Exclusive measurements of the reactions pd→3Heπ+π− and
pd→3Heπ0π0 have been carried out at Tp=0.895 GeV at the
CELSIUS storage ring using the WASA detector. The π+π− channel
evidences a pronounced enhancement at low invariant ππ masses - as
anticipated from previous inclusive measurements of the ABC effect. This
enhancement is seen to be even much larger in the isoscalar π0π0
channel. The differential distributions prove this enhancement to be of
scalar-isoscalar nature. ΔΔ calculations give a good description of
the data, if a boundstate condition is imposed for the intermediate
ΔΔ system.Comment: extended version, 8 pages, 7 figures, theoretical model calculations
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