atom collision experiments with oxygen ions in the rest frame of the target atoms. The calculations have been performed in impulse approximation using numerical Hartree-Fock wave functions. Compton profiles of neutral oxygen atoms, available in the literature, are in excellent agreement with the present calculation. The variation of Compton profile with the degree of ionization is investigated.     

Microscopic study of the 12C + 16O system

An angular momentum projected microscopic calculation is performed for the ¹²C + ¹⁶O system with an effective nuclear force and the exact Coulomb interaction. The ¹²C wave function is projected on a 0⁺ state. Parametrizations of the Coulomb interaction between the nuclei are fitted. The L-projected energy curves present a quite complicated structure especially for the negative parity states. The role played by critical angular momenta is put into evidence. A generator coordinate calculation gives several bands of bound, quasibound and virtual states. Excellent agreement in energy and angular momentum is obtained with the 13.7 MeV (J = 9), 19.7 MeV (J = 14), 22.7 MeV (J = 15) and other resonances.     

Series expansion for mesonic masses in multicolor QCD

A systematic procedure for the calculation of mesonic masses in QCD with large number of colors is proposed. The masses are expanded in terms of an auxiliary parameter α, which is set to 1 at the end of the calculation. The expansion coefficients are expressed in general in terms of the Feynman integrals of QCD.The terms of order αⁿ involve diagrams with n loops. Explicit expressions are found up to α³. These terms appear to be rather small, so that one may try to extrapolate to α = 1. The qualitative properties of the spectrum are plausible, but for quantitative predictions further calculations are required.     

Electron momentum distribution in multiply-ionized neon atoms

We present momentum-space properties of multiply ionized neon atoms as a function of the degree of ionization of the atom. In particular, we have calculated the Compton profiles of all possible ionized states of neon atoms with electronic configurations 1s^m2sⁿ2p^q, m=1-2, n=0-2, q=0-6. The radial single-electron radial wave functions, obtained from the Hartree-Fock atomic model, were converted into momentum space wave functions by applying appropriate Fourier transformation. The values of the Compton profiles from the present calculation can be used to interpret experimental cross sections of variously ionized neon atoms colliding with other atoms. Compton profiles of neutral neon atoms, available in the literature, are in excellent agreement with the present calculation.     

A comment on the common one-dimensional derivation of the van der Waals forces

In many physical text-books a simple one-dimensional model is used to derive the characteristic 1/R ⁷-dependence of the attractive van der Waals forces. We show that this calculation is wrong. The long range forces in this simple model are not attractive but repulsive proportional to 1/R ⁶. Only a three-dimensional calculation yields the correct behavior.     

Accurate theoretical vibration-rotation energies and transition moments for HD+, HT+, and DT+

In this paper we report a theoretical calculation of vibration-rotation transition wavenumbers and transition moments for HD⁺, HT⁺, and DT⁺ for v, N ≤ 5. The results for HD⁺ agree with the experimental results to within 0.015 cm^?1.     

QED to lowest order ine + e −→e + e −γγγ

We calculate the cross-section for the production ofe ⁺ e ^?γγγ ine ⁺ e ^? annihilation. The results are in agreement with the first observation of such a process by the ASP experiment at SLAC. The calculation also provides another example of the power of ‘spinor techniques’ in calculating Feynman amplitudes.     

Optimized perturbation theory applied to jet cross sections ine + e − annihilation

The optimized perturbation theory proposed by Stevenson to deal with coupling constant scheme dependence is applied to the calculation ofπ _tot and jet multiplicities ine ⁺ e ^? annihilation. The results are compared with those of simple perturbation theory and with recent experimental cluster multiplicities.     

Theoretical Study of the 4He(γ, p)3H and 4He(γ, n)3He Reactions

Ab initio calculation of the total cross section for the reactions ⁴He(γ, p)³H and ⁴He(γ, n)³He is presented, using state-of-the-art nuclear forces. The Lorentz integral transform (LIT) method is applied, which allows exact treatment of the final state interaction (FSI). The dynamic equations are solved using the effective interaction hyperspherical harmonics method. In this calculation of the cross sections the three-nucleon force is fully taken into account, except in the source term of the LIT equation for the FSI transition matrix element.     

A local versus non-local t-matrix in the N(p, 2p)C reaction at 46 MeV

The angular distributions for the ¹⁴N(p, 2p)¹³C reactions at 46 MeV incident proton energy are calculated in the distorted wave t-matrix approximation (DWTA) where approximate optical-model waves are used. A comparison is made between the calculation using a local t-matrix to that of a non-local t-matrix. The (p, 2p) angular distribution is smaller in magnitude where a non-local t-matrix is employed compared to the calculation using a local t-matrix which implies that there is an overall enhancement of absorption associated with the non-local t-matrix. This also implies that differences between the local and non-local off-energy-shell effects can be significant. Parameter studies were undertaken for the distorted waves and bound state wave function and the effects on the angular distributions were similar in the local and non-local cases. The distortion effect due to the final-state focus phase dramatically changes the shape of the angular distribution. The calculations are considered to be a test of the off-energy-shell effects due to non-local interaction. This calculation is also a test of the approximate distorted waves at 46 MeV and the comparison to the ¹⁴N(p, 2p)¹³C data indicates that the distortion is reasonably well described.     

Production of two hard isolated photons ine + e − →μ + μ − γ γ at LEP

A calculation of the hard bremsstrahlung processe ⁺ e ^? →μ ⁺ μ ^? γ γ is presented and compared with recent results from the L3 Collaboration.