A dependence of the (pi( ),pi( )pi( /-)) reaction near the 2m(pi) threshold
F Bonutti, P Camerini, E Fragiacomo, N Grion, R Rui, PA Amaudruz, JT Brack, L Felawka, EF Gibson, GJ Hofman, M Kermani, EL Mathie, S McFarland, R Meier, D Ottewell, K Raywood, ME Sevior, GR Smith, R Tacik
PHYSICAL REVIEW LETTERS | AMERICAN PHYSICAL SOC | Published : 1996
The 2H, 12C, 40Ca, 208Pb(π +, π+ π±)reactions have been studied at Tπ+=282.7 MeV, and the π+ π± invariant mass distributions Mπ+ π±Ameasured down to the 2mπthreshold. The Mπ+ π±Ayield near threshold is close to zero for A = 2, and increases dramatically with increasing A (from 12 to 40 to 208). A phase analysis indicates that the π +, π−pairs in this range of Mπ+ π±Ahave J=I=0. In the case of Mπ+ π±A, there is some strength near threshold regardless of A, and the π+ π+pairs have J=0, I = 2. The experimental results indicate that nuclear matter strongly modifies the π π interaction in the J = I = 0 channel. © 1996 The American Physical Society.