Excitation functions of the analyzing power in elastic proton-proton scattering from 0.45 to 2.5 GeV

Abstract

Excitation functions AN (p lab , Θc.m.) of the analyzing power in elastic proton-proton scattering have been measured in an internal target experiment at the Cooler Synchrotron COSY with an unpolarized proton beam and a polarized atomic hydrogen target. Data were taken continuously during the acceleration and deceleration for proton kinetic energies T lab (momenta p lab ) between 0.45 and 2.5 GeV (1.0 and 3.3 GeV/c) and scattering angles 30 • ≤ Θc.m. ≤ 90 • . The results provide excitation functions and angular distributions of high precision and internal consistency. The data can be used as calibration standard between 0.45 and 2.5 GeV. They have significant impact on phase shift solutions, in particular on the spin triplet phase shifts between 1.0 and 1.8 GeV. PACS. 25.40.Cm Elastic proton scattering -13.75.Cs Nucleon-nucleon interactions -24.70.+s Polarization phenomena in reactions -21.30.-x Nuclear forces

Evidence for a New Resonance from Polarized Neutron-Proton Scattering

“…This was also measured in parallel by detecting one of the protons in the forward detector and the other one in the central detector, in addition, checking their angular correlation for elastic events. Our results for the quasifree pp analyzing power are in quantitative agreement both with the EDDA measurements [15] of free pp scattering and with the current SAID phase shift solution SP07 [16].…”

The legacy of the hadron physics programme at COSY

“…Nevertheless, it is clear that COSY has completely revolutionised the understanding of pp scattering up to 3 GeV. Left: ANKE measurements of the analysing power in pp elastic scattering at two energies (circles/triangles) [6] compared to EDDA (crosses) data [4] and the SAID SP07 fit (solid line) [3] and a revised one (dashed). Middle: ANKE pp differential cross sections [7], scaled by factors within the overall uncertainties, compared to the SAID SP07 solution (dashed) [3] and modified fit (solid line).…”

Resonances at COSY — the dibaryon issue

“…In energy scan runs the energy range between π and φ thresholds could be scanned with sub-MeV resolution in high-statistics runs, which would have been able to reveal even very narrow, weakly excited dibaryon resonances. Though no indications for any narrow resonances in the proton-proton system have been found, this EDDA data set [14] is of indispensable value, since it constitutes the backbone of highquality proton-proton scattering data in the SAID data base [15] ¿xing the empirical partial-wave amplitudes with unprecedented precision. Unfortunately the EDDA experiment was not continued to examine also the proton-neutron scattering with similar precision -historically possibly a big mistake, as we will see below.…”