The 3He(p, π+)4He reaction near threshold

doi:10.1016/0375-9474(89)90100-0

Nuclear Physics A

Volume 493, Issues 3–4, 13–20 March 1989, Pages 509-520

https://doi.org/10.1016/0375-9474(89)90100-0 Get rights and content

Abstract

We apply a recently developed microscopic model of nuclear pion production to the ³He(p, π⁺)⁴He reaction at T_p = 200 MeV and show the approximate equivalence for this reaction of a one-nucleon mechanism (ONM) calculation with full proton and pion distortions to a more microscopic calculation involving the coherent sum of the ONM amplitude with proton and nonresonant pion distorted waves and the pion-exchange projectile-emission part of the two-nucleon mechanism amplitude with proton and full pion distortions. A full microscopic calculation including target-emission and ρ-meson exchange contributions describes qualitatively the shapes of the differential cross section and analyzing power angular distributions but underestimates the magnitude of the measured cross sections. The sensitivity of the calculations to D-state admixtures in the bound-state wave functions is shown to be small.

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Cited by (7)

Exclusive pion production in proton-nucleus collisions and the relativistic two nucleon dynamics
1995, Nuclear Physics, Section A
The exclusive pion production in a proton-nucleus collision, leading to two-body final states, is examined in a fully covariant two-nucleon model. We focus on the amplitudes which are dominated by the Δ(1232) resonance. Retaining the full covariant forms of the πNN and πNΔ vertices and employing a relativistic propagator for the delta isobar, expressions for various reaction amplitudes are derived. The bound state nucleon wave functions are obtained by solving the Dirac equation with appropriate scalar and vector potentials whereas the continuum wave functions are approximated by plane waves. The sensitivity of the calculated cross sections to the in-medium self-energy of the intermediate pion is investigated. It is found that the relative magnitudes of the so called target-emission and projectile-emission amplitudes depend strongly on the pion self-energy. A comparison with the available data for the ¹²C and ¹⁶O targets at the incident proton energy of 800 MeV supports our conclusions.
Role of the Δ-isobar in the A(p, π)A+1 reaction
1992, Nuclear Physics, Section A
We have applied a microscopic model of the A(p, π)A+1 reaction that includes both the one-nucleon mechanism and the resonance p-wave rescattering part of the two-nucleon mechanism to the $^{16} O (p, π^{+})^{17} O and^{12,13,14} C (p, π^{−})^{13,14,15} O$ reactions leading to two-particle one-hole final states to test separately the two-nucleon mechanism part of the model. The calculations reproduce fairly well the differential cross section and analyzing power data for $^{16} O (p ̄, π^{+})$ transitions leading to high-spin, two-particle one-hole states in ¹⁷O at $7.76 MeV (112^{−}) and 15.8 MeV (132^{−})$ at bombarding energies of 200, 250 and 354 MeV, but underestimate appreciably the differential cross sections for $^{12,13,14} C (p ̄, π^{−})$ transitions leading to the ground states ^13,14,15O and the $7.28 MeV (72^{+})$ excited state of ¹⁵O and fail to reproduce the analyzing-power angular distributions for these (p, π⁻) transitions. These results verify that NN → NNΔ → NNπ is the underlying two-nucleon process in the ¹⁶O(p, π⁺) reactions, but that non-Δ channels dominate the ^12,13,14C(p, π⁻) reactions. The latter conclusions is consistent with results of recent studies of the pn ↔ π⁻pp reaction.
Energy dependence of the 3He(p, π+)4He and 3H(n, π-)4 He reactions
1990, Nuclear Physics, Section A
We examine in detail the energy dependence of the various components of a microscopic calculation of the ³He(p, π⁺)⁴He reaction from the near-threshold region (T^lab_p = 178 MeV, T^c.m._π = 10.5 MeV) to an energy at which the Δ₁₂₃₂ resonance should clearly dominate the reaction mechanism (T^lab_p = 325 MeV, T^c.m._π = 110 MeV) and demonstrate the sensitivity of the calculations to pion and proton distortions. The discrepancy in size between the calculated and measured cross sections at the lower energies (T^lab_p = 178 and 200 MeV), persisting in two earlier publications, is found to disappear when Coulomb effects are properly taken into account. Our present calculations give a reasonably good description of the measured cross section and analyzing-power data at these lower energies and predict a smooth energy dependence of the cross section at the higher energies reflecting the increasing importance of the Δ-resonance. Calculations for the charge-symmetric ³H(n, π⁻)⁴He reaction are compared with existing cross-section data for the time-reversed ⁴He(π⁻, n)³H reaction at the higher energies using detailed balance, while differences between the ³He(p, π⁺)⁴He and ³H(n, π⁻)⁴He reactions due to Coulomb effects are investigated.
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Measurement of the C12(p,0)13N reaction by recoil detection
1992, Physical Review C

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¹: Present address: NIKHEF, P.O. Box 41882, 1009 DB Amsterdam, The Netherlands.

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Nuclear Physics A

Abstract

References (9)

Nucl. Phys.

Phys. Reports

Phys. Reports

Nucl. Phys.

Cited by (7)

Exclusive pion production in proton-nucleus collisions and the relativistic two nucleon dynamics

Role of the Δ-isobar in the A(p, π)A+1 reaction

Energy dependence of the <sup>3</sup>He(p, π<sup>+</sup>)<sup>4</sup>He and <sup>3</sup>H(n, π<sup>-</sup>)<sup>4</sup> He reactions

Exclusive pion production from few nucleon systems in the region of the 1232 resonance

Phenomenological ppd + model of A(p, +)B reactions

Measurement of the C12(p,0)13N reaction by recoil detection