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Porquet, M. G.; Deloncle, I.; Minkova, A.; Wilson, A. N.; Gall, B. J. P.; Hoellinger, F.; Schulz, N.; Kutsarova, T.; Venkova, T.; Sergolle, H.; Duprat, J.; Azaiez, F.; Bouneau, S.; Bourgeois, C.; Gautherin, C.; Lucas, R.
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About thirty nuclei in theA≈100 mass region have been produced as fission fragments following the fusionevaporation reactions^{28,30}Si+^{176}Yb at 145 MeV bombarding energy. These nuclei have been individually identified from their γray cascades detected with the Eurogam2 array. The level schemes of several stable or neutronrich nuclei have been extended to higher spins. From cross coincidences between transitions in complementary fragments, γrays deexciting highspin states of new isotopes can be identified and some aspects of the fission mechanism can be analyzed.
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Murray, Michael; Beker, H.; Bearden, I. G.; Bøggild, H.; Bussman, K.; Boissevain, J.; Dodd, J.; Hardtke, D.; Hamelin, M.; Esumi, S.; Fabjan, C. W.; Fields, D. E.; Franz, A.; Erazmus, B.; Gaardhøje, J.; Hansen, O.; Holzer, E. B.; Humanic, T. J.; Hummel, P.; Jacak, B. V.; Jayanti, R.; Kalechofsky, H.; Kobayashi, T.; Kvatadze, R.; Leltchouk, M.; Lörstad, B.; Maeda, N.; Medvedev, A.; Miake, Y.; Miyabayashi, A.; Murray, M.; Nishimura, S.; Ohnishi, H.; Paic, G.; Pandey, S. U.; Piuz, F.; Pluta, J.; Polychronakos, V.; Potekhin, M.; Poulard, G.; Sakaguchi, A.; Sarabura, M.; Shigaki, K.; SimonGillo, J.; SchmidtSørensen, J.; Sondheim, W.; Spegel, M.; Sugitate, T.; Sullivan, J. P.; Sumi, Y.; Hecke, H.; Willis, W. J.; Wolf, K.; Xu, N.; Zachary, D. S.; the NA44 Collaboration
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The yields and inverse slopes ofK^{±} M_{T} distributions at central rapidity are presented for pBe, pS, pPb, SS, SPb and PbPb collisions. The ratios ofK^{−}/K^{+} and
$${{\bar p} \mathord{\left/ {\vphantom {{\bar p} p}} \right. \kern\nulldelimiterspace} p}$$
decrease with system size and centrality. Comparing the slopes of pions, kaons and protons suggests that transverse flow is present in AA collisions but not in pPb collisions. For PbPb collisions the inverse slopes of theK^{−} andK^{+} M_{T} spectra are very close but for pPb the inverse slope ofK^{+} exceeds that ofK^{−}. These results suggest that thermal equilibrium is reached in central heavy ion collisions but not in pPb collisions.
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Kovács, Tamás G.; Schram, Zsolt
A simple Abelian model with both Higgs and gauge field degrees of freedom is investigated on a simplicial lattice of arbitrary dimension. We use group character expansion for both fields to get a diagrammatic expansion of the partition function. The diagrams consist of gauge group representation valued 1 and 2chains. The diagrams are proved to satisfy the constraint that the boundary of the 2chain representing the gauge field is equal to the 1chain representing the Higgs field. Otherwise they identically vanish. Simple consequences of this are current conservation and the vanishing of nonnullhomologous Wilson loops. Finally we use this picture for giving a lowest order estimate for the critical length of a string. This is the length at which the fluxtube string connecting two opposite charges is likely to break into two pieces due to pair creation.
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Csernai, L. P.; Biró, T. S.; Feng, Z. H.; Mishustin, I. N.; Mócsy, Á.; Molnár, D.; Scavenius, O.
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A fast hadronization scenario is presented where a central role is played by the chiral symmetry breakdown in the expanding QuarkGluon Plasma. This mechanism can become effective when thermal damping ceases after the thermal freezeout of the quark system. We estimate time scales and spatial characteristics of chiralsymmetry breaking instabilities on the basis of an effective fieldtheoretical model. It is argued that this fast process provides a basis to understand the measured large abundances of strange antibaryons in heavy ion collisions.
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Simpson, J.
Euroball is a European project to build a highly efficient and powerful gammaray spectrometer for nuclear structure spectroscopy. The project is an amalgamation of recent technical advances in detectors, electronics and data acquisition. In the first phase the spectrometer consists of 30 large single crystal Ge detectors, 26 Clover Ge detectors and 15 Cluster Ge detectors each with an associated suppression shield. The 239 individual Ge detector elements will have a total photopeak efficiency ∈_{p} of ≈ 10% and will enable the properties of the atomic nucleus to be studied with a sensitivity up to or better than 10^{−5} of the production crosssection. The elements of the spectrometer, including the detectors, the electronics and the data acquisition system, some of the planned ancillary detectors and the first results will be presented. Several developments are under investigation for the upgrade of Euroball for its second phase. These include an inner BGO ball for multiplicity and summed energy determination and inner particle detectors for charged particle identification. These developments will also be discussed.
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Mishustin, I. N.; Pedersen, J.; Scavenius, O.
We investigate the dynamics of the chiral transition in an expanding quarkantiquark plasma. The calculations are made within a linear σmodel with explicit quark and antiquark degrees of freedom. We solve numerically the classical equations of motion for chiral fields coupled to the fluid dynamical equations for the plasma. Fast initial growth and strong oscillations of the chiral field and strong amplification of long wavelength modes of the pion field are observed in the course of the chiral transition.
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Bracco, A.; Camera, F.; Maj, A.; Herskind, B.; Atac, A.; Bosetti, P.; Bark, R.; Bearden, I. G.; Gaardhøje, J. J.; Kmiecik, M.; Leoni, S.; Mattiuzzi, M.; Turri, G.
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The γdecay of the Giant Dipole Resonance (GDR) built on excited nuclear states has been measured for the nucleus^{143}Eu. The reaction^{110}Pd(^{37}Cl, 4n)^{143}Eu at a beam energy of 165 MeV has been employed. This experiment aimed at searching the γdecay of the GDR built on the superdeformed^{143}Eu states, populated at high spins. Highenergy γrays were detected in 8 large BaF_{2} scintillators in coincidence with discrete transitions measured with the NORDBALL array (in the configuration consisting of 17 HPGe detectors and a 2π multiplicity filter). The spectrum of highenergy γrays gated by lowenergy transitions between states fed by the superdeformed states shows some excess of yield in the 7–10 MeV region with respect to that gated by transitions between states not populated by the superdeformed states. This excess should be due to the γdecay of the the giant dipole oscillation along the superdeformed axis of the nucleus that is expected to have a frequency corresponding to ≈9–10 MeV (lowenergy component of the GDR strength function). The measured excess, in spite of the large error bars, is found to be of the same order as predicted statistical model values.
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Brenner, M.; Källman, K. M.; Máté, Z.; Vertse, T.; Zolnai, L.
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The addition of a resonance scattering contribution to the shape elastic scattering improves the fit in analysing experimental angular distributions. Spins from 7 to 10 ħ characterize the resonances, which have a dominant influence on the six analysed angular distributions of 12.80 to 20 meV alpha particles elastically scattered from^{34}S. The relation between the energy of the resonances and their spin compares well with the results from alpha scattering from^{28}Si. As in the scattering from silicon, the occurrence of a dominating spins supports the assumption that they belong to cluster states formed when alpha particles hit the target nuclei.
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Polonyi, Janos
Some features of the high temperature gluonic matter, such as the breakdown of the fundamental group symmetry by the kinetic energy, the screening of test quarks by some unusual gluon states and the explanation of the absence of isolated quarks in the vacuum without the help of infinities are presented in this talk. Special attention is paid to separate the dynamical imput inferred from the numerical results of lattice gauge theory from the kinematics.
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Ko, C. M.; Li, B. A.; Li, G. Q.
Using transport models that include explicitly the kaon degree of freedom, we have studied kaon flow, i.e., the average kaon transverse momentum as a function of rapidity, and the associated flow parameter in heavy ion collisions at both SIS and AGS energies. It is found that the pattern of kaon flow in heavy ion collisions is sensitive to the kaon potential used in the model and thus provides a useful means for studying the kaon properties in nuclear medium.
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