Measurement of thepn→ppπ0π−Reaction in Search of the ABC Resonance

T. Skorodko, M. Bashkanov, H. Clement, E. Doroshkevich, E. Perez del Rio, A. Pricking, G. J. Wagner, A. Wrońska, R. Skibiński, C. Guaraldo, St. Kistryn, H. Ströher
2012 EPJ Web of Conferences  
With pd collisions at T p = 1.2 GeV exclusive measurements of the quasi-free pn → ppπ 0 π − reaction have been carried out. Using the WASA detector setup at COSY total and differential cross sections have been obtained for the energy region √ s = 2.35 -2.48 GeV. Though this includes the region of the ABC effect and its associated resonance structure, no low-mass enhancement (ABC effect) is found in the π 0 π − -invariant mass spectrum -in agreement with the constraint from Bose statistics
more » ... se statistics demanding the isovector pion pair to be in relative p-wave. Conventional calculations including t-channel processes for Roper, ∆(1600) and ∆∆ excitations and their decays, which are well-known from the study of the two-pion production in pp collisions, provide a reasonable description of the data at high energies, but fall low at low energies. From this we conclude that a large contribution from a so far unknown isoscalar low-energy process is missed in the calculations. Inclusion of the ABC resonance at m = 2.37 GeV with Γ = 70 MeV and I(J P ) = 0(3 + ), which was recently observed in the pn → dπ 0 π 0 reaction, leads to a much improved description of the data at low energies.
doi:10.1051/epjconf/20123709033 fatcat:fgcgsrdvkbglxfabg7b3qflcnu