Recently published excitation functions in proton-proton (pp) elastic scattering observables in the laboratory energy range 0.5-2.5GeV provide an excellent data base to establish firm upper limits on the elasticities ηel = Γel/Γtot of possible isovector resonant contributions to the nucleon-nucleon (NN) system. Such contributions have been predicted to arise from dibaryonic states, with c.m. masses between 2.1-2.9GeV/c2, but have not been confirmed experimentally. A method to determine quantitatively the maximum value of ηel compatible with experimental data is presented. We use energy-dependent phase shift fits to the pp data base to model the non-resonant interaction. Based upon the differential cross-section data measured by the EDDA Collaboration an unbiased statistical test is constructed to obtain upper limits on ηel, that exclude larger values with a 99% confidence level. Results in the c.m. mass range 2.05-2.85GeV/c2 and total widths of 10-100MeV/c2 in the partial waves 1 S 0, 1 D 2, 3 P 0, 3 P 1, and 3 F 3 are presented and discussed.

Excitation functions of the spin correlation coefficients A(NN)(p(lab),theta(c.m.)),A(SS)(p(lab),theta(c.m.)), and A(SL)(p(lab),theta(c.m.)) have been measured with the polarized proton beam of the Cooler Synchrotron and an internal polarized atomic beam target. Data were taken continuously during the acceleration for proton momenta p(lab) ranging from 1000 to 3300 MeV/c (kinetic energies T-lab 450-2500 MeV) as well as for discrete momenta of 1430 MeV/c and above 1950 MeV/c covering angles theta(c.m.) between 30(degrees) and 90(degrees). The data are of high internal consistency. Whereas A(SL)(p(lab,)theta(c.m.)) is small and without structures in the whole range, A(NN) and, even more, A(SS) show a pronounced energy dependence. The angular distributions for A(SS) are at variance with predictions of existing phase-shift analyses at energies beyond 800 MeV. The impact of our results on phase-shift solutions is discussed. The direct reconstruction of the scattering amplitudes from all available pp elastic scattering data considerably reduces the ambiguities of solutions.

Excitation functions AN(plab,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 Tlab (momenta plab) 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.

At the Cooler Synchrotron COSY/Jülich spin-correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A(NN), A(SS), and A(SL) for c.m. scattering angles between 30 degrees and 90 degrees. Our data on A(SS)--the first measurement of this observable above 800 MeV--clearly disagrees with predictions of available pp scattering phase-shift solutions while A(NN) and A(SL) are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced.

Excitation functions of the differential cross sections dσdgw, analyzing powers AN and spin correlation parameters ANN, ASS and ASL have been measured with internal targets at the Cooler Synchrotron COSY. Data were taken continously during the acceleration and deceleration of the internal beam for kinetic energies between 450 and 2500 MeV and scattering angles 30° ⩽ σcm ⩽ 90°. Details of the experimental method are presented. The results provide excitation functions and angular distributions of high precision and internal consistency. No evidence for narrow structures are found. Upper limits on the coupling of narrow resonances to elastic scattering in the mass range √s = 2.2…2.8 GeV are deduced. The data have significant impact on phase shift solutions.

At the Cooler-Synchrotron COSY/Jülich polarized and unpolarized elastic proton-proton scattering has been investigated with the EDDA-Experiment in the energy range (T p ≈ 0.5−2.5 GeV). By taking scattering data during the acceleration of the beam with a large-acceptance (θ c.m. ≈ 30°−90°) detector, precise excitation functions for differential cross-section and analyzing power have been measured in small energy steps with consistent normalization with respect to luminosity and polarization. These data have helped to improve the determination of phase-shifts at higher energies and impose tight quantitative upper bounds on possible resonant contributions to pp elastic scattering, as they might arise from exotic 6-quark configurations. Recently, with polarized beam and target, the spin-correlation parameters A NN, A SS, and A SL have been determined at 10 energies between 0.8 and 2.5 GeV. The observable Ass has been measured the first time above 800 MeV and our results are in sharp contrast to phase-shift predictions at higher energies.

Measurements of the eta meson production with a polarised proton beam in the reaction (p) over barp --> ppeta have been carried out at an excess energy of Q = 40 MeV. The dependence of the analysing power A,. on the polar angle theta(q)(*) of the 17 meson in the q center of mass system (CMS) has been studied. The data indicate the possibility of an influence of p- and d-waves to the close to threshold 17 production. (C) 2002 Elsevier Science B.V. All rights reserved.

The EDDA experiment at the cooler synchrotron COSY measures four polarization observables of the elastic proton-proton scattering. Excitation functions of the analyzing power AN and the three spin correlation parameters A(SS), A(NN) and A(SL) are acquired during beam acceleration for projectile moments from 1.0 to 3.3 GeV/c, using a polarized atomic beam target. While the analyzing power measurements have been recently completed yielding about 850 data points, first results for the three spin correlation coefficients have been obtained at fixed energies with the polarized COSY beam. The results are compared to predictions of phase shift analyses.

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.

A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9°⩽Θ⩽72° and 0°⩽ϕ⩽360° in the lab frame. The detector length is 590mm, the inner diameter 161mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes.

A polarimeter for use in recirculating beams of proton synchrotrons with energies from 300 MeV up to several GeV has been developed. The polarimetry is based on the asymmetry measurement of elastic (p) over right arrow p scattering on an internal CH2 fiber target. The forward going protons are detected with two scintillator systems on either side of the beam pipe close to the angle Theta(f) of maximum analyzing power A(N). Each one operates in coincidence with a broad (Delta Theta(b) = 21.4 degrees), segmented detector system for the recoil proton of kinematically varying direction Theta(b); this position resolution is also used for a concurrent measurement of the (p) over right arrow C and nonelastic (p) over right arrow p background. The CH2 fiber can be replaced by a carbon fiber for detailed background studies; "false" asymmetries are accounted for with a rotation of the polarimeter around the beam axis. Polarimetry has been performed in the internal beam of the Cooler Synchrotron COSY at fixed energies as well as during proton acceleration across depolarizing or spin flipping resonances. With luminosities in the order of 10(30) cm(-2) s(-1), count rates allow precise polarimetry within 10 min (6-10 h) at fixed energies (over the whole acceleration ramp). (C) 1999 Elsevier Science B.V. All rights reserved.