Longitudinal and transverse momentum distributions of "9Li fragments from break-up of "1"1Li

Transverse and longitudinal momentum distributions of "9Li fragments from "1"1Li break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was measured to be #sigma#_-_2_n=0.26#+-#0.02 b for the carbon target, #sigma#_-_2_n=0.47#+-#0.08 b for the aluminum target and #sigma#_-_2_n=1.9#+-#0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM#approx#47 MeV/c) of the transverse and longitudinal momentum distributions of the "9Li fragments. The physical implications of this are discussed. (orig.)Available from TIB Hannover: RA 3692(95-01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

First energy-loss-straggling experiments with relativistic heavy ions in solids

First energy-loss-straggling measurements performed at the high-momentum-resolution magnetic spectrometer FRS with bare and highly-charged _8O, _5_4Xe, _7_9Au and _9_2U ions with specific kinetic energies (700... 1000) MeV/u are reported. The results are in good agreement with excact calculations recently reported by Lindhard and Soerensen and reveal systematic deviations from the well-known relativistic Bohr formula, which was obtained within the framework of the first-order Born approximation. (orig.)Available from TIB Hannover: RO 801(96-28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Charge state and energy loss of relativistic heavy ions in matter

Relativistic heavy-ion collisions of few-electron projectiles ranging from argon up to uranium have been investigated in solid and gaseous media. Electron-loss and electron-capture cross sections, charge-state distributions, as well as energy loss and energy deposition have been measured and are compared with theoretical predictions. Especially fully-ionized heavy projectiles represent a unique possibility to test atomic-collision theories. (orig.)Part of the Ph.D. thesis of C. ScheidenbergerAvailable from TIB Hannover: RO 801(93-77) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Subthreshold production of kaons and antikaons in nucleus-nucleus collisions at equivalent beam energies

Kaon production has been studied in Ni+Ni collisions at beam energies of 0.8-1.8 GeV/nucleon with the Kaon Spectrometer at GSI. The K"+ production cross section increases as E_b_e_a_m"5"."3"#+-#"0"."2. Both K"+ and K"- mesons are predominantly produced in central collisions. The K"-/K"+ ratio measured at equivalent beam energies below the respective particle production threshold is considerably larger for Ni+Ni collisions than for nucleon-nucleon collisions near threshold. This is evidence for an enhanced K"- production in the nuclear medium. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Nuclear matter distributions in "6He and "8He from small angle pHe scattering in inverse kinematics at intermediate energy

Differential cross sections for p"6He and p"8He elastic scattering have been measured in inverse kinematics at small momentum transfers up to vertical stroke t vertical stroke =0.05 (GeV/c)"2 and projectile energies of about 700 MeV/u. Nuclear matter densities deduced from the data are consistent with the concept that "6He and "8He nuclei have an #alpha#-like core and a significant neutron skin. The r.m.s. radii of the nuclear matter distributions were determined to be R_m("6He)=2.30#+-#0.07 fm and R_m("8He)=2.45#+-#0.07 fm. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Kaon and pion production in nuclear collisions

Kaon production has been studied in proton-nucleus, deuteron-nucleus, alpha-nucleus and in symmetric nucleus-nucleus collisions at bombarding energies above and below the K"+ production threshold for free NN collisions. The K"+ double differential cross section measured in p+C collisions at 2.5 GeV beam energy can be explained by kaon production in first chance nucleon-nucleon collisions with the target nucleon having a momentum-energy distribution according to the nuclear spectral function. The K"+ production cross section measured in p+C and p+Pb collisions at 1.2 and 1.5 GeV beam energy exceeds the prediction of the first chance collision model by a factor of 5 to 10. The projectile and target dependence of K"+ and #pi#"+ production as measured in d+C, d+Pb, #alpha#+C and #alpha#+Pb collisions at 1.15 AGeV yields evidence for K"+ production via collisions of high energetic pions with nucleons. In Au+Au collisions at 1 AGeV the K"+ multiplicity per participating nucleon increases with increasing number of participating nucleons. The azimuthal emission pattern and the inverse slope parameter of K"+ mesons and high energetic pions are a hint for a simultaneous freeze-out of these particles during the hot and dense phase of the collision. Transport calculations have to assume a soft equation of state in order to reproduce the measured K"+ cross sections. The in-medium K"-cross section measured in Ni+Ni collisions is enhanced by a factor of 7#+-#3 as compared to the free cross section when using the K"+ cross section at equivalent beam energies as a normalization. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Direct observation of systematic deviations from the Bethe stopping theory for relativistic heavy ions

The SIS accelerator facilities at GSI in combination with the magnetic spectrometer FRS allow the direct measurement of stopping powers for relativistic heavy ions up to uranium with high precision for the first time. Here, we report on representative results obtained for projectiles up to xenon in the energy range from (700-1000) MeV/u. Systematic deviations from the Bethe stopping-power theory are observed, whereas the data are in good agreement with theory one Mott and Bloch corrections and the Fermi density effect are included. (orig.)Part of the Ph.D. thesis of C. ScheidenbergerAvailable from TIB Hannover: RO 801(94-11) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Production and identification of heavy Ni isotopes: Evidence for the doubly magic nucleus "7"8_2_8Ni Short note

We report the first observation of the doubly magic nucleus "7"8Ni_5_0 and the heavy isotopes "7"7Ni, "7"3","7"4","7"5Co, "8"0Cu. The isotopes were produced by nuclear fission in collisions of 750 A.MeV projectiles of "2"3"8U on Be target nuclei. The fully-stripped fission products were separated in-flight by the fragment separator FRS and identified event-by-event by measuring the magnetic rigidity, the trajectory, the energy deposit, and the time of flight. Production cross-sections and fission yields for the new Ni-isotopes are given. (orig.)Available from TIB Hannover: RO 801(95-35) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Half-life measurements of bare, mass-resolved isomers in a storage-cooler ring

Secondary beams from fragmentation of "5"8Ni have been produced with energies of 200-220 A.MeV, separated with the fragment separator FRS and injected into the storage-cooler ring ESR for half-life measurements. The relative momentum spread #DELTA#p/p#approx#1.10"-"6 (FWHM) which we achieved allowed us to resolve the ground and isomeric states of cooled "5"2Mn and "5"3Fe nuclei in the measured mass spectra. The circulating beams were fully ionized which rendered possible, for the first time, to measure pure #beta#"+ branches for "5"2"gFe and "5"3"gFe and the sum of pure #beta#"+ and #gamma# branches in the decay of the isomers "5"2"mMn and "5"3"mFe. (orig.)15 refs.Available from TIB Hannover: RO 801(95-53) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Study of the out-of-plane emission of protons and light fragments in symmetric heavy-ion collisions

Midrapidity protons from "2"0"9Bi+"2"0"9Bi collisions were measured with the Kaon Spectrometer at SIS at incident energies of E_L_a_b/A=400, 700 and 1000 MeV. Additionally, light fragments were analysed at 400 MeV. We have investigated the azimuthal emission pattern of the particles relative to the reaction plane as function of transverse momentum, bombarding energy and impact parameter. We observe an enhanced emission of particles perpendicular to the reaction plane at all bombarding energies. The ratio of the number of particles emitted out-of-plane/in-plane increases strongly with the particles transverse momentum. The anisotropy decreases with increasing beam energy. Composite particles show a much stronger effect than protons. (orig.)31 refs.SIGLEAvailable from TIB Hannover: RO 801(96-01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman