Study of sigma(750) and rho0(770) production in measurements of piN(polarized) -> pi(+)pi(-)n on a polarized target at 5.98,11.85 and 17.2 GeV/c

Abstract

We present a new and improved model independent amplitude analysis of reactions $\ddot{I}{€}^{+}{n}_{\uparrow }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}p$ at 5.98 and 11.85 GeV/c and $\ddot{I}{€}^{-}{p}_{\uparrow }\to \ddot{I}{€}^{-}\ddot{I}{€}^{+}n$ at 17.2 GeV/c measured with transversely polarized targets at the CERN Proton Synchrotron. A clear signal for $\ddot{I}ƒ(750)$ resonance emerges in all four solutions for $S$-wave intensity $I_S$ at 5.98 and 11.85 GeV/c and in both solutions for $S$-wave amplitude $|\overline{S}{|}^2\hat{I}\pounds$ at 17.2 GeV/c. Its $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ decay width is estimated to be in the range 200--300 MeV. We find significant suppression of $\ddot{I}{}^0$ production in the amplitudes $|U{|}^2\hat{I}\pounds$, $|\overline{N}{|}^2\hat{I}\pounds$ and, at 17.2 GeV/c, in $|L{|}^2\hat{I}\pounds$. The mass dependence of amplitudes $|\overline{L}{|}^2\hat{I}\pounds$ and $|L{|}^2\hat{I}\pounds$ shows unexpected structures within the $\ddot{I}{}^0$ mass region which correlate the mass spectra corresponding to opposite nucleon spins. These features of $P$-wave moduli reveal the essential role of nucleon spin in pion production process and contradict the factorization hypothesis. Our results emphasize the need for a systematic study of pion production on the level of amplitudes in a new generation of dedicated experiments with spin at the recently proposed high-intensity hadron facilities.

73 pages