Examination of the production of an isotensor dibaryon in the pp → ppπ+π− reaction

The quasifree pp → ppπ+π− reaction has been measured by means of pd collisions at Tp = 1.2 GeV using the WASA detector setup at COSY enabling exclusive and kinematically complete measurements. Total and differential cross sections have been extracted for the energy region Tp = 1.08–1.36 GeV (√s = 2.35–2.46 GeV) covering thus the regions of N∗(1440) and (1232)(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange as well as isospin relations based on the pp → ppπ0π0 data underpredict substantially the measured total cross section. The calculations are also at variance with specific experimental differential cross sections. An isotensor N dibaryon resonance with I (J P ) = 2(1+) produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong [Phys. Rev. Lett. 13, 815 (1964)] and more recently calculated by A. Gal and H. Garcilazo [Nucl. Phys. A 928, 73 (2014)].