abstract

In 1905 Albert Einstein published four papers which revolutionized physics. Einstein’s ideas concerning energy quanta and electrodynamics of moving bodies were received with scepticism which only very slowly went away in spite of their solid experimental confirmation.

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The paper discusses application of parity violating polarized electron scattering off nucleons to study strange form factors of the nucleon. The results from the recent HAPPEX experiment are discussed in more detail.

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The status of the search for an exotic baryonic state, a pentaquark system, is reported on. Evidence from some experiments as well as its lack from other investigations is reviewed; problems and (possible) solutions in searches for a pentaquark are discussed, second generation experiments are described.

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Measurement of double polarization asymmetries for \(\phi \) photoproduction with the polarized target and a polarized photon beam is a sensitive means to investigate small and exotic amplitudes, such as an \(s\bar {s}\)-quark content of nucleons, via interferences with dominant amplitudes and the determination of the spin value of produced hadrons as the pentaquark. In order to realize the double polarization measurements to study the \(s\bar {s}\)-quark content as well as exotic hadron structures, We started to construct a frozen-spin polarized HD target at the LEPS facility on the new basis of recent technology developments in cryogenic and high magnetic field. We discuss the experiment for \({\phi }\)-meson photoproduction which will be performed in 10 days (40 days) with the result of 20% (10%) accuracy for the double polarization asymmetry measurement.

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We discuss two processes, the \(\pi N \rightarrow e^+e^- N\) and the \(\gamma N \rightarrow e^+e^- N\) reactions, below and close to the vector meson production threshold (\(1.40\lt \sqrt s \lt 1.75\) GeV). The aim is to gain understanding of the coupling of vector fields (associated with \(\rho ^0\)- and \(\omega \)-mesons) to low-lying baryon resonances. These couplings are not well-known and important for baryon structure studies and for dynamical descriptions of vector meson propagation in the nuclear medium. The \(e^+e^-\) pair production amplitudes are determined by the \(\pi N \rightarrow \rho ^0 N\), \(\pi N \rightarrow \omega N\), \(\gamma \,N\rightarrow \rho ^0 N\) and \(\gamma \,N\rightarrow \omega N\) amplitudes supplemented by the Vector Meson Dominance assumption. The vector meson production amplitudes are calculated consistently using a relativistic and unitary coupled-channel approach to meson–nucleon scattering. We display results showing the importance of the quantum interference between \(\rho ^0\)- and \(\omega \)-mesons in the \(e^+e^-\) channel to unravel the strength of the coupling of \(\rho ^0\)- and \(\omega \)-mesons to specific baryon excitations. The \(\pi N \rightarrow e^+e^- N\) and \(\gamma N \rightarrow e^+e^- N\) reactions underlie the more complex \(\pi A \rightarrow e^+e^- X\) and \(\gamma A \rightarrow e^+e^- X\) nuclear processes whose measurement is planned at GSI (with the HADES detector) and under analysis at JLab (with the CLAS detector).

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The most precise and convincing confirmation of the conservation of the vector current (CVC) comes from measurements of superallowed nuclear \(\beta \) decay. It also provides the most demanding test available of the unitarity of the Cabibbo–Kobayashi–Maskawa (CKM) matrix, a basic pillar of the Electroweak Standard Model. Current experiments focus on tests of the small correction terms that must be applied to the data, with the goal of improving the precision of these tests. A recent result raises unexpected questions.

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The analyses of the strangeness exchange \((K^{~-},\pi )\) and the associated production (\(\pi ^-,K^{~+}\)) reactions are presented. They indicate — together with the observed properties of \({\mit \Sigma }\) atoms — that the \({\mit \Sigma }\) single particle potential \(V_{\mit \Sigma }\) is repulsive inside nuclei and has a shallow attractive pocket at the nuclear surface. This conclusion is consistent with the Nijmegen model F of the hyperon–nucleon interaction. It is demonstrated how the strong-interaction shifts and widths measured in \({\mit \Sigma }\) atoms may be used to obtain information on the nucleon density distributions.

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We show with the model for the parton distribution in nuclei, that nuclear Fermi motion fully accounts for the collective motion of partons in nuclear medium. The sea parton distributions are described by additional virtual pions in interacting nucleon in such a way as to reproduce the nuclear lepton pair production data and saturate the energy-momentum sum rule. The influence of Fermi motion changes the nucleon rest energy and consequently the transverse momentum square of partons inside bound nucleons.

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The shell energies of spherical nuclei obtained by folding in the particle-number space and in the energies of individual nucleons are compared. The effect of coupling of the single-particle motion with the shape vibration on the magnitude of the both types of the shell corrections is discussed.

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State-dependent \(\delta \)-force is used to analyze isovector (\(T=1\)) and isoscalar (\(T=0\)) superfluidity in the framework of the generalized BCS model with an approximate Lipkin–Nogami particle-number projection. Calculations are performed with the single-particle levels generated in axially symmetric Skyrme–Hartree–Fock code with SIII force for several medium-mass \(N\sim Z\) nuclei.

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Experiments on strangeness production in nucleus–nucleus collisions at SIS energies address fundamental aspects of modern nuclear physics: the determination of the nuclear equation-of-state at high baryon densities and the properties of hadrons in dense nuclear matter. Experimental data and theoretical results will be reviewed. Future experiments at the FAIR accelerator aim at the exploration of the QCD phase diagram at highest baryon densities. The proposal for the Compressed Baryonic Matter (CBM) experiment will be presented.

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Experimental evidence for medium modifications of hadron properties is discussed. A first generation of experiments has reported interesting effects, and second-generation experiments such as HADES at GSI Darmstadt are in progress. In the future, these studies will be extended into the charm sector using PANDA, a state-of-the-art universal detector for strong interaction studies at the high-energy antiproton storage ring HESR at the future FAIR facility.

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The HADES (High Acceptance Di-Electron Spectrometer) is a tool designed for lepton pair (\(e^{+}e^{-}\)) spectroscopy in pion, proton and heavy ion induced reactions in the 1–2 \(A\) GeV energy range. One of the goals of the HADES experiment is to study in-medium modifications of hadron properties like effective masses, decay widths, electromagnetic form factors etc. Such effects can be probed with vector mesons (\(\rho \), \(\omega \), \(\phi \)) decaying into \(e^{+}e^{-}\) channel. The identification of vector mesons by means of a HADES spectrometer is based on invariant mass reconstruction of \(e^{+}e^{-}\) pairs. The combined information from all spectrometer sub-detectors is used to reconstruct the di-lepton signal. The recent results from 2.2 GeV \(p+p\), \(1\,A\) GeV and \(2\,A\) GeV C+C experiments are presented.

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CASTOR, a unique experimental design to probe the forward rapidity region at the LHC, is presented. Motivation and possibilities to search for a QGP, via unconventional signatures and in a region largely left unexplored by current and future high energy heavy ion experiments, are discussed.

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Neutral pions produced in Ar-induced reactions at 95\(A\) MeV on C, Al, Ag and Au targets were identified through their \(\gamma \gamma \) decay photons, measured with TAPS spectrometer installed at GANIL Caen. Angular distributions of neutral pions are reasonably well described within a phenomenological model of pion reabsorption, taking into account momentum-dependent absorption length. The angular distribution of primary neutral pions (before absorption) seems to be independent of the beam energy and mass numbers of colliding nuclei. This distribution is described by the formula: \(1+A_2P_2(\cos \vartheta )\) with \(A_2=0.33\pm 0.05\), determined from the comparison to all available angular distributions of neutral pions. The transverse momentum spectra of neutral pions can be fitted within the thermal model only for momenta above 60 MeV/\(c\). Assuming, that the model of pion reabsorption is correct, the transverse momentum spectra of primary pions were reconstructed. These spectra are surprisingly well described by the thermal model with temperatures about 22 MeV.

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Pion-induced reactions were studied with the FOPI detector at an incident momentum of 1.15 GeV/\(c\). Data were taken for five different targets: C, Al, Cu, Sn and Pb. A preliminary comparison of the phase-space distribution of the reconstructed \(K^0_{\rm S}\) to the results of the IQMD transport-model calculations, as well as the preliminary study of the scaling behavior of the inclusive \(\pi ^-A~\rightarrow ~K^0~X\) cross–section as a function of the mass of the target nucleus is reported. A preliminary estimate of the elementary \(\pi ^-p~\rightarrow ~K^0~Y\) cross section in the presence of the surrounding nuclear medium is discussed.

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The space-time dimensions of the Ta+Au collision zone at \(40A\) MeV energy are investigated using the HBT interferometry technique of \(\gamma \gamma \) pairs. The bremsstrahlung photon energy spectrum exhibits 2 exponential contributions, described by the inverse slopes \(13.0 \pm 0.2\) MeV and \(5.1 \pm 0.3\) MeV, and the ratio of integrated intensities \(2.2 \pm 0.3\). The correlation function, investigated inclusively and for peripheral reactions, reveals no HBT signal. For central collisions there is a strong indication for such signal, best described by the invariant radius \(10.3 \pm 2.7\) fm within the model of the Gaussian space-time distribution of the photon emission source. The appearance of the HBT signal for central collisions only can be explained within simple models of photon emission in two stages of reaction.

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The yield of light charged particles and intermediate mass fragments is studied for the neutron-rich, \(^{124}\)Sn+\(^{64}\)Ni, and neutron-poor, \(^{112}\)Sn+\(^{58}\)Ni, reactions at 35 MeV/nucleon as a function of the impact parameter. Our main observations are: (i) The yields of \(^{1}\)H, \(^{3}\)He and \(^{4}\)He particles in the neutron-poor system are enhanced with respect to the neutron-rich system and the yield of \(^{3}\)H is suppressed at all impact parameters, (ii) The ratio of \(^{3}\)H to \(^{3}\)He yield is three times larger for neutron poor system, (iii) The \(N\)/\(Z\) ratio of the emitted intermediate-mass fragments shows dependence on the isospin of the system, (iv) The neutron richness of detected intermediate mass fragments depends strongly on their rapidity. The gross features of the experimental data are reproduced by quantum molecular dynamics model calculations.

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A systematic study of mass and isospin effects in the breakup of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory (Darmstadt). Four different projectiles \(^{197}\)Au, \(^{124}\)La, \(^{124}\)Sn and \(^{107}\)Sn, all with an incident energy of 600 \(A\) MeV, have been used, thus allowing a study of various combinations of masses and \(N\)/\(Z\) ratios in the entrance channel. The status of the project and first results are presented and discussed.

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Production of intermediate mass fragments (IMF) has been studied in semi-peripheral \(^{124}\)Sn (35 \(A\) MeV) + \(^{64}\)Ni and \(^{112}\)Sn (35 \(A\) MeV) + \(^{58}\)Ni reactions. Our recently proposed new method of an analysis of the neck-like fragmentation processes that provides information on the IMFs time sequence and time scale is reviewed. Isotopic analysis of so characterized IMFs gives evidence for neutron enrichment of mid-velocity fragments. A clear isoscaling behavior is found despite the short emission time scale. Evolution of the isoscaling parameters from semi-peripheral to central collisions is discussed.

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Probability of isospin mixing at high excitation has been determined only for few nuclei. Thus, we attempted to extract the degree of isospin mixing in several light, self-conjugate compound nuclei at excitation energy around 50 MeV and study its dependence on atomic mass number. For this purpose we have studied the statistical decay of the Giant Dipole Resonance (GDR) built on excited states formed in heavy-ion fusion reactions. We have measured the \(^{20}\)Ne + \(^{12}\)C, \(^{12}\)C + \(^{24}\)Mg, \(^{20}\)Ne + \(^{24}\)Mg and \(^{36}\)Ar + \(^{24}\)Mg reactions populating \(N = Z\) compound nuclei: \(^{32}\)S, \(^{36}\)Ar, \(^{44}\)Ti, \(^{60}\)Zn and the \(^{19}\)F + \(^{12}\)C, \(^{12}\)C + \(^{25}\)Mg, \(^{20}\)Ne + \(^{25}\)Mg and \(^{36}\)Ar + \(^{25}\)Mg reactions populating neighbouring compound nuclei with \(N \neq Z\) at close excitation energy (temperature). Heavy-ion beams from the Warsaw Cyclotron have been used. High-energy \(\gamma \)-rays emitted in the reactions have been measured with the JANOSIK set-up. Measured spectra have been fitted with the CASCADE statistical model calculations assuming a Lorentzian GDR strength function.

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A measurement of the analyzing powers for the \(^{1}\!H(\vec {d},pp)n\) breakup reaction at 130 MeV polarized deuteron beam energy was carried out at KVI Groningen. The experimental setup covered a large fraction of the phase space. Obtained tensor analyzing powers \(T_{22}\) for selected kinematical configurations have been compared to theoretical predictions based on various approaches: the rigorous Faddeev calculations using the realistic nucleon–nucleon potentials with and without three nucleon force (3NF) models, predictions of the chiral perturbation theory, and coupled channel calculations with the explicit \({\mit \Delta }\) degrees of freedom. In the presented configurations the results of all predictions are very close to one another and there are no significant 3NF influences. Not all of the data can be satisfactory reproduced by the theoretical calculations.

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Elastic cross sections for the scattering of \(^{6}\)He projectiles by \(^{208}\)Pb at energies around the Coulomb barrier measured at the Cyclotron Research Center of Louvain la Neuve (Belgium) have been analyzed using a simple analytic expression for the elastic cross section obtained in a semiclassical model. The results are consistent with recent Optical Model calculations.

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The Clara–Prisma setup is a powerful tool for spectroscopic studies of neutron-rich nuclei produced in multi-nucleon transfer and deep-inelastic reactions. It combines the large acceptance spectrometer Prisma with the \(\gamma \)-ray array Clara. Currently at Lnl is being constructed the heavy-ion detector Dante, based on Micro-Channel Plates, that will be installed at the Clara–Prisma setup. Dante will open the possibility of measuring \(\gamma \)–\(\gamma \) Doppler-corrected coincidences for the events outside the acceptance of Prisma. In this manuscript some results obtained with the Clara–Prisma setup will be discussed, in addition to the description and performance of the first prototype for the heavy-ion detector Dante.

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At the Kernfysisch Vensneller Institiutr (KVI) in Groningen, NL, a new facility (TRI\(\mu \)P) is under development. It aims for producing, slowing down, and trapping of radioactive isotopes in order to perform accurate measurements on fundamental symmetries and interactions. A production target station and a dual magnetic separator installed and commissioned. We will slow down the isotopes of interest using an ion catcher and in a further stage a radiofrequency quadropole gas cooler (RFQ). The isotopes will finally be trapped in an atomic trap for precision studies.

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Electron–positron pairs have been observed in the 10.95 MeV \(0^-\rightarrow 0^+\) decay in \(^{16}\)O. This magnetic monopole (M0) transition cannot proceed by \(\gamma \)-ray decay and is, to first order, forbidden for internal pair creation. However, the transition may also proceed by the emission of a light neutral \(0^{-}\) or \(1^{+}\) boson, which might play a role in the current quest for light dark matter in the Universe.

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The KamLAND experiment uses reactor anti-neutrinos to study the solar neutrino oscillation parameters. KamLAND recently updated the reactor neutrino measurement, with five times more statistics than previously reported. The measured spectral distortion in the anti-neutrino spectrum strongly favors neutrino oscillation as the explanation for neutrino disappearance and provides the most accurate value of \(\Delta m^{2}_{12}\) to date. KamLAND also performed a first observation of geologically produced anti-neutrinos, which can help in understanding the Earth’s heat generation and interior composition.

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Gamma Ray Bursts (GRB) have been discovered 38 years ago and still remain one of the most intriguing puzzles of astrophysics. In this paper we remind briefly the history of GRB studies and review the current experimental evidence with the emphasis on GRB optical counterparts. At the end we introduce “\(\pi \) of the Sky” project designed to catch prompt optical emission from GRB sources.

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The \(\mathrm {e} ^{-}\) and \(\mathrm {e} ^{+}\) energy spectra from the SN1987A Supernova neutrino burst interactions are calculated and compared to the observed spectra in Kamiokande-II and IMB experiments. Neutrino oscillations in Supernova and regeneration effects in the Earth, for four combinations of neutrino mass hierarchy (Direct/Inverted) and the value of the mixing angle \(\theta _{13}\) (Large/Small), are taken into account. The influence of the (anti)neutrino production spectra in Supernova on the observed, in Kamiokande-II and IMB detectors, \(\mathrm {e} ^{-}\)/\(\mathrm {e} ^{+}\) spectra is shown.

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We study the localization of protons in the core of neutron stars for ten realistic nuclear models that share a common behavior of nuclear symmetry energy which saturates and eventually decreases at high densities. This results in the low proton fraction of beta-stable neutron star matter. Protons form a small admixture in the neutron star core, which is localized at sufficiently high densities. For every model we calculate the density \(n_{\rm loc}\) above which the localization effect is present. Our results indicate that localization occurs at densities above 0.5–1.0 fm\(^{-3}\). The phase with localized protons occupies a spherical shell or a core region inside neutron stars which contains significant fraction of all nucleons. Proton localization is of great importance for astrophysical properties of neutron stars as it strongly affects transport coefficients of neutron star matter and can produce spontaneous magnetization in neutron stars.