Excitation Functions of the Analyzing Power inpp→Scattering from 0.45 to 2.5 GeV

Abstract

Excitation functions A(N)(p(p),Theta(c.m.)) of the analyzing power in pp--> elastic scattering have been measured with a polarized atomic hydrogen target for projectile momenta p(p) between 1000 and 3300 MeV/ c. The experiment was performed for scattering angles 30 degrees </=Theta(c.m.)</=90 degrees using the recirculating beam of the proton storage ring COSY during acceleration. The resulting excitation functions and angular distributions of high internal consistency have significant impact on the recent phase shift solution SAID SP99, in particular, on the spin triplet phase shifts between 1000 and 1800 MeV, and demonstrate the limited predictive power of single-energy phase shift solutions at these energies.

On the history of dibaryons and their final observation

“…In energy scan runs the energy range between T p = 0.5 -2.5 GeV, i.e. between π and φ production thresholds, could be scanned with sub-MeV resolution in with high statistics [296,297,298,299,300,301,302]. This provided the instrumental and analytical possibility to reveal even very narrow, weakly excited dibaryon resonances 1 in the mass range of 2200 -2800 MeV.…”

The legacy of the experimental hadron physics programme at COSY

“…1. The systematic EDDA studies [37,66,67,68,69,70] of the differential cross section and a wide variety of spin observables in elastic proton-proton scattering over almost all the COSY energy range have led to radical changes in the extraction of isospin I = 1 phase shifts. These data have been supplemented by measurements at small angles at ANKE but only of the differential cross section and analyzing power and at discrete energies [63,78].…”

“…On the other hand, the possibility of using a thin windowless target at an internal target station of COSY offers significant advantages over the methods used in standard external experiments. By exploiting the repeated passage of the recirculating polarized or unpolarized proton beam through such a polarized or unpolarized target in COSY it was possible to measure the differential cross section [66,67], the proton analyzing power [68,37], and spin-correlations [69,70] with the EDDA detector described in Section 2.2 and illustrated in Fig. 10.…”

“…A full partial wave analysis clearly needs information from spin-dependent measurements and so we now turn to the contributions in this field made by the EDDA collaboration. The EDDA proton analyzing power, A y , measurements were carried out using the unpolarized COSY proton beam incident on a polarized hydrogen target [68,37]. This approach avoids the difficulties associated with the depolarizing resonances in COSY so that all the EDDA A y results are inversely proportional to the same factor, namely the polarization of the target.…”

Absolute measurement of the differential cross section for pp elastic scattering at ANKE-COSY

“…Experiments of this type have been carried out for the pp system up to about 3.0 GeV [5]. The well-known EDDA experiment at COSY has produced a very extensive and important data set of pp → pp differential cross sections and the various single and multi-spin observables [6], allowing the construction of reliable isospin I = 1 phase shifts up to at least 2 GeV [5]. Laboratory differential cross section for elastic proton-proton scattering at 2.65 GeV.…”