The inclusive reaction MeV above the 2π0 threshold

Structure in two-pion production in thedd→αXreaction

“…There are two measurements at even lower energies, one close to threshold at T d = 570 MeV [13] and another at 650 MeV [12]. In both cases the data are structureless, and consistent with pure phase space, with total cross sections of σ(570) ∼ 43 nb and σ(650) ∼ 600 nb, respectively.…”

“…It is thus impossible to explain the ABC enhancement in terms of some peculiarity of the ππ interaction and one has to include effects resulting from the presence of other particles in the reactions and consider the structure of the single pion production mechanism itself. In all three reactions there are indications that the ABC effect disappears at low beam energies [10,11,12,13], suggesting that the subprocesses in any explanation should be strongly energy and angular dependent in order to reproduce the quite different dynamics observed in the different energy regions.…”

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

“…3. Missing-mass distribution for the dd → 4 He X reaction measured at 570 MeV [6]. The chain curve corresponds to π 0 π 0 production within the two-step model whereas the solid one represents the sum of this and π + π − production.…”

“…The experimental data from Ref. [6] (star) and Ref. [13] (circle) are compared to the predictions of the two-step model scaled by a factor of 17.6.…”

Study of the ABC enhancement in the reaction

“…Whether this remains true closer to threshold, where the ABC peaks are not seen [15], would require the measurement of analysing powers over a greater range in energy. This is no longer possible at Saturne following its final closure on December 2 nd 1997.…”