J. Bisplinghoff

Excitation functions of spin correlation parameters ANN, ASS, and ASL in elastic pol.p pol.p scattering between 0.45 and 2.5 GeV

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 COSY 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 2000 MeV/c covering angles theta_{c.m.} between 30 deg and 90 deg. 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.

Fusion ofNi58,60,62with 113-170 MeVCa40ions

Results of measurements of the fusion excitation functions of /sup 58,60,62/Ni targets with 113 --170 MeV (lab) /sup 40/Ca ions are reported. These results are used to extract fusion barrier heights and radii by several different methods. Subbarrier fusion cross sections are analyzed in terms of static deformations. Possible importance of dynamic deformation is discussed. Conclusions as to the role of static deformation are similar to those from the /sup 35/Cl+/sup 58,60,62/Ni fusion system; a large part of the subbarrier behavior can be attributed to this cause.

Near threshold two meson production with the pd→3Heπ+π− and pd→3HeK+K− reactions

Near threshold two meson production via the reactions pd→3Heπ+π− and pd→3HeK+K− was measured kinematically complete with the MOMO experiment at COSY. The obtained two pion invariant mass spectra and angular distributions depict a remarkable deviation from phase space. The two kaon data are consistent with phase space topped by a clear signal of the φ meson.

Experimental study of thepd(dp)→He3ππreactions close to threshold

New experimental data on the pd -> 3He pi+ pi- reaction obtained with the COSY-MOMO detector below the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam and the higher counting rates achieved were especially important at low excess energies. The comparison of these data with inclusive pd -> 3He+X rates allowed estimates also to be made of pi0 pi0 production. The results confirm our earlier findings that close to threshold there is no enhancement at low excitation energies in the pi+ pi- system, where the data seem largely suppressed compared to phase space. Possible explanations for this behavior, such as strong p- waves in the pi+pi- -system or the influence of two-step processes, are explored.

Study of the pd(dp) -> 3He pi pi reactions close to threshold

New experimental data on the pd -> 3He pi+ pi- reaction obtained with the COSY-MOMO detector below the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam and the higher counting rates achieved were especially important at low excess energies. The comparison of these data with inclusive pd -> 3He+X rates allowed estimates also to be made of pi0 pi0 production. The results confirm our earlier findings that close to threshold there is no enhancement at low excitation energies in the pi+ pi- system, where the data seem largely suppressed compared to phase space. Possible explanations for this behavior, such as strong p- waves in the pi+pi- -system or the influence of two-step processes, are explored.

Excitation functions of spin correlation parameters A{sub NN},A{sub SS}, and A{sub SL} in elastic ({yields}/p)({yields}/p) scattering between 0.45 and 2.5 GeV

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 COSY 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 2000 MeV/c covering angles theta_{c.m.} between 30 deg and 90 deg. 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.

Fusion of /sup 58,60,62/Ni with 113 --170 MeV /sup 40/Ca ions

Results of measurements of the fusion excitation functions of /sup 58,60,62/Ni targets with 113 --170 MeV (lab) /sup 40/Ca ions are reported. These results are used to extract fusion barrier heights and radii by several different methods. Subbarrier fusion cross sections are analyzed in terms of static deformations. Possible importance of dynamic deformation is discussed. Conclusions as to the role of static deformation are similar to those from the /sup 35/Cl+/sup 58,60,62/Ni fusion system; a large part of the subbarrier behavior can be attributed to this cause.

Fusion of Ni-58, Ni-60, Ni-62 with 113-170 MeV Ca-40 ions

Results of measurements of the fusion excitation functions of /sup 58,60,62/Ni targets with 113 --170 MeV (lab) /sup 40/Ca ions are reported. These results are used to extract fusion barrier heights and radii by several different methods. Subbarrier fusion cross sections are analyzed in terms of static deformations. Possible importance of dynamic deformation is discussed. Conclusions as to the role of static deformation are similar to those from the /sup 35/Cl+/sup 58,60,62/Ni fusion system; a large part of the subbarrier behavior can be attributed to this cause.

Statistical analysis of heavy-ion induced fission excitation functions

The Bohr-Wheeler model has been used with the rotating liquid drop model to calculate fission excitation functions using a computer code with multiple particle emission competition. Calculations were performed for fission induced by /sup 35/Cl ions with laboratory energies up to 170 MeV on /sup 62/Ni, /sup 116/Sn, and /sup 141/Pr targets. The dependence of the fission cross sections on angular momentum, barrier heights, ground state and saddle point level density parameters, and for first versus multiple chance fission is illustrated. One set of parameters, not necessarily unique, is shown which gives fair reproduction of the measured /sup 116/Sn and /sup 141/Pr + /sup 35/Cl fission excitation functions. It is shown that fission barriers considerably lower than the rotating liquid drop values are required and that variations of other parameters alone cannot reproduce the experimental excitation functions. Asymptotic weaknesses of the statistical treatment at high excitation energies are discussed and qualitatively shown to give errors in the direction observed in the comparisons of experimental and calculated results.