[en] A striking energy dependence was observed in the difference between the p--p total cross sections for parallel and antiparallel longitudinal spin states, Δ sigma/sub L/. The structure appears around p/sub lab/ = 1.5 GeV/c, where Δ sigma/sub L/ = -16.7 mb and is seen in sigma/sup Tot/(arrow-right arrow-right) rather than sigma/sup Tot/(arrow-right arrow-left). The experiments were performed at ANL using a standard transmission technique. From the dispersion analysis of a forward p--p scattering amplitude using the data on Δ sigma/sub L/, Grein and Kroll have shown that the Argand plot of the amplitude has a clear resonance-like behavior around proton incident momentum of 1.5 GeV/c. At the same energy range, the p--p polarization at fixed -t also shows a remarkable energy dependence. In addition, we have observed a prominent energy dependence for C/sub LL/, the spin correlation parameter for elastic pp scattering with beam and target both longitudinally polarized. The possibility of a resonance was further pursued by studying Legendre expansion coefficients of p--p differential cross section and polarization data. The analysis showed a partial wave, ³F₃, consistent with having a resonant behavior. This resonant state would have the quantum number J/sup P/ = 3^-, mass approximately 2260 MeV, width approximately 200 MeV and elasticity 20 to 30%. This exotic state may be described by the MIT bag model. Also several more diproton resonances are speculated in the mass region 2100 to 2800 MeV. 23 references