The twofold emergence of the $a_1$ axial vector meson in high energy\n hadronic production

The high statistics COMPASS results on diffractive dissociation $\\pi N\n\\rightarrow \\pi \\pi \\pi N$ suggest that the isospin $I=1$ spin-parity $J^{PC}=\n1^{++}$ $a_1(1260)$ resonance could be split into two states: $a_1(1260)$\ndecaying into an S-wave $\\rho\\pi$ system, and $a_1^\\prime(1420)$ ... View More