Erratum to “Exclusive measurements of pp→dπ+π0: Double-pionic fusion without ABC effect” [Phys. Lett. B 684 (2–3) (2010) 110]

Abstract

Exclusive measurements of the reaction pp → dπ + π 0 have been carried out at Tp = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector π + π 0 channel exhibits no enhancement at low invariant ππ masses, i. e. no ABC effect. Therefore this most basic isovector double-pionic fusion reaction qualifies as an ideal test case for the conventional t-channel ∆∆ excitation process. Indeed, the obtained differential distributions reveal the conventional t-channel ∆∆ mechanism as the appropriate reaction process, which also accounts for the observed energy dependence of the total cross section. This is an update of a previously published version-see important note at the end of the article.

On the history of dibaryons and their final observation

“…(4). For the pn → dπ + π − and pp → dπ + π 0 reactions there are also some results from previous measurements [358,359,317,319,328,333], they are depicted by open symbols in Fig. 12, top and bottom.…”

“…Starting first with the WASA/PROMICE detector setup, followed by the completed WASA detector at CELSIUS and finally at COSY all ppinduced, i.e. isovector two-pion production channels from threshold up to √ s = 2.5 GeV have been studied [323,324,325,326,327,328,329,330,331] complemented by a corresponding program with polarized beam at COSY-TOF [314,332]. The results for the total cross sections are shown in Fig.…”

“…As a result it was found [350] that there is, indeed, a highly visible low-mass enhancement but no high-mass enhancement as seen in previous σ 0 π + π pn → pp Figure 9: Energy dependence of the pp-induced total cross sections for two-pion production and their isospin decomposition. Open symbols denote results from bubble-chamber measurements [317,318,319,320,321,322], solid symbols represent measurements from WASA/PROMICE (triangles) [323,324,325], CELSIUS/WASA (circles) [326,327,328,329,330] and COSY-TOF (squares) [314]. At the top the reaction channels pp → ppπ 0 π 0 (left) and pp → nnπ + π + (right) are shown together with their isospin decomposition.…”

ABC effect and resonance structure in the double-pionic fusion toHe3

“…In marked difference to the double-pionic fusions to d and 4He, the main contribution to the total cross section in the 3He case does not originate from the d* resonance, but from the conventional /-channel A A process, which has a large isovector contribution. This process peaks at around 2m A + m N and has a width of about 2TA [13,16].…”

“…In contrast, the basic isovector fusion process pp -> d n +n () exhibits neither an ABC effect nor a narrow resonance structure [13,16] in agreement with the observations in all other pp initiated two-pion channels [17][18][19][20][21], Isospin decom position of all three reactions pn -* d n°n°, pn -*■ d n +n~, and pp -> d n +n {) leading to the double-pionic fusion of deuterium ensured that the resonance structure is of purely isoscalar nature [13]. Also recently published data on the pn -> p p ji°n~ reaction show evidence for the resonance structure, though in this case of an isovector pion pair the ABC effect is absent [22].…”