abstract

The state of physics in 1900 is reviewed by making use of the documents of that year, in particular the material of the I\(^{\rm st}\) International Congress of Physics. Contrary to simplified accounts which portrait 1900 as the year of revolutionary transition from classical to quantum physics it is shown that almost all physicists at that time were satisfied with classical physics and were actively enriching and expanding it.

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The structure of the nucleon has been investigated by studying the photoexcitation of nucleon resonances and their subsequent meson decay. The photon spectrometer TAPS has been used in a series of corresponding experiments at the Mainz microtron MAMI. A comparison of the photoproduction of mesons on the free nucleon and on nucleons bound in nuclei reveales differences attributed to changes in the properties of hadrons in the nuclear medium. Most of the nucleon resonances exhibit only a small shift in mass but an appreciable broadening. The largest effect is observed for the D\(_{13}\)-resonance which may be attributed to its \(\rho \)-meson decay. Various calculations predict a change in the spectral function of this vector meson in the nuclear medium. First experimental evidence for medium modifications of vector mesons may have been observed in ultra-relativistic heavy-ion collisions, e.g. with the CERES detector. A dedicated program focusing on the properties of mesons in the nuclear environment at different temperatures and baryon densities will be taken up with the HADES di-lepton spectrometer at GSI, utilizing the \(\pi \)- and heavy-ion beams from SIS. Photonuclear, hadron and heavy-ion induced reactions are thus complementary approaches to study the properties of hadrons in nuclear matter.

abstract

The nuclear equation of state (EoS) is investigated by flow phenomena in relativistic heavy-ion collisions, both in transverse and radial direction, in comparison to experimental data from 150 A MeV to 11 A GeV. To this aim the collective dynamics of the nucleus–nucleus collision is described within a transport model of the coupled channel RBUU type. There are two factors which dominantly determine the baryon flow at these energies: the momentum dependence of the scalar (\(U_S\)) and vector potentials (\(U_\mu \)) for baryons and the resonance/string degrees of freedom for energetic hadron excitations. We fix the explicit momentum dependence of the nucleon–meson couplings by the nucleon optical potential up to 1 GeV and extrapolate to higher energy. When assuming the optical potential to vanish identically for \(E_{\rm kin} \geq 3.5\) GeV we simultaneously describe the sideward flow data of the PLASTIC BALL, FOPI, EoS and E877 collaborations, the elliptic flow data of the E895 and E877 collaborations and approximately the rapidity and transverse mass distribution of protons at AGS energies without employing any explicit assumption on a phase transition in the EoS. However, the gradual change from hadronic to string degrees of freedom with increasing bombarding energy can be viewed as a transition from hadronic to string matter, i.e. a dissolution of hadrons at high energy density.

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A review of pion emission in heavy ion collisions is given and it is discussed whether these spectra and the various particle yields can be interpreted within a thermal model with an emission at a unique temperature. A careful inspection of the high-energy pions reveals that they are emitted during the early phase of the collisions while pions with lower energies are emitted mainly later and over a long time interval.

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The intention of this lecture is to review the dynamical role of the lowest excited state of the nucleon, the Roper resonance or \(N^*\)(1440), in nuclear systems. We discuss first its couplings to meson–nucleon channels and, based on these couplings, its contribution to the two-body and three-body interaction respectively. The importance of the Roper resonance as baryonic excitation for particle production in relativistic heavy ion collisions is then examined, particularly in view of recent results obtained at the GSI-SIS Facility.

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The thermodynamic (statistical) description of the atomic nucleus works well at low excitation energies. Difficulties appear at higher excitations, where phase transitions are expected.

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A review of available data on strangeness production in relativistic ion collision at AGS and SPS accelerators is given. A hierarchy of strangeness enhancement and its centrality dependence is discussed.

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The manuscript reviews several nuclear physics aspects of relevance for supernova simulations. In particular, it stresses the role played by stellar weak interaction rates in the presupernova collapse and the recent progress achieved to calculate these rates based on large-scale shell model calculations. It further discusses the ‘hot neutrino bubble’ above a newly formed neutron star in a type II supernova as the possible site of the nuclear r-process, pointing to several still open questions. Finally the possible role of neutrinos in this r-process scenario is investigated.

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The paper discusses the reaction rates at low energies, needed for the description of nucleosynthesis processes. In contrast to the stellar environment, the laboratory measurements are complicated by the coulomb potential screening caused by bound electrons. The consequences of recent \(^7\)Be+p reaction measurements on solar modelling are presented. The new high-energy laser facilities will open new possibilities for measurements of stellar reaction rates. Abstract provided by the editors.

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We apply the realistic shell model which includes the coupling between many-particle (quasi-)bound states and the continuum of one-particle scattering states, to the spectroscopy of mirror nuclei as well as to the description of low energy cross section in the capture reactions.

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In spite of lapse of time of nearly 90 years since the discovery of cosmic rays, the basic questions: “Where are cosmic rays coming from? How are they accelerated to extremely high energies and propagate through the interstellar and intergalactic space?” are largely not clarified. Contemporary theoretical models describe the acceleration of nuclei in the Cosmos by strong shocks, either of galactic or extragalactic origin, which are effectively produced in supernova remnants, supersonic stellar winds, active galactic nuclei and other phenomena. All the models and conjectures towards an explanation of the energy spectrum, in particular of the conspicuous discontinuity (“knee”) observed in the energy region of about \(3 \cdot 10^{15}\,\)eV, do not only predict the shape of the spectrum, they imply also specific variations of the elemental composition of the primary cosmic rays. The lecture discusses the experimental approaches investigating the shape of the primary spectrum and the elemental composition of cosmic rays.

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The properties of the coupling of mean field excitations to doorway states and to a chaotic background are discussed. Recent applications to the study of single-particle and giant resonance states in exotic nuclei and in fast rotating hot nuclei are presented.

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Pairing in nuclei is shortly overviewed from the perspective of mean-field theory which is the only model where particle-particle channel is uniquely defined. Attention is paid to the effects of pairing correlations on odd-even mass staggering and nuclear rotational motion. Basic theoretical concepts and effects associated with proton–neutron pairing in \(N\approx Z\) nuclei are also discussed. It is pointed out that, with the present accuracy of mean-field calculations, no clear constraints can be set on spatial characteristics or density dependence of pairing interaction.

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The accelerator COSY at the Forschungszentrum Jülich 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 \(p\,^{12}{\rm C}\) collisions.

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The transition from the fusion mechanism to binary processes in central heavy-ion collisions is investigated within the Landau-Vlasov semiclassical transport model. The threshold energy of the binary mechanism displays a regular dependence on the value of the nucleon-nucleon cross section and could be a right observable to determine its value in nuclear medium.

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Up to now, the results on nuclear viscosity are rather contradictory. Values of the dissipation coefficient between \(\beta \approx 0.5\cdot 10^{21}{\rm s}^{-1}\) and \(\beta \) \(\approx 20\cdot 10^{21}{\rm s}^{-1}\) have been deduced from previous experiments. A new experimental access to the dynamics of fission is given by peripheral nuclear collisions at relativistic energies. This method has important advantages with respect to the traditional ones, since highly excited nuclei are produced with low angular momenta and small shape distortions. Preliminary results of applying this procedure at GSI Darmstadt are presented.

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The study of correlations of different two-nucleon systems, which were measured simultaneously in recent E286 experiment at GANIL, is regarded as an appropriate method to shed light on dynamics of intermediate energy heavy-ion collisions. The Quantum Molecular Dynamics model is argued to be a perspective approach for such an analysis.

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Simultaneous measurement of two-nucleon \((nn,\ np,\ pp)\) correlations have been performed at GANIL for the reaction \(^{40}{\rm Ar}+^{58}\)Ni at 77 MeV/u. The aim of the experiment was to find the space-time properties of nucleon emission process in intermediate energy heavy ion collisions and to clarify some related questions. Comparative analysis for protons and neutrons indicates an important role of Coulomb effects. Quantitative analysis is in progress.

abstract

Results of a search for an intermittency signal in Au+Au collisions at 800 AMeV beam energy are presented. Data from the FOPI detector at GSI Darmstadt were analysed. No intermittency signal was found in either rapidity or charge distributions. Intermittency is present in azimuthal angle distribution.

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A novel method to study fluctuations in distributions of reaction products has been applied to investigate the process of chemical and thermal equilibration of nuclear matter in Ru+Ru reaction at 1.69 \(A\) GeV. The analysed data were obtained with the FOPI detector. Nontrivial fluctuations of the chemical composition and of transverse momenta, and their dependence on centrality were studied. Fluctuations of pion multiplicity were found to decrease with increasing centrality. This kind of dependence is less evident in the case of proton transversal momentum fluctuations.

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The 4\(\pi \)-multidetector INDRA was installed in GSI for one and a half years, including three experimental periods between June 1998 and March 1999. The goal of the experiments was to extend the study of the multifragmentation, of the liquid-gas phase transition of nuclear matter and of the production and decay modes of highly excited nuclei to energies beyond those previously studied at GANIL. This experimental campaign proceeded smoothly and the analysis of the data is in progress.

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The comparison of phase space distributions of \(K^{-}\, \) and \(K^{+}\, \) mesons produced in collisions of \(^{96}\)Ru+\(^{96}\)Ru at 1.69 \(A\) GeV, \(^{96}\)Ru+\(^{96}\)Zr at 1.69 \(A\) GeV and \(^{58}\)Ni+\(^{58}\)Ni at 1.93 \(A\) GeV incident beam kinetic energy is presented. The distribution of \(K^{+}\, \) mesons is compatible with the emission from an isotropic, thermalized source of which parameters describe as well the spectra of more abundant reaction products: pions, protons and deuterons. The yield ratio of \(K^{-}\, \) to \(K^{+}\, \) mesons 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 kaon properties are taken into account.

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At COSY-Jülich the lifetime of very heavy hypernuclei, produced in the reactions induced by protons, was measured for non-mesonic \({\mit \Lambda }\) decay by the recoil shadow method. The measurements were performed at proton energies of 1.5 and 1.9 GeV and the background was determined at 1.0 GeV. The \({\mit \Lambda }\) hyperon lifetime of (211 \(\pm \) 30) ps was obtained in the \(p\)+U reactions and (160 \(\pm \) 15) ps in the \(p\)+Bi reactions, respectively.

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Single particle nuclear levels are calculated on the basis of the potentials derived from the Extended Thomas–Fermi type Skyrme models for the Skyrme forces SkIII, SkM\(^*\) and SLy4.

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The \(^{91}\)Zr\((p,t)^{89}\)Zr reaction has been studied in a high resolution experiment at an incident energy of 25 MeV. Angular distributions for transitions to the levels of \(^{89}\)Zr up to an excitation energy of \(\sim \) 3.400 MeV have been measured. The data are compared with the DWBA predictions.The energy levels of \(^{89}\)Zr has been studied in the framework of shell model.

abstract

High energy \(\gamma \)-ray spectrum and angular distribution for the \(^{18}\)O + \(^{27}\)Al reaction at 8.3 \({\rm MeV}/u\) have been analysed assuming the statistical decay of giant dipole resonance and the nucleon-nucleon bremsstrahlung emission. Simple parabolic energy dependence of the inverse slope parameter \(E_0(E_{\gamma })\) has been proposed. The bremsstrahlung contribution was estimated also at 6 \({\rm MeV}/u\) and found to be negligible.

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Lifetimes of 15 levels build on the \(\pi \)g\(_{9/2}\) hole state in the \(^{119}\)I nuclei have been measured. The Doppler Shift Attenuation and Recoil Distance Methods were used. Modified model of “conflict coupling”, being an extension of “shears mechanism” model, reproduces experimental values of \(B\)(M1).

abstract

A closed-form approach for average description of the \(E1\) radiative strength functions is examined. It gives simple and rather accurate method of simultaneous description of the \(\gamma \)-decay and photoabsorption dipole strength functions in the medium and heavy nuclei. The approach is able to cover a relatively wide gamma-ray energy interval, ranging from zero to values above GDR peak energy.

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Recently, the neutron–proton correlations have been once again considered in rich neutron exotic nuclei with \(N=Z\). In this contribution the measure of neutron–proton pairing correlations is obtained using the elementary method based on the exact group theory treatment. The transparent and simple algebraic formulas for average values of neutron, proton and neutron–proton parts of pairing energies are then applied to two examples.

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\(A=110\) isobars separated by IGISOL on-line mass separator from fission products has been investigated by using Beta–gamma and gamma–gamma coincidence techniques. A new quasi-particle level at 2261 keV in \(^{110}\)Pd was observed. Systematics of logft-values and excitation energies of the quasi-particle levels in even–even Pd isotopes is remarkably smooth. An excited \(0^{+}\) state at 1137 keV in \(^{110}\)Ru was identified and the \(2_{3}^{+}\) state at 1396 keV was confirmed. Systematics of these low-spin excited states in even–even Ru isotopes gives a hint for intruder character of these states.

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Results of a measurement of relative yields of nuclei populated in heavy ion induced fusion-evaporation reactions in the region of \(^{100}\textrm {Sn}\) are presented. Yields for altogether 18 products of the \(^{58}\textrm {Ni}(^{50}\textrm {Cr},xpy\alpha zn)\) reaction, were determined at 5 beam energies, basing on intensities of \(\gamma \) rays feeding ground states of respective nuclei.

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The role of pairing collective degrees of freedom is investigated within microscopic approach based on the general collective Bohr model which includes the effect of coupling with the pairing vibrations. The excitation energies observed in transitional Gd and Er isotopes are reproduced in the frame of the calculation containing no free parameters.

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The measurements of the muon charge ratio representing the ratio of positive to negative atmospheric muons are performed using a small compact device, WILLI, by detecting the life time of the muonic atoms. Avoiding the difficulties of measurements with magnetic spectrometers, this method gives precise results on muon charge ratio especially in the low energy range relevant for the atmospheric neutrino anomaly. The detector, the method and the results on muon charge ratio for five energy ranges below 1 GeV are presented. The results can be used to improve hadronic interaction models.

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The elastic scattering data of \(p + ^{4,6}\)He, available in the 40\(A\)–45\(A\) MeV energy range have been analyzed in a microscopic framework using an isospin, density and momentum-dependent finite-range effective interaction in a single folding model. The folded potentials explain the \(p + ^4\)He angular distribution data. For \(^6\)He, several density prescriptions of varied rms radii are employed. All these prescriptions lead to almost same fit to the \(^6{\rm He} + p\) elastic angular distribution data with slight variations of the imaginary strength. Microscopic calculations assuming proton scattering from the smeared \(^4\)He-core in \(^6\)He, ignoring the halo, can also reproduce the experimental data if the strength of the imaginary part of the microscopic potential is enhanced. Implications of these results are discussed.

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In the presented work we make an attempt to describe the cold fusion reaction of the type X + (Pb,Bi) \(\rightarrow \) SHE + 1n at subbarrier energies. The presented model describes well the available experimental cross-section data and allows for predicting cross-section values for the synthesis of so far unknown heavier elements.

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Spontaneous fission and alpha-decay half-lives of even–even superheavy nuclei \(112 \leq Z \leq 120\) are calculated on the basis of the deformed Woods-Saxon potential in WKB approximation by the multi-dimensional dynamical programing method in space of parameters describing the shape of nuclei \(\{\beta _2,\beta _4,\beta _6\}\) and the pairing degrees of freedom \(\{{\mit \Delta }_p,{\mit \Delta }_n\}\). The direct comparisons of the spontaneous fission and \(\alpha \)-decay half-lives calculated by the Viola–Seaborg formula establish the regions of dominance of the spontaneous fission and the \(\alpha \) mode of desintegration.

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Our studies on \(K\beta \)/\(K\alpha \) X-ray intensity ratios of some of the technologically important \(3d\)-transition metal compounds have been reviewed. Comparison of the experimental results with single-configuration Dirac-Fock calculations provided important information on the valence states of the transition metals in various compounds, which can be helpful in understanding the nature of bonding in the compounds.

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\(K\) X-ray spectra from zirconium, niobium, molybdenum and paladium targets bombarded with 25 MeV/amu helium and 22.5 MeV/amu oxygen ions were measured using a high resolution transmission bent crystal spectrometer. Ratios of the double to single \(K\)-shell ionization cross sections were obtained from yields of the \(K\) hypersatellites and diagram lines. The results are compared to the semiclassical approximation predictions within the independent-particle model.

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Extensive single-configuration Dirac–Fock (DF) calculations (within the multiconfiguration DF method) have been performed for sulphur to explain the influence of removing electrons from \(L\) and \(M\) shells on the average \(K\beta \) and \(K\alpha \) x-ray transition energies and the values of \(K\beta \)/\(K\alpha \) intensity ratio. Our results can be used for interpreting the measured \(K\) X-ray spectra accompanying the ionization of sulphur projectiles or sulphur targets.

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The \(K\alpha \) and \(K\beta \) energy shifts and \(K\beta \)/\(K\alpha \) intensity ratios of highly ionized sulphur projectiles passing through carbon foils have been measured. Comparing these data with the results of single-configuration Dirac-Fock calculations it has been found that the average number of holes in the \(L\) shell of sulphur projectile strongly increases with its energy.

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We discuss an extension of the theory of spin-orbit pendulum phenomenon to relativistic approach. It is done within the so called Dirac Oscillator. Our first results, focusing on circular wave packet motion have been published recently. The scope of this paper is motion of a linear wave packet. In relativistic approach we found Zitterbewegung in spin-orbit motion (in Dirac representation) due to coupling to negative energy states. This effect is washed out in the Foldy-Wouthuysen representation. Another important change with respect to non-relativistic case is the loss of periodicity. The phenomenon reminds the time evolution of population inversion in Jaynes-Cummings model.

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An exact solution of the Einstein–Maxwell equations enables us to construct a hypothesis on the production of tachyons. The hypothesis determines the kinematical relations for the produced tachyon. It also makes possible to estimate the empiric conditions necessary for the production. These conditions can occur when nonpositive subatomic particles of high energy strike atomic nuclei other than the proton. This suggests how experiments to search for tachyons can be performed. According to the hypothesis properly designed experiments with air showers or with the use of the strongest colliders may be successful. Failure of the air showers experiments performed hitherto is explained on the grounds of the hypothesis.