Inner-shell ionization by relativistic electron impact

K-, L andM-shell ionization cross sections have been measured for 23 elements, 12≦Z≦92, after bombardment with relativistic electrons, 15≦E ₀65MeV, by means of high resolution semiconductor detectors and a recently developed gas-scintillation proportional counter. For constant electron bombarding energyE ₀ the ionization cross sections follow a power law dependence,σ∽Z ^?α, and forE ₀=50MeV we deducedα =2.45±0.02 for theK shell andα=3.00 ±0.09 for theL shell. The observedZ dependence exhibits significant systematic deviations from theoretical predictions which exceed the experimental values up to 15 % at lowZ elements for theK shell and on the average about 11% for theL andM shell. The same behaviour of too low experimental values, i.e. an overestimation by the theory, is observed for the energy dependence of the cross sections for all shells. A scaling behaviour describing theZ andE ₀ dependence for allK-, L andM-shell data points is observed which also predicts the experimental values by other groups at lower and higher energies correctly. The comparsion of the measuredLΒ/Lα, andLγ/Lα intensity ratios for highZ elements with the values obtained by other groups in the energy range 0.3≦E₀≦1,000 MeV exhibits an increase with bombarding energy that cannot merely be explained by the energy dependence of the subshellionization cross sections for theL shell. An attempt to explain this effect with the change of the Coster-Kronig transition probability is described.     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

Study of high energetic electrons emitted during heavy ion collisions

Double differential cross sectionsd ² σ/dΩdE were measured for high energetic electrons emitted in heavy ion collisions. Electrons were detected in the energy range of 60 keV-500 keV for various target projectile combinations 66≦Z _u =Z _t +Z _p ≦145 and projectile velocities between 7 % and 10 % of the speed of light. Clear evidence was found that these electrons stem from the united atom formed during the collision. Slope and height of the spectra are discussed with respect to the momentum distribution of strongly bound states (i.e. theL-shell) at momenta far above the mean value. In addition for the systems S, Ni, Br→Pb electrons were detected in coincidence withK x-rays of Pb. By this method the contribution of theK-shell of the combined system to the total spectrum could be separated. Binding energies of theK-shell were estimated by a slope comparison between the coincident and single spectrum. The resulting values are close to the united atom limit.     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK _α- andK _β-lines and theK _α/K _β-intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

Measurements ofK-shell ionization with132Xe and208Pb projectiles in the energy range of 1.4–5.9 MeV/u

Projectile and targetK-shell ionization cross sections induced by 3.6-, 4.7-, and 5.9 MeV/u¹³²Xe ions and 1.4-, 3.6-, 4.7-, and 5.9 MeV/u²⁰⁸Pb ions from the UNILAC in thin solid targets between C and U are measured. The cross sections are discussed in terms of the molecular model of innershell vacancy production in heavy ion-atom collisions. The sharing of 2p _1/2σ vacancies between theK shells of the two collision partners in these very heavy ion-atom collisions is found to deviate from the Meyerhof-Demkov formula forR≦10^?2. The measured ionization cross sections are compared with theoretical calculations for 1sσ and 2p _1/2σ excitation cross sections. AZ _UA=Z₁+Z ₂ dependence is found independent ofZ ₁/Z ₂. Outer-shell vacancy configurations measured in these close encounters are reported.     

Hadronic ϕ production and the lund model for lowp T interactions

Experimental results on inclusive ? production are compared with the Lund model for lowp _T hadronic interactions. The data is based on a sample of 600,000 ? mesons in the kinematic rangep _T <1.0 (GeV/c)² and 0.0<x _F<0.4, produced in π^±,K ^±,p and \(\bar p\) Be interactions at 100 GeV/c and 120 GeV/c incident momentum. The Lund model reproduces the shapes of the longitudinal differential cross sections reasonably well, but the relative cross sections for incident, π,K andp show a discrepancy with the data.     

Direct photon production from pions and protons at 200 GeV/c

Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦P _T ≦6 GeV/c and center-of-mass rapidity ?0.4≦y ^*≦1.2. Inclusive cross sections are given for incident π^± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.     

K-shell ionization by protons for Cr,Cu, In and by alpha-particles for Cr,Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.     

Charged pion production in 32GeV/c K + p interactions

Final data on topological cross sections are presented. Inclusive single particle distributions for the reactionsK ⁺ p→ π^± X at 32 GeV/c are discussed and compared with data at lower energies. Early scaling in the fragmentation regions is confirmed, while cross sections in th central region continue to rise with energy even faster than inpp interactions. Thex-andp _T -dependence of the π⁺/π^? ratio inK ⁺ p interactions is discussed and a comparison of reactionsK ⁺ p→ π^± X andK ^? p→ π^± X at 32 GeV/c is made in the context of constituent models. We also present transverse momentum distributions, show prominent seagull effects and study how they are influenced by resonance production.     

Investigation of inclusive production ofK 0 andK * (892)0 mesons inK + A interactions at 11.2 GeV

Inclusive production ofK ⁰ andK ^* (892)⁰ mesons inK ⁺ A-interactions (A=Be, Cu, Pb) at the energy 11.2 GeV has been investigated to study hadronisation of the leading \(\bar s\) -quark; the results are presented. Double differential cross sections d²σ/dx _f dp _t ² were measured in the region of incident particle fragmentation (0.4≦x _f ≦1,p _t ≦0.5 GeV/c). The experimental data obtained were analysed on the basis of the Lund model FRITIOF and a quark-gluon model that takes into account colour screening and hadron formation length effects. The experimental data confirm the picture of hadronisation of the leading \(\bar s\) -quark developed in the latter model.     

K-shell X-ray production for fluorine ions on target elements Ti to La

The production of target atomK-shell X-rays has been studied for 2 to 28 MeV fluorine ions incident on thin solid targets of 14 elements with atomic numbers Z₂=22 to 57. Total X-ray production cross sections, energy shifts ofK _α andK _β lines andK _α/K _β intensity ratios were measured with a Si(Li) detector. The results of cross section measurements are compared with theoretical predictions of inner shell ionization. In most cases, satisfactory agreement between measured cross sections and theoretical Coulomb ionization cross sections, corrected for the perturbation of the target atom by the projectile charge and for relativistic effects, was obtained.     

Oxygen inducedK-shell ionization of selected elements from sulphur to bromine

K-shell X-ray production cross sections for oxygen ions on thin solid targets of 13 selected elements with atomic numbers between 16 and 35 were measured by a Si(Li) detector at incident ion energies from 7 to 24 MeV. Ionization cross sections are compared with calculations assuming Coulomb-ionization. Best agreement is found with theoretical cross sections that include corrections for binding energy and Coulomb deflection effects. Energy shifts ofK _α andK _β X-rays andK _α /K _β intensity ratios were also measured and are used to deduce information about outer shell ionization.     

TheL 1 subshell fluorescence and Coster-Kronig yields forZ=96

High resolution Si(Li)-Si(Li) and Si(Li)-Ge(Li) detector arrangements have been used to studyL x-ray spectra in coincidence withL-shell internal conversion electrons, gamma rays, andK x-rays emitted in²⁴⁹Cf decay. TheL ₁ subshell fluorescence and Coster-Kronig yields determined forZ=96 from these spectra are ω₁=0.25±0.06,f ₁₂≦0.10, andf ₁₃=0.69 ±0.08. The presence of theL ₁-L ₃ radiative transition is also further confirmed in this work.     

Low mass-scale parity restoration in expanded gauge theories

It is shown that schemes of grand unification withSU(2n)⁴ gauge symmetry permit the embedding of the left-right symmetricSU(2) _L ×SU(2) _R ×U(1)×SU(3) ^c intermediate symmetry at relativelylow energies [between 250 GeV and a few TeV] as well as allows light unification mass-scales (≦10⁵ TeV) ifn≧3 for values of the weak angle Sin² θ _W and the strong coupling α _S in the ranges 0.20≦Sin² θ _W ≦0.25, 0.10≦α _S ≦0.15.     

Coulomb-nuclear interference in π±p and K±p elastic scattering below 3 GeV: Measurements,real parts and K±p dispersion relations

The differential cross sections for π⁺p elastic scattering at0.6, 1.0, 1.5, 2.0, GeV/c for π^-p at 1.0, 1.5, 2.0 GeV/c, for K^-p at 1.2, 1.8, 2.6 GeV/c and for K^-p at 0.9, 1.2, 1.4, 1.6, 1.8, 2.6 GeV/c have been measured with an overall accuracy ofthe order of 1 to 2% in an electronics experiment over the angular region corresponding to momentum transfer t between 0.0005 and 0.10 GeV². Making use of the interference effects between the Coulomb and the nuclear interaction, we have determined the magnitude and sign of the real part of the scattering amplitude near t = 0. The K^±p real parts have been used in a dispersion relation to derive the value of the KNΛ coupling constant.     

L-shell vacancy production in Ag,Ta and Au for incident ionsZ 1≦10 in the energy range of 0.125–4 MeV/amu

Absolute Ag, Ta and AuL-shell X-ray cross sections were measured using protons,⁴He,¹⁴N as well as²⁰Ne ions in the energy range of 0.125–4 MeV/amu. By means of single-hole fluorescence yields experimental ionization cross sections were deduced and compared with calculations according to the corrected PWBA model — PWBA(BPCR). With decreasing asymmetry of the collision system the experimental cross sections exceed the predictions of the direct ionization theory. This is caused by an increasing contribution of a competing KL charge exchange mechanism which was investigated in detail for Ne+Ag. The Lapicki and Losonsky capture model was found to fail at energiesE<1 MeV/amu because adiabatic relaxation effects in the projectileK-shell become important. An estimation by means of the Nikitin model led to more physically comprehensible results at the lowest ion velocities investigated.     

Electrons ejected in resonant Raman scattering of X-rays on krypton

In the resonant Raman scattering of x-rays on krypton gas the ejected electrons were investigated by a proportional counter spectrometer. The cross sections for the process were determined for three energies of the incident photons (181 eV, 89 eV, and 33 eV below theK edge). The results agree with the theoretical predictions, thus independently confirming the theory that has so far only been tested by scattered photon data. From the cross sections the width of theK-shell excited state of krypton is extracted asΓ _K =(2.75±0.10) eV.     

η production in nuclei by protons at Tp≦ 1 GeV

The reactionpA →η X has been measured on⁶Li, C and Cu targets at a proton energy of 0.9 GeV at the SATURNE accelerator. The doubly differential cross sections at T_p=0.9 GeV together with data at T_p=1 GeV, previously presented [1], are analysed in the frame of a recent folding model [3].     

InclusiveK *+(890),K *+(1430) and\bar K^{ * - } (890) production inK + p interactions at 32 GeV/c

We present final results on inclusive production ofK ^*+(890),K ^*+(1430) andK ^*?(890) in \(\bar K^ + p\) interactions at 32 GeV/c, based on a statistics of ～27 events/μb. Total cross sections,p _T -andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK ^*+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks \(\bar s\) andu of theK ⁺ intoK ^*+(890), responsible in the Lund model for ～45% of theK ^*+(890) cross section, is strongly suppressed.     

K-shell ionization by protons for Cr, Cu, In and by alpha-particles for Cr, Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.