abstract

Physics of elementary particles changed profoundly in January 1957 when it was experimentally demonstrated that parity is not conserved in the weak interactions. An account is given of events which led to the parity revolution.

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Nuclear physics plays an essential role in the dynamics of a type II supernova (a collapsing star). Recent advances in nuclear many-body theory allow now improved calculations of the stellar weak-interaction rates involving nuclei. The most important process is the electron capture on finite nuclei with mass numbers \(A\gt 55\). This process is the source of neutrinos during the collapse phase. Neutrino–nucleus reactions occur during the collapse and explosion phase. They play an interesting role for supernova nucleosynthesis. Spectroscopy by supernova neutrino detectors is a fascinating goal for the observation of the next close-by supernova.

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I discuss some theoretical aspects of how to observe leptonic CP violation. It is divided into two parts, one for CP violation due to Majorana, and the other more conventional leptonic Kobayashi–Maskawa (KM) phases. In the first part, I estimate the effect of Majorana phase to observable of neutrino-less double beta decay experiments by paying a careful attention to the definition of the atmospheric scale \(\Delta m^2\). In the second part, I discuss Tokai-to-Kamioka-Korea two detector complex which receives neutrino superbeam from J-PARC as a concrete setting for discovering CP violation due to the KM phase, as well as resolving mass hierarchy and the \(\theta _{23}\) octant degeneracy. A cautionary remark is also given on comparison between various projects aiming at exploring CP violation and the mass hierarchy.

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Experimental searches for medium-modifications of vector mesons in photon and proton induced nuclear reactions are reviewed. Results on \(\rho , \omega \), and \({\mit \Phi }\) mesons are presented. At normal nuclear matter density, the \(\omega \) and \({\mit \Phi }\) meson are found to be lowered in mass by 9–14\(\%\) and 3.5\(\%\), respectively. Compared to the free particle properties increases in widths by factors of about 16 and 3.6, respectively, are observed. For the \(\rho \) meson conflicting results on in-medium mass shifts and broadening have been reported.

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Dilepton spectroscopy in heavy ion collisions is one of the most promising tools to investigate hadron properties in hot and dense nuclear matter. Spectral functions of light vector mesons, in particular short lived \(\rho \), are the key observables to study such effects. The connection of the mesons to virtual radiation from hot and dense nuclear matter is emphasized. Recent experimental results on dilepton production in relativistic heavy ion collisions obtained by various experiments at RHIC, SPS and low energy SIS/Bevelac facilities are presented and discussed.

abstract

Nucleus–nucleus collisions provide the unique opportunity to create and to investigate dense nuclear matter in the laboratory. The collision experiments address fundamental aspects of strong-interaction physics: the nuclear equation-of-state at high baryon densities, and the modification of hadron properties in the dense nuclear medium. The experimental results are relevant for our understanding of the dynamics of core-collapse supernovae, and of the structure of neutron stars. In particular, strange particles are promising diagnostic probes of dense nuclear matter. Existing experimental data, their theoretical interpretations, and future experiments will be discussed.

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The search for nuclear states of \(K\)-mesons and \(\eta \)-mesons is presented. Methods of theoretical descriptions and the related difficulties: off shell extrapolation of meson–nucleon scattering amplitudes, behavior of hadronic resonances in nuclei and extrapolation to high density nuclear regions are discussed. Variational calculations for the binding energies in light nuclei are described.

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We show in the simple model independent of photon momentum transfer the density evolution for the parton distribution in nuclear matter. The correction to the Fermi energy from term proportional to the pressure are very important.

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We calculate in the impulse approximation the kaon spectrum from the \((\pi ^-,K^{~+})\) reaction on \(^{28}\)Si. The strength \(V_0\) of the real part of the single particle potential of the \({\mit \Sigma }\) hyperons produced in the reaction is treated as a free parameter, and the strength \(W_0\) of the imaginary (absorptive) part is determined by the \({\mit \Sigma } N\) cross sections for the \({\mit \Sigma }{\mit \Lambda }\) conversion and also for the elastic \({\mit \Sigma } N\) scattering (this elastic scattering introduces a strong dependence of \(W_0\) on the \({\mit \Sigma }\) momentum). By fitting to the kaon spectrum measured at KEK, we obtain a repulsive \(V_0\simeq \) 40–60 MeV. This result is much closer to previous estimates of \(V_0\) than the results of other analyses of the KEK experiments.

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In this paper the production of \(K^{~+}\), \(K^{~-}\) and \(\phi \) mesons in Al+Al collisions at incident beam energy of 1.9\(A\) GeV is studied. The experiment was performed in GSI/Darmstadt using the FOPI spectrometer. The \(K^{~-}/K^{~+}\) yields ratio was extracted in a substantial part of the phase-space. The yields ratio was found to be in a good agreement with previous experimental results that served as a proof for in-medium modifications of kaons’ properties. In order to quantify the contribution of \(\phi \) mesons decays to the observed \(K^{~-}\) mesons yield, the \(\phi \) meson production probability was estimated. The preliminary result differs by almost two orders of magnitude from the earlier estimate available for heavier (Ni+Ni) system at similar beam energy, in which the number of \(K^{~-}\) mesons that could stem from \(\phi \) mesons decays was found to be as high as 20%.

abstract

Angular distributions of \(K^0\) mesons produced in 1.15 GeV/\(c\) \({\pi }^-\) reactions on carbon and lead targets, measured with the FOPI spectrometer at GSI Darmstadt, are not isotropic. The ratio of these angular distributions shows a strong forward–backward asymmetry, which might be understood as a result of the reabsorption of forward produced kaons in lead nuclei. This effect agrees with the results of IQMD transport model. A simple geometrical model developed in order to estimate the effect of the absorption allows to determine the kaon mean free path equal to about 4 fm.

abstract

The decay of 2-gluon colour singlets in quarks: \(2g\rightarrow q\bar q +2q2\bar q\) has been simulated with the Monte-Carlo method, taking into account an effective 1-gluon exchange interaction between the emitted quarks, which was folded with a 2-gluon density determined self-consistently. 2-gluon densities were found with different radii, which correspond to \(0^{++}\) glueballs of the size of light \(q\bar q\), \(s\bar s\), \(c\bar c\), \(b\bar b\) and heavier \(q\bar q\) systems. Binding potentials between the two gluons have been deduced, which are consistent with the confinement potential from lattice results. However, self-consistency for the deduction of 2-gluon densities requires massless (or very light) quarks for all flavours. The masses are given by the binding energies of quarks and gluons, yielding excitation spectra of \(0^{++}\) glueballs and \({\mit \Phi }\), \(J/{\mit \Psi }\) and \({\mit \Upsilon }\) states consistent with observation. The sum of \(q\)–\(q\) potentials yields a strong coupling \(\alpha _{\rm s}\) consistent with the available data up to large momenta. The nucleon is described by a gluonium state coupled to 3 valence quarks, yielding ground state and radial excitations consistent with experiment. Finally, we discuss the compressibility of the nucleon and relate it to that of nuclear matter.

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Measurements and predictions for \(T\)-odd asymmetries deduced from the azimuthal distribution of hadrons relative to the lepton plane are discussed for unpolarised deep inelastic \(ep\) scattering. The measurements were performed for neutral current deep inelastic \(ep\) scattering at a centre-of-mass energy of \(300\) GeV for the kinematic range of the exchanged boson virtuality \(100 \lt Q^2 \lt 8000\) GeV\(^2\), and in the hadronic centre-of-mass system using the energy-flow method.

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Continuum-coupling correction to binding energies in neutron rich oxygen and fluorine isotopes and to excitation energies of \(2_1^+\) states in \(^{36}\)Ca and \(^{36}\)S mirror nuclei are studied using the real-energy continuum shell model.

abstract

High-precision vector and tensor breakup analyzing powers for the reaction \(^1{\rm H}(\vec {d},pp)n\) at 130 MeV were evaluated for a large phase space region. Results are compared with rigorous theoretical calculations based on realistic nucleon–nucleon potentials as well as on chiral perturbation theory approach. Theoretical predictions generally describe data quite well, only in a few cases influence of three-nucleon forces is significant.

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We study the formation of toroidal nuclear configurations in central and semi-central \(^{124}\)Sn\(\,+^{124}\)Sn and Au+Au collisions. BUU simulations indicate that the threshold energy for toroidal configuration formation decreases with increasing mass of the interacting system.

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This paper presents results of experiment which studied (using the Nuclear-Orientation technique) the \(\gamma \)-decay of isomeric \(^{180m}\)Hf. The described experiment used the newly developed mass-separated \(^{180m}\)Hf beam at ISOLDE, CERN which was implanted into an iron foil polarized at millikelvin temperatures. The observed irregular admixture of E2 to M2/E3 multipolarity in 501 keV \(8^{-} \rightarrow 6^{+}\) \(\gamma \)-transition was the clear experimental evidence for parity mixing in nuclear states. The temperature dependence of the forward–backward asymmetry of the angular distribution has been measured over extended range of temperatures (and therefore nuclear polarizations), proving a parity mixing of the 8\(^{-}\) and 8\(^{+}\) nuclear levels. The value found for the E2/M2 mixing ratio \(\varepsilon =-0.032(2)\) of this transition is in close agreement with averaged value of all previously published results \(\varepsilon =-0.030(2)\).

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The nuclear level-density parameters obtained in the Yukawa folded potential approach are presented. The particle-number averaging (\(\cal {N}\) averaging) Strutinsky shell-correction method is used to extract the shell-correction energy and its change with temperature and the macroscopic nuclear energy for 130 spherical even-even nuclei. A liquid-drop type expression is proposed for the level-density parameter. The best agreement is achieved between our results and the phenomenological formula of von Egidy based on a back-shifted Fermi gas model.

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A new method is proposed to describe masses of nuclei belonging to single a major shell. It is based on a global formula for the macroscopic part of the nuclear mass while the remaining (shell + deformation) part is considered in the context of the interacting boson model. The framework enables a simultaneous calculation of spectra and binding energies.

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Electromagnetic ion traps have become essential instruments for the precise and accurate mass determination of rare isotopes. Penning trap mass spectrometers are now successfully operated at several radioactive beam facilities in the world. Accurate masses values obtained with these devices provide key data for the test of fundamental interactions, the modeling of the nuclear synthesis of the elements, and for improving our understanding of nuclear structure far from stability. This paper gives an overview of the basic techniques, the specific challenges, and the status of Penning trap mass spectrometry of rare isotopes.

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A radiofrequency quadrupole (RFQ) cooler and buncher and two Penning traps form the JYFLTRAP setup, which is located at the Department of Physics, University of Jyväskylä, Finland. It is used as a high-resolution mass filter for decay-spectroscopy experiments as well as for high-precision mass measurements. Recent developments have enabled JYFLTRAP to prepare isomerically clean beams with a mass resolving power \(R = \frac {M}{\Delta M} \geq 10^6\).

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For precision mass measurements of short-lived rare isotopes, a new experimental apparatus, named “Rare-RI Ring”, has recently been proposed. A unique possibility of the project is discussed, comparing with other experimental techniques. The current status is presented.

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The JYFLTRAP mass spectrometer was used to measure the masses of neutron-rich nuclei in the region of \(28 \leq N \leq 82\) with uncertainties better than 10 keV. The impacts on nuclear structure and the r-process paths are reviewed.

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The MLLTRAP, presently under construction at the Maier—Leibnitz Laboratory (Garching), is a Penning trap system designed to decelerate, purify, charge-breed and cool the radioactive ions with the aim to perform the high-accuracy nuclear mass measurements. It involves novel techniques, like sympathetic cooling of highly-charged ions of interest with laser-cooled Mg\(^{+}\) ions. The goal is to reach an accuracy of 10\(^{-10}\), which is required for high precision fundamental physics studies like the determination of fundamental constants and measurement of electron binding energies for QED at strong fields.

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The decay of extremely neutron-deficient isotope \(^{45}\)Fe has been studied by using a new type of gaseous detector in which a technique of optical imaging is used to record tracks of charged particles. The two-proton radioactivity and the \(\beta \)-decay channels accompanied by proton(s) emission were clearly identified. For the first time, the angular and energy correlations between two protons emitted from the \(^{45}\)Fe ground-state were measured. The obtained distributions were confronted with predictions of a three-body model. Studies of \(\beta \)-decay channels of \(^{45}\)Fe provided first unambiguous evidence for the \(\beta \)-delayed three proton emission.

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In a measurement of the angular correlation of \(e^+e^-\) pairs in the isovector M1 decay from \(1^+\) level at 17.64 MeV in \(^{8}\)Be, a large deviation was found from quantum electrodynamics(QED)-prediction for internal pair conversion (IPC). By postulating the emission of a neutral particle with a mass of 12 (2.5) MeV\(/c^2\) the structure of the angular correlation can be described.

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The beam pulse structure of the HIL cyclotron and thick target \(\gamma \)–\(\gamma \) coincidence measurements in the in-beam and off-beam modes have been used to search for isomers in the \(A \approx 120\) mass region using heavy-ion reactions. The half-life of the 2721 keV, (25/2\(^{+}\)) level in \(^{121}\)Sb was determined in the off-beam mode to be \(167 \pm 19\) \(\mu \)s. Two deexcitation sequences of this isomer are proposed. The isomeric state is considered to be of 3-quasiparticle nature \(\pi (d_{5/2})\nu (h_{11/2}^{2})_{10^{+}}\).

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The first “in-beam” spectra of the internal conversion electrons were collected in the \(^{197}\)Au\((^{14}\)N\(,5n)^{206}\)Rn fusion evaporation reaction by new constructed electron spectrometer. The measurements were carried out in electron–gamma and gamma–gamma coincidence mode with use of electron spectrometer coupled to OSIRIS II gamma array at Heavy Ion Laboratory (HIL) of the Warsaw University. The analysis of the data for \(\gamma \)–\(\gamma \) coincidence measurement disclosed new transitions in \(^{206}\)Rn excited nucleus. Experimentally obtained internal conversion coefficient allowed to determine multipolarity of the new observed transition in \(^{206}\)Rn nucleus.

abstract

For the first time the electron capture and \(\beta ^+\) decay rates of H-like \(^{140}\)Pr ions have been measured at the FRS-ESR facility by using the Schottky noise technique. The H-like \(^{140}\)Pr\(^{58+}\) decay rate was found to be larger by a factor of 1.5 than in the case of neutral atom. This non-intuitive result can be explained by taking into account hyperfine splitting of nuclear levels in the decaying nuclei and the conservation law of the total angular momentum of the system.

abstract

Stopping power of Au ions in nickel was measured using B-TOF method with accuracy of better than 1.5 % in the energy range from 0.15 to 5 MeV/\(u\). The results are compared favourable with theoretical and semi empirical predictions. For this combination of ion and absorber there are no previously published experimental results.

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Low-lying \(0^+\) states, close in energy to the first excited \(2^+\) state, have been observed in even–even molybdenum isotopes, indicating shape coexistence in these nuclei. Results of our previous Coulomb excitation measurements of \(^{96}\)Mo and \(^{98}\)Mo supported the shape coexistence scenario. A series of Coulomb excitation experiments to study the neighboring stable \(^{100}\)Mo isotope was performed on beams of the Warsaw Cyclotron. During the recent experiment with \(^{100}\)Mo target the new dedicated set-up for Coulomb excitation measurements was used at HIL. First results are presented. The performance of the new detection system opens promising possibilities for future Coulomb excitation experiments.

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The weakening of the \(N=28\) shell closure and the development of deformation and shape coexistence were addressed in a low-energy Coulomb excitation experiment using a radioactive \(^{44}\)Ar beam from SPIRAL. The 2\(^+_1\) and one higher-lying state in \(^{44}\)Ar were excited on \(^{208}\)Pb and \(^{109}\)Ag targets at two different beam energies. From the collected data it will be possible to extract the B(E2) values between all observed states and to determine the quadrupole moment of the first 2\(^+\) state, providing information on the prolate or oblate character of the deformation.

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The properties of \(\beta \)-\(\gamma \) and \(\beta \)-delayed neutron emission from \(^{76-79}\)Cu and \(^{83-85}\)Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed.

abstract

The phenomenon of chiral symmetry breaking is discussed and a review of a wide spectrum of the experimental data is given. In addition to the basic description of this phenomenon an analysis of the level schemes and electromagnetic properties observed in nuclei expected to show the chiral symmetry breaking is presented.