Evidence for pion exchange currents in the analysis of the 4He (p, d)3He reaction at intermediate energies

doi:10.1016/0370-2693(79)90065-0

Physics Letters B

Volume 89, Issue 1, 31 December 1979, Pages 13-16

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Abstract

Previous unsuccessful analyses of ⁴He (p, d)³He at intermediate energies have employed densities based directly on the measured e⁻+⁴He elastic scattering. When the effects of pion exchange currents are removed, the resulting DWBA analysis is in qualitative agreement with the experimental data.

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Cited by (11)

Parametrization of the nucleon-trinucleon overlap function in 4He and the effect of meson exchange corrections
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Analyzing power measurements for the 13C(p,d)12C reaction at 200 and 400 MeV
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Cross sections and analyzing powers for the ¹³C( $p$ ,d) reaction have been measured at 200 and 400 MeV to the 0⁺, ground state and 2⁺, 4.44 MeV state of ¹²C. While the cross sections are rather structureless, DWBA calculations in exact finite range account well for both the magnitude and shape of the angular distributions. On the other hand, the measured analyzing powers are in serious disagreement with the DWBA calculations.
Energy dependence of the 3He(p, π+)4He and 3H(n, π-)4 He reactions
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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.
Microscopic description of the A(p, π)A + 1 reaction
1988, Nuclear Physics, Section A
We have developed a flexible and thoroughly tested computer program for microscopic calculations of proton-induced pion production in nuclei at bombarding energies up to 500 MeV. The model used includes explicitly both the one-nucleon (pionic stripping) mechanism and the resonant p-wave rescattering part of the two-nucleon mechanism. Initial and final state interactions are included through proton-nucleus and pion-nucleus optical model distortions, with careful consideration of the multiple scattering series. The intermediate delta in the two-nucleon mechanism is treated as static with possible inclusion of a local density approximation for the delta-nucleus interaction. We explain the philosophy of the model, detail the parametrization of the microscopic dynamics, and give the formalism for the calculation of experimental observables. We also describe the testing of the computer program and present preliminary results for the ³He(p, π⁺)⁴He reaction.
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¹: Work supported in part by the U.S. Department of Energy.

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Physics Letters B

Abstract

References (15)

Phys. Lett.

Nucl. Phys.

Nucl. Phys.

Ann. Phys.

Phys. Lett.

Phys. Rev.

Cited by (11)

Parametrization of the nucleon-trinucleon overlap function in <sup>4</sup>He and the effect of meson exchange corrections

Analyzing power measurements for the <sup>13</sup>C(p,d)<sup>12</sup>C reaction at 200 and 400 MeV

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

Microscopic description of the A(p, π)A + 1 reaction

He4(4He,3He)5He(g.s.) reaction at 118 MeV, and its distorted wave Born approximation interpretation

(p4,d)3He reaction at 200 and 400 MeV