Coherent pion production in 3He3He collisions

doi:10.1016/0370-2693(81)90254-9

Physics Letters B

Volume 106, Issue 6, 26 November 1981, Pages 449-452

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Abstract

A model is proposed to describe the near-threshold production of pions in the $^{3} He (^{3} He, π^{+})^{6} Li$ reaction. Taking experimental data on the $^{3} He (p, π^{+})^{4}$ He process as input the cross sections for the first three levels of ⁶Li are reproduced semi-quantitatively.

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Cited by (19)

Pionic fusion in light-ion systems
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The role of pions in the nuclear interaction has been studied in pionic fusion experiments using the AGOR accelerator facility at KVI. Pionic fusion is a highly coherent process in which two nuclei fuse to a united nucleus and the available centre-of-mass (C.M.) energy is emitted through the pion channel. The examined reactions were ⁴He(³He, $π^{0}$ )⁷Be and ⁶Li(⁴He, $π^{0}$ )¹⁰B^⁎ and both reactions were performed at C.M. energies about 10 MeV above the coherent pion production threshold. Here, the experimental results for the ⁶Li(⁴He, $π^{0}$ )¹⁰B^⁎ reaction will be presented and discussed. In order to provide sensitivity to the full dynamics and relevant processes involved in the pionic fusion reaction, almost the full angular distribution of neutral pions has been determined. In a phenomenological analysis, the contributions of Legendre polynomials to reproduce the behaviour of the angular distribution have been studied. The results of this analysis confirm the importance of the clustering correlations for the ⁶Li(⁴He, $π^{0}$ )¹⁰B^⁎ reaction. The mass dependence of the pionic fusion reaction is in agreement with the results of the existing models extrapolated to this reaction.
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The halo nucleus ⁶He has been studied in a pionic fusion experiment at the CELSIUS ring in Uppsala. The aim of the experiment was to investigate, in particular, the high-momentum part of the halo wave function by measuring the differential cross section for the ⁴He(d, ⁶He) $π^{+}$ reaction 0.6, 1.2 and 5.0 MeV above threshold in the centre-of-mass frame. The ⁶He ions were detected in a $Δ E - E$ solid-state detector telescope inserted into the ring vacuum. The result for the total cross section is, respectively, 22(1), 38(1) and 57(9) nb with a common systematic uncertainty of $\pm 35 %$ . The differential cross section is clearly anisotropic: $[\frac{d σ}{d Ω} (0 °) - \frac{d σ}{d Ω} (180 °)] / [\frac{d σ}{d Ω} (0 °) + \frac{d σ}{d Ω} (180 °)] = - 0.25 (5)$ , $- 0.29 (5)$ and $- 0.35 (15)$ at the same three energies. The preferred direction of emission for the pion is parallel to the momentum of the ⁴He ion in the initial state. In terms of a simple model for the reaction the results depend sensitively on the state of motion of the centre of mass of the halo relative to that of the core.
Pionic fusion to a halo state, the d(α,6Li*) π0 reaction studied close to threshold
2000, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
The d(α,⁶Li $^{∗}_{3.56}$ )π⁰ reaction has been studied at E_c.m.=1.2 and 1.9 MeV above threshold with an alpha-particle beam incident on a deuterium cluster-jet target in CELSIUS. Complete differential cross sections were measured at both energies, integrated to σ=228±6+70 nb and 141±12+42 nb respectively. Observed large anisotropies are discussed in relation to the cluster structure of the ⁶Li $^{∗}$ halo.
A study of the 6Li(π+, 3He)3He reaction at 60, 80, 100 and 140 MeV incident pion beam energies
1986, Nuclear Physics, Section A
Angular distributions of the $^{6} Li (π^{+},^{3} He)^{3} He$ differential cross section are presented for incident pion beam energies of 60, 80 and 100 MeV, together with a few values at 140 MeV. The results are compared with previously published data and two theoretical predictions. The 60, 80 and 100 MeV data, and previously published results for 15.4 MeV, were fit to Legendre polynomials. The fitted coefficients, which allow the energy dependence of the total and differential cross sections at a fixed c.m. angle to be determined, are also presented. These coefficients show the increasing importance of higher-order partial-waves with increasing pion energy.
Inclusive (p, π±) reactions at 201 and 180 MeV
1985, Nuclear Physics, Section A
Angular dependence of the 6Li(π+, 3He)3He reaction at 60 and 80 MeV
1985, Physics Letters B

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¹: Supported in part by the Fonds National Suisse pour la Recherche Scientifique.

²: Supported in part by the Science Research Council.

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Physics Letters B

Abstract

References (11)

Nucl. Phys.

Phys. Rev.

Phys. Rev.

J. Phys.

Cited by (19)

Pionic fusion in light-ion systems

Pionic fusion study of the <sup>6</sup>He halo

Pionic fusion to a halo state, the d(α,<sup>6</sup>Li*) π<sup>0</sup> reaction studied close to threshold

A study of the <sup>6</sup>Li(π<sup>+</sup>, <sup>3</sup>He)<sup>3</sup>He reaction at 60, 80, 100 and 140 MeV incident pion beam energies

Inclusive (p, π<sup>±</sup>) reactions at 201 and 180 MeV

Angular dependence of the <sup>6</sup>Li(π<sup>+</sup>, <sup>3</sup>He)<sup>3</sup>He reaction at 60 and 80 MeV