The energies of the ground and excited $2^{+}$ states of ${}_{\Lambda \Lambda }^{10}\mathrm{Be}$ have been calculated variationally in the Monte Carlo framework. The hypernucleus is treated as a partial ten-body problem in the $\Lambda \Lambda +\alpha \alpha$ model where nucleonic degrees of freedom of $\alpha$'s are taken into consideration ignoring the antisymmetrization between two $\alpha$'s. The central two-body $\Lambda N$ and $\Lambda \Lambda$ and the three-body dispersive and two-pion exchange $\Lambda \mathit{NN}$ forces, constrained by the $\Lambda p$ scattering data and the observed ground state energies of ${}_{\Lambda }^5\mathrm{He}$ and ${}_{\Lambda \Lambda }^6\mathrm{He}$, are employed. The product-type trial wave function predicts binding energy for the ground state considerably less than for the event reported by Danysz et al.; however, it is consistent with the value deduced assuming a $\gamma$ ray of 3.04 MeV must have escaped undetected in the decay of the product ${}_{\Lambda }^9\mathrm{Be}{}^{*}\hspace{0.5em}\to \hspace{0.5em}{}_{\Lambda }^9\mathrm{Be}+\gamma$ of the emulsion event ${}_{\Lambda \Lambda }^{10}\mathrm{Be}\to \hspace{0.5em}{\pi }^{-}+p+{}_{\Lambda }^9\mathrm{Be}{}^{*}$ and for the excited $2^{+}$ state closer to the value measured in the Demachi-Yanagi event. The hypernucleus ${}_{\Lambda \Lambda }^{10}\mathrm{Be}$ has an oblate shape in the excited state. These results are consistent with the earlier four-body $\alpha$ cluster model approach where $\alpha$'s are assumed to be structureless entities.

Gamma rays from ${}^{52}\mathrm{Ti}$ have been studied with Gammasphere and the Fragment Mass Analyzer using reactions induced by a ${}^{48}\mathrm{Ca}$ beam on a ${}^9\mathrm{Be}$ target. The data have been used in combination with information from deep-inelastic reactions of ${}^{48}\mathrm{Ca}$ beams on a thick ${}^{238}\mathrm{U}$ target at an energy about $25\%$ above the Coulomb barrier. The ${}^{52}\mathrm{Ti}$ level scheme was expanded considerably, and the lifetimes of some of the identified states were determined for the first time. The excitation of two protons and two neutrons outside the ${}^{48}\mathrm{Ca}$ core provide new tests of effective interactions in the full $\mathit{pf}$-shell model space. The positive-parity states in ${}^{52}\mathrm{Ti}$ were compared to theoretical predictions obtained with the GXPF1A, FPD6, and KB3G effective interactions. The comparisons favor, to a degree, the results computed with the GXPF1A interaction.

Differential cross sections and complete sets of polarization observables are presented for the Gamow-Teller ${}^{12}\mathrm{C}(\overrightarrow{p},\overrightarrow{n}){}^{12}\mathrm{N}(\mathrm{g}.\mathrm{s}.,1^{+})$ reaction at a bombarding energy of 296 MeV with momentum transfers $q$ of 0.1 to $2.2\hspace{0.5em}{\mathrm{fm}}^{-1}$. The polarization transfer observables are used to deduce the spin-longitudinal cross section, ${\mathit{ID}}_q$, and spin-transverse cross sections, ${\mathit{ID}}_p$ and ${\mathit{ID}}_n$. The data are compared with calculations based on the distorted-wave impulse approximation (DWIA) using shell-model wave functions. Significant differences between the experimental and theoretical results are observed for all three spin-dependent ${\mathit{ID}}_i$ at momentum transfers of $q\gtrsim 0.5\hspace{0.5em}{\mathrm{fm}}^{-1}$, suggesting the existence of nuclear correlations beyond the shell model. We also performed DWIA calculations employing random-phase approximation (RPA) response functions and found that the observed discrepancy is partly resolved by the pionic and ρ-mesonic correlation effects.

The Hartree-Fock approximation to the many-fermion problem can break exact symmetries, and in some cases by changing a parameter in the interaction one can drive the Hartree-Fock minimum from a symmetry-breaking state to a symmetry-conserving state (also referred to as a “phase transition” in the literature). The order of the transition is important when one applies the random-phase approximation (RPA) to the of the Hartree-Fock wave function: if first order, RPA is stable through the transition, but if second-order, then the RPA amplitudes become large and lead to unphysical results. The latter is known as “collapse” of the RPA. While the difference between first- and second-order transitions in the RPA was first pointed out by Thouless, we present for the first time nontrivial examples of both first- and second-order transitions in a uniform model, the interacting shell-model, where we can compare to exact numerical results.

High-spin states in the neutron-rich nucleus ${}^{185}\mathrm{Ta}$, populated in the decay of a long-lived, three-quasiparticle state, have been studied using deep-inelastic reactions with ${}^{136}\mathrm{Xe}$ ions and a ${}^{186}\mathrm{W}$ target. The lifetime of the isomer has been measured as 17(2) ms and the spin and parity determined to be $K^{\pi }=21/2^{-}$, leading to a $\pi 7/2^{+}[404]\nu 3/2^{-}[512]11/2^{+}[615]$ configuration assignment. The isomer decays into the rotational band built upon the $\pi 9/2^{-}[514]$ intrinsic state via $K$-forbidden transitions with reduced hindrances of 52 and 71. The $\pi 9/2^{-}[514]$ state is itself an isomer with a lifetime of 17(3) ns. It decays via $K$-allowed $E1$ transitions to states in the $\pi 7/2^{+}[404]$ band with strengths that are similar to equivalent transitions in the lighter tantalum isotopes.

Evolution of the nuclear shapes and deformations under the influence of temperature and rotation is investigated in Te isotopes with neutron number ranging from the proton drip line to the stability valley. Spin dependent critical temperatures for the shape transitions in Te nuclei are computed. Shape transitions from prolate at low temperature and spin to oblate via triaxiality are seen with increasing neutron number and spin.

We suggest two new representations of the data on rotational nuclei. The first is reference-free and the second arises from a natural reference related to the variable moment of inertia model parameters of the ground-state band of the system. As such, neither representation contains any free parameters. By defining a “configuration spin” we show how a new ground-state band reference can be applied. Its use allows a complete description of the changes associated with the first, and higher, band crossings. We apply these new representations to discuss the nature of the first band crossing along even-even isotopic chains in the erbium and osmium isotopes and to odd-even nuclei in the vicinity of ${}^{158}\mathrm{Er}$.

We calculate nuclear cross sections on excited nuclei in the fast neutron energy range. We partition the whole process into two contributions: the direct reaction part and the compound nuclear reactions. A coupled-channels method is used for calculating the direct transition of the nucleus from the initial excited state, which is a member of the ground-state rotational band, to the final ground and excited low-lying levels. This process is strongly affected by the channel coupling. The compound nuclear reactions on the excited state are calculated with the statistical Hauser-Feshbach model, with the transmission coefficients obtained from the coupled-channels calculation. The calculations are performed for a strongly deformed nucleus ${}^{169}\mathrm{Tm}$, and selected cross sections for the ground and first excited states are compared. The calculation is also made for actinides to investigate possible modification to the fission cross section when the target is excited. It is shown that both the level coupling for the entrance channel, and the different target spin, change the fission cross section.

High-energy $\gamma$ rays and light charged particles from the ${}^{36}\mathrm{Ar}+{}^{96}\mathrm{Zr}$ and ${}^{40}\mathrm{Ar}+{}^{92}\mathrm{Zr}$ reactions at $E_{\mathrm{lab}}=16$ and 15.1 MeV/nucleon, respectively, were measured in coincidence with evaporation residues by means of the MEDEA multidetector array coupled to four parallel plate avalanche counters. The aim of this experiment was to investigate the prompt $\gamma$ radiation, emitted in the decay of the dynamical dipole mode, in the $~16$ MeV/nucleon energy range and to map its beam energy dependence, comparing the present results with our previous ones obtained at lower energies. The studied reactions populate, through entrance channels having different charge asymmetries, a compound nucleus in the region of Ce under the same conditions of excitation energy and spin. Light charged particle energy spectra were used to pin down the average excitation energy and the average mass of the system. By studying the $\gamma$-ray spectra of the charge symmetric reaction ${}^{40}\mathrm{Ar}+{}^{92}\mathrm{Zr}$, the statistical giant dipole resonance (GDR) parameters and angular distribution were extracted, and a comparison of the linearized ${90}^{°}\gamma$-ray spectra of the two reactions revealed a 12% extra yield in the GDR energy region for the more charge asymmetric system. The center-of-mass angular distribution data of this extra $\gamma$ yield, compatible with a dipole oscillating along the symmetry axis of the dinuclear system, support its dynamical nature. The experimental findings are compared with theoretical predictions performed within a Boltzmann-Nordheim-Vlasov transport model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics. An interesting sensitivity to the symmetry term of the equation of state and to in-medium effects on nucleon-nucleon ($\mathit{nn}$) cross sections is finally discussed.

Forward recoil ranges of heavy reaction products have been measured to disentangle full and/or partial linear momentum transfer events in the ${}^{16}\mathrm{O}+{}^{169}\mathrm{Tm}$ system at $E_{\mathrm{proj}}\approx 76$ and 81 MeV. The experimentally measured forward recoil ranges of complete and/or incomplete fusion products are found to be in satisfactory agreement with that estimated using range-energy formulations. The angular distributions of several heavy reaction products have also been measured at $E_{\mathrm{proj}}\approx 81$ MeV to get complementary information about incomplete fusion. To figure out the influence of incomplete fusion on complete fusion at such low projectile energies, the relative strengths of their contributions in $\alpha$-emitting channel(s) have been deduced from the measurement of recoil range distributions.

We report the observation at the Relativistic Heavy Ion Collider of suppression of back-to-back correlations in the direct photon+jet channel in $\mathrm{Au}+\mathrm{Au}$ relative to $p+p$ collisions. Two-particle correlations of direct photon triggers with associated hadrons are obtained by statistical subtraction of the decay photon-hadron ($\gamma \text{−}h$) background. The initial momentum of the away-side parton is tightly constrained, because the parton-photon pair exactly balance in momentum at leading order in perturbative quantum chromodynamics, making such correlations a powerful probe of the in-medium parton energy loss. The away-side nuclear suppression factor, $I_{\mathrm{AA}}$, in central $\mathrm{Au}+\mathrm{Au}$ collisions, is $0.32\pm 0.{12}^{\mathrm{stat}}\pm 0.{09}^{\mathrm{syst}}$ for hadrons of $3<p_T^h<5$ in coincidence with photons of $5<p_T^{\gamma }<15$ GeV/$c$. The suppression is comparable to that observed for high-$p_T$ single hadrons and dihadrons. The direct photon associated yields in $p+p$ collisions scale approximately with the momentum balance, $z_T\equiv p_T^h/p_T^{\gamma }$, as expected for a measurement of the away-side parton fragmentation function. We compare to $\mathrm{Au}+\mathrm{Au}$ collisions for which the momentum balance dependence of the nuclear modification should be sensitive to the path-length dependence of parton energy loss.

We present inclusive charged hadron elliptic flow ($v_2$) measured over the pseudorapidity range $\left|\eta \right|<0.35$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. Results for $v_2$ are presented over a broad range of transverse momentum $(p_T=0.2\text{−}8.0$ GeV/$c$) and centrality (0–60%). To study nonflow effects that are correlations other than collective flow, as well as the fluctuations of $v_2$, we compare two different analysis methods: (1) the event-plane method from two independent subdetectors at forward ($\left|\eta \right|=3.1\text{−}3.9$) and beam ($\left|\eta \right|>6.5$) pseudorapidities and (2) the two-particle cumulant method extracted using correlations between particles detected at midrapidity. The two event-plane results are consistent within systematic uncertainties over the measured $p_T$ and in centrality 0–40%. There is at most a 20% difference in the $v_2$ between the two event-plane methods in peripheral (40–60%) collisions. The comparisons between the two-particle cumulant results and the standard event-plane measurements are discussed.

We have studied the dissociation of heavy quarkonium states in a hot QCD medium by investigating the medium modifications to a heavy quark potential. Our model shows that in-medium modification causes the screening of the charge in contrast to the screening of the range of the potential. We have then employed the medium-modified potential to estimate the dissociation pattern of the charmonium and bottomonium states and also explore how the pattern changes as we go from the perturbative to nonperturbative domain in the Debye mass. The results are in good agreement with the other current theoretical works both from the spectral function analysis and the potential model study.

We investigate the effects of two-body currents on elastic electron-deuteron scattering in an exactly Poincaré invariant quantum mechanical model with a null-plane kinematic symmetry. While calculations using single-nucleon currents as input produce good qualitative agreement with experiment, the two-body current that we investigate produces a good quantitative agreement between theory and experiment for all three elastic scattering observables.

We study the influence of the isovector-scalar meson on the spinodal instabilities and the distillation effect in asymmetric nonhomogenous nuclear matter under strong magnetic fields of the order of ${10}^{18}\text{−}{10}^{19}$ G. Relativistic nuclear models both with constant couplings (NLW) and with density-dependent parameters (DDRH) are considered. A strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. It is shown that for neutron-rich matter the inclusion of the δ meson increases the size of the instability region for NLW models and decreases it for the DDRH models. The effect of the δ meson on the transition density to homogeneous $\beta$-equilibrium matter is discussed. The DDRHδ model predicts the smallest transition pressures, about half the values obtained for NLδ.

Deuteron induced quasifree scattering and reactions have been extensively investigated in the past few decades as well as ${}^6\mathrm{Li}$, ${}^3\mathrm{H}$, ${}^3\mathrm{He}$, and ${}^9\mathrm{Be}$ induced reactions. This was done not only for the investigation of nuclear structure and reaction mechanisms but also for important astrophysical applications (Trojan horse method). In particular the widths of the spectator momentum distributions in several nuclei, which have been used as Trojan horses, have been obtained as a function of the transferred momentum. Applications of Trojan horse method will also be discussed because the momentum distribution of the spectator particle inside the nucleus is a important input for this method. This gives hints on distortion effects at low energies important for nuclear astrophysics.

The neutron and proton odd-even mass differences are studied with Hartree-Fock $+$ BCS ($\mathrm{HF}+\mathrm{BCS}$) calculations with Skyrme interactions and an isospin dependent contact pairing interaction, which is recently derived from a microscopic nucleon-nucleon interaction. To this end, we perform $\mathrm{HF}+\mathrm{BCS}$ calculations for even and odd semi-magic tin and lead isotopes together with even and odd $Z$ isotones with $N=50$ and 82. The filling approximation is applied to the last unoccupied particle in odd nuclei. Comparisons with the experimental data show a clear manifestation of the isospin dependent pairing correlations in both proton and neutron pairing gaps.

Deeply virtual electroproduction of pions in an exclusive reaction $p(e,e^{\text{'}}{\pi }^{+})n$ is studied using a two-component model that includes soft hadronic and hard partonic reaction mechanisms. The results are compared with the experimental data measured at HERMES in the deep inelastic region for values of $Q^2>1\hspace{0.5em}{\mathrm{GeV}}^2$ and $W^2>10\hspace{0.5em}{\mathrm{GeV}}^2$. At forward angles the ${\pi }^{+}$ cross section is longitudinal and is dominated by exchange of Regge poles, with π being the dominant trajectory. The off-forward region with $-t>1\hspace{0.5em}{\mathrm{GeV}}^2$ is transverse and shows the dominance of partonic subprocesses. An implication of the present results for the future JLab facilities is briefly discussed.

The effects of a zero-range tensor component of the effective interaction on nuclear response functions are determined in the random phase approximation approach. Explicit formulas in the case of symmetric homogeneous isotropic nuclear matter are given for each spin-isospin excitation channel. It is shown for a typical interaction with tensor couplings that the effects are quantitatively important, mainly in vector channels.

We construct effective two-body Hamiltonians and $E2$ operators for the $p$ shell by performing $16\hslash \Omega$ ab initio no-core shell model (NCSM) calculations for $A=5$ and $A=6$ nuclei and explicitly projecting the many-body Hamiltonians and $E2$ operator onto the $0\hslash \Omega$ space. We then separate the effective $E2$ operator into one-body and two-body contributions employing the two-body valence cluster approximation. We analyze the convergence of proton and neutron valence one-body contributions with increasing model space size and explore the role of valence two-body contributions. We show that the constructed effective $E2$ operator can be parametrized in terms of one-body effective charges giving a good estimate of the NCSM result for heavier $p$-shell nuclei.