Amplitude Analysis of πNBackward Scattering at 6 GeV/cand the Peripherality

Abstract

An amplitude analysis of πN backward scattering is performed at plab=6 GeV/c from the viewpoint of the peripherality (the dominance of peripheral waves). A functional form Aexp (Bu')Jν(R√-u') is assumed for Im Δ+± and Im N+- where Δ and N denote Iu=3/2 and Iu=1/2 exchange amplitudes, respectively, and ++(+-) denotes the final and initial nucleon helicities and corresponds to ν=1 (ν=0). The resultant Im N++ is shown to be consistent with the above Bessel function representation, too. The parameters B and R can be taken as B ∼1.5 (GeV/c)-2 and R ∼1 fm commonly for Im Δ+± and Im N+±, of which values are consistent with those obtained previously by amplitude analyses of various meson-baryon scattering and photo-vector-meson production process in the forward region. The results for Δ++ and N+- are consistent with the Regge phase of Δδ trajectory for u \gtrsim-0.15 (GeV/c)2 and of Nα trajectory for u \gtrsim-0.6 (GeV/c)2, respectively. The spin rotation parameters for π±p elastic scattering and the polarization for charge exchange scattering in the backward direction are given as predictions.