We construct effective two- and three-body Hamiltonians for the $p$-shell by performing $12\hslash \Omega$ ab initio no-core shell model (NCSM) calculations for $A=6$ and 7 nuclei and explicitly projecting the many-body Hamiltonians onto the $0\hslash \Omega$ space. We then separate these effective Hamiltonians into inert core, one- and two-body contributions (also three-body for $A=7$) and analyze the systematic behavior of these different parts as a function of the mass number $A$ and size of the NCSM basis space. The role of effective three- and higher-body interactions for $A>6$ is investigated and discussed.

The fusion excitation function of ${}^{36}\mathrm{S}+{}^{48}\mathrm{Ca}$ has been measured from well above the barrier down to very small cross sections at sub-barrier energies. A steady decrease of the fusion cross sections is observed below the barrier with no pronounced change of slope. The logarithmic derivative saturates and does not reach the value expected for a constant astrophysical S-factor. The S-factor does not show any maximum in the measured energy range. Coupled-channels calculations using a Woods-Saxon potential have been performed.

We compute diffractive structure functions for both protons and nuclei in the framework of color glass condensate models with impact parameter dependence. These models have previously been shown to provide good agreement with inclusive $F_2$ measurements and exclusive vector meson measurements at DESY's Hadron-Electron Ring Accelerator (HERA). For nuclei, they provide good (parameter free) agreement with the inclusive $F_2$ data. We demonstrate good agreement of our computations with HERA measurements on inclusive diffraction. We extend our analysis to nuclei and predict the pattern of enhancement and suppression of the diffractive structure functions that can be measured at an electron-ion collider. We discuss how the impact parameter dependence crucially affects our analysis, in particular for large invariant masses at fixed $Q^2$.

The volume part of the phenomenological optical potential is interpreted in terms of the microscopic theory of nuclear matter. The latter is based on the Brueckner-Hartree-Fock approach with a new version of three-body force, reproducing the empirical saturation properties of nuclear matter. The self-energy is calculated and its on-shell matrix elements are related to the volume part of the optical potential. A comparison is made with a recent parametrization of the optical model potential fitting the experimental nucleon-nucleus elastic scattering. The isospin effects and Coulomb corrections are emphasized.

A search for nuclear resonance fluorescence excitations in ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ within the energy range of 1.0- to 2.5-MeV was performed using a 4-MeV continuous bremsstrahlung source at the High Voltage Research Laboratory at the Massachusetts Institute of Technology. Measurements utilizing high purity Ge detectors at backward angles identified nine photopeaks in ${}^{235}\mathrm{U}$ and 12 photopeaks in ${}^{239}\mathrm{Pu}$ in this energy range. These resonances provide unique signatures that allow the materials to be nonintrusively detected in a variety of environments including fuel cells, waste drums, vehicles, and containers. The presence and properties of these states may prove useful in understanding the mechanisms for mixing low-lying collective dipole excitations with other states at low excitations in heavy nuclei.

The $(d,{}^2\mathrm{He})$ charge-exchange reaction on ${}^{76}\mathrm{Se}$ was studied at an incident energy of 183 MeV. The outgoing two protons in the ${}^1{S}_0$ state, referred to as ${}^2\mathrm{He}$, were both momentum analyzed and detected by the same spectrometer and detector. The experiment was performed at KVI, Groningen, using the magnetic spectrometer BBS at three angular positions: $0^{°},2.5^{°}$, and $5^{°}$. Excitation-energy spectra of the residual nucleus ${}^{76}\mathrm{As}$ were obtained with an energy resolution of about 120 keV (FWHM). Gamow-Teller (${\mathrm{GT}}^{+}$) transition strengths were extracted up to 5 MeV and compared with those from an $(n,p)$ experiment at low resolution. Together with the ${\mathrm{GT}}^{-}$ transition strengths from the ${}^{76}\mathrm{Ge}(p,n)$ experiment leading to the same intermediate nucleus, the nuclear matrix element of the two-neutrino double-$\beta$ decay of ${}^{76}\mathrm{Ge}$ was evaluated.

Within the dinuclear system model we analyze the production of yet unknown neutron-deficient isotopes of U, Np, Pu, Am, Cm, and Cf in various complete fusion reactions. Different deexcitation channels of the excited compound nucleus are treated. The results are obtained without special adjustment to the selected evaporation channel. The fusion probability is an important ingredient of the excitation function. The results are in good agreement with the available experimental data. The alpha decay half-life times in the neutron-deficient actinides are discussed.

To investigate pre-equilibrium emission of light nuclear particle(s), an experiment has been performed using $\alpha$ beams at the Variable Energy Cyclotron Center (VECC), Kolkata, India. In the present work, excitation functions for ${}^{58}\mathrm{Ni}(\alpha ,p){}^{61}\mathrm{Cu},{}^{58}\mathrm{Ni}(\alpha ,\mathit{pn}){}^{60}\mathrm{Cu},{}^{60}\mathrm{Ni}(\alpha ,p2n){}^{61}\mathrm{Cu},{}^{60}\mathrm{Ni}(\alpha ,n){}^{63}\mathrm{Zn},{}^{60}\mathrm{Ni}(\alpha ,2n){}^{62}\mathrm{Zn},{}^{61}\mathrm{Ni}(\alpha ,3n){}^{62}\mathrm{Zn}$, and ${}^{61}\mathrm{Ni}(\alpha ,2n){}^{63}\mathrm{Zn}$ reactions have been measured by using the stacked foil activation technique followed by off-line $\gamma$-ray spectroscopy. Experimentally measured excitation functions have been compared with the prediction of the theoretical model code ALICE-91 with and/or without the inclusion of pre-equilibrium emission. Analysis of the data suggests that an admixture of both equilibrium and pre-equilibrium emission is needed to reproduce experimental data at energies $\approx 8\text{−}40$ MeV and reveals significant contribution from pre-equilibrium emission. An attempt has also been made to estimate the pre-equilibrium contribution, which has been found to depend on projectile energy and on number of emitted particle(s).

It is shown that the “barrier distribution” derived from quasi-elastic backscattering of heavy ions gives us, in fact, information about the “total reaction threshold distribution” and not about the “fusion barrier.”

Coulomb corrections for quasielastic scattering of electrons by nuclei are calculated using eikonal distorted waves. Corrections to the lowest-order eikonal approximation are included to obtain accurate results. Spin-dependent eikonal phase shifts are evaluated and they yield very small corrections to the longitudinal and transverse cross sections at electron energies of 500 MeV or higher. Because of this the Rosenbluth procedure is accurate for separation of the longitudinal and transverse response functions. The effective-momentum approximation is also found to be accurate with regard to removal of the remaining Coulomb effects from the distorted waves. Calculations are presented for electron scattering from ${}^{208}\mathrm{Pb}$ and ${}^{56}\mathrm{Fe}$ nuclei at energies of 500 and 800 MeV and momentum transfers $q=550$ and 900 MeV/$c$.

We present a coupled Boltzmann and hydrodynamics approach to relativistic heavy ion reactions. This hybrid approach is based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport approach with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. Event-by-event fluctuations are directly taken into account via the nonequilibrium initial conditions generated by the initial collisions and string fragmentations in the microscopic UrQMD model. After a ($3+1$)-dimensional ideal hydrodynamic evolution, the hydrodynamical fields are mapped to hadrons via the Cooper-Frye equation and the subsequent hadronic cascade calculation within UrQMD proceeds to incorporate the important final state effects for a realistic freeze-out. This implementation allows us to compare pure microscopic transport calculations with hydrodynamic calculations using exactly the same initial conditions and freeze-out procedure. The effects of the change in the underlying dynamics—ideal fluid dynamics versus nonequilibrium transport theory—is explored. The freeze-out and initial state parameter dependencies are investigated for different observables. The time evolution of the baryon density and particle yields are also discussed. We find that the final pion and proton multiplicities are lower in the hybrid model calculation owing to the isentropic hydrodynamic expansion whereas the yields for strange particles are enhanced owing to the local equilibrium in the hydrodynamic evolution. The results of the different calculations for the mean transverse mass excitation function, rapidity, and transverse mass spectra for different particle species at three different beam energies are discussed in the context of the available data.

A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=62.4$ and 200 GeV, and $\mathrm{Cu}+\mathrm{Cu}$ collisions at $\sqrt{s_{\mathit{NN}}}=22.5,62.4$, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for nondynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon $p+p$ data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. A comparison of the data with a model where hadrons are independently emitted from a number of hadron clusters suggests that the mean number of hadrons per cluster is small in heavy ion collisions.

Neutrino losses from proto-neutron stars play a pivotal role to decide if these stars would be crushed into black holes or explode as supernovae. Recent observations of subluminous Type II-P supernovae (e.g., 2005cs, 2003gd, 1999br, 1997D) were able to rejuvenate the interest in 8–10 $M_{\odot }$ stars that develop $\mathrm{O}+\mathrm{Ne}+\mathrm{Mg}$ cores. Simulation results of $\mathrm{O}+\mathrm{Ne}+\mathrm{Mg}$ cores show varying results in converting the collapse into an explosion. The neutrino energy loss rates are important input parameters in core collapse simulations. Proton-neutron quasiparticle random-phase approximation (pn-QRPA) theory has been used for calculation of neutrino energy loss rates due to ${}^{24}\mathrm{Mg}$ in stellar matter. The rates are presented on a detailed density-temperature grid suitable for simulation purposes. The calculated neutrino energy loss rates are enhanced up to more than one order of magnitude compared to the shell-model calculations and favor a lower entropy for the core of these massive stars.

It has recently been pointed out that if the surface tension of quark matter is low enough, the surface of a strange star will be a crust consisting of a crystal of charged strangelets in a neutralizing background of electrons. This affects the behavior of the surface and must be taken into account in efforts to observationally rule out strange stars. We calculate the thickness of this “mixed phase” crust, taking into account the effects of surface tension and Debye screening of electric charge. Our calculation uses a generic parametrization of the equation of state of quark matter. For a reasonable range of quark matter equations of state, and surface tension of order a few MeV/fm${}^2$, we find that the preferred crystal structure always involves spherical strangelets, not rods or slabs of quark matter. We find that for a star of radius 10 km and mass $1.5M_{\odot }$, the strangelet-crystal crust can be from zero to hundreds of meters thick, the thickness being greater when the strange quark is heavier and the surface tension is smaller. For smaller quark stars the crust will be even thicker.

Sub-barrier fusion of ${}^{132}\mathrm{Sn}$ and ${}^{64}\mathrm{Ni}$ was measured at $E_{\mathrm{beam}}=465$ MeV with an improved apparatus. The result of this new measurement is well reproduced by a coupled-channel calculation and a density-constrained time-dependent Hartree-Fock calculation. The previously measured cross section at $E_{\mathrm{beam}}=453$ MeV was reanalyzed. Only an upper limit of the cross section was obtained.

A simple approach that highlights the effects of shell or sub-shell changes in mediating shape/phase transitions in the equilibrium structure, and in the development of deformation, is presented. It uses only simple data such as $R_{4/2}\equiv E(4_1^{+})/E(2_1^{+})$ and $1/E(2_1^{+})$ and reveals the character of transitional regions through the appearance of bubble and crossing topologies. Recent microscopic calculations are also considered from the same perspective. Since the method uses only the simplest data [$E(2_1^{+})$ is sufficient], it should be particularly valuable for future studies of exotic nuclei.

Background: Experimental information on the structure of low-lying levels with isospin 3/2 in systems with 13 nucleons can be used to evaluate the quality of modern theoretical predictions for the light exotic systems. This level structure is poorly known at present. Purpose: Search for $T=3/2$ states in ${}^{13}\mathrm{C}$ was performed in this work. Method: These states were observed in the resonance elastic scattering of radioactive beam ${}^{12}\mathrm{B}$ on protons using the thick target inverse kinematics technique. Results: Six new states in ${}^{13}\mathrm{C}$ were identified as $T=3/2$ states. Tentative spin-parity assignments are suggested. Comparison to the previous knowledge of the level structure of $T=3/2$ $A=13$ system and to shell-model predictions is given. Conclusion: The elastic scattering of neutron-rich beams on proton target is a convenient tool for isobaric analog states search. The observed ${}^{12}\mathrm{B}$$+p$ excitation function is determined by the $T=3/2$ states and no features associated with $T=1/2$ states were found. Although the level scheme of $T=3/2$ states in $A=13$ systems is still far from being complete the emerging picture shows significant disagreements with predictions of contemporary shell models.

Using a unified description on multiplicity distributions of final-state particles, the spallation residues in ${}^{56}\mathrm{Fe}+p$ reactions and fragmentation products in ${}^{136}\mathrm{Xe}({}^{124}\mathrm{Xe})+\mathrm{Pb}$ reactions at intermediate energy and at the low end of high energies are studied. The isotopic production cross sections of fragments produced in the reactions are calculated by using a multisource ideal gas model. Each source contributes multiplicity-like distribution of neutrons like a radioactive object.