International Journal of Modern Physics E

The Mainz Microtron MAMI is an ideal facility to study the hadron structure with the electromagnetic probe. With the fourth accelerator stage (MAMI-C) which went into operation in 2007 high-intensity polarized electron and photon beams with energies up to 1.5 GeV are delivered to the experiments. Polarized targets and recoil polarimeters in combination with dedicated detectors are available for precision experiments in hadron physics. In this article, an overview over selected recent results on the study of low-lying baryon resonances and future perspectives will be given.

We analyzed experimental data obtained for the mass distribution of fission fragments in the reactions ³⁶S+²³⁸U and ³⁰Si+²³⁸U at several incident energies, which were performed by the JAEA group. Using the dynamical model with the Langevin equation, we precisely investigate the incident energy dependence of the mass distribution of fission fragments. We also consider the fine structures in the mass distribution of fission fragments caused by the nuclear structure at a low incident energy. It is explained why the mass distribution of fission fragments has different features in the two reactions. The fusion cross sections are also estimated.

The near-term radioactive beam capabilities of ATLAS include radioactive beams produced in flight in a gas cell, or starting in the fall of 2009, re-accelerated beams of ²⁵²Cf fission fragments provided by the new CARIBU injector. The availability of such exotic beams will allow for detailed studies of the single-particle aspects of nuclear structure in neutron-rich nuclei reaching out to the astrophysical r-process path by employing light-ion reactions in inverse kinematics. The HELIOS spectrometer is based on a new concept that is especially well suited for such studies. This concept was recently demonstrated using the reactions D(²⁸Si,p)²⁹Si with a (stable) 168 MeV ²⁸Si beam. Since then D(¹²B,p)¹³B, D(¹⁷O,p)¹⁸O, and D(¹⁵C,p)¹⁶C have been studied successfully. The combination of neutron-rich beams from CARIBU and the HELIOS spectrometer opens a fertile research area of precision studies of the single particle strengths and collective excitations in exotic nuclei, and is likely to have applications in other reactions as well.

The CLAS Collaboration is operating the CLAS detector at theThomas Jefferson National Laboratory (JLab) in USA. The unique combination of detector acceptance and high intensity of the continuous electron beam of CEBAF has opened the way to a comprehensive study of the hadron structure in the kinematic domain between nuclear and particle physics. Hadron spectroscopy plays a central role in the physics program of the Collaboration. Many exclusive channels have been studied with virtual and real photon beams over a wide kinematic range providing key information about the hadronic structure as well as the reactions dynamics. In this contribution, the rich physics program covered by present and future experiments will be reviewed.

A proposed set of instrumentation, collectively referred to as the Super Bigbite project, is presented. Used in three different configurations it will allow measurements of three nucleon electromagnetic form factors , , and with unprecedented precision to Q²-values up to three times higher than existing data.

Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. High Energy Collisions are studied in order to access nuclear matter properties at high density. Particular attention is devoted to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent covariant transport simulations built on effective field theories we are testing isospin observables ranging from nucleon/cluster emissions, collective flows (in particular the elliptic, squeeze out, part) and meson production. The possibility to shed light on the controversial neutron/proton effective mass splitting in asymmetric matter is also stressed.

The "symmetry" repulsion at high baryon density will also lead to an "earlier" hadron-deconfinement transition in n-rich matter. The phase transition of hadronic to quark matter at high baryon and isospin density is analyzed. Nonlinear relativistic mean field models are used to describe hadronic matter, and the MIT bag model is adopted for quark matter. The boundaries of the mixed phase and the related critical points for symmetric and asymmetric matter are obtained. Isospin effects appear to be rather significant. The binodal transition line of the (T,ρ_B) diagram is lowered in a region accessible to heavy ion collisions in the energy range of the new planned FAIR/NICA facilities. Some observable effects of the mixed phase are suggested, in particular a neutron distillation mechanism. Theoretically a very important problem appears to be the suitable treatment of the isovector part of the interaction in effective QCD lagrangian approaches.

The puzzle of the excitation spectrum of the nucleon, composed of broad and overlapping resonances, is still unresolved. For a complete experiment at least 8 well chosen single and double polarisation observables are needed. At the electron accelerator ELSA of the University of Bonn single- and double polarisation experiments are currently performed with the Crystal Barrel/TAPS experiment. The experimental setup includes a ɸ-symmetric calorimeter system covering almost the complete solid angle and it is ideally suited to detect single and multiple neutral meson final states. Circularly or linearly polarised photon beams impinge on a longitudinal polarised butanol target in the center of the setup. The linearly polarised photon beams provide the basis for the measurement of azimuthal beam asymmetries, such as Σ and, in combination with the polarised target, G. Circularly polarised photon beams allow the extraction of the beam-target asymmetry E. Preliminary results for the polarisation observables Σ, G and E will be presented.

In order to explore the possibilities to synthesize the new superheavy elements with Z=120, 122, 124, 126 some hot-fusion (mass asymmetric) reactions and cold-fusion (less mass asymmetric) reactions are studied. The dynamics of reaction with massive nuclei and the formation probability of heavy and superheavy elements with Z=90-126 in the asymmetric and symmetric reactions are discussed. The systematics of fusion probability P_CN and evaporation residue cross section σ_ER in these reactions are presented. Moreover, we explore the possibility of synthesis of superheavy nuclei by the use of reaction with the neutron rich radioactive beam ¹³²Sn, and by symmetric reactions like ¹³⁶Xe+¹³⁶Xe and ^139,149La+ ^139,149La.

The production of pseudo scalar, η, η′, and vector, ω, ρ, ϕ, mesons in NN collisions at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. It is shown that a good description of cross sections and angular distributions, for vector meson production, can be accomplished by considering meson and nucleon currents only, while for pseudo scalar production an inclusion of nucleon resonances is needed. The di-electron production from subsequent Dalitz decay of the produced mesons, η′ → γγ* → γe⁺e^- and ω → πγ* → πe⁺e^- is also considered and numerical results are presented for intermediate energies and kinematics of possible experiments with HADES, CLAS and KEK-PS. We argue that the transition form factor ω → γ*π as well as η′ → γ*γ can be defined in a fairly model independent way and the feasibility of an experimental access to transition form factors is discussed.

We are carrying out hadron photoproduction experiments by using polarized photon beams with energies of 1.5-2.9 GeV at SPring-8 in Japan. In 2005, we started developing a polarized HD target for future LEPS experiments using both the polarized photon beams and the polarized target. To introduce a polarized target plays an important role in upgrading the LEPS experiments to the next higher step. The measurement of double polarization asymmetries is expected to give important informations to investigate the nucleon hidden structure, hadron photoproduction dynamics, and exotic hadron property. We report on the present status of the development of the polarized HD target at RCNP. We will carry out a test experiment to confirm that the polarized HD target can be transported from Osaka university to SPring-8 without any problems in 2010. If we succeed in the test experiment, we will carry out a long experiment to take physics data in 2011-2012.

In a series of experiments at the tagged photon facilities of the Bonn ELSA accelerator and the Mainz MAMI accelerator photoproduction of mesons from light nuclear targets (deuteron, ³He) has been studied. The experiments used the combined Crystal Barrel/TAPS setup in Bonn and the Crystal Ball/TAPS setup in Mainz. Meson photoproduction off the neutron has been investigated for the π^o, π^oπ^o, π^oπ^-, η, η′, and ηπ^o final states. A surprising finding was a narrow structure in the γn → nη excitation function, which is not seen in the proton case. Measurements of η- and π^o-photoproduction off a liquid ³He-target have provided further evidence for the formation of η-mesic ³He.

We discuss the current status and prospects of an experimental program of parity-violating asymmetry measurements in the scattering of longitudinally polarized electrons off unpolarized fixed targets. In particular, we focus on those measurements where judicious choices of target species and kinematics allows the theoretical predictions to be made purely in terms of fundamental electroweak couplings with little theoretical uncertainty. If such asymmetries are measured with sufficient precision, they are sensitive to new physics at the TeV scale. After reviewing recent results, two new experimental initiatives called MOLLER and SoLID being designed for the Jefferson Laboratory 12 GeV upgrade are discussed.

The CBELSA/TAPS experiment is a set up installed at the accelerator facility ELSA in Bonn. It is used to measure cross sections of hadronic reactions by observing final state particles. The set up is well suited for the identification of neutral particles such as neutrons and photons (e.g. from π₀ decay). It is planed to access the major part of η and η′ photo production and decays as also strangeness. This requires a neutral trigger capability for the detector set up and a tracking detector for charged particles.

A new generation of self-consistent calculations has deepened our understanding of how nuclei are bound and the structure and spatial extent of their wavefunctions. New methods are being developed to calculate nuclear properties starting from realistic unrenormalized two-body nucleon-nucleon potentials. Higher order correlations are needed to reproduce both masses and spectra, and the special importance of three-body correlations has become clear. Precise experimental measurements can help improve the calculations and constrain the form and strength of three body Hamiltonians. In this contribution, I will review new calculations on A=10 nuclei made with the Greens Function Monte Carlo method (GFMC) using a variety of three-body interactions, and new experiments designed to measure the lifetime of excited states with an improved Doppler Shift Attenuation Method (DSAM*). The electromagnetic matrix elements are determined to a level of precision, <5%, that really challenge GFMC and other contemporary theories.

Experiments of ²³Al and ²²Mg radioactive beams bombarding a ¹²C target at an energy of 60 ~70 A MeV have been performed at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility to study the two-proton emission from ²³Al and ²²Mg excited states, respectively. The trajectorie of the decay products, namely ²¹Na + p + p from ²³Al and ²⁰Ne + p + p from ²²Mg, are clean identified. The relative momentum and opening angle between two protons in the rest frame of three body decay channels are obtained by relativistic-kinematics reconstruction. The results demonstrate that there are some di-proton emission components from ²He cluster for the excited ²³Al and ²²Mg.

We present the analysis of data performed in order to identify the events of the γ + n → π^- + p reaction obtained by bombarding a liquid Deuterium target with a polarised γ beam of 0.55-1.5 GeV at the Graal-experiment. We show the effect of different kinematic and hardware constraints used to reduce the contamination coming from the concurrent reaction channels. By the simulation we estimate the contamination degree due to the other reaction channels so we can test the reliability of our method. We describe a new three-dimensional cut based on the Fermi momentum reconstruction and its effect on the suppression of the concurrent double charged pion photoproduction. We present the preliminary beam asymmetry Σ of the π^- fotoproduction off quasi-free neutron up to about θ_{c.m., π^-} = 165° together with some theoretical multipolar analysis. For a comparison we also report the data present in literature on the same reaction for E_γ =850-1740 MeV and θ_{c.m., π^-} ≤105°.

This work presents an overview of the latest experiments performed to study the reaction dynamics induced from light weakly-bound Radioactive Ion Beams on medium-mass and heavy targets at near-barrier energies. Production reactions, secondary beam intensities and experimental results on elastic scattering, transfer, breakup and fusion processes are presented and discussed. A comparative analysis of fusion and reaction cross section data for different projectile-target combinations is finally given.

We have measured quasi-elastic backward scattering in the reactions of ⁴⁸Ti, ⁵⁴Cr, ⁵⁶Fe, ⁶⁴Ni, ⁷⁰Zn, ⁷⁶Ge and ⁸⁶Kr + ²⁰⁸Pb to study the nucleus-nucleus interaction in Pb-based cold fusion. The barrier distributions were obtained from the first derivative of the measured excitation functions of quasi-elastic scattering cross sections normalized to the Rutherford scattering cross sections. The centroids of the barrier distributions showed deviations from several predicted barrier heights toward the low energy side except for the Christensen-Winther potential and the Aküz-Winther potential. The shapes of the barrier distributions were well reproduced by the results of a coupled-channel calculation taking account of the coupling effects of multi-phonon excitations of the quadrupole vibration for the projectiles and of the octupole vibration for the ²⁰⁸Pb target. The present barrier distributions were also well reproduced by a semiclassical calculation taking into account the couplings of transfer channels and single-phonon excitations in the projectiles and the target.

The mixing of the quasifission component to the fissionlike cross section causes ambiguity in the quantitative estimation of the complete fusion cross section from the observed angular and mass distributions of the binary products. We show that the partial cross section of quasifission component of binary fragments covers the whole range of the angular momentum values leading to capture. The calculated angular momentum distributions for the compound nucleus and dinuclear system going to quasifission may overlap: competition between complete fusion and quasifission takes place at all values of initial orbital angular momentum. Quasifission components formed at large angular momentum of the dinuclear system can show isotropic angular distribution and their mass distribution can be in mass symmetric region similar to the characteristics of fusion-fission components. As result the unintentional inclusion of the quasifission contribution into the fusion-fission fragment yields can lead to overestimation of the probability of the compound nucleus formation.

The first measurements of the helicity dependence for the γd reactions were carried out at MAMI (Mainz) in the energy range E_γ=200-800 MeV. The experiment used a 4π detection system, a circularly polarized tagged photon beam and a frozen spin target which provided longitudinally polarized deuterons. Results on both the total inclusive photoabsorption cross section and of the πNN channels will be presented. These data give important information about the the Gerasimov-Drell-Hearn sum rule on the neutron and allow a detailed comparison with state-of-the-art calculations of the γd interaction.

Many baryon resonances are predicted studying the channels with π, but very few established. This is the so-called "missing resonance" problem. It is important to provide data to investigate the spectrum of baryon (N* and Δ) resonances, with the decay in KY. A comprehensive study of the electromagnetic strangeness production has been undertaken at Jefferson Lab using circularly and linearly polarized photon beam and polarized hydrogen and deuterium target. Recent results in strangeness photoproduction on protons, including cross sections and spin observables, are discussed in this paper, as well preliminary results on photoproduction on bound neutron. Also an overview of the future perspectives for the 12 GeV upgrade.

The prompt γ-ray emission, associated with the dynamical dipole mode decay, was investigated in the ^32,36S + ^100,96Mo and ^36,40Ar + ^96,92Zr fusion-evaporation reactions in the energy range E_lab= 6 - 16 MeV/nucleon. The above reaction pairs populate, through entrance channels having different charge asymmetries, a compound nucleus in the ¹³²Ce mass region at excitation energies of 117, 174 and 284 MeV with identical spin distribution. By studying the differential γ-ray multiplicity spectra of the considered systems, the features of the dynamical dipole mode as a function of the beam energy were extracted while the γ-ray angular distributions were used to prove its pre-equilibrium character. The experimental findings were compared with theoretical predictions performed within a BNV transport model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics. As a fast cooling mechanism on the fusion path, the prompt dipole radiation could be of interest for the synthesis of super heavy elements through hot fusion reactions providing a way to cool down the hot fusion paths, so ending up with a larger survival probability. To shed light on this hypothesis, the dynamical dipole mode investigation was extended to a heavier compound nucleus, ¹⁹²Pb, by means of the ⁴⁰Ca + ¹⁵²Sm and ⁴⁸Ca + ¹⁴⁴Sm reactions at E_lab= 11 and 10.1 MeV/nucleon, respectively. Preliminary results of this measurement, concerning both fusion-evaporation and fission events are presented.

At the electron accelerator facility ELSA of the University of Bonn presently the new BGO-OpenDipole experiment is being setup. It is optimized for meson photoproduction final states of mixed charges. The detector combines hermetic coverage for photon detection through the BGO ball of the former GRAAL experiment with high resolution detection of forward going charged particles in the Open Dipole spectrometer. This setup is well suited for many different channels, including pseudoscalar, vectormeson and associated strangeness photoproduction. This contribution highlights the strangeness channels associated with the Λ and Σ ground states and the Λ(1405) excited state.

Properties of heaviest nuclei at their saddle point are studied in a multidimensional deformation space. The main attention is given to deformation and the shell correction to energy of the nuclei at this point. The analysis is performed within a macroscopic-microscopic approach. A 10-dimensional deformation space is used. A large number of about 300 even-even heavy and superheavy nuclei with proton number 98 ≤ Z ≤ 126 and neutron number 134 ≤ N ≤ 192 are considered. Detailed results are illustrated for nuclei of the element 120. A large shell correction (up to about 7 MeV) is found for these nuclei. For most of them, the correction is larger than the height of the barrier, itself, as the macroscopic contribution to this height is negative.

Experiments with real photons have been performed for many years at the Mainz accelerator MAMI with different detectors. The upgraded MAMI C accelerator recently delivered electrons with an energy of 1604MeV. The A2 collaboration performs experiments with energy tagged polarised real photons produced via 'Bremsstrahlung'. Linear and circular photon polarisation is possible. In the years 2005/2006 the Crystal Ball detector with its unique detection capability for multi photon final states was set up in Mainz. The Crystal Ball at MAMI setup offers an excellent possibility to study decays of the η and η′ mesons. Due to the high intensity photon beam the apparatus can be seen as an η-factory. Recent results from the Crystal Ball experiment at MAMI are presented. In the future we plan to use a longitudinal and transverse polarised frozen spin target to investigate the spin polarisibilities of the nucleons.

Fragment yields of projectile fragmentation reactions using primary beams of ^36,40Ar at 50 MeV/nucleon on ⁶⁴Ni target have been measured. Fragment yields of different isotopes were obtained for Z ≥ 5 in RIBLL fragment seperator. We compare the extracted yields to the predictions of the empirical parametrization of fragmentation cross-sections(EPAX) and Statistical Abration-Ablation model(SAA) considering the RIBLL separator transmission rate. Isotope yield ratios between these 2 reactions were calculated, isoscaling parameters α and β, their dependence on fragment atomic number Z and neutron number N were calculated.

Experiment PREX will take place in Hall A at TJNAF in 2010. It will measure the neutron radius R_n in the ²⁰⁸Pb nucleus through the measurement of the parity violating asymmetry in electron scattering , with σ_R and σ_L the cross sections for right handed and left handed electrons respectively. The projected accuracy of 1% on R_n constitutes a fundamental test of nuclear theory. This measurement of R_n will provide the best determination of the density dependence of the symmetry energy at the density of ordinary nuclear matter. As a consequence, the PREX result will have a big impact on phenomena like neutron star structure, heavy ion collisions and atomic parity violation.

Intermediate energy beams of light exotic nuclei have been produced at LNS by the FRIBs facility. Thanks to these beams, a complex study of the structure of halo nuclei in the ¹¹Be region has been started exploiting the performances of the CHIMERA array.

The contribution of the direct radiative capture of protons by ¹⁰B and ²⁴Mg nuclei at low energies to the astrophysical S-factors in the reactions ₁₀B(p,γ)¹¹C and ²⁴Mg(p,γ)²⁵Al have been calculated within the R-matrix formalism by using empirical proton asymptotical normalization coefficients (ANC). The ANCs for bound proton configurations {¹⁰B+p} and {²⁴Mg+p} were obtained from the analysis of the reactions (³He, d). The ANCs were also estimated from the values of the neutron ANCs in the mirror nucleus ²⁵Mg following the suggestion that the neutron and the proton in the mirror states have equivalent nuclear potentials. It has been found that the S-factor for the reaction ¹⁰B(p,γ)¹¹C extrapolated to zero energy contributes ~100 keV b to the radiative capture to the ground state of ¹¹C. For the reaction ²⁴Mg(p,γ)²⁵Al the value S(0) gives 58 keV b with a direct capture contribution of 41 keV b.

The FINUDA experiment has performed a systematic study of the Mesonic Weak Decay (MWD) of Λ hypernuclei by analyzing all the data collected from 2003 up to 2007. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for , , and . Branching ratio Γ_π-/Γ_tot were derived from the measured spectra. Based on these measurements, the spin-parity assignment 1/2⁺ for and 5/2⁺ for ground-state are confirmed and a spin-parity 3/2⁺ for ground-state is assigned for the first time.

Ideas for precision measurements of MWD at the J-PARC accelerator's complex are finally presented.

Stopping powers of superheavy ion with Z=120 and A=300 have been estimated in several media in the energy region 0.0177≤E/A≤0.141 MeV/amu. The electronic and nuclear stopping powers of ions with 6≤Z≤92 calculated by SRIM have been used to estimate the corresponding stopping powers of the superheavy ion. The media included two solid compounds (UF₄ and Mylar) and two gases (He and butane). The results were compared with those deduced from Northcliffe and Schilling's stopping-power tables.

The dynamic model is proposed for description of the angular distributions of quasifission fragments. The model is able to describe experimental anisotropy of the angular distributions of fissionlike fragments for the ³²S, ²⁸Si+²⁰⁸Pb reactions. It is also shown that the new model allows the description of the experimental mass-angular correlations in the quasifission fragment yields for the ⁶⁴Ni+¹⁹⁷Au reaction at 383 and 418 MeV of incident energies. The analysis was performed with the angular momentum and deformation dependent relaxation time of the tilting mode. Information on the dinuclear system lifetimes were obtained.

Theoretical description of the experimentally obtained spectra for protons and α-particles and model calculations for the neutron spectra in the reactions with heavy ions has been presented. The hybrid model of non-equilibrium processes was used. Equilibrium evaporation process was analyzed in the framework of the statistical theory of nuclear reactions with Monte-Carlo simulation including certain dynamical and kinematical characteristics. This approach was included in PACE code, which permits to simulate Monte-Carlo de-excitation nuclear process. The Fermi-gas model and level-density phenomenological model for the variation of the nuclear level density parameters was used. In this approach data on ¹⁶O+¹¹⁶Sn reaction with E_beam = 130, 250 MeV were analyzed. Double-differential light charged particle spectra for this reaction were measured using the GARFIELD apparatus in coincidence with evaporation residues. The experimental data were collected in four angular ranges from 29 to 41, 41 to 53, 53 to 67 and 67 to 82 degrees in the laboratory system. The results of the calculations are shown and discussed for these four angular ranges. The contributions from the evaporative and pre-equilibrium processes were analyzed in connection with different nucleus equilibration mechanisms.

The decay of ¹⁸Ne excited states into 2p+¹⁶O channel has been studied. The ¹⁸Ne secondary beam, at 33 AMeV incident energy, was produced by fragmentation of a primary ²⁰Ne beam at the LNS-FRIBs facility. Coulomb excitation on a ^natPb secondary target was found to be the main interaction process leading to the population of ¹⁸Ne excited levels. The two-proton decay of the 6.15 MeV (1^-) level has been detected, but in addition other high-lying states decaying via 2p emission were observed. A significant branching ratio of ²He decay has been deduced from the analysis of the relative angle and energy correlation spectra of the two protons emitted from the 6.15 MeV (1^-) state.

The longitudinal velocity and isotopic distributions of forward emitted fragments have been measured in the ¹¹B (32.9 AMeV) + ⁹Be (²⁷Al,¹⁹⁷Au) reactions. The range of isotopes from Helium to Nitrogen has been observed. The particular interest of this experiment has been to investigate the influence of direct and dissipative processes on the fragment production for different targets. The fast velocity component characterized by a Gaussian shape is rather well described in the frame of simple statistical fragmentation model, but with smaller value of the width of the distribution. Isotopic and velocity distributions have been compared to Universal Parameterization model implemented in the LISE + + code. Increased yields of ⁴He and ⁷Li isotopes are observed as a possible influence of the cluster structure of the ¹¹B nuclei on the total reaction mechanisms.

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collisions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay times of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emission time is found to be less than 40 fm/c.

We report the first results of a kinematically complete experiment on measurement of nd breakup reaction yield at neutron beam RADEX of Institute for Nuclear Research. In the experiment two neutrons are detected in geometry of neutron-neutron final-state interaction which allow one to determine the ¹S₀ neutron-neutron scattering length a_nn. Experimental dependence of the reaction yield on relative energy of two secondary neutrons was compared with predictions of Watson-Migdal theory. For ∆Θ=6° and E_n=40 MeV the value of neutron-neutron scattering length a_nn = -17.9 ± 1.0 fm is obtained. The further improving of experimental uncertainty will allow one to remove the existing difference of results obtained in various experiments.

Various aspects observed in the reactions ⁴⁰Ca+^40,48 Ca,⁴⁶Ti at E=25 MeV/nucleon, studied by means of the CHIMERA detector, will be discussed. An isospin effect on the competition between heavy residue production and binary-like channels has been observed in incomplete fusion events. From the thermodynamical point of view, kinetic energy spectra of protons emitted in fusion-evaporation events were fitted with two maxwellian functions. Despite of the different neutron richness of the populated sources, the average temperatures obtained for the quasi-fused systems are similar (T≃5.2MeV). We also performed a preliminary reconstruction of the excitation energy reached by quasi-fusion sources populated in the studied reactions.

The γp → η′p reaction was studied near the threshold, in the 1.44 GeV> E_γ < 1.55GeV energy range with the tagged photons of the former GRAAL experiment. The two neutral decays γγ(Γ_i/Γ = 2.10 ± 0.12%) and π⁰π⁰η(Γ_i/Γ = 20.7 ± 1.2%) were analized and preliminary results of the beam asymmetry were extracted together with the invariant masses.

High energy bremsstrahlung emission during spontaneous fission of ²⁵²Cf is observed. The new experimental method to detect rare coincident events by digital storage oscilloscope is used. The γ-rays with energies up to 60 MeV have been measured (by a BGO detector) in coincidence with neutrons detected by a plastic scintillator. The determination of γ-ray emission probability up to the value of about 8 × 10^-9event/(MeV × fission) at E_γ= 60 MeV is achieved.

We present the first results in our study of the bremsstrahlung emission of photons accompanying the spontaneous fission of the ²⁵²Cf nucleus. We compare calculations obtained on the basis of our fully quantum model with the experimental data available in literature for photon energies up to about 25 MeV. We find a well agreement between theory and experiment. The results of the bremsstrahlung emission accompanying the α-decay of the ²²⁶Ra nucleus, which has a relevant quadrupole deformation, are also included in the paper.

The preliminary results obtained by the GRAAL collaboration for the π⁰π⁺ photoproduction on the free and quasi-free proton (deuteron) at E_γ = 0.7-1.5 GeV are presented. The total cross section of the γp → π⁰π⁺n reaction and invariant mass spectra for the π⁺π⁰, π⁺n and π⁰n systems are presented in the photon energy range from 0.7 to 1.5 GeV. These results are in good agreement with the 2π-MAID calculations.

In the framework of a recently developed alpha-cluster model a nucleus is represented as a core (alpha-cluster liquid drop with dissolved excess neutron pairs in it) and a nuclear molecule on its surface. From analysis of experimental nuclear binding energies one can find the number of alpha-clusters in the molecule and calculate the nuclear charge radii. It was shown that for isotopes of one Z with growing A the number of alpha-clusters in the molecule decreases to three, which corresponds to the nucleus ¹²C for even Z and ¹⁵N for odd Z, and the specific density of the core binding energy ρ grows and reaches its saturation value. In this paper it is shown that the value ρ=2.55 MeV/fm³ explains the particular number of excess neutrons in stable nuclei.

The new applications of the three-dimensional tunnelling and time analysis to low-energy nuclear processes are presented. The three-dimensional tunnelling is strictly quantum-mechanical and considers the internal multiple reflections. The time analysis of the nucleon-nucleons scattering near a resonance, distorted by the non-resonant background, does show the solution in the L-system of the paradox of the delay-advance in the C-system.

The decay properties of nuclear unbound states formed in the reactions with three particles in the final state are reviewed. The modification of resonance parameters observed in these reactions and caused by the influence of the Coulomb field of accompanied particles is analyzed for the resonances with excitation energy near and far from the decay threshold.

A large set of experimental observables for the ²³²Th, ²³⁵U(α, xnf) reactions has been analyzed within the dynamic-statistical approach with allowance for the nuclear dissipation phenomenon, the double humped structure of fission barrier, and also the temperature damping of shell effects. The energy dependences of the lifetime effect (experimentally measured by the crystal blocking technique) along the corresponding data on the fission fragment angular anisotropy and also fission probabilities of U and Pu isotopes produced in the reactions were chosen for the analysis. Reliable information on the nuclear viscosity at the low excitation energies (< 30 MeV) was obtained.

In this contribution, results concerning different reaction channels for the collisions induced by the three Be isotopes, ^9,10,11Be, on a ⁶⁴Zn target at energies around the Coulomb barrier will be presented. The experiments with the radioactive ^10,11Be beams were performed at REX-ISOLDE (CERN) whereas the experiment with the stable weakly bound ⁹Be beam was performed at LNS Catania. Elastic scattering angular distributions have been measured for the three systems ^9,10,11Be + ⁶⁴Zn at the same center of mass energy. The angular distributions were analyzed with optical potentials and reaction cross sections were obtained from optical model calculations, performed with the code PTOLEMY. For the ¹¹Be + ⁶⁴Zn reaction, the break-up angular distribution was also measured.

The study of meson photoproduction on the nucleon is a very important tool to complete the puzzle of baryon excited states. GRAAL aim is the measurement of cross sections and of beam asymmetries for all the photonuclear reactions accessible in the energy range from 600 MeV up to 1.5 GeV. In the following preliminary results of the Σ beam asymmetry for ω photoproduction on the free proton in Hydrogen and on the quasi-free nucleon in Deuterium are shown. GRAAL is the first experiment in which both the charged and the radiative decay of ω meson are studied. Since the beam asymmetry is independent of the decay mode, the comparison of the results from the two channel allows an important check on data consistency. Results on the free proton are in good agreement with theoretical prediction from Zhao model and confirm the presence of P₁₃(1720) state. The analysis performed for the radiative decay is applied to the process of ω photoproduction on the quasi free nucleon in Deuterium.

It is developed a new approach to analyze the induced fission of heavy nuclei, which takes into account the nuclear dissipation phenomenon and the shell structure of nuclei in determination of fission barriers. The approach is based on the combined dynamical and statistical simulations. In the framework of this approach the method of calculation the fission fragment angular distributions in a wide energy range is discussed. The ability of the method is demonstrated in the simultaneous description of the experimental data of the fission probabilities on the Am and Pu nuclei, yields of the spontaneous fission of isomers for the α + ²³⁸U reaction at E_α = (20 - 32) MeV and the d + ^242,240Pu reactions at E_d = (20 - 30) MeV, the fission times for the α + ²³⁸U reaction and angular distribution of fission fragments for the α + ²³⁸U, ²³⁷Np reactions at E_α = (20 - 100) MeV. A further information on the value of the nuclear dissipation at low excitation energies is obtained. In addition, it is demonstrated that the influence of the shell effects on the deformation potential energy holds up to excitation energies of about (50 - 60) MeV.