Isospin resolved double pion production in the reaction p+d→3He+2π

Andersson, Mathias H.; Bargholtz, Chr.; Calén, H.; Fransson, K.; Fumero, E.; Holmberg, L.; Johanson, Jan; Johansson, T.; Lindh, K.; Mårtensson, L.; Sitnikova, I.; Суханов, А.; Tegnér, P. E.; Engblom, P. Thörngren; Weiß, G.; Rolander, K. Wilhelmsen; Złomańczuk, J.

doi:10.1016/s0370-2693(00)00721-8

Cited by 10 publications

(49 citation statements)

References 12 publications

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“…The interaction of the low energy pions with the final 4 He nucleus might enhance the cross section since it is known that the p-wave pion-nucleus interaction is attractive near threshold [24]. However, the effect will steadily diminish with energy and eventually change sign at the resonance.…”

Section: Results and Conclusionmentioning

confidence: 99%

“…Crude estimates indicate that any effects due to such final-state interactions are likely to be less than 50%, even very close to threshold, and so they are very unlikely to provide the explanation of the defect. Now, although we have normalised the 4 He wave function as if it consisted purely of p 3 H/n 3 He pairs, in reality the 3 H in such a nucleus is on average smaller than the physical triton. Nevertheless we have taken the amplitudes for pd → 3 He π 0 from the measured data.…”

Section: Results and Conclusionmentioning

confidence: 99%

“…The resulting form factor 16) where N α is the normalisation of the 4 He wave function and the extra form-factor contribution coming from the interchange of the two incident deuterons is indicated. All isospin factors have been included, but it must be stressed that in eq.…”

Section: The Reaction Modelmentioning

confidence: 99%

“…These include studies in pion-proton [1] and proton-proton collisions [2], as well as in the pd → 3 He ππ [3,4,5] and dd → 4 He ππ [6,7,8] reactions. For excess energies Q below about 100MeV one sees no sign of the low mass s-wave ππ enhancement, known as the ABC effect [9], and the maxima in the invariant mass distributions tend more to be pushed to the highest possible values.…”

Section: Introductionmentioning

confidence: 99%

“…The swave term is sufficient, in the two-step model, to lead to reasonable agreement with the available data on the pd → 3 He ππ total cross section. Moreover, combined with p-waves required by the decay chain, it reproduces the shift of the mass spectrum away from the ABC region towards that of higher missing masses [3,4]. It is therefore reasonable to ask whether a similar approach could not be usefully tried for the low energy dd → 4 He ππ reaction.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Two-pion production in deuteron-deuteron collisions at low energies

Fäldt¹,

Tengblad²,

Wilkin

2006

Eur. Phys. J. A

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Abstract. The cross section for the dd → 4 He ππ reaction is estimated near threshold in a two-step model where a pion created in a first interaction produces a second pion in a subsequent interaction. This approach, which describes well the rates of 2π and η production in the pd → 3 He ππ and dd → 4 He η reactions, leads to predictions that are much too low compared to experiment. Alternatives to this and the double-∆ model will have to be sought to explain these data.

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Section: Results and Conclusionmentioning

confidence: 99%

Section: Results and Conclusionmentioning

confidence: 99%

Section: The Reaction Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Two-pion production in deuteron-deuteron collisions at low energies

Fäldt¹,

Tengblad²,

Wilkin

2006

Eur. Phys. J. A

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Exclusive measurement of two-pion production in the reaction

et al. 2009

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The results from the first kinematically complete measurement of the 4 He dd ππ → reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar ππ−invariant mass distributions appearing in double pion production in light ion collisions, the socalled ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV, with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low ππ-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN dπ → sub-processes.

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