Publications

Andronenko, M.N., L.N. Andronenko, W. Neubert, D.M. Seliverstov

Abstract: Nuclear temperatures were extracted from fragment yields obtained in inclusive measurements of p+A collisions at 1 GeV. All thermometers based on double-isotopic yield-ratios provide temperatures T @ 4 MeV nearly independent of the target mass.
 

Balestra, F., Y. Bedfer, R. Bertini, L.C. Bland, A. Brenschede, F. Brochard, M.P. Bussa, V. Chalyshev, Seonho Choi, M. Debowski, M. Dzemidzic, J.-Cl. Faivre, I.V. Falomkin, L. Fava, L. Ferrero, J. Foryciarz, V. Frolov, R. Garfagnini, D. Gill, A. Grasso, S. Heinz, V.V. Ivanov, W.W. Jacobs, W. Kühn A. Maggiora, M. Maggiora, A. Manara, D. Panzieri, H.-W. Pfaff, G. Piragino, G.B. Pontecorvo, A. Popov, J. Ritman, P. Salabura, F. Tosello, S.E. Vigdor, G. Zosi  (DISTO Collaboration)

Abstract: We report the first polarization transfer measurements for exclusive hyperon production reactions. The normal spin transfer coefficient D_NN for pp® pK⁺K^-L is large and negative for forward L production at a beam momentum of 3.67GeV/c, a result qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering. The sign of D_NN is opposite to that observed in the fragmentation regime for inclusive L production at much higher energies.
 

Balestra, F., Y. Bedfer, R. Bertini, L.C. Bland, A. Brenschede, F. Brochard, M.P. Bussa, V. Tchalyshev, Seonho Choi, M. Debowski, M. Dzemidzic, J.-Cl. Faivre, I.V. Falomkin, L. Fava, L. Ferrero, J. Foryciarz, I. Fröhlich, V. Frolov, R. Garfagnini, D. Gill, A. Grasso, E. Grosse, S. Heinz, V.V. Ivanov, W.W. Jacobs, W. Kühn, A. Maggiora, M. Maggiora, A. Manara, D. Panzieri, H.-W. Pfaff, G. Piragino, G.B. Pontecorvo, A. Popov, J. Ritman, P. Salabura, F. Tosello, S.E. Vigdor, G. Zosi

Abstract: The total cross section of the reaction pp® ppK⁺K^- has been determined for proton-proton reactions with p_beam = 3.67 GeV/c. This represents the first cross section measurement of the pp ® ppK^-K⁺ channel near threshold, and is equivalent to the inclusive pp® ppK^-X cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive pp® ppK⁺X meson production at the same CM energy above the corresponding threshold. This large difference in the K⁺ and K^- meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.
 

Barsov, S., U. Bechstedt, G. Borchert, W. Borgs, M. Buscher, M. Debowski, W. Erven, R. Esser, P. Fedorets, D. Gotta, M. Hartmann, H. Junghans, A. Kacharava, B. Kamys, F. Klehr, H.R. Koch, V.I. Komarov, V. Koptev, P. Kulessa, A. Kulikov, V. Kurbatov, G. Macharashvili, R. Maier, S. Mikirtychyants, S. Merzlyakov, H. Müller, A. Mussgiller, M. Nioradze, H. Ohm, A. Petrus, D. Prasuhn, K. Pysz, F. Rathmann, <u>B. Rimarzig</u>, Z. Rudy, R. Schleichert, C. Schneider, H. Schneider, O.W.B. Schult, H. Seyfarth, K. Sistemich, H.J. Stein, H. Ströher (ANKE Collaboration)

Abstract: The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. It enables the study of forward going ejectiles from proton-induced reactions at internal targets in COSY. First measurements of the double differential cross sections for the subthreshold K⁺-production in pA collisions have been performed at projectile energies as low as 1.0 GeV, i.e. 0.58 GeV below the free nucleon-nucleon threshold.
 

Barsov, S., U. Bechstedt, G. Borchert, W. Borgs, M. Buscher, M. Debowski, W. Erven, R. Esser, P. Fedorets, D. Gotta, M. Hartmann, H. Junghans, A. Kacharava, B. Kamys, F. Klehr, H.R. Koch, V.I. Komarov, V. Koptev, P. Kulessa, A. Kulikov, V. Kurbatov, G. Macharashvili, R. Maier, S. Mikirtychyants, S. Merzlyakov, H. Müller, A. Mussgiller, M. Nioradze, H. Ohm, A. Petrus, D. Prasuhn, K. Pysz, F. Rathmann, B. Rimarzig, Z. Rudy, R. Schleichert, C. Schneider, H. Schneider, O.W.B. Schult, H. Seyfarth, K. Sistemich, H.J. Stein, H. Ströher (ANKE Collaboration)

Abstract: The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich. An initial scientific goal is to study K⁺-production in pA collisions at subthreshold energies bellow the free NN-threshold of T=1.58 GeV. First measurements of double differtial cross sections in p¹²C collisions at emission angles around 0^o have been performed at T=1.0, 1.2 and 2.0 GeV. The challenge is to identify the kaons in a huge background of pions and protons, since the signal to background ratio decreases to about 10^-6 at T=1.0 GeV. For background suppression detectors and a trigger system based on energy-loss and time-of-flight measurements have been developed. In the analysis the decay of kaons (t=12.4 ns) stopped in the detection system into m⁺ and p⁺ is exploited as well as the track information from the wire chambers.

Barsov, S., U. Bechstedt, G. Borchert, W. Borgs, M. Buscher, M. Debowski, W. Erven, R. Esser, P. Fedorets, D. Gotta, M. Hartmann, H. Junghans, A. Kacharava, B. Kamys, F. Klehr, H.R. Koch, V.I. Komarov, V. Koptev, P. Kulessa, A. Kulikov, V. Kurbatov, G. Macharashvili, R. Maier, S. Mikirtychyants, S. Merzlyakov, H. Müller, A. Mussgiller, M. Nioradze, H. Ohm, A. Petrus, D. Prasuhn, K. Pysz, F. Rathmann, B. Rimarzig, Z. Rudy, R. Schleichert, C. Schneider, H. Schneider, O.W.B. Schult, H. Seyfarth, K. Sistemich, H.J. Stein, H. Ströher (ANKE Collaboration)

Abstract: The accelerator COSY at the Forschungszentrum Juelich provides proton beams with energies up to 2.6 GeV for medium-energy hadron research. ANKE, an internal target magnetic spectrometer at the internal beam of COSY, is used to investigate medium effects in proton-nucleus reactions. It has been installed in the accelerator ring and commissioned in 1998. As a first experiment, subthreshold K⁺-production has been studied in p¹²C collisions.

Böhm, A., K.-Th. Brinkmann, S. Dshemuchadse, H. Freiesleben, P. Herrmann, B. Jakob, H. Koch, J. Krug, E. Kuhlmann, J.S. Lange, P. Michel, K. Möller, A. Schamlott, P. Schönmeier, A. Schülke, M. Steinke, G.Y. Sun, M. Würschig-Pörsel, U. Zielinski

Abstract: A barrel-shaped scintillator hodoscope was developed as part of the time-of-flight spectrometer TOF operated at an external beam line of the cooler synchrotron COSY. The COSY-TOF spectrometer is used mainly to perform kinematically complete experiments on light meson production and proton-proton bremsstrahlung in proton-proton collisions for laboratory energies up to 2.5 GeV. The newly developed scintillator hodoscope (BARREL1), one of several detector segments of the COSY-TOF spectrometer, consists of one layer of 96 scintillator bars of 15 mm thickness arranged to form a barrel with 3 m in diameter and 2.85 m in length. For any given interaction process the TOF spectrometer allows to determine the velocity vectors of all charged ejectiles emerging from the target by measuring the time of flight between the start and the stop detector as well as the point of impact on the stop detector. For the BARREL1 detector the position information is obtained by two-sided light read-out of the scintillator bars. For minimum ionizing particles the spatial resolution was measured to be D z(FWHM) = 8 cm, corresponding to a polar angle resolution in the range 0.57 to 2.86 degrees, depending on the hit position. The binning in azimuthal angular direction amounts to 360/96 = 3.75 degrees. For the time-of-flight resolution of minimum ionizing particles a value of D t(FWHM) = 0.61 ns was obtained.
 

Chiara, C.J., S.J. Asztalos, B. Busse, R.M. Clark, M. Cromaz, M.A. Deleplanque, R.M. Diamond, P. Fallon, D.B. Fossan, D.G. Jenkins, S. Juutinen, N.S. Kelsall, R. Krücken, G.J. Lane, I.Y. Lee, A.O. Macchiavelli, R.W. MacLeod, G. Schmid, J.M. Sears, J.F. Smith, F.S. Stephens, K. Vetter, R. Wadsworth, S. Frauendorf

Abstract: Lifetimes of high-spin states in two DI = 1 bands and one DI = 2 band in ¹⁰⁹Cd have been measured using the Doppler shift attenuation method in an experiment performed using the ⁹⁶Zr(¹⁸O,5n) reaction with the GAMMASPHERE array. Experimental total angular momenta and reduced transition strengths for both DI = 1 bands were compared with tilted axis cranking (shears mechanism) predictions and the DI = 2 band with principal axis cranking predictions, based on configurations involving two proton g_9/2 holes and one or three valence quasineutrons from the h_11/2 and mixed g_7/2/d_5/2 orbitals. Good overall agreement for angular momentum versus rotational frequency has been observed in each case. The DI = 2 band is shown to have a large Á ⁽²⁾/B(E2) ratio suggestive of antimagnetic rotation. Additionally, both dipole bands show a decreasing trend in B(M1) strength as a function of spin, a feature of the shears mechanism. The experimental results are also compared with a semiclassical model that employs effective interactions between the proton holes and neutrons as an alternate interpretation for the shears mechanism.
 

Crochet, P., N. Herrmann, K. Wisniewski, Y. Leifels, A. Andronic, R. Averbeck, A. Devismes, C. Finck, A. Gobbi, O. Hartmann, K.D. Hildenbrand, P. Koczon, T. Kress, R. Kutsche, W. Reisdorf, D. Schüll, J.P. Alard, V. Barret, Z. Basrak, N. Bastid, I. Belyaev, A. Bendarag, G. Berek, R. Caplar, N. Cindro, P. Dupieux, M. Dzelalija, M. Eskef, Z. Fodor, Y. Grishkin, B. Hong, J. Kecskemeti, Y.J. Kim, M. Kirejczyk, M. Korolija, R. Kotte, M. Kowalczyk, A. Lebedev, K.S. Lee, V. Manko, H. Merlitz, S. Mohren, D. Moisa, W. Neubert, A. Nianine, D. Pelte, M. Petrovici, C. Plettner, F. Rami, B. de Schauenburg, Z. Seres, B. Sikora, K.S. Sim, V. Simion, K. Siwek-Wilczynska, V. Smolyankin, A. Somov, M. Stockmeier, G. Stoicea, M. Vasiliev, P. Wagner, D. Wohlfarth, J.T. Yang, I. Yushmanov, A. Zhilin

Abstract: Experimental data on K⁺ meson and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru+Ru at 1.69 AGeV and Ni+Ni at 1.93 AGeV are presented. The K⁺ sideward flow is found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the data favour the existence of an in-medium repulsive K⁺ nucleon potential.
 

Debus, J., Th. Haberer, D. Schulz-Ertner, O. Jäkel, F. Wenz, W. Enghardt, W. Schlegel, G. Kraft, M. Wannenmacher

Abstract: Background: Radiobiological and physical examinations suggest clinical advantages of heavy ion irradiation. We report the results of 23 women and 22 men (median age 48 years) with skull base tumors irradiated with carbon ion beams at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, from December 1997 until September 1999.
Patients and Methods: The study included patients with chordomas (17), chondrosarcomas (10) and other skull base tumors (Table 1). It is the first time that the intensity-controlled rastercan-technique and the application of positron-emission tomography (PET) for quality assurance was used. All patients had computed tomography for three-dimensionaltreatment planning (Figure 1). Patients with chordomas and chondrosarcomas underwent fractionated carbon ion irradiation in 20 consecutive days (median total dose 60 GyE). Other histologies were treated with a carbon ion boost of 15 to 18 GyE delivered to the macroscopic tumor after fractionated stereotactic radiotherapy (median total dose 63 GyE).
Result: Mean follow-up was 9 months. Irradiation was well tolerated by all patients. Partial tumor remission was seen in 7 patients (15.5%)(Figure 2). One-year local control rate was 94%. One patient (2.2%) deceased. No severe toxicity and no local recurrence within the treated volume were observed.
Conclusion: Clinical effectiveness and technical feasibility of this therapy modality could clearly be demonstrated in our study. To evaluate the clinical relevance of the different beam modalities studies with larger patient numbers are necessary. To continue our projects a new heavy ion accelerator exclusively for clinical use is planned to be constructed in Heidelberg.

Dimitrov, V.I., S. Frauendorf, F. Dönau

Abstract: A hybrid version the deformed nuclear potential is suggested, which combines a spherical Woods Saxon potential with a deformed Nilsson potential. It removes the problems of the conventional Nilsson potential in the mass 130 region. Based on the hybrid potential, tilted axis cranking calculations are carried out for the magnetic dipole band in ¹²⁸Ba.

Dimitrov, V.I., S. Frauendorf, F. Dönau

Abstract: It is shown that the rotating mean field of triaxial nuclei can break the chiral symmetry. Two nearly degenerate DI = 1 rotational bands originate from the left-handed and right-handed solutions.
 

Dohrmann, F., for the KaoS Collaboration

Abstract: We have conducted systematic experimental studies of K⁺ and K^- production and propagation in nucleus-nucleus collisions at beam energies close to and below the production threshold for free nucleon-nucleon (NN) collisions. In noncentral Au+Au collision, the K⁺ mesons are preferentially emitted perpendicular to the reaction plane and the excitation functions for K⁺ and K^- mesons nearly coincide when correcting for the threshold energy. In contrast, for NN collisions the K⁺ yield exceeds the K^- yield by two orders of magnitude near the respective NN threshold. Both effects are considered to be experimental signatures of a modification of kaon properties in the nuclear medium.

Enders, J., P. von Brentano , J. Eberth , A. Fitzler , C. Fransen , R.-D. Herzberg, H. Kaiser, L. Käubler, P. von Neuman-Cosel, N. Pietralla, V.Yu. Ponomarev, A. Richter, H. Schnare, R. Schwengner, S. Skoda, H.G. Thomas, H. Tiesler, D. Weisshaar, I. Wiedenhöver

Abstract: Results of a ²⁰⁸Pb (g,g^¢) experiment are presented aiming at an identification of the 2⁺ member of the long-sought two-octupole phonon multiplet. Four E2 excitations have been observed below 6.5 MeV excitation energy, two of them for the first time. However, in contrast to new results of calculations within the quasiparticle-phonon nuclear model (QPM), no obvious candidate for the two-octupole phonon vibration could be found in the present study. We discuss the J = 2⁺ states detected in this as well as previous experiments with respect to their possible two-octupole phonon structure.
 

Egidy von, T., P. Figuera, J. Galin, F. Goldenbaum, Ye.S. Golubeva, M. Hasinoff, D. Hilscher, A.S. Iljinov, U. Jahnke, M. Krause, W. Kurcewicz, X. Ledoux, B. Lott, L. Maier, M. Manrique de Lara, G. Pausch, L. Pienkowski, B. Quednau, W. Schott, W.U. Schröder, J. Toke

Abstract: Inclusive neutron energy spectra were measured by time of flight using 1.22 GeV antiprotons from LEAR,CERN, as projectiles and targets from natural Al, Cu, Ag, Ho, Ta, Au, Pb, Bi, U. The sum of two Maxwellian distributions was fitted to the spectra d²s/dWdE) obtained at several forward and backward angles yielding neutron multiplicities M_i and slope or temperature parameters T_i for the low-energy (evaporative, i=1) and high-energy (pre-equilibrium, i=2) parts, respectively. M₁ increases with A, proportional to the nuclear volume, and M₂ is growing with A^1/3, proportional to the nuclear radius. The T parameters are nearly independent of A. The results are compared with previous multiplicity measurements with a 4p neutron detector, intranuclear cascade calculations and neutron spectra from stopped antiproton annihilation on nuclei. With the measured proton spectra also the ratio of emitted neutrons to protons was determined for Au.
 

Enghardt, W., J. Debus, T. Haberer, B.G. Hasch, R. Hinz, O. Jäkel, M. Krämer, K. Lauckner, J. Pawelke, F. Pönisch

Abstract: Positron emission tomography (PET) offers the possibility of in-situ monitoring the tumour treatment with light ion beams by means of imaging the spatial distribution of b⁺-activity that is produced as a byproduct of the therapeutic irradiation via nuclear fragmentation reactions between the projectiles and the atomic nuclei of the tissue within the target volume. The implementation of this PET technique at the experimental tumour therapy facility at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt and first results of its clinical application are presented.

Frauendorf, S., J.A. Sheikh, P.M. Walker, K. Neergard

Abstract: Tilted-axis cranking calculations have been performed for multi-quasiparticle states in well deformed A » 180 nuclei. In the limit of zero pairing, not only are the calculated moments of inertia substantially smaller than for rigid rotation, but also they are close to the experimental values. The moments of inertia are found to be insensitive to dynamic pair correlations
 

Frauendorf, S.

Abstract: The selfconsistent cranking approach is extended to the case of rotation about an axis which is tilted with respect to the principal axes of the deformed potential (Tilted Axis Cranking). Expressions for the energies and the intra bands electromagnetic transition probabilities are given. The mean field solutions are interpreted in terms of quantal rotational states. The construction of the quasiparticle configurations and the elimination of spurious states is discussed. The application of the theory to high spin data is demonstrated by analysing the multi quasiparticle bands in the nuclides with N = 102,103 and Z = 71,72,73.
 

Fritz, S., C. Schwarz, R. Bassini, M. Begemann-Blaich, S.J. Gaff-Ejakov, D. Gourio, C. Groß, G. Immè, I. Iori, U. Kleinevoß, G.J. Kunde, W.D. Kunze, U. Lynen, V. Maddalena, M. Mahi, T. Möhlenkamp, A. Moroni, W.F.J. Müller, C. Nociforo, B. Ocker, T. Odeh, F. Petruzzelli, J. Pochodzalla, G. Raciti, G. Riccobene, F.P. Romano, A. Saija, M. Schnittker, A. Schüttauf, W. Seidel, V. Serfling, C. Sfienti, W. Trautmann, A. Trzcinski, G. Verde, A. Wörner, Hongfei Xi, B. Zwieglinski

Abstract: Proton-proton correlations and correlations of protons, deuterons and tritons with a particles from spectator decays following ¹⁹⁷Au + ¹⁹⁷Au collisions at 1000 MeV per nucleon have been measured with two highly efficient detector hodoscopes. The constructed correlation functions, interpreted within the approximation of a simultaneous volume decay, indicate a moderate expansion and low breakup densities, similar to assumptions made in statistical multifragmentation models.
 

Gabriel, F., P. Gippner, E. Grosse, D. Janssen, P. Michel, H. Prade, A. Schamlott, W. Seidel, A. Wolf, R. Wünsch and ELBE-crew

Abstract: The Forschungszentrum Rossendorf (FZR) is constructing a superconducting Electron Linac [F. Gabriel, J. Voigtländer, et al., ELBE Design Report 1998, http://www.fz-rossendorf.de/FWQ/report_d.htm; Annual Report 1996, FZR-179 (1997) 3; Annual Report 1997, FZR-215 (1998) 3] with high Brilliance and low Emittance (ELBE) which can deliver a 1 mA cw beam of 40 MeV. ELBE will be equipped with a free-electron laser (FEL) system for the production of infrared (IR) light in the range 5-300 mm and will thus cover the range from the infrared to the THz regime. The electron beam can also be used to generate X-rays, bremsstrahlung, positrons or fast neutrons.
 

Gallmeister, K., B. Kämpfer, O.P. Pavlenko

Abstract: An analysis of the dilepton measurements in the reactions Pb(158 A·GeV + Au, Pb points to a unique thermal source contributing to the invariant mass and transverse momentum spectra.
 

Gallmeister, K., B. Kämpfer, O.P. Pavlenko

Abstract: The data of direct single-photon measurements of the WA98 Collaboration in the reaction Pb(158A GeV) + Pb are analyzed within a thermal model with a minimum number of parameters adjusted to the dilepton data obtained by the CERES and NA50 Collaborations in the reactions Pb(158A GeV) + Au, Pb. The agreement of our model with the WA98 data points to a unique large thermal source emitting electromagnetic radiation is observable in both the real and virtual photon channels.
 

Gontchar, I.I., A.E. Gettinger, L.V. Guryan, W. Wagner

Abstract: A multidimensional stochastic model of decay of excited nuclei is presented. In the model the dynamics of thermal fluctuations of collective variables as well as dissipation of collective kinetic energy and particle emission are accounted for. Potential energy of deformed nucleus is calculated in the framework of both the liquid drop model with sharp surface and the finite range model. The friction parameters are computed by means of the one-body dissipation model. In order to find the inertia parameters the Werner-Wheeler approximation is used. The drift forces are calculated via the entropy of excited nucleus. The entropy is found in the Fermi-gas approximation with a deformation-dependent level density parameter. In the framework of the stochastic model following quantities are calculated and compared with data: 1) the fission probability, 2) the average multiplicity of the neutrons being emitted before scission (precission neutrons), 3) the variance of fission-fragment mass distribution. Dependence of the values of these quantities upon the parameters of the model is considered in details.
 

Grigoryan, L.Sh., A.R. Mkrtchyan, B.V. Khachtryan, H.F. Khachtryan, H. Prade, W. Wagner

Abstract: The solutions of the Dirac equation for a positron channeled in a single crystal which is excited by a longitudinal hypersonic wave have been obtained for the energy interval of 10 MeV < E £ 100 MeV, and the resonance condition for the interaction between hypersound and positron was deduced. It is shown that the total intensity of the channeling radiation emitted by the relativistic positron in the hypersonic field is formed by the partial intensities of several dominating radiative transitions for which the appropriate conservation law and the Doppler shift of the photon frequency have been determined. Owing to the hypersound the transverse energy of the positron may increase which leads to a larger bandwidth of the emitted lines.
 

Grigoryan, L.Sh., A.H. Mkrtchyan, H.F. Khachtryan, R.P. Vardapetian, H. Prade, W. Wagner

Abstract: Transition probabilities and the intensity of channeling radiation has been calculated for positrons of energy 10 MeV < E £ 100 MeV channeled in a longitudinal hypersonic crystal-superlattice. It has been found that the hypersound can excite inverse radiative transitions through which the transverse energy of the channeled positron is increased. These transition have a resonant nature if the wavelengths of the hypersound and of the oscillations of the positron during channeling match. This can lead to a considerable intensification of the positron channeling radiation.
 

Grigoryan, L.Sh., A.R. Mkrtchyan, H.F. Khachtryan, A.H. Mkrtchyan, H. Prade, W. Wagner

Abstract: The wave function of an electron of energy 10 MeV £ E £ 100 MeV axially channeled in a longitudinal hypersonic superlattice has been obtained within the framework of a quantum mechanical approach. Conditions for the resonant influence of the hypersonic wave excited in the single crystal on the quantum states of the channeled electron have been deduced.
 

Grosse, E.

Abstract: In a systematic experimental study of K⁺ and K^- production in nuclear collisions at energies close to and below the free nucleon-nucleon production threshold we have found several features indicating a change of kaon properties within the nuclear medium.
 

Herzberg, R.-D., C. Fransen, P. von Brentano, J. Eberth, J. Enders, A. Fitzler, L. Käubler, H. Kaiser, P. von Neumann-Cosel, N. Pietralla, V.Yu. Ponomarev, H. Prade, A. Richter, H. Schnare, R. Schwengner, S. Skoda, H.G. Thomas, H. Tiesler, D. Weisshaar, I. Wiedenhöver

Abstract: The electromagnetic dipole response of ¹³⁸Ba was measured up to 6.7 MeV excitation energy in a photon scattering experiment. Two Euroball Cluster detectors were used to detect the scattered photons under 94 and 132 degrees. The Cluster at 94 degrees served as a Compton polarimeter. The total observed dipole cross strength and the electric character of most of the transitions has been determined on a state-by-state basis. The data show a concentration of E1 strength around 6 MeV. For one of the strongest excitations M1 character is suggested. The results of model calculations using the quasiparticle phonon model (QPM) agree with the observed electric dipole strength distribution.
 

Iwasa, N., F. Boué, G. Surówka, K. Sümmerer, T. Baumann, B. Blank, S. Czajkowski, A. Förster, M. Gai, H. Geissel, E. Grosse, M. Hellström, P. Koczon, B. Kohlmeyer, R. Kulessa, F. Laue, C. Marchand, T. Motobayashi, H. Oeschler, A. Ozawa, M.S. Pravikoff, E. Schwab, W. Schwab, P. Senger, J. Speer, C. Sturm, A. Surowiec, T. Teranishi, F. Uhlig, A. Wagner, W. Walus, C.A. Bertulani

Abstract: We have measured the Coulomb dissociation of ⁸B into ⁷Be and proton at 254 MeV/nucleon using a large-acceptance focusing spectrometer. The astrophysical S₁₇ factor for the ⁷Be(p,g)⁸B reaction at E_c.m. = 0.25-2.78 MeV is deduced yielding S₁₇(0) = 20.6±1.2 (exp.) ± 1.0 (theor .) eV-b. This result agrees with the presently adopted zero-energy S₁₇ factor obtained in direct-reaction and with the results of other Coulomb-dissociation studies performed at 46.5 and 51.2 MeV/nucleon.
 

Jahnke, U., W. Bohne, T. von Egidy, P. Figuera, J. Galin, F. Goldenbaum, D. Hilscher, J. Jastrzebski, B. Lott, M. Morjean, G. Pausch, A. Péghaire, L. Pienkowski, D. Polster, S. Proschitzki, B. Quednau, H. Rossner, S. Schmid, W. Schmid

Abstract: Annihilation of 1.2 GeV antiprotons has been explored as a means to generate high thermal excitation in heavy nuclei (U, Au, Ho) and to observe their decay with a minimal contribution from dynamical E^* » 1000 MeV. Both modes are increasingly accompanied by a modest emission of intermediate-mass fragments (up to 1 on average), but true multifragmentation is not observed. These features are in agreement with the predictions of the statistical model with no need for a fission delay t_f > 0.5 × 10^-21 s.

Jungklaus, A., D. Kast, K.P. Lieb, C. Lingk, C. Teich, O. Iordanov, T. Härtlein, D. Schwalm, I.P. Johnstone, R. Schwengner

Abstract: The magnetic moments of the 12⁺ and 11^- yrast states in ⁹⁴Ru and of the 25/2^-, 29/2⁺ and 35/2⁺, levels in ⁹⁵Rh have been measured via the IMPAD technique. The nuclei were produced in the reaction ⁵⁸Ni + ⁴⁰Ca and recoil-implanted into polarized Ni and Fe hosts. The g-factors were deduced from the measured time-integral Larmor precessions. The comparison between the experimental results and large-scale shell model calculations suggests that the 12⁺ and 11^- states in ⁹⁴Ru and the 25/2^- level in ⁹⁵Rh are pure proton states whereas the 29/2⁺ and 35/2⁺ states in ⁹⁵Rh contain a neutron excitation across the N=50 shell gap. This interpretation supports the conclusion drawn from recent lifetime measurements.
 

Kämpfer, B., O.P. Pavlenko

Abstract: The polarisation of a surrounding QCD medium modifies the induced gluon radiation spectrum of a high-energy parton at small transverse momenta for a single interaction and for multiple scatterings as well. This effect is an analogue of the Ter-Mikaelian effect in QED, superimposed to the Landau-Pomeranchuk effect. We study the Ter-Mikaelian effect in a phase space region where Abelian radiation does occur. In this region the induced gluon radiation is shown to be suppressed due to polarization properties of the medium
 

Kämpfer, B.

Abstract: The sequence of phase transitions during the hot history of the universe is followed within a phenomenological framework. Particular emphasis is put on the QCD confinement transition, which is at reach under earth laboratory conditions. A tepid inflationary scenario on the GUT scale with bubble growth at moderate supercooling is discussed.
 

Käubler, L., H. Schnare, R. Schwengner, P. von Brentano, F. Dönau, J. Eberth, J. Enders, A. Fitzler, C. Fransen, M. Grinberg, E. Grosse, R.-D. Herzberg, H. Kaiser, P. von Neumann-Cosel, N. Pietralla, H. Prade, A. Richter, S. Skoda, Ch. Stoyanov, H.-G. Thomas, H. Tiesler, D. Weisshaar, I. Wiedenhöver

Abstract: A nuclear resonance fluorescence experiment on ⁸⁸Sr has been performed with bremsstrahlung of 6.7 MeV endpoint energy. The g-ray linear polarisation has been measured with a EUROBALL CLUSTER detector used as a Compton polarimeter. The results indicate positive parity for the J=1 state at 4.742 MeV in ⁸⁸Sr, in contrast to the previous interpretation as a 1^- two -phonon (2⁺₁ Ä 3^-₁) state and in conflict with the predictions of the quasiparticle-phonon model. On the basis of such calculations the 1⁺ state at 3.486 MeV may be considered as the 1⁺₁ one-phonon state and the very strong 1⁺₁ ® 0⁺₁deexcitation as proton spin-flip 2p_1/2 ® 2p_3/2 transition.
 

Kaptari, L.P., B. Kämpfer, S.M. Dorkin, S.S. Semikh

Abstract: The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the deuteron vertex function obtained by the Bethe-Salpeter equation with realistic meson-exchange interaction. Contributions of the one-nucleon and one-pion exchange mechanisms to the cross section and polarization observables are investigated in explicit form. Results of numerical calculations for the cross section, tensor analyzing power and spin transfers are presented. The one-pion exchange contribution is essential for describing the spin-averaged cross section, while in polarization observables it is found to have a small effect.
 

Kaptari, L.P., B. Kämpfer, E. Grosse

Abstract: A covariant model based on the Bethe-Salpeter formalism is proposed for investigating the solar proton burning process pp® De⁺n_e and the near-threshold deuteron disintegration via electromagnetic and weak interactions. Results of numerical calculations of the energy dependence of relevant cross sections and the astrophysical low-energy cross section factor S_pp of the proton burning process are presented. Our results confirm previous canonical values, and the energy dependence of the S_pp factor is rather close to phenomenological extrapolations commonly adopted in computations of solar nuclear reaction rates.
 

Kapusta, M., M. Balcerzyk, M. Moszynski, J. Pawelke

Abstract: A energy resolution of 4.38±0.11% was obtained for 662 keV g-rays with a 3×3×20 mm³ YAP: Ce crystal with its long face coupled to an XP2020Q photomultiplier. The measured number of photoelectrons of 5290±80 phe/MeV implies a photoelectron statistical contribution of 4.18±0.04% and hence a YAP intrinsic energy resolution of 1.3±0.5% the lowest value ever observed for scintillators. The relative light output of the YAP crystal measured for energies between 14.4 keV and 1.275 MeV was constant within ±2%. These observations are consistent with the assumption that there is a direct correlation between the energy resolution of scintillators and nonproportionality of their light output versus energy.
 

Kapusta, M., M. Moszynski, M. Balcerzyk, J. Pawelke

Abstract: We investigate the application of LSO and YSO scintillating crystals for Positron Emission Tomography (PET). Properties such as light output, energy resolution, detection efficiency for various energy threshold, and timing resolution are presented. These data allow us to evaluate the usage of finger-like LSO:Ce and YSO:Ce crystals coupled to photomultiplier tube, and to establish optimal operating conditions for high-resolution PET. Both crystals have advantages over BGO currently used in PET and LSO is considered as a possible replacement for BGO based systems.
 

Kelsall, N.S., R. Wadsworth, S.J. Asztalos, B. Busse, C.J. Chiara, R.M. Clark, M.A. Deleplanque, R.M. Diamond, P. Fallon, D.B. Fossan, D.G. Jenkins, S. Juutinen, R. Krücken, G.J. Lane, I.Y. Lee, A.O. Macchiavelli, C.M. Parry, G.J. Schmid, J.M. Sears, J.F. Smith, F.S. Stephens, K. Vetter, S. Frauendorf

Abstract: High-spin states were populated in ¹⁰⁸Cd using the ⁹⁶Zr(¹⁶O,4n) reaction at a beam energy of 72 MeV. Two magnetic dipole bands have been observed, both of which contain weak E2 crossover transitions. Lifetimes for the stronger of the two bands were measured via the Doppler shift attenuation method. The configuration assignment for this band has been determined from comparison with tilted axis cranking model calculations to be p[g_9/2^-3g_7/2] Ä n[h_11/2(g_7/2d_5/2)¹] and p[g_9/2g_7/2] Ä n[h³_11/2(g_7/2d_5/2)¹], before and after the nh²_11/2 band crossing, respectively. The deduced B(M1) strengths decrease rapidly with increasing spin after the nh²_11/2 alignment, which is a characteristic behavior of a shears band.
 

Kotte, R., H.W. Barz, W. Neubert, C. Plettner, D. Wohlfarth, J.P. Alard, A. Andronic, R. Averbeck, Z. Basrak, N. Bastid, N. Bendarag, G. Berek, R. Caplar, N. Cindro, P. Crochet, A. Devismes, P. Dupieux, M. Dzelalija, M. Eskef, Z. Fodor, A. Gobbi, Y. Grishkin, N. Herrmann, K.D. Hildenbrand, B. Hong, J. Kecskemeti, Y.J. Kim, M. Kirejczyk, M. Korolija, M. Kowalczyk, T. Kress, R. Kutsche, A. Lebedev, K.S. Lee, Y. Leifels, V. Manko, H. Merlitz, D. Moisa, A. Nianine, D. Pelte, M. Petrovici, F. Rami, W. Reisdorf, B. de Schauenburg, D. Schüll, Z. Seres, B. Sikora, K.S. Sim, V. Simion, K. Siwek-Wilczynska, A. Somov, G. Stoicea, M.A. Vasiliev, P. Wagner, K. Wisniewski, J.T. Yang, Y. Yushmanov, A. Zhilin

Abstract: Small-angle correlations of pairs of nonidentical light charged particles produced in central collisions of heavy ions in the A=100 mass region at a beam energy of 400 A·MeV are investigated with the FOPI detector system at GSI Darmstadt. The difference of longitudinal correlation functions with the relative velocity parallel and anti-parallel to the center-of-mass velocity of the pair in the central source frame is studied. This method allows extracting the apparent space-time differences of the emission of the charged particles. Comparing the correlations with results of a final-state interaction model delivers quantitative estimates of these asymmetries. Time delays as short as 1 fm/c or - alternatively - source radius differences of a few tenth fm are resolved. The strong collective expansion of the participant zone introduces not only an apparent reduction of the source radius but also a modification of the emission times. After correcting for both effects a complete sequence of space-time emission points of p, d, t, ³He, a particles is presented for the first time.
 

Laue, F., I. Böttcher, M. Debowski, E. Grosse, P. Koczon, B. Kohlmeyer, M. Mang, L. Naumann, H. Oeschler, F. Pühlhofer, E. Schwab, P. Senger, Y. Shin, J. Speer, H. Ströbele, C. Sturm, G. Surowka, F. Uhlig, A. Wagner, W. Walus

Abstract: Production cross sections of charged pions, kaons and antikaons have been measured in C+C and C+Au collisions at beam energies of 1.0 and 1.8 AGeV for different polar emission angles. The kaon and antikaon energy spectra can be described by Boltzmann distributions whereas the pion spectra exhibit an additional enhancement at low energies. The pion multiplicity per participating nucleon M(p⁺)/A_part is a factor of about 3 smaller in C+Au than in C+C collisions at 1.0 AGeV whereas it differs only little for the C and the Au target at a beam energy of 1.8 AGeV. The K⁺ multiplicities per participating nucleon M(K⁺)/A_part are independent of the target size at 1 AGeV and at 1.8 AGeV. The K^- multiplicity per participating nucleon M(K^-)/A_part is reduced by a factor of about 2 in C+Au as compared to C+C collisions at 1.8 AGeV. This effect might be caused by the absorption of antikaons in the heavy target nucleus. Transport model calculations underestimate the K^-/K⁺ ratio for C+C collisions at 1.8 AGeV by a factor of about 4 if in-medium modifications of K mesons are neglected.
 

Menzel, M., I. Böttcher, M. Debowski, F. Dohrmann, A. Förster, E. Grosse, P. Koczon, B. Kohlmeyer, F. Laue, L. Naumann, H. Oeschler, F. Pühlhofer, E. Schwab, P. Senger, Y. Shin, H. Ströbele, C. Sturm, G. Surowka, F. Uhlig, A. Wagner, W. Walus (KaoS Collaboration)

Abstract: Differential production cross sections of K^- and K⁺ mesons have been measured as function of the polar emission angle in Ni+Ni collisions at a beam energy of 1.93 AGeV. In near-central collisions, the spectral shapes and the widths of the rapidity distributions of K^- and K⁺ mesons are in agreement with the assumption of isotropic emission. In non-central collisions, the K^- and K⁺ rapidity distributions are broader than expected for a single thermal source. In this case, the polar angle distributions are strongly forward-backward peaked and the nonisotropic contribution to the total yield is about one third both for K⁺ and K^- mesons. The K^-/K⁺ ratio is found to be about 0.03 independent of the centrality of the reaction. This value is significantly larger than predicted by microscopic transport calculations if in-medium modifications of K mesons are neglected.
 

Navin, A., D. Anthony, T. Aumann, T. Baumann, D. Bazin, Y. Blumenfeld, B. A. Brown, T. Glasmacher, P. G. Hansen, R.W. Ibbotson, P.A. Lofy, V. Maddalena, K. Miller, T. Nakamura, B.V. Pritychenko, B.M. Sherrill, E. Spears, M. Steiner, J.A. Tostevin, J. Yurkon, A. Wagner

Abstract: Partial cross sections and corresponding momentum distributions have been studied in the one-neutron knockout reaction (¹²Be, ¹¹Be + g) on a ⁹Be target at 78 MeV/nucleon. The resulting spectroscopic factors for the only two bound states of ¹¹Be are 0.42±0.06 (1/2⁺) and 0.37±0.06 (1/2^-), where the errors are experimental only. This result shows that N = 8 is not a good closed shell in the neutron-rich 12Be and that the last neutron pair is two-thirds in the (1s² + 0^d2) intruder configuration.
 

Neubert, W., A.S. Botvina

Abstract: We show that coalescence of nucleons emitted prior to thermalization in highly excited nuclei can explain the anomaly of kinetic energies of helium fragments. This mechanism accomplishes the statistical approach to nuclear rections formerly used to describe intermediate mass fragment production.
 

Odeh, T., R. Bassini, M. Begemann-Blaich, S. Fritz, S.J. Gaff-Ejakov, D. Gourio, C. Groß, G. Immé, I. Iori, U. Kleinevoß, G.J. Kunde, W.D. Kunze, U. Lynen, V. Maddalena, M. Mahi, T. Möhlenkamp, A. Moroni, W.F.J. Müller, C. Nociforo, B. Ocker, F. Petruzzelli, J. Pochodzalla, G. Raciti, G. Riccobene, F.P. Romano, A. Saija, M. Schnittker, A. Schüttauf, C. Schwarz, W. Seidel, V. Serfling, C. Sfienti, W. Trautmann, A. Trzcinski, G. Verde, A. Wörner, Hongfei Xi, B. Zwieglinski

Abstract: Kinetic energies of light fragments (A £ 10) from the decay of target spectators in ¹⁹⁷Au + ¹⁹⁷Au collisions at 1000 MeV per nucleon have been measured with high-resolution telescopes at backward angles. Except for protons and apart from the observed evaporation components, the kinetic-energy spectra exhibit slope temperatures of about 17 MeV, independent of the particle species, but not corresponding to the thermal or chemical degrees of freedom at breakup. It is suggested that these slope temperatures may reflect the intrinsic Fermi motion and thus the bulk density of the spectator system at the instant of becoming unstable.
 

Parodi, K., W. Enghardt

Abstract: Our investigation supporting the feasibility of in  situ PET monitoring in proton therapy is presented. We simulated by means of the FLUKA code the number and the spatial distribution of the main b⁺ emitters created in PMMA targets by protons at typical therapeutic energies. The quantitative comparison with the activation induced by ¹²C ions of energies corresponding to the same range shows that the available signal at the same physical dose level should be up to twice as intense for protons than actually successfully used for the control of carbon ion therapy at GSI Darmstadt. The spatal correlation between the activity and the dose profile for protons is poorer than for ¹²C nuclei. However, an important check of the particle range, dose localization and stability of the treatment during all the fractions seems to be possible.
 

Pausch, G., H. Prade, M. Sobiella, H. Schnare, R. Schwengner, L. Käubler , C. Borcan, H.-G. Ortlepp, U. Oehmichen, H. Grawe, R. Schubart, J. Gerl, J. Cederkäll, A. Johnson, A. Kerek, W. Klamra, M. Moszynski, D. Wolski, M. Kapusta, A. Axelsson, M. Weiszflog, T. Härtlein, D. Pansegrau, G. de Angelis, S. Ashrafi, A. Likar, M. Lipoglavsek

Abstract: A 4p silicon ball for detection and identification of light charged particles in large multidetector g-arrays as EUROBALL is presented. The design is based on a N=42 ball with 12 pentagons and 30 hexagons as used in the GASP array. The absorptive material for g-rays is minimized to the detector thickness of 300 or 500mm and a 0.63 mm ceramic backing. The geometrical coverage is designed for about 90% of 4p. A pulse shape discrimination method with totally depleted detectors working in the reverse mount allows identifying protons and a-particles above an energy threshold of about 2 MeV. The performances of the ball were tested at the tandem - booster accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228 MeV ⁵⁸Ni+⁴⁶Ti and the low-recoil reaction of 95 MeV ¹⁶O+⁵⁸Ni. The two-dimensional spectra of zero-crossing (ZC) versus energy confirmed an excellent discrimination of protons and a-particles in all the detectors at different angles. The energy spectra of protons and a-particles measured in the experiments are presented, too. The g-spectra measured in coincidence with various combinations of emitted particles showed a high selectivity of the ball. The reduced total efficiency for protons of 59% and 55% and a-particles of 44% and 32% measured in a nuclear spectroscopy application is analyzed in a Monte-Carlo simulation (GEANT). It is due to a combined influence of a thick target needed to stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extrapolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channels with heavy ions.
 

Peshier, A., M.H. Thoma

Abstract: Under very general assumptions we show that the quark dispersion relation in the quark-gluon plasma is given by two collective branches, of which one has a minimum at a non-vanishing momentum. This general feature of the quark dispersion relation leads to structures (van Hove singularities, gaps) in the low mass dilepton production rate, which might provide a unique signature for the quark-gluon plasma formation in relativistic heavy ion collisions.
 

Peshier, A., B. Kämpfer, G. Soff

Abstract: A quasiparticle description of the thermodynamics of deconfined matter, reproducing both the perturbative limit and nonperturbative lattice QCD data at finite temperature, is generalized to finite chemical potential. By a flow equation resulting from Maxwell's relation, the equation of state is extended from zero to nonzero quark densities. The impact of the massive strange flavor is considered and implications for cold, charge-neutral deconfined matter in b equilibrium in compact stars are given.
 

Pienkowski, L., W. Bohne, T. von Egidy, P. Figuera, J. Galin, F. Goldenbaum, D. Hilscher, U. Jahnke, J. Jastrzebski, B. Lott, M. Morjean, G. Pausch, A. Péghaire, D. Polster, S. Proschitzki, B. Quednau, H. Rossner, S. Schmid, W. Schmid

Abstract: Reactions of 1.2 GeV antiprotons with Cu and Ag targets have been studied. It was found that in such reactions, excitation energies are generated in excess of the total binding energy of the nuclei involved. Accordingly, one observes in these reactions the onset of vaporization and multifragmentation processes. In the [`p] + Cu reaction, the vaporization is observed to set in about 7.5 MeV/nucleon. However, its probability remains relatively small and below 15% up to the highest excitation energies identified in the present studies (approximately 15 MeV/nucleon). The threshold excitation energy for multifragmentation prosesses, defined as the detection of a least 3 intermediate mass fragments, is observed at about 4 MeV/nucleon for both studied reactions. Multifragmentation is seen to account for no more than approximately 5% and 20% of the corresponding inclusive yield for Cu and Ag targets, respectively
 

Plettner, C., H. Schnare, R. Schwengner, L. Käubler, F. Dönau, I. Ragnarsson, A.V. Afanasjev, A. Algora, G. de Angelis, A. Gadea, D.R. Napoli, J. Eberth, T. Steinhardt, O. Thelen, M. Hausmann, A. Müller, A. Jungclaus, K .P. Lieb, D.G. Jenkins, R. Wadsworth, A. N. Wilson, S. Frauendorf

Abstract: Rotational bands in ⁷³Br have been investigated up to spins of I = 65/2 using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency (^h/_2p)w = 1.85 MeV reported to date in nuclei with A ³ 25. At high frequencies, the experimental Á⁽²⁾ dynamic moment of inertia for all bands decreases to very low values, Á⁽²⁾ £ 10(^h/_2p) ² MeV^-1. The bands are described in the configuration-dependent cranked Nilsson-Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2. This result establishes the first band termination in the A » 70 mass region.
 

Plettner, C., I. Ragnarsson, H. Schnare, R. Schwengner, L. Käubler, F. Dönau, A. Algora, G. de Angelis, D.R. Napoli, A. Gadea, J. Eberth, T. Steinhardt, O. Thelen, M. Hausmann, A. Müller, A. Jungclaus, K.P. Lieb, D.G. Jenkins, R. Wadsworth, A.N. Wilson

Abstract: High-spin states in ⁷²Br were studied with the EUROBALL III spectrometer using the ⁴⁰Ca(⁴⁰Ca, a3p1n) reaction. The negative-parity band observed in this experiment displays a signature inversion around spin I=16. The interpretation within the cranked Nilsson-Strutinsky approach shows that this signature pattern is a signal of a substantial triaxial shape change with increasing spin where the nucleus evolves from a triaxial shape with rotation about the intermediate axis at low spin through a collective prolate shape to a triaxial shape but with rotation about the shortest principal axis at high spin
 

Rami, F., Y. Leifels, B. de Schauenburg, A. Gobbi, B. Hong, J.P. Alard, A. Andronic, R. Averbeck, V. Barret, Z. Basrak, N. Bastid, I. Belyaev, N. Bendarag, G. Berek, R. Caplar, N. Cindro, P. Crochet, A. Devismes, P. Dupieux, M. Dzelalija, M. Eskef, C. Finck, Z. Fodor, H. Folger, L. Fraysse, A. Genoux-Lubain, Y. Grigorian, Y. Grishkin, N. Herrmann, K.D. Hildenbrand, J. Kecskemeti, Y.J. Kim, P. Koczon, M. Kirejczyk, M. Korolija, R. Kotte, M. Kowalczyk, T. Kress, R. Kutsche, A. Lebedev, K.S. Lee, V. Manko, H. Merlitz, S. Mohren, D. Moisa, J. Mösner, W. Neubert, A. Nianine, D. Pelte, M. Petrovici, C. Pinkenburg, C. Plettner, W. Reisdorf, J. Ritman, D. Schüll, Z. Seres, B. Sikora, K.S. Sim, V. Simion, K. Siwek-Wilczynska, A. Somov, M.R. Stockmeier, G. Stoicea, M.A. Vasiliev, P. Wagner, K. Wisniewski, D. Wohlfahrt, J.T. Yang, Y. Yushmanov, A. Zhilin

Abstract: Four different combinations of ⁹⁶₄₄Ru and ⁹⁶₄₀Zr nuclei, both as projectile and target, were investigated at the same bombarding energy of 400A MeV using a 4p detector. The degree of isospin mixing between projectile and target nucleons is mapped across a large protion of the phase space using two different isospin-tracer observables, the number of measured protons and the t/³He yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium (n,n) cross section used in microscopic transport calculations.
 

Schwarz, J., H. Kaden, G. Pausch

Abstract: Mobile analysis with potentiometric sensors is well suited for field measurements. Ion-selective electrodes (ISE) based on polymeric membranes for in-situ determination of nitrate and ammonium contents in ground water, drinking water and surface water have been developed. The ISE are integrated in a multisensor module (MSM) for monitoring these ions over longer time intervals. The receptor is a PVC-membrane with tridodecyl-ammonium nitrate (TDDA) for nitrate- and nonactine for ammonium-electrodes as ionophores. As plasticizer dibutylphthalate (DBT) was used. The main parameters for assessing the efficiency of these ISE are presented.
 

Scheinast, W.

Abstract: For the first time, a systematic study of differential production cross sections of antikaons in proton nucleus collisions close to threshold has been performed, using the first proton beam a t GSI. Preliminary results on K⁺ and K^- production in p+Au collisions at a beam energy of 2.5 GeV are presented
 

Schwengner, R., H. Schnare, C. Borcan, F. Dönau, L. Käubler

Abstract: In nuclei in the mass region of A » 70-90 a variety of phenomena is observed which are based on single-particle and collective motion of the nucleons. We discuss the properties of Br and Rb isotopes with neutron numbers of 38-48. In light Br isotopes (N=37,38) rotational bands have been observed up to spins of 65/2 and rotational frequencies of 1.8 MeV. Both features can be described in terms of the cranked Nilsson-Strutinsky formalism. In Rb nuclei with N=45, 47 we found regular magnetic dipole bands evolving at high spin whereas the low-spin structure of those less deformed nuclei is irregular. These magnetic dipole bands represent magnetic rotation, a new rotational mode predicted by the tilted-axis cranking model. In nuclei at N=48 we found small collectivity in low-spin states and multiplets based on multi-particle excitations a high spin. These properties are interpreted in terms of the shell-model.
 

Schwengner, R., H. Schnare, S. Frauendorf, F. Dönau, L. Käubler, H. Prade, E. Grosse, J. Jungclaus, K.P. Lieb, C. Lingk, S. Skoda, J. Eberth, G de Angelis, A. Gadea, E. Farnea, D.R. Napoli, C.A. Ur, G. Lo Bianco

Abstract: We have studied the isotopes ⁸²Rb₄₅, ⁸³Rb₄₆, and ⁸⁴Rb₄₇ to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A= 80. Excited states in these nuclei were populated via the reaction ¹¹B + ⁷⁶Ge with E = 50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a g-coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei ⁸²Rb and ⁸⁴Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13^- £ J^p £ 16^-. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type p(fp) pg²_9/2 ng_9/2. This is the first evidence of magnetic rotation in the A » 80 region. In contrast, the M1 sequences in the odd-even nucleus ⁸²Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.
 

Stefanova, E.A., R. Schwengner, J. Reif, H. Schnare, F. Dönau, M. Wilhelm, A. Fitzler, S. Kasemann, P. von Brentano, W. Andrejtscheff

Abstract: High-spin states of the nucleus ⁸⁸Sr have been studied via the reaction ⁸⁰Se(¹¹B,p2n) at a beam energy of 45 MeV. Gamma rays were detected with the six-detector array OSIRIS CUBE. The level scheme of ⁸⁸Sr has been extended up to E » 11 MeV and J=17. Mean lifetimes of three levels have been determined using the Doppler-shift-attenuation method. The level structures in ⁸⁸Sr have been interpreted in terms of the shell model. The calculations were performed in the configuration space (0f_5/2,1p_3/2,1p_1/2,0g_9/2) for the protons and (1p_1/2,0g_9/2,1d_5/2 for the neutrons. These calculations describe the high-spin level sequences linked by M1 transitions with strengths of B(M1) » 0.3 to 1.4 W.u. as multiplets of seniority u=4 and 6 states including proton configurations and neutron-core excitations.
 

Titov, A.I., B. Kämpfer, B.L. Reznik

Abstract: We analyze the production of f mesons in pN and NN reactions in the nearthreshold region, using throughout the conventional ''non-strange'' dynamics based on such processes which are allowed by the non-ideal w - f mixing. We show that the occurrence of the direct fNN interaction may show up in different unpolarized and polarization observables in pN® N f reactions. We find a strong non-trivial difference between observables in the reactions pp® ppf and pn ® pnf caused by the different role of the spin singlet and triplet states in the entrance channel. A series of predictions for the experimental study of this effect is presented.
 

Thummerer, S., B. Gebauer, H.G. Bohlen, W. von Oertzen, D. Bazzacco, S.M. Lenzi, A. Algora, G. de Angelis, A. Gadea, D.R. Napoli, C. Borcan, F. Dönau, L. Käubler, H. Schnare, R. Schwengner, I. Peter, C. Beck, C. Bhattacharya, M. Rousseau, R. Nouicer, J. Lisle

Abstract: A first experiment was performed with the Binary Reaction trigger Spectrometer (BRS) for Euroball, as second last experiment of phase III. The reaction ²⁴Mg(³²S,⁵⁶Ni ^*) at E=163.5 MeV was chosen in order to populate a specific hyperdeformed resonance state in the compound nucleus ⁵⁶Ni^* at E=84 MeV (J^p=46⁺) and to investigate the spectroscopy of its binary descendents. The experimental setup combined the g-detector array Euroball III, without the phase I Ge detectors, the two large-area gas detector telescopes of the BRS at forward angles and 31 of the 40 detectors of the 4p silicon ball EUROSiB (now called ROSiB) at backward angles. We report on results of binary reaction triggers collected with one BRS telescope. Binary events are separated from evaporation residues due to (i) the large laboratory scattering angles of the detected reaction fragments, the opening angle of the BRS telescope being q=12^° - 46^°, and (ii) by means of particle identification in the telescope. In this paper channels with emission of ⁸Be plus two protons and of ¹²C will be discussed.
 

Wagner, A., C. Müntz, H. Oeschler, C. Sturm, R. Barth, M. Cieslak, M. Debowski, E. Grosse, P. Koczon, F. Laue, M. Mang, D. Miskowiec, E. Schwab, P. Senger, P. Beckerle, D. Brill, Y. Shin, H. Ströbele, W. Walus, B. Kohlmeyer, F. Pühlhofer, J. Speer, I.K. Yoo

Abstract: The emission pattern of charged pions has been measured in Au+Au collisions at 1 GeV/nucleon incident energy. In peripheral collisions and at target rapidities, high-energy pions are emitted preferentially towards the target spectator matter. In contrast, low-energy pions are emitted predominantly in the opposite direction. The corresponding azimuthal anisotropy is explained by the interaction of pions with projectile and target spectator matter. This interaction with the spectator matter causes an effective shadowing which varies with time during the reaction. Our observations show that high-energy pions stem from the early stage of the collision whereas low-energy pions freeze out later.
 

Wagner, A., W.P. Tan, K. Chalut, R.J. Charity, B. Davin, Y. Larochelle, M.D. Lennek, T.X. Liu, W.G. Lynch, A.M. Ramos, R. Shomin, L.G. Sobotka, R.T. de Souza, M.B. Tsang, G. Verde, H.S. Xu

Abstract: This article describes the crystal selection and quality control utilized to develop and calibrate a high resolution array of CsI(TI) scintillator crystals for the detection of energetic charged particles. Alpha sources are used to test the light output variation due to thallium doping gradients. Selection of crystals with better than 1% non-uniformity in light output is accomplished using this method. Tests with 240 MeV alpha beam reveal that local light output variations within each of the tested CsI(TI) crystals limit the resolution to about 0.5%. Charge and mass dependences in the energy - light output relationship are determined by calibrating with energetic projectile fragmentation beams.
 

Wisniewski, K., P. Crochet, N. Herrmann, A. Andronic, R. Averbeck, A. Devismes, C. Finck, A. Gobbi, O. Hartmann, K.D. Hildenbrand, P. Koczon, T. Kress, R. Kutsche, Y. Leifels, W. Reisdorf, D. Schüll, J. P. Alard, V. Barret, Z. Basrak, N. Bastid, I. Belyaev, A. Benderag, G. Berek, R. Caplar, N. Cindro, P. Dupieux, M. Dzelalija, M. Eskef, Z. Fodor, Y. Grishkin, B. Hong, J. Kecskemeti, Y.J. Kim, M. Kirejczyk, M. Korolija, R. Kotte, M. Kowalczyk, A. Lebedev, K.S. Lee, V. Manko, H. Merlitz, S. Mohren, D. Moisa, W. Neubert, A. Nianine, D. Pelte, M. Petrovici, C. Plettner, F. Rami, B. de Schauenburg, Z. Seres, B. Sikora, K. Sim, V. Simion, K. Siwek-Wilczynska, V. Smolyankin, A. Somov, M. Stockmeier, G. Stoicea, M. Vasiliev, P. Wagner, D. Wohlfarth, J.T. Yang, I. Yushmanov, A. Zhilin

Abstract: The ratio of K^- to K⁺ meson yields has been measured in the systems ⁹⁶Ru+⁹⁶Ru at 1.69 A GeV, ⁹⁶Ru+⁹⁶Zr at 1.69 A GeV, and ⁹⁶Ni+⁹⁶Ni at 1.93 A GeV incident beam kinetic energy. The yield ratio is observed to vary across the measured phase space. Relativistic transport-model calculations indicate that the data are best understood if in-medium modifications of the kaons are taken into account.
 

Xu, H.S, M.B. Tsang, T.X. Liu, X.D. Liu, W.G. Lynch, W.P. Tan, A. Vander Molen, G. Verde, A. Wagner

Abstract: Isotopic distributions for light particles and intermediate mass fragments have been measured for ¹¹²Sn + ¹¹²Sn, ¹¹²Sn + ¹²⁴Sn,¹²⁴Sn + ¹¹²Sn, and ¹²⁴Sn + ¹²⁴Sn collisions at E/A = 50 MeV. Isotope, isotone, and isobar yield ratios are utilized to estimate the isotopic composition of the gas phase at freeze-out. Analyses within the equilibrium limit imply that the gas phase is enriched in neutrons relative to the liquid phase represented by bound nuclei. These observations suggest that neutron diffusion is commensurate with or more rapid than fragment production.
 

Yan, X., A.M. MacLeod, W.A. Gillespie, G.M.H. Knippels, D. Oepts, A.F.G. van der Meer, W. Seidel

Abstract: Time-resolved measurements of the transverse electric field associated with relativistic electron bunches are presented. Using an ultrafast electro-optic sensor close to the electron beam, the longitudinal profile of the electric field was measured with subpicosecond time resolution and without time-reversal ambiguity. Results are shown for two cases: inside the vacuum beam line in the presence of wake fields, and in air behind a beryllium window, effectively probing the near-field transition radiation. Especially in the latter case, reconstruction of the longitudinal electron bunch shape is straightforward.
 IKH 06/27/01 © Annual Report 2000