We calculate unpolarized quark distribution functions and $F_2$ structure functions for the proton and the neutron. The calculation is preformed in the light-cone frame. For the bare nucleon three different distributions—namely, spin-0 diquark, spin-0 plus spin-1 diquark, and no diquark models—have been used. Using perturbative QCD an initial gluon distribution is generated inside the core nucleon. The physical nucleon is assumed to be a superposition of the bare nucleon plus virtual light-cone Fock states of baryon octets and baryon decuplets along with the corresponding pseudoscalar mesons and vector mesons. The initial distributions are evolved. The $F_2$ structure functions are calculated from the evolved distributions and it is shown that they are in reasonable agreement with the NMC and ZEUS results along with a CTEQ6M fit. Also, it is shown that the meson cloud is a major contributing factor to the sea quark asymmetry and one needs both pseudoscalar mesons and vector mesons to account fully for Gottfried sum rule violation.

In the present work we use the large-$N_c$ approximation to investigate quark matter described by the SU(2) Nambu–Jona-Lasinio model subject to a strong magnetic field. The Landau levels are filled in such a way that usual kinks appear in the effective mass and other related quantities. $\beta$ equilibrium is also considered and the macroscopic properties of a magnetar described by this quark matter is obtained. Our study shows that the magnetar masses and radii are larger if the magnetic field increases but only very large fields ($⩾{10}^{18}$ G) affect the equation of state in a non-negligible way.

Using new techniques developed for measuring angular correlations with large detector arrays, the $g$ factors of $2^{+}$ states in ${}^{140,142}\mathrm{Xe}$ are measured for the first time by the method of correlation attenuation in randomly oriented magnetic fields. $g$ factors in ${}^{146}\mathrm{Ba}$ and ${}^{146,148}\mathrm{Ce}$ are measured to establish the method by comparison with previous values. The results are discussed in terms of IBM-2 and rotation-vibration models.

The observed almost complete dominance of prolate over oblate deformations in the ground states of deformed even-even nuclei is related to the splitting of high $\ell$ “surface” orbits in the Nilsson diagram: on the oblate side the occurrence of numerous strongly avoided crossings which reduce the fanning out of the low Λ orbits, while on the prolate side the same interactions increase the fanning out. It is further demonstrated that the prolate dominance is rather special for the restricted particle number of available nuclei and is not generic for finite systems with mean-field potentials resembling those in atomic nuclei.

Bubble nuclei are characterized by a depletion of their central density. Their existence is examined within three different theoretical frameworks: the shell model and nonrelativistic and relativistic microscopic mean-field approaches. We analyze ${}^{34}\mathrm{Si}$ and ${}^{22}\mathrm{O}$ as possible candidates for proton and neutron bubble nuclei, respectively. In the case of ${}^{22}\mathrm{O}$, we observe a significant model dependence, thereby calling into question the bubble structure of ${}^{22}\mathrm{O}$. In contrast, an overall agreement among the models is obtained for ${}^{34}\mathrm{Si}$. Indeed, all models predict a central proton density depletion of about 40% and a central charge density depletion of 25%–30%. This result provides strong evidence in favor of a proton bubble in ${}^{34}\mathrm{Si}$.

Two prompt $\gamma$ rays of energies 2020 and 554 keV were observed in coincidence with delayed transitions depopulating the ${19/2}^{-}$ isomer in the $Z=29$, $N=42$ ${}^{71}\mathrm{Cu}$ nucleus. The newly identified transitions are proposed to deexcite the 4776- and 5330-keV levels above the ${19/2}^{-}$ isomer. Based on the comparison with the low-lying positive-parity states observed in the $Z=42$, $N=50$ ${}^{92}\mathrm{Mo}$ nucleus, spin and parity ${23/2}^{-}$ are proposed for the 4776-keV level in ${}^{71}\mathrm{Cu}$. The high-energy, 2020-keV transition is interpreted as arising from the breaking of the $N=40$ neutron core. Shell-model calculations with a ${}^{56}\mathrm{Ni}$ core reproduce the $(23/2^{-})\to (19/2^{-})$ gap well, suggesting that the ${23/2}^{-}$ state is dominated by $\pi p_{3/2}\nu ((\mathit{fp}){}^{10}(g_{9/2}){}^4)$ configurations. The present result constitutes further evidence supporting the view that the $N=40$ subshell closure persists in ${}^{71}\mathrm{Cu}$, herewith challenging recent suggestions that the coupling of two or more proton or neutron quasiparticles induces a large polarization of the ${}^{68}\mathrm{Ni}$ core.

Measurements of $\beta$-decay properties of $A\lesssim 110$ r-process nuclei have been completed at the National Superconducting Cyclotron Laboratory at Michigan State University. $\beta$-decay half-lives for ${}^{105}\mathrm{Y}$, ${}^{106,107}\mathrm{Zr}$, and ${}^{111}\mathrm{Mo}$, along with $\beta$-delayed neutron emission probabilities of ${}^{104}\mathrm{Y}$, ${}^{109,110}\mathrm{Mo}$ and upper limits for ${}^{105}\mathrm{Y}$, ${}^{103-107}\mathrm{Zr}$, and ${}^{108,111}\mathrm{Mo}$ have been measured for the first time. Studies on the basis of the quasi-random-phase approximation are used to analyze the ground-state deformation of these nuclei.

Identified charged-particle spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\overline{p}$ at midrapidity ($\left|y\right|<0.1$) measured by the $\mathit{dE}/\mathit{dx}$ method in the STAR (solenoidal tracker at the BNL Relativistic Heavy Ion Collider) time projection chamber are reported for $\mathit{pp}$ and $d+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV and for $\mathrm{Au}+\mathrm{Au}$ collisions at 62.4, 130, and 200 GeV. Average transverse momenta, total particle production, particle yield ratios, strangeness, and baryon production rates are investigated as a function of the collision system and centrality. The transverse momentum spectra are found to be flatter for heavy particles than for light particles in all collision systems; the effect is more prominent for more central collisions. The extracted average transverse momentum of each particle species follows a trend determined by the total charged-particle multiplicity density. The Bjorken energy density estimate is at least several GeV/${\mathrm{fm}}^3$ for a formation time less than 1 fm/$c$. A significantly larger net-baryon density and a stronger increase of the net-baryon density with centrality are found in $\mathrm{Au}+\mathrm{Au}$ collisions at 62.4 GeV than at the two higher energies. Antibaryon production relative to total particle multiplicity is found to be constant over centrality, but increases with the collision energy. Strangeness production relative to total particle multiplicity is similar at the three measured RHIC energies. Relative strangeness production increases quickly with centrality in peripheral $\mathrm{Au}+\mathrm{Au}$ collisions, to a value about 50% above the $\mathit{pp}$ value, and remains rather constant in more central collisions. Bulk freeze-out properties are extracted from thermal equilibrium model and hydrodynamics-motivated blast-wave model fits to the data. Resonance decays are found to have little effect on the extracted kinetic freeze-out parameters because of the transverse momentum range of our measurements. The extracted chemical freeze-out temperature is constant, independent of collision system or centrality; its value is close to the predicted phase-transition temperature, suggesting that chemical freeze-out happens in the vicinity of hadronization and the chemical freeze-out temperature is universal despite the vastly different initial conditions in the collision systems. The extracted kinetic freeze-out temperature, while similar to the chemical freeze-out temperature in $\mathit{pp}$, $d+\mathrm{Au}$, and peripheral $\mathrm{Au}+\mathrm{Au}$ collisions, drops significantly with centrality in $\mathrm{Au}+\mathrm{Au}$ collisions, whereas the extracted transverse radial flow velocity increases rapidly with centrality. There appears to be a prolonged period of particle elastic scatterings from chemical to kinetic freeze-out in central $\mathrm{Au}+\mathrm{Au}$ collisions. The bulk properties extracted at chemical and kinetic freeze-out are observed to evolve smoothly over the measured energy range, collision systems, and collision centralities.

Transverse momentum distributions in ultrarelativistic heavy ion collisions carry considerable information about the dynamics of the hot system produced. Direct comparison with the same spectra from $p+p$ collisions has proved invaluable in identifying novel features associated with the larger system, in particular, the “jet quenching” at high momentum and the apparently much stronger collective flow dominating the spectral shape at low momentum. We point out possible hazards of ignoring conservation laws in the comparison of high- and low-multiplicity final states. We argue that the effects of energy and momentum conservation actually dominate many of the observed systematics, and that $p+p$ collisions may be much more similar to heavy ion collisions than generally thought.

We report on an attempt to produce and detect ${}^{268}\mathrm{Hs}$ and ${}^{269}\mathrm{Hs}$ in the nuclear fusion reaction ${}^{25}\mathrm{Mg}+{}^{248}\mathrm{Cm}$ using the gas phase chemistry apparatus COMPACT. No decay chains attributable to the decay of hassium isotopes were observed during the course of this experiment. From the nonobservation of ${}^{269}\mathrm{Hs}$ we derive a cross section limit of 0.4 pb (63% confidence limit) for the reaction ${}^{248}\mathrm{Cm}({}^{25}\mathrm{Mg},4n){}^{269}\mathrm{Hs}$ at a center-of-target beam energy of 140 MeV. The evaluated cross section limit for the ${}^{248}\mathrm{Cm}({}^{25}\mathrm{Mg},5n){}^{268}\mathrm{Hs}$ reaction depends on the assumed half-life of unknown ${}^{268}\mathrm{Hs}$. Current systematics of the half-lives for even-even Hs isotopes suggests a value of 0.5 s, resulting in a cross section limit of 1.3 pb.

The $Q_{\mathrm{EC}}$ value of the superallowed $\beta$ emitter ${}^{26}\mathrm{Si}$ has been measured with the JYFLTRAP Penning trap facility to be 4840.85(10) keV which is ten times more precise than any previous measurement. This leaves only the branching ratio to be improved before the $\mathcal{F}t$ value of ${}^{26}\mathrm{Si}$ can be used to test the conserved vector current hypothesis. As a consequence, the ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction $Q$-value ($Q_{p\gamma }$) was improved to be 5513.7(5) keV, limited now by the mass excess of ${}^{25}\mathrm{Al}$. The new $Q_{p\gamma }$ value changes the stellar production rate of ${}^{26}\mathrm{Si}$ in nova ignition temperatures by about 10%.

Low-spin states of ${}^{130}\mathrm{Xe}$ have been populated by a fusion evaporation reaction followed by $\beta$-decay ${}^{126}\mathrm{Te}({}_3^7\mathrm{Li},3n){}^{130}\mathrm{Cs}\stackrel{\mathrm{EC}}{\to }{}^{130}\mathrm{Xe}$. Two candidates for $2_{1,\mathrm{ms}}^{+}$-states could be found, by measuring the $E2/M1$ mixing ratio of the transitions of the $2_3^{+}$ and $2_4^{+}$, at 2150 keV and 2296 keV, to the first excited $2^{+}$ state. The experimental results are supported by a shell model calculation and are in a good agreement with interacting boson model-2 (IBM-2) calculations. The mixing of the $2_{1,\mathrm{ms}}^{+}$ with a symmetric $2^{+}$-state and its fragmentation into the $2_3^{+}$ and $2_4^{+}$ states are discussed.

The bound state problem of $D^0{\overline{D}}^{*0}({\overline{D}}^0{D}^{*0})$ is relevant to the molecular interpretation of the X(3872). We investigated this problem in a chiral quark model by solving the resonating group method equation. We found the system is unbound through $S$-wave π and σ interactions. The inclusion of ρ and ω meson exchanges is helpful to the formation of a molecule. Because the binding energy relies on the coupling constants, we cannot draw a definite conclusion as to whether a molecular state exists in the $D^0{\overline{D}}^{*0}({\overline{D}}^0{D}^{*0})$ system. When moving on to the bottom counterpart, we obtained an $S$-wave $B{\overline{B}}^{*}$ state.

The neutron capture reaction on ${}^{14}\mathrm{C}$ leading to the ${}^{15}\mathrm{C}$ ground state, which plays an important role in various nucleosynthesis processes, has been studied using the Coulomb breakup of ${}^{15}\mathrm{C}$ on a Pb target at 68 MeV/nucleon. The breakup cross section has been converted into the energy-dependent neutron capture cross section using the principle of detailed balance. The energy spectrum shows typical $p$-wave neutron capture characteristics, which is explained by the fact that the ground state of ${}^{15}\mathrm{C}$ possesses a strong single-particle $s$-wave component and a moderate-sized neutron halo structure. The capture cross section for the ${}^{14}\mathrm{C}(n,\gamma ){}^{15}\mathrm{C}$ reaction derived from the present experiment has been found to be consistent with the most recent data, directly measured using a ${}^{14}\mathrm{C}$ target. This result assures the validity of the Coulomb breakup method in deriving the neutron capture cross section for neutron-rich nuclei.

The usual formula employed to estimate the barrier distribution in fusion reactions contains a systematic error. The origin of this error is related to the numerical approximation of the second derivative appearing in the expression of the barrier distribution. We show how to approximately correct for this systematic error. Previous determinations of the uncertainties in the barrier distribution, that did not include this error, could be severely underestimated. Furthermore, we find that minimization of the total error leads to an optimal energy grid at which the fusion cross section data should be taken.

A coupled-channel analysis of the ${}^{18,20,22}\mathrm{O}(p,p^{\text{'}})$ data has been performed to determine the neutron transition strengths of the $2_1^{+}$ states in oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density- and isospin-dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hartree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar (${\delta }_0$) and isovector (${\delta }_1$) deformation lengths of the $2_1^{+}$ states in ${}^{18,20,22}\mathrm{O}$ have been extracted from the folding model analysis of the $(p,p^{\text{'}})$ data. A specific $N$ dependence of ${\delta }_0$ and ${\delta }_1$ has been established which can be linked to the neutron shell closure occurring at $N$ approaching 16. The strongest isovector deformation was found for the $2_1^{+}$ state in ${}^{20}\mathrm{O}$, with ${\delta }_1$ about 2.5 times larger than ${\delta }_0$, which indicates a strong core polarization by the valence neutrons in ${}^{20}\mathrm{O}$. The ratios of the neutron/proton transition matrix elements ($M_n/M_p$) determined for the $2_1^{+}$ states in ${}^{18,20}\mathrm{O}$ have been compared with those deduced from the mirror symmetry, using the measured $B(E2)$ values of the $2_1^{+}$ states in the proton-rich ${}^{18}\mathrm{Ne}$ and ${}^{20}\mathrm{Mg}$ nuclei, to discuss the isospin impurity in the $2_1^{+}$ excitation of the $A=18$, $T=1$ and $A=20$, $T=2$ isobars.

The excitation energy per residue nucleon ($E^{*}/A$) and fast and thermal light particle multiplicities are studied as a function of centrality defined as the number of grey tracks emitted $N_{\mathrm{grey}}$ and by the mean number of primary hadron-nucleon scatterings ($\langle \nu \rangle$) and the mean impact parameter ($\langle b\rangle$) extracted from it. The value of $E^{*}/A$ and the multiplicities show an increase with centrality for all systems, 14.6 GeV p-Au and 8.0 GeV π-Au and $\overline{\mathrm{p}}$-Au collisions, and the excitation energy per residue nucleon exhibits a uniform dependence on $N_{\mathrm{grey}}$.

The growing consensus that a strongly coupled quark-gluon plasma (sQGP) has been observed at the SPS and RHIC experiments suggests a different framework for examining heavy-quark dynamics. We present both a semianalytical treatment of Fokker-Planck (FP) evolution in pedagogical examples and numerical Langevin simulations of evolving $c\overline{c}$ pairs on top of a hydrodynamically expanding fireball. In this way, we may conclude that the survival probability of bound charmonia states is greater than previously estimated, as the spatial equilibration of pairs proceeds through a “slowly dissolving lump” stage related to the pair interaction.

We investigate charged and neutral current neutrino induced incoherent pion production off nuclei at MiniBooNE and K2K energies within the GiBUU model. We assume impulse approximation and treat the nucleus as a local Fermi gas of nucleons bound in a mean-field potential. In-medium spectral functions are also taken into account. The outcome of the initial neutrino nucleon reaction undergoes complex hadronic final state interactions. We present results for neutral current ${\pi }^0$ and charged current ${\pi }^{+}$ production and compare to MiniBooNE and K2K data.