Coincidence Cross Sections Research Articles

Target K-shell X-ray emission associated with single and double electron capture for [formula omitted] + Ar collisions

Cross sections for target Ar K-shell ionization associated with single and double electron capture, as well as the same cross sections corresponding to projectile F K X-rays and the total cross sections for single and double capture, were determined for 1.8–2.2 MeV/u F9+,8+,7+ projectiles. This work was performed at Western Michigan University using the tandem Van de Graaff accelerator. Coincidences between emitted X-rays and their corresponding charge-changed particles were detected. The Ar K X-ray coincidence cross section ratios for double to single capture are found to depend strongly on the incident charge state, with the ratios for F9+ well exceeding unity. Possible explanations for this anomalous behavior are discussed but a conclusive explanation is not found. The results are compared to previous experiments using fully-stripped fluorine where coincidence techniques were not employed.

Single and double electron capture associated with characteristic K-shell X-ray emission for F9+,8+,7++Ar

SynopsisCross sections for target Ar K-shell ionization associated with single and double electron capture, as well as the corresponding cross sections for total electron capture and the projectile F K x rays, were determined for 1.8-2.2 MeV/u F9+,8+,7+ projectiles. The Ar K x-ray coincidence cross section ratios for double to single capture are found to vary strongly with the incident charge state, with the ratios for F9+ well exceeding unity.

Revisit of (e,2e) & (e,3e) processes on atoms with twisted electron impact

SynopsisWe compute Triple Differential Cross Section (TDCS) and Five-fold Differential Cross Section (FDCS) for (e,2e) & (e,3e) processes on atoms respectively to investigate the effects of non zero angular momentum and the apex angle of the twisted electron. We observed that the differential coincidence cross sections largely depend on these parameters.

Continuous connection of two adjacent pipe parts defined by line, bézier and hermit center curves

A shape of pipe part consist of the longitudinal and cross section boundary curve. Also, it can be defined by only its center curve of the pipe. To build a complete pipe, we can connect continually the pipe parts. This paper discuss about continuous connection of two adjacent pipe parts that are defined by line, Bézier and Hermit curves. The method is as follows, we join continually two adjacent center curves of the pipe parts and then by using the same formulae, we define its coincidence cross section boundary curves of the pipes. Finally, the joining of the longitudinal section boundary curves of the pipe parts can be done. The results of this study show that we can evaluate the joint continuity between two adjacent pipe parts defined by line, Bézier and Hermit curves, using the various forms of its center and cross-longitudinal section boundary curves.

Coincidence charged-current neutrino-induced deuteron disintegration

Deuteron disintegration by charged-current neutrino (CC$\nu$) scattering offers the possibility to determine the energy of the incident neutrino by measuring in coincidence two of the three resulting particles: a charged lepton (usually a muon) and two protons, where we show that this channel can be isolated from all other, for instance, from those with a pion in the final state. We discuss the kinematics of the process for several detection scenarios, both in terms of kinematic variables that are natural from a theoretical point of view and others that are better matched to experimental situations. The deuteron structure is obtained from a relativistic model (involving an approximation to the Bethe-Salpeter equation) as an extension of a previous, well-tested model used in deuteron electrodisintegration. We provide inclusive and coincidence (semi-inclusive) cross sections for a variety of kinematic conditions, using the plane-wave impulse approximation, introducing final-state hadronic exchange terms (plane-wave Born approximation) and final-state hadronic interactions (distorted-wave Born approximation).

EXTENDED OPTICAL MODEL ANALYSES FOR 9Be + 144Sm SYSTEM NEAR COULOMB BARRIER ENERGIES

Within the framework of an extended optical model, we study elastic scattering and fusion cross section data for 9 Be + 144 Sm system near Coulomb barrier energies to determine the polarization potential decomposed into direct reaction and fusion parts. We show that the direct reaction and fusion potentials extracted from χ2 analyses separately satisfy the dispersion relation and that the threshold anomaly exhibits in the fusion part. The analyses using only elastic scattering and fusion data can furnish very consistent and reliable predictions of cross sections even though the direct reaction cross section data are not enough. From these analyses, we also obtain the semi-experimental α single and α–α coincidence cross sections, [Formula: see text] and [Formula: see text], for 9 Be + 144 Sm system.

Ionization of helium by impact of negative B, O, and F ions

Single and double ionization processes for helium under the impact of B, O, and F anions were studied in the 1.1-1.9 a.u. velocity range. Coincidence cross sections were measured for direct ionization (DI), i.e., no projectile electron loss, and single (SL) and double projectile electron loss. The results show that DI is dominated by large impact parameters and SL is essentially the elastic scattering of the extra electron by the target. The cross section ratios taken between double and single helium ionization for single and double loss are projectile independent and grow almost linearly with the velocity.

Covariant description of inelastic electron-deuteron scattering: Predictions of the relativistic impulse approximation

Using the covariant spectator theory and the transversity formalism, the unpolarized, coincidence cross section for deuteron electrodisintegration, $d(e,e'p)n$, is studied. The relativistic kinematics are reviewed, and simple theoretical formulae for the relativistic impulse approximation (RIA) are derived and discussed. Numerical predictions for the scattering in the high $Q^2$ region obtained from the RIA and five other approximations are presented and compared. We conclude that measurements of the unpolarized coincidence cross section and the asymmetry $A_\phi$, to an accuracy that will distinguish between different theoretical models, is feasible over most of the wide kinematic range accessible at Jefferson Lab.

Quasifree kaon photoproduction on nuclei

Investigations of the quasifree reaction A( γ, KY)B are presented in the distorted wave impulse approximation (DWIA). For this purpose, we present a revised tree-level model of elementary kaon photoproduction that incorporates hadronic form factors consistent with gauge invariance, uses SU(3) values for the Born couplings and uses resonances consistent with multichannel analyses. The potential of exclusive quasifree kaon photoproduction on nuclei to reveal details of the hyperon–nucleus interaction is examined. Detailed predictions for the coincidence cross section, the photon asymmetry, and the hyperon polarization and their sensitivities to the ingredients of the model are obtained for all six production channels. Under selected kinematics these observables are found to be sensitive to the hyperon–nucleus final-state interaction. Some polarization observables are found to be insensitive to distortion effects, making them ideal tools to search for possible medium modifications of the elementary amplitude.

Light-charged-particle emission in the matched reactions 280 MeV40Ar+27Aland 670 MeV55Mn+12C:Coincidence results

Exclusive measurements of light-charged-particle ({sup 1}H, {sup 2}H, and {sup 4}He) energy spectra, angular distributions, and emission multiplicities are reported for the two reactions {sup 40}Ar+{sup 27}Al and {sup 55}Mn+{sup 12}C at a matched excitation energy of 127 MeV. Comparisons are made with statistical model predictions for the evaporative processes in these reactions, which can be characterized as emissions from rotational-energy-dominated systems. The model simulations do well in reproducing a broad range of angular distribution data and the {sup 4}He/{sup 1}H cross-section ratio, using spin distributions derived from fusion cross-section systematics. The same model parameters, however, predict particle energy spectra and coincidence cross sections which are inconsistent with the measurements for both reactions. These results support previous conclusions from model comparisons with inclusive data, and suggest fundamental flaws in the statistical model as applied to light-mass, high-spin, nuclear systems. (c) 2000 The American Physical Society.

Out-of-plane measurements of the fifth response function of the exclusive electronuclear response

The first measurements of fLT′, known as the fifth response function, have been made for the 2H(e→,e′p) and 12C(e→,e′p) reactions. This response is directly related to the imaginary part of the interference between the transverse and longitudinal nuclear electromagnetic currents. Its observation requires longitudinally polarized electron beams and out-of-plane detection, the latter made possible by the newly developed out-of-plane spectrometer system. The initial measurements were made by using a 560-MeV polarized electron beam and quasielastic kinematics at Q2=3.3 fm−2. The development of the methodology for out-of-plane physics, and the analysis of the data from the initial experiments are described in detail. The measured fifth response and the related asymmetry in the coincidence cross section are in agreement, albeit with large statistical errors, with the theoretical predictions. Future extensions of the out-of-plane program are also discussed.Received 16 December 1998DOI:https://doi.org/10.1103/PhysRevC.60.064622©1999 American Physical Society

Higher nucleon resonances in exclusive(γ,πN)reactions on nuclei

We report calculations for exclusive pion photoproduction on nuclei beyond the first resonance region in the distorted wave impulse approximation. The elementary operator contains contributions from the resonances ${P}_{33}(1232),$ ${P}_{11}(1440),$ ${D}_{13}(1520),$ ${D}_{33}(1700),$ ${S}_{11}(1535),$ ${S}_{11}(1650),$ and ${F}_{15}(1680),$ in addition to the usual Born plus vector meson contributions. It gives a good description of single pion photoproduction data up to about 1.1 GeV. Final state interactions are incorporated via optical potentials and are found to be substantial in the coincidence cross sections, but insensitive to the photon asymmetry. Clear signatures of possible medium modifications of the ${D}_{13}$ and ${F}_{15}$ resonances are predicted under selected kinematics.

Coulomb and nuclear breakup of8B

The cross sections for the ${(}^{8}{\mathrm{B},}^{7}\mathrm{Be}\ensuremath{-}p)$ breakup reaction on ${}^{58}\mathrm{Ni}$ and ${}^{208}\mathrm{Pb}$ targets at the beam energies of 25.8 MeV and 415 MeV have been calculated within a one-step prior-form distorted-wave Born approximation. The relative contributions of Coulomb and nuclear breakup of dipole and quadrupole multipolarities as well as their interference have been determined. The nuclear breakup contributions are found to be substantial in the angular distributions of the ${}^{7}\mathrm{Be}$ fragment for angles in the range of $30\ifmmode^\circ\else\textdegree\fi{}--80\ifmmode^\circ\else\textdegree\fi{}$ at 25.8 MeV beam energy. The Coulomb-nuclear interference terms make the dipole cross section larger than that of quadrupole even at this low beam energy. However, at the incident energy of 415 MeV, these effects are almost negligible in the angular distributions of the ${(}^{7}\mathrm{Be}\ensuremath{-}p)$ coincidence cross sections at angles below $4\ifmmode^\circ\else\textdegree\fi{}.$

Measurement of the interference structure functionRLTfor the12C(e,e′p)reaction in the quasielastic region

The coincidence cross section and the interference structure function, ${R}_{\mathrm{LT}},$ were measured for the ${}^{12}\mathrm{C}{(e,e}^{\ensuremath{'}}p){}^{11}\mathrm{B}$ reaction at quasielastic kinematics and central momentum transfer of $|\stackrel{\ensuremath{\rightarrow}}{q}|=400\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{c}.$ The measurement was at an opening angle of ${\ensuremath{\theta}}_{\mathrm{pq}}=11\ifmmode^\circ\else\textdegree\fi{},$ covering a range in missing energy of ${E}_{m}=0$ to 65 MeV. The ${R}_{\mathrm{LT}}$ structure function is found to be consistent with zero for ${E}_{m}g50\mathrm{MeV},$ confirming an earlier study which indicated that ${R}_{L}$ vanishes in this region. The integrated strengths of the $p$- and $s$-shell are compared with a distorted wave impulse approximation (DWIA) calculation. The $s$-shell strength and shape are also compared with a Hartree Fock--random phase approximation (HF-RPA) calculation. The DWIA calculation does not succeed in giving a consistent description of both the cross section data and the extracted ${R}_{\mathrm{LT}}$ response for either shell. The HF-RPA calculation describes the data more consistently, which may be due to the inclusion of 2-body currents in this calculation.

The three-spectrometer facility at the Mainz microtron MAMI

A set-up of three high-resolution magnetic spectrometers, for simplicity named A, B and C, has been built as the central facility for the precise determination of double and triple coincidence cross sections of hadron knock-out and meson production through the scattering of electrons at the Mainz microtron MAMI. The spectrometers A and C with point-to-point optics in the dispersive plane and parallel-to-point optics in the non-dispersive plane have a solid angle of 28 msr and a momentum acceptance of 20 and 25%, respectively. They each consist of a quadrupole, a sextupole and two dipole magnets, reaching maximum momenta of 735 and 550 MeV/c, respectively. The spectrometer B has a solid angle of 5.6 msr and a somewhat reduced momentum acceptance of 15%, but it reaches a maximum momentum larger than that of the MAMI electron beam (855 MeV/c). It consists of a single-clamshell dipole magnet with point-to-point optics in both planes. Each spectrometer is equipped with a position-sensitive detector system consisting of four planes of vertical drift chambers, two planes of plastic scintillators and a threshold gas Cherenkov detector. The operational experiences demonstrate that all three spectrometers exceed the specifications. Selected results of double (e, e′ x) and triple (e, e′ x 1 x 2) coincidence experiments, x 1 and x 2 standing for charged hadrons, are presented, which demonstrate the performance of the whole set-up.

Damping mechanisms of theΔresonance in nuclei

The damping mechanisms of the {Delta}(1232) resonance in nuclei are studied by analyzing the quasifree decay reactions {sup 12}C({pi}{sup +},{pi}{sup +}p){sup 11}B and {sup 12}C({sup 3}He,t{pi}{sup +}p){sup 11}B and the 2p emission reactions {sup 12}C({pi}{sup +},pp){sup 10}B and {sup 12}C({sup 3}He,tpp){sup 10}B. The coincidence cross sections are calculated within the framework of the isobar-hole model. It is found that the 2p emission process induced by the decay of the {Delta} resonance in the nucleus can be consistently described by a {pi}+{rho}+g{sup {prime}} model for the {Delta}+N{r_arrow}N+N decay interaction. {copyright} {ital 1997} {ital The American Physical Society}

High-momentum proton removal from16Oand the(e,e′p)cross section

The cross section for the removal of high-momentum protons from ${}^{16}\mathrm{O}$ is calculated for high missing energies. The admixture of high-momentum nucleons in the ${}^{16}\mathrm{O}$ ground state is obtained by calculating the single-hole spectral function directly in the finite nucleus with the inclusion of short-range and tensor correlations induced by a realistic meson-exchange interaction. The presence of high-momentum nucleons in the transition to final states in ${}^{15}\mathrm{N}$ at 60--100 MeV missing energy is converted to the coincidence cross section for the ${(e,e}^{\ensuremath{'}}p)$ reaction by including the coupling to the electromagnetic probe and the final state interactions of the outgoing proton in the same way as in the standard analysis of the experimental data. Detectable cross sections for the removal of a single proton at these high missing energies are obtained which are considerably larger at higher missing momentum than the corresponding cross sections for the $p$-wave quasihole transitions. Cross sections for these quasihole transitions are compared with the most recent experimental data available.

Quasifree pion electroproduction from nuclei in theΔregion

We present calculations of the reaction ${A(e,e}^{\ensuremath{'}}\ensuremath{\pi}N)B$ in the distorted (and plane) wave impulse approximation. The reaction allows for the study of the production process in the nuclear medium without being obscured by the details of nuclear transition densities. First, a pion electroproduction operator suitable for nuclear calculations is obtained by extending the Blomqvist-Laget photoproduction operator to the virtual photon case, which describes the existing data reasonably well. It is applied in nuclei to predict nuclear cross sections under a variety of kinematic arrangements. Issues such as the effects of the interference of the $\ensuremath{\Delta}$ resonance with the background, sensitivities to the quadrupole component of the $\ensuremath{\Delta}$ excitation and to the electromagnetic form factors, and the role of final-state interactions are studied in detail. It is found that the longitudinal and the LT interference structure functions in ${(e,e}^{\ensuremath{'}}{\ensuremath{\pi}}^{0}N)$ are sufficiently sensitive to extract medium modifications of the $\ensuremath{\Delta}$ quadrupole component. Methods on how to experimentally separate the various pieces in the coincidence cross section are suggested. Finally, the model is compared to a recent SLAC experiment.

Electroproduction of neutral pions on the proton

The double-differential coincidence cross section for the reaction 1H(e,e′π 0)p has been measured at Q 2 = 0.1 (GeV/ c) 2 for a range in the invariant energy W of 1 to 14 MeV above threshold in order to determine the s-wave multipoles E 0+ and L 0+. The experiment was performed with a 525 MeV electron beam of the Amsterdam Pulse Stretcher and a cryogenic hydrogen target. The scattered electron and the recoiling proton were detected in two high-resolution magnetic spectrometers. By using a recent LET prediction for the relevant combinations of p-wave multipoles, values for E 0+ and L 0+ were extracted from the cos ϑ π ∗ and cos φ π ∗ dependent terms in the cross section. The data are compared to calculations from Chiral Perturbation Theory and from several Lagrangian models. All models give a fair to good description of L 0+. ChPT gives also a good description of E 0+, but the Lagrangian models tend to underestimate its value. The data for the angle-independent part of the cross section indicate that the value for the 2 M 1+ + M 1− combination of p-wave multipoles is overestimated by a recent ChPT prediction.

The 12C(e, e′p) and 12C(e, e′pp) reactions in the Δ-resonance region

Abstract Coincidence cross sections for the 12 C(e, e′pp) and 12 C(e, e′p) reactions have been measured in the Δ-resonance region. The 12 C(e, e′pp) reaction has been measured at three different angular settings of the proton detectors to investigate the angular correlation between the emitted protons. The data, which have a low statistical accuracy, are compared with a calculation based on the direct-knockout mechanism, which includes one- and two-body currents. NN-correlations are accounted for via a correlation function, Δ-excitation via a two-body current and final-state interactions of the emitted protons via an optical potential. The 12 C(e, e′p) data, taken at large proton-emission angles, cover the region of high missing-energy values (145–275 MeV). The data are compared to results of a calculation taking into account meson exchange, intermediate Δ-excitation and pion production. This comparison shows that there is ample evidence for processes leading to multi-nucleon knockout.