An extrapolation method in shell model calculations with a deformed basis is presented, which uses a scaling property of energy and energy variance for a series of systematically approximated wave functions to the true one. Such approximated wave functions are given by the variation-after-projection method concerning the full angular momentum projection. This extrapolation needs energy variance, which amounts to calculation of the expectation value of the square of the Hamiltonian ${\widehat{H}}^2$. We present a method to evaluate this matrix element and show that a large reduction of its numerical computation can be done by taking advantage of time-reversal symmetry. The numerical tests are presented for $fp$-shell calculations with a realistic residual interaction.

We study the evolution of charmonia as they collide with the constituents of the fireball produced in high-energy nucleus-nucleus collisions. The latter evolves in a manner controlled by the equation of state as given by lattice QCD, and is constructed in such a way that the observed hadronic spectra are correctly reproduced. A kinetic description of charmonium interactions with both quark-gluon and hadronic degrees of freedom allows us to study in detail the evolution in different regimes, controlled by collision energy, kinematics, and geometry. The data collected at the CERN-SPS accelerator are well described and new estimates for $J∕\psi$ production at BNL-RHIC are presented.

We investigate the relation between the $\eta \text{−}{}^3\mathrm{H}\mathrm{e}$ binding energy and width and the (complex) $\eta \text{−}{}^3\mathrm{H}\mathrm{e}$ scattering length. Following our systematic analysis of the $\eta \text{−}{}^3\mathrm{H}\mathrm{e}$ scattering length we set limits on the $\eta \text{−}{}^3\mathrm{H}\mathrm{e}$ binding. If bound states exist the binding energy (width) should not exceed $5\mathrm{MeV}$ $\left(10\mathrm{MeV}\right)$. In addition, we comment on a recently claimed observation of an $\eta$ mesic ${}^3\mathrm{H}\mathrm{e}$ quasibound state by the TAPS collaboration based on $\eta$ photoproduction data. Although our limits are in reasonable agreement with the values reported by this collaboration, our analysis of these data does not lead to a solid conclusion concerning the existence of an $\eta$-mesic bound state. More dedicated experiments are necessary for further clarification.

Cross sections for the dipole radiative capture reactions ${}^7\mathrm{Li}(n,\gamma ){}^8\mathrm{Li}$ and ${}^7\mathrm{Be}(p,\gamma ){}^8\mathrm{B}$ are calculated in a two-body model, which is based on a Woods-Saxon parametrization of the nuclear interaction. The well depth is adjusted for each reaction channel so that the measured separation energies and $s$-wave scattering lengths are reproduced. The calculations are repeated for a wide range of the radius and the diffuseness of the interaction. The predicted $S$ factor for the radiative proton capture on ${}^7\mathrm{Be}$ falls within a surprisingly narrow range of values when the model is calibrated to reproduce measurements of the mirror reaction ${}^7\mathrm{Li}(n,\gamma ){}^8\mathrm{Li}$. The simplified model used here is consistent with the shell model approach for proton capture on ${}^7\mathrm{Be}$ but it gives a significantly smaller cross section for neutron capture on ${}^7\mathrm{Li}$.

Several recent studies have dealt with the effects of short-range correlations on the momentum distribution of nucleons in nuclei. Here we investigate the correlation effects on the density and spectral distribution in coordinate space. A combination of experimental data and spectral functions calculated from realistic nucleon-nucleon interactions allows us to resolve a recently uncovered discrepancy with occupation of quasiparticle states derived from $(e,e^{\prime }p)$ data.

We extract values for the free symmetry energy as a function of the fragment size (the proton number $Z$) from antisymmetrized molecular dynamics calculations of calcium collisions. Simple statistical physics describe well the distribution of hot nuclei at breakup, provided the surface symmetry term in the free energy is much smaller at high excitation than in ground state nuclei. This result may reflect the condition of low density and finite temperature when these systems disassemble.

Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken. The decay constants of their radial excitations vanish. These features and aspects of their impact on the meson spectrum are illustrated using a manifestly covariant and symmetry-preserving model of the kernels in the gap and Bethe-Salpeter equations.

The masses of the radioactive nuclei and have been measured with the Canadian Penning trap on-line mass spectrometer to a precision of and , respectively. A value of for the superallowed decay of is obtained from the difference of these two masses. With this precise value, the value for this decay is determined with improved precision and is found to be consistent with the existing precision data set of superallowed Fermi emitters. This provides an important test of the isospin symmetry-breaking corrections. If the mass of determined here is used in the calibration of a recent measurement, part of the discrepancy observed in that measurement is removed.

The chiral SU(3) quark model is extended to include an antiquark in order to study the kaon-nucleon system. The model input parameters $b_u,m_u,m_s$ are taken to be the same as in our previous work which focused on the nucleon-nucleon and nucleon-hyperon interactions. The mass of the scalar meson $\sigma$ is chosen to be 675 MeV and the mixing of ${\sigma }_0$ and ${\sigma }_8$ is considered. Using this model the kaon-nucleon $S$ and $P$ partial waves phase shifts of isospin $I=0$ and $I=1$ have been studied by solving a resonating group method equation. The numerical results of $S_{01},S_{11},P_{01},P_{03}$, and $P_{11}$ partial waves are in good agreement with the experimental data while the phase shifts of $P_{13}$ partial wave are a little bit too repulsive when the laboratory momentum of the kaon meson is greater than 500 MeV in this present calculation.

The odd-odd ${}^{146}\mathrm{Tb}$ nucleus has been investigated using the ${}^{115}\mathrm{In}({}^{34}\mathrm{S},3n)$ reaction at 140 MeV incident energy using an array of eight Compton-suppressed Clover detectors. Based on the observed $\gamma \text{−}\gamma$ coincidences, the level structure of ${}^{146}\mathrm{Tb}$ has been extended up to $E_x\sim 10\mathrm{MeV}$. Linear polarization measurements have been combined with angular correlations of the observed $\gamma$ rays to assign the electromagnetic nature to the transitions. Probable origin of a cascade of $M1$ transitions observed around 8 MeV excitation energy has been discussed.

The first exclusive breakup measurements for the nucleus ${}^9\mathrm{Be}$ are presented. Breakup via several discrete states is observed following scattering off ${}^{12}\mathrm{C}$ and ${}^{208}\mathrm{Pb}$. The results support the prediction of a recent microscopic cluster calculation for a strong $n+{}^8\mathrm{Be}\left(2^{+}\right)$ state component in the second excited state.

The paper is devoted to the experimental determination of the space-time characteristics for the target multifragmentation in $p\left(8.1\mathrm{GeV}\right)+\mathrm{Au}$ collisions. The experimental data on the fragment charge distribution and kinetic energy spectra are analyzed within the framework of the statistical multifragmentation model. It is found that the partition of hot nuclei is specified after expansion of the target spectator to a volume equal to $V_t=(2.9\pm 0.2)V_o$, with $V_o$ as the volume at normal density. However, the freezeout volume is found to be $V_f=(11\pm 3)V_o$. At freezeout, all the fragments are well separated and only the Coulomb force should be taken into account. The results are in accordance with a scenario of spinodal disintegration of hot nuclei.

It is shown that the dilute density distribution of $\alpha$ particles in nuclei can be observed in the Airy structure in nuclear rainbow scattering. We have analyzed $\alpha +{}^{12}\mathrm{C}$ rainbow scattering to the $0_2^{+}\left(7.65\mathrm{MeV}\right)$ state of ${}^{12}\mathrm{C}$ in a coupled-channel method with the precise wave functions for ${}^{12}\mathrm{C}$. It is found that the enhanced Airy oscillations in the experimental angular distributions for the $0_2^{+}$ state is caused by the dilute density distribution of this state in agreement for the idea of Bose-Einstein condensation of the three alpha particles.

Two recent experiments yield conflicting results on the possibility of a low-lying $1∕2^{-}$ state in ${}^7\mathrm{He}$ at $E_n^{\mathrm{c.m.}}\sim 1\mathrm{MeV}$. A calculation with the recoil corrected continuum shell model reproduces this state as well as results that are compatible with the data from both reports, but only with the conclusion of one.

The polarized longitudinal-transverse structure function ${\sigma }_{L{T}^{\prime }}$ has been measured using the $p\left(\vec{e},e^{\prime }{\pi }^{+}\right)n$ reaction in the $\Delta \left(1232\right)$ resonance region at $Q^2=0.40$ and $0.65{\mathrm{GeV}}^2$. No previous ${\sigma }_{L{T}^{\prime }}$ data exist for this reaction channel. The kinematically complete experiment was performed at the Jefferson Lab with the CEBAF large acceptance spectrometer using longitudinally polarized electrons at an energy of $1.515\mathrm{GeV}$. A partial-wave analysis of the data shows generally better agreement with recent phenomenological models of pion electroproduction compared to the previously measured ${\pi }^{0}p$ channel. A fit to both ${\pi }^{0}p$ and ${\pi }^{+}n$ channels using a unitary isobar model suggests the unitarized Born terms provide a consistent description of the nonresonant background. The $t$-channel pion pole term is important in the ${\pi }^{0}p$ channel through a rescattering correction, which could be model dependent.

We show that the cross sections of the ${\mathrm{\Theta }}^{+}$-pentaquark production in different processes decrease with energy faster than the cross sections of production of the conventional three-quark hyperons. Therefore, the threshold region with the initial energy of a few GeV or less seems to be more favorable for the production and experimental study of ${\mathrm{\Theta }}^{+}$ pentaquark.

New shell model Hamiltonians are derived for the $T=1$ part of the residual interaction in the $f_{5∕2}{p}_{3∕2}{p}_{1∕2}{g}_{9∕2}$ model space based on the analysis and fit of the available experimental data for ${}_{28}{}^{57}\mathrm{Ni}_{29}–{}_{28}{}^{78}\mathrm{Ni}_{50}$ isotopes and ${}_{29}{}^{77}\mathrm{Cu}_{50}–{}_{50}{}^{100}\mathrm{Sn}_{50}$ isotones. The fit procedure, properties of the determined effective interaction as well as new results for valence-mirror symmetry and seniority isomers for nuclei near ${}^{78}\mathrm{Ni}$ and ${}^{100}\mathrm{Sn}$ are discussed.

The grand canonical ensemble has been used to make predictions for composite yields using simple models for nuclear fragmentation. While this gives correct model prediction for high energy collisions, it can give very inaccurate results at intermediate energy.

This paper was published online on 28 September 2004 with two typographical errors. In the first column of page 3, the first line should read “…at a scale of $1\mathrm{GeV}$, and…”. In the second column of page 5, the second line beneath Eq. (37) should read “The mixing formula (37)…”. The paper has been corrected as of 1 October 2004. The text is correct in the printed version of the journal.

The nucleus ${}^{98}\mathrm{Ru}$, the lightest collective $\mathrm{Ru}$ isotope with $N>50$, has been studied employing the $\left(\alpha ,2n\right)$ reaction using YRAST Ball detectors. The new data, as well as a systematic set of limits on the intensities of unobserved transitions, reveal a structure that resembles a near harmonic vibrator spectrum up through the two-phonon triplet but show an almost complete breakdown of vibrator structure thereafter. These results are not understood theoretically and are at variance with previous interpretations of this nucleus. A rare anomaly in yrast $B\left(E2\right)$ values is also pointed out.