We study the Bjorken x dependence of the virtual photon spin asymmetry in polarized deep inelastic scattering of electrons from hadrons. We use an exactly solved relativistic potential model of the hadron, treating the constituents as independent massless Dirac particles bound to an infinitely massive force center. The potential is chosen to have spin symmetry and a linear radial dependence with spherical symmetry. The effect of interactions of the struck constituent with the remainder of the target on the longitudinal photon asymmetry is demonstrated. In particular, the small-x suppression of the photon asymmetry observed in polarized deep inelastic scattering from the proton is shown to be a consequence of these interactions. The effect of p-wave components of the Dirac wave function, long known to give an important contribution to the spin of hadrons, is explicitly demonstrated through their interference with the s-wave term.

A variational Monte Carlo (VMC) calculation for the binding energy $B_{\Lambda \Lambda }$ of the lightest hypernucleus ${}_{\Lambda }{}_{\Lambda }^{4}H$ has been performed in the four-body $\Lambda \Lambda pn$ model. A range of input $\Lambda \Lambda$ potentials of moderate strength produce a particle-stable ${}_{\Lambda }{}_{\Lambda }^{4}H$ for the simulated NSC97e and f $\Lambda N$ potentials, whereas the phenomenological Minnesota $\Lambda N$ potential needs a much stronger $\Lambda \Lambda$ potential to bind. The VMC results for $B_{\Lambda \Lambda }$ agree with the prediction of the stochastic variational model but contradict the recent Faddeev-Yakubovsky calculation. As reported earlier, $B_{\Lambda \Lambda }$ is sensitive to the triplet $\Lambda N$ channel for a given $\Lambda \Lambda$ potential. The $B_{\Lambda \Lambda }$ of ${}_{\Lambda }{}_{\Lambda }^{4}H$ in the three-body $\Lambda \Lambda d$ cluster model is consistent with but slightly lower than the Faddeev calculation. The VMC method predicts a stable ${}_{\Lambda }{}_{\Lambda }^{4}H$ system in both models and thus offers the possibility of identifying ${}_{\Lambda }{}_{\Lambda }^{4}H$ in a future extension of E906 or of a related experiment at KEK, provided the simulated potentials are true representations of realistic Nijmegen potentials.

The present study is both a reanalysis and an extension of the approach initiated by S. Eremin and S. Voloshin [Phys. Rev. C, 67, 064905 (2003)]. We attempt to interpret here the rapidity spectra of the various particles produced in both $\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{Au}+\mathrm{Au}$ collisions at SPS-CERN (Super Proton Synchrotron at Conseil Européen pour la Recherche Nucléaire) and RHIC-BNL (Relativistic Heavy Ion Collider at Brookhaven National Laboratory). The study made here is wider in scope and is more species specific than earlier ones, and the results obtained here are compared with those found in previous works based on HIJING, VENUS, etc., at various centralities. The study reconfirms that the constituent parton picture of the particles provides a better and more unified description of the rapidity-density yields for the various secondaries, including some light cluster particles such as deuteron, even in heavy ion collisions.

Using an angular-momentum-projected single-particle basis, a proton-neutron quasiparticle random-phase approximation approach is used to study the $2\nu \beta \beta$ properties of 10 isotopes, exhibiting various quadrupole deformations. The parent and daughter nuclei exhibit different quadrupole deformations. Since the projected basis enables a unified description of deformed and spherical nuclei, situations where the nuclei involved in the double β decay process are both spherical, both deformed, or one spherical and the other deformed can be treated through a single formalism. Dependence of single ${\beta }^{-}$ and ${\beta }^{+}$ strength distribution on atomic mass number and nuclear deformation is analyzed. For the double β decay process, the Gamow-Teller transition amplitudes and half-lives are calculated. Results are compared with experimental data as well as with predictions of other theoretical approaches. The agreement between the present results and experimental data is fairly good.

Hadron production at forward rapidities in $d+\mathrm{Au}$ collisions is studied in the framework of parton recombination in the final state. Multiple scattering and gluon saturation in the initial state are not explicitly considered. The recombination of soft and shower partons is found to be important. The soft parton densities are determined by extrapolation from the parametrization fixed at $\eta =0$ with no unconstrained adjustments. The suppression of $R_{\mathrm{CP}}$ observed at high η is understood as the simple consequence of the reduction of the soft parton density on the deuteron side compared to that on the gold side. The effect of momentum degradation responsible for baryon stopping is also considered. The asymmetry of backward-to-forward spectra can be reproduced within the same framework without any change in the basic physics.

We have measured the neutron energy spectrum of the ${}^{18}\mathrm{O}$($p,n$)${}^{18}\mathrm{F}$ reaction at a proton energy of 2582 keV, 8 keV above the reaction threshold. At this energy the resulting neutron spectrum resembles almost perfectly a Maxwellian distribution at a thermal energy of $\mathrm{kT}=5.1\pm 0.1\mathrm{keV}$. Since all neutrons are emitted in a forward cone of 140${}^{\circ }$ opening angle, this reaction can be used for neutron activation measurements similar to the ${}^7\mathrm{Li}$(p,n)${}^7\mathrm{Be}$ reaction, which is known for producing a thermal spectrum with $\mathrm{kT}=25\mathrm{keV}$. Measured neutron capture cross sections at $\mathrm{kT}=5.1\mathrm{keV}$ and $\mathrm{kT}=25\mathrm{keV}$ can be used to interpolate to $\mathrm{kT}=8\mathrm{keV}$, which characterizes the dominant neutron exposure during s-process nucleosynthesis in thermally pulsing low-mass AGB stars. In a first application of this new method the Maxwellian-averaged neutron capture cross section of ${}^{138}\mathrm{Ba}$ was measured to be $〈\sigma v〉/v_T=13.0\pm 0.5\mathrm{mb}$ at $\mathrm{kT}=5.1\mathrm{keV}$.

The ratios of the yields of primary charged antiparticles to particles have been obtained for pions, kaons, and protons near midrapidity for $p+p$ collisions at $\sqrt{s_{NN}}=200\text{GeV}$. Ratios of $\langle {\pi }^{-}/{\pi }^{+}\rangle =1.000\pm 0.012$ (stat.) $\pm 0.019$ (syst.), $\langle K^{-}/K^{+}\rangle =0.93\pm 0.05$ (stat.) $\pm 0.03$ (syst.), and $\langle \overline{p}/p\rangle =0.85\pm 0.04$ (stat.) $\pm 0.03$ (syst.) have been measured. The reported values represent the ratio of the yields averaged over the rapidity range of $0.1<y_{\pi }<1.3$ and $0<y_{K,p}<0.8$, and for transverse momenta of $0.1<p_T^{\pi ,K}<1.0\text{GeV}/c$ and $0.3<p_T^p<1.0\text{GeV}/c$. Within the uncertainties, all three ratios are consistent with the values measured in $d+\mathrm{Au}$ collisions at the same energy. The data are compared to results from other collision systems and energies.

Cross sections for the charge-exchange reaction $(d,{}^2\mathrm{He})$ on ${}^{50}\mathrm{V}$, the only odd-odd stable nucleus in the $pf$ shell, have been measured at an incident energy of 171 MeV. The two correlated protons of the unbound ${}^2\mathrm{He}$ system were both momentum analyzed and detected by the same spectrometer and detector. Measurements have been carried out at forward center-of-mass angles up to 6°. The $\mathrm{GT}{}^{+}$ strength distribution has been extracted up to about 12 MeV of excitation energy. Because charge-exchange reactions from ${}^{50}\mathrm{V}$ provide a unique opportunity to probe Gamow-Teller response from an odd-odd nucleus of the $pf$ shell, the present study serves as important test case for model calculations and astrophysical processes that proceed through GT-type transitions. Consequently, the experimental result is compared with a large-scale shell-model calculation, and the implications for electron-capture processes in presupernova environments are discussed.

The peripheral heavy-ion collisions of ${}^{112,124}\mathrm{Sn}+{}^{86}\mathrm{Kr}$ at $E_b=25A$ MeV are studied by means of the improved quantum molecular dynamics model (ImQMD). It is shown that the slope of the average N/Z ratio of emitted nucleons versus impact parameters for these reactions is very sensitive to the density dependence of the symmetry energy. Our study also shows that the yields of ${}^3\mathrm{H}$ and ${}^3\mathrm{He}$ decrease with impact parameters and that the slope of the yield of ${}^3\mathrm{H}$ versus impact parameters as well as the ratio of $Y({}^3\mathrm{H})/Y({}^3\mathrm{He})$ depends strongly on the symmetry potential for peripheral heavy-ion collisions.

A multichannel R-matrix formalism was used to fit ${}^{21}\mathrm{Na}+$ p resonant elastic and inelastic scattering data taken at the TRIUMF UK detector array facility at TRIUMF-ISAC. Five resonances were observed corresponding to states in ${}^{22}\mathrm{Mg}$ above the proton threshold. Four of these corresponded to states seen in previous transfer reaction studies where firm spin-parity assignments could not be made. One new resonance, previously unobserved in any reaction, was also seen. Where possible, resonance energies, partial widths, and spin-parity values of these resonances were extracted. The correspondence between these states and possible analogs in the mirror nucleus ${}^{22}\mathrm{Ne}$ is discussed, as well as the relation to $T=1$ states in the nucleus ${}^{22}\mathrm{Na}$.

The $3\alpha$ resonance states in ${}^{12}\mathrm{C}$ are investigated by using the method of analytic continuation in the coupling constant combined with the complex scaling method (ACCC+CSM). We obtain a new $0^{+}$ resonance state with energy $E_r=1.66$ MeV and width $\Gamma =1.48$ MeV, which is of interest as a candidate for the recently observed $0^{+}$ state at $E_x=10.3$ MeV.

Very neutron-deficient francium and radium isotopes have been produced in fusion evaporation reactions using ${}^{63}\mathrm{Cu}$ and ${}^{65}\mathrm{Cu}$ ions on ${}^{141}\mathrm{Pr}$ targets and ${}^{36}\mathrm{Ar}$ ions on ${}^{170}\mathrm{Yb}$ targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam. The activities were implanted into a position-sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and decays. Two new α decaying radium isotopes, ${}^{201}\mathrm{Ra}$ and ${}^{202}\mathrm{Ra}$, were identified. The α decay energy and half-life of ${}^{203}\mathrm{Ra}$ were measured with improved precision. The α decay properties measured for the francium isotopes ${}^{201}\mathrm{Fr},{}^{202}\mathrm{Fr},{}^{203}\mathrm{Fr}$, and ${}^{204}\mathrm{Fr}$ were confirmed, in many cases with improved precision. For the first time, a $(\pi s_{1/2}^{-1})1/2^{+}$ proton intruder state was identified in francium isotopes, namely in ${}^{201}\mathrm{Fr}$ and tentatively in ${}^{203}\mathrm{Fr}$. The measured decay properties for the neutron-deficient odd-mass Fr isotopes suggest an onset of substantial deformation at $N=112$.

A systematic study of terminating states in the $A~50$ mass region using the self-consistent Skyrme-Hartree-Fock model is presented. The objective of this study is to demonstrate that the terminating states, due to their intrinsic simplicity, offer unique and so far unexplored opportunities to study different aspects of the effective NN interaction or nuclear local energy density functional. In particular, we show that the agreement of the calculations to the data depends on the spin fields and the spin-orbit term which, in turn, allows us to constrain the appropriate Landau parameters and the strength of the spin-orbit potential. The present study reveals that the structure and energy of terminating states can be used as a tool to differentiate among the many Skyrme force parametrizations.

The heavy ion cross section for continuum $e^{+}{e}^{-}$ pair production has been calculated to all orders in $Z\alpha$. The formula resulting from an exact solution of the semiclassical Dirac equation in the ultrarelativistic limit is evaluated numerically. An energy-dependent spatial cutoff of the heavy ion potential is used, leading to an exact formula agreeing with the known perturbative formula in the ultrarelativistic, perturbative limit. Cross sections and sample momentum distributions are evaluated for heavy ion beams at SPS, RHIC, and LHC energies. $e^{+}{e}^{-}$ pair production probabilities are found to be reduced from perturbation theory with increasing charge of the colliding heavy ions and for all energy and momentum regions investigated.

We have measured the energy spectra of pions and protons emitted in the weak decay of ${}^{\Lambda }{}_{12}\mathrm{C}$, ${}^{\Lambda }{}_{28}\mathrm{Si}$, and ${}^{\Lambda }{}_{}\mathrm{Fe}$ hypernuclei produced via the $({\pi }^{+},K^{+})$ reaction. The decay widths of the ${\pi }^{-}$ mesonic decay $(\Lambda \to p{\pi }^{-})$ and the nonmesonic decay $(\Lambda N\to NN)$ were extracted. The present results demonstrate an increase of the mesonic decay width due to a distortion of the pion wave function in nuclear medium for the first time. The ratios of the neutron- to proton-induced nonmesonic decay widths, ${\Gamma }_n(\Lambda n\to nn)/{\Gamma }_p(\Lambda p\to np)$, were evaluated by a direct comparison of the measured proton energy spectra with the calculated ones. No theoretical calculation which has been proposed so far can simultaneously account for both the nonmesonic decay widths and the ${\Gamma }_n/{\Gamma }_p$ ratios in the present data.

Leading-order three-nucleon forces that violate isospin symmetry are calculated in heavy-baryon chiral perturbation theory. The effect of the charge-symmetry-breaking three-nucleon force is investigated in the trinucleon systems using Faddeev calculations. We find that the contribution of this force to the ${}^3\mathrm{He}-{}^3\mathrm{H}$ binding-energy difference is given by $\Delta E_{3\mathrm{NF}}^{\mathrm{CSB}}\approx 5$ keV.

The differential np scattering cross section has been measured at 96 MeV in the angular range ${\theta }_{c.m.}={20}^{°}$–${76}^{°}$. Together with an earlier data set at the same energy, covering the angles ${\theta }_{c.m.}={74}^{°}$–${180}^{°}$, a new data set has been formed in the angular range ${\theta }_{c.m.}={20}^{°}$–${180}^{°}$. This extended data set has been normalized to the experimental total np cross section, resulting in a renormalization of the earlier data of 0.7%, which is well within the reported normalization uncertainty for that experiment. A novel normalization technique has been investigated. The results on forward np scattering are in reasonable agreement with theory models and partial wave analyses and have been compared with data from the literature.

The Hartree-Fock-Bogoliubov method implemented with the Gogny-D1S force and used in a systematic study of the even-even $N=16$ isotones from stability to the neutron drip line strongly suggests that a subshell gap, approximately 4 MeV wide, is opening at $N=16$. The first $2^{+}$ levels as well as $B(E2;0_{\mathrm{gs}}^{+}\to 2^{+})$ reduced $E2$ transition probabilities have also been predicted in configuration mixing and standard random phase approximation calculations using D1S. These results compare favorably with experimental information available for the $Z=10–18$ nuclei and with expectations for ${}^{24}\mathrm{O}$ properties. They also fully support our mean-field predictions, namely that $N=16$ is a spherical magic number at the oxygen neutron drip line.