We find that a simple extension of the coalescence model is sufficient to incorporate the perfect quark number scaling behavior of the elliptic flow in transverse kinetic energy, recently discovered by the PHENIX Collaboration. The flavor dependence of the elliptic flow can be consistently described in the low and intermediate $p_T$ if the transverse kinetic energy is conserved in the $2\to 1$ or $3\to 1$ parton coalescence process at the hadronization. Thus suggesting the quark coalescence as a possible hadronization mechanism at low $p_T$ as well.

The capture of electrons by the nucleus ${}^7\mathrm{Be}$ from the three-body initial state $p+e^{-}+$${}^7\mathrm{Be}$ in the continuum is studied. On the basis of the expansion of the three-body continuum wave function in the small parameter $\epsilon \approx (m_e/m_p){}^{1/2}$ [$m_e$ ($m_p$) is the electron (proton) mass], the role of the protons on the electron capture is considered. The results are compared with the traditional treatment of the electron capture by the nucleus ${}^7\mathrm{Be}$. For stars with density and temperature like in the center of the Sun the studied mechanism can make a non-negligible contribution to the capture rate.

We present a semianalytical method to determine which partial cross sections of nuclear fragmentations most affect the shielded dose equivalent due to exposure to galactic cosmic rays. The cross sections thus determined will require more theoretical and/or experimental studies for us to better predict, reduce, and mitigate the radiation exposure in human space explorations.

An experimental program at Los Alamos Neutron Science Center (LANSCE) has been developed to precisely measure fission cross sections over ten decades in incident neutron energy for a range of actinides relevant to advanced nuclear reactor designs and transmutation concepts. The first completed measurement is of ${}^{237}\mathrm{Np}$($n,f$), and the above-reaction-threshold part of the measurement is reported here. The result is in close agreement with ENDF/B-VI in the energy region of first- and second-chance fission. The cross section ratio to ${}^{235}\mathrm{U}$ is shown to be constant from 30 MeV to the highest measured energy of 200 MeV.

We calculate the classical gluon field of a fast projectile passing through a dense medium. We show that this allows us to calculate both the initial state gluon production in proton-nucleus collisions and the final state gluon radiation off a hard parton produced in nucleus-nucleus collisions. This unified description of these two phenomena makes the relation between the saturation scale $Q_s$ and the transport coefficient $\widehat{q}$ more transparent. Also, we discuss the validity of the eikonal approximation for gluon propagation inside the nucleus in proton-nucleus collisions at RHIC energy.

The dependence of interparticle correlations on the orientation of particle relative momentum can yield unique information on the space-time features of emission in reactions with multiparticle final states. In the present paper, the benefits of a representation and analysis of the three-dimensional correlation information in terms of surface spherical harmonics is presented. The harmonics include the standard complex tesseral harmonics and the real Cartesian harmonics. Mathematical properties of the lesser known Cartesian harmonics are illuminated. The physical content of different angular harmonic components in a correlation is described. The resolving power of different final-state effects with regard to determining angular features of emission regions is investigated. The considered final-state effects include identity interference, strong interactions, and Coulomb interactions. The correlation analysis in terms of spherical harmonics is illustrated with the cases of Gaussian and blast-wave sources for proton-charged meson and baryon-baryon pairs.

We have performed a partial-wave analysis of $K^{+}$-nucleon scattering in the momentum range from 0 to 1.5 GeV/$c$ addressing the uncertainties of the results and comparing them with several previous analyses. It is found that the treatment of the reaction threshold behavior is particularly important. We find a $T=0$ scattering length which is not consistent with zero, as has been claimed by other analyses. The $T=0$ phase shifts for $\ell >0$ are consistent with a pure spin-orbit potential. Some indications for the production of a $T=0$ pentaquark with spin-parity-$D5/2+$ are discussed.

In the threshold region, the cross section and the associated overlap integral obey the Wigner threshold law that results in the Wigner-cusp phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests itself in other open channels, even if their respective thresholds appear at a different energy. The shape of a threshold cusp depends on the orbital angular momentum of a scattered particle; hence, studies of Wigner anomalies in weakly bound nuclei with several low-lying thresholds can provide valuable spectroscopic information. In this work, we investigate the threshold behavior of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow shell model, which takes into account many-body correlations and the continuum effects. The presence of threshold anomalies is demonstrated and the implications for spectroscopic factors are discussed.

We have measured the transverse asymmetry $A_{T^{\text{'}}}$ in the quasielastic ${}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\text{'}})$ process with high precision at $Q^2$ values from 0.1 to $0.6(\mathrm{GeV}/c){}^2$. The neutron magnetic form factor $G_M^n$ was extracted at $Q^2$ values of 0.1 and $0.2(\mathrm{GeV}/c){}^2$ using a nonrelativistic Faddeev calculation which includes both final-state interactions (FSI) and meson-exchange currents (MEC). Theoretical uncertainties due to the FSI and MEC effects were constrained with a precision measurement of the spin-dependent asymmetry in the threshold region of ${}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\text{'}})$. We also extracted the neutron magnetic form factor $G_M^n$ at $Q^2$ values of 0.3 to $0.6(\mathrm{GeV}/c){}^2$ based on plane wave impulse approximation calculations.

A collective $S$ and $D$ nucleon pair approximation of the shell model is applied to even-even Sn, Te, Xe, Ba, and Ce isotopes with mass number $A~$120–150 and neutron number ranging from 74 to 90. Our Hamiltonian employs monopole pairing, quadrupole pairing plus quadrupole-quadrupole-type interactions between like valence nucleons and quadrupole-quadrupole interactions between valence neutrons and valence protons. With very few parameters, the low-lying states of even-even Sn, Te, Xe, Ba, and Ce isotopes are well described. The calculated $B(E2)$ values and $g$ factors are consistent with recent experimental data. Our systematic calculations also predict $B(E2)$ values and $g$ factors (in particular, for nuclei with valence neutrons in the 82–126 region) if these data are not available.

The combined data of two Coulomb excitation experiments has verified the purely electromagnetic population of the $K^{\pi }=4^{+},6^{+},8^{-}$, and ${16}^{+}$ rotational bands in ${}^{178}\mathrm{Hf}$ via $2\le \nu \le 14$ $K$-forbidden transitions, quantifying the breakdown of the $K$-selection rule with increasing spin in the low-$K$ bands. The γ-, $4^{+}$, and $6^{+}$ bands were extended, and four new states in a rotational band were tentatively assigned to a previously known $K^{\pi }=0^{+}$ band. The quasiparticle structure of the $6^{+}$ ($t_{\frac{1}{2}}=77$ ns) and $8^{-}$ ($t_{\frac{1}{2}}=4$ s) isomer bands were evaluated, showing that the gyromagnetic ratios of the $6^{+}$ isomer band are consistent with a pure $\pi {\frac{7}{2}}^{+}[404],\pi {\frac{5}{2}}^{+}[402]$ structure. The $8^{-}$ isomer band at 1147 keV and the second $8^{-}$ band at 1479 keV, thought to be predominantly $\nu {\frac{7}{2}}^{-}[514],\nu {\frac{9}{2}}^{+}[624]$ and $\pi {\frac{9}{2}}^{-}[514],\pi {\frac{7}{2}}^{+}[404]$, respectively, are mixed to a degree approaching the strong-mixing limit. Based on measured $\langle K^{\pi }={16}^{+}\Vert E2\Vert K^{\pi }=0^{+}\rangle$ matrix elements, it was shown that heavy-ion bombardment could depopulate the ${16}^{+}$ isomer at the $~1$% level, although no states were found that would mediate photodeexcitation of the isomer via low-energy x-ray absorption.

The ${}^{191}\mathrm{Ir}$$(n,2n)$${}^{190}\mathrm{Ir}$ cross section was measured by means of the activation technique at four neutron energies in the range 10.0–11.3 MeV. The quasimonoenergetic neutron beam was produced via the ${}^2\mathrm{H}$$(d,n)$${}^3\mathrm{He}$ reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR “Demokritos.” The cross section for the population of the second high spin (${11}^{-}$) isomeric state was measured along with the sum of the reaction cross section populating both the ground ($4^{-}$) and the first isomeric state ($1^{-}$). Statistical model calculations taking into account pre-equilibrium emission were performed and compared with all the available experimental data. The experimentally deduced excitation function for populating both the ground and first isomeric state was well reproduced by the theoretical calculations. The statistical model calculations of populating the second metastable state revealed its strong dependence on the details of the introduced level scheme, as well as on the ratio between the effective moment of inertia and the rigid body moment of inertia of the residual nucleus. The experimental cross-section data corresponding to the second isomeric state and to the isomeric ratio were reproduced in a quite consistent way by the calculations.

High-spin states in neutron-rich ${}^{180}\mathrm{Hf}$ and ${}^{182}\mathrm{Hf}$ nuclei were populated through inelastic and transfer reactions with a ${}^{136}\mathrm{Xe}$ beam incident on a thin ${}^{180}\mathrm{Hf}$ target, and investigated using particle-γ coincidence techniques. New collective band structures were observed, and previously known rotational and vibrational bands in these nuclei were extended to higher angular momenta. No obvious nucleon alignment was observed in the ground state band of either nucleus up to $\hslash \omega =0.43$ MeV, a significant delay compared to lighter even-even Hf isotopes. Woods-Saxon cranking calculations were performed to predict the nature of the first band crossings and shape evolution in ${}^{180,182}\mathrm{Hf}$.

We investigate in self-consistent cranked Nilsson plus quasiparticle random-phase approximation the structure of ${}^{190,192,194}\mathrm{Hg}$ in their evolution from normal to superdeformation and from low to high rotational frequencies. The analysis of the energy levels suggests a splitting of few normally deformed bands into two or more branches. The investigation of the dynamical moments of inertia supports the octupole character of the low-lying negative parity superdeformed bands, in agreement with previous theoretical predictions and experimental findings. As a more direct confirm of their octupole nature, we obtain strong $E1$ transitions linking those bands to the yrast superdeformed band, in agreement with experiments. A similar result is shown to hold also for ${}^{152}\mathrm{Dy}$. Like in ${}^{152}\mathrm{Dy}$, the collectivity of the low-lying scissors mode gets enhanced with the onset of superdeformation.

We extend a recent study that explained the steep falloff in the fusion cross section at energies far below the Coulomb barrier for the symmetric dinuclear system ${}^{64}\mathrm{Ni}+{}^{64}\mathrm{Ni}$ to another symmetric system, ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$, and the asymmetric system ${}^{64}\mathrm{Ni}+{}^{100}\mathrm{Mo}$. In this scheme, the very sensitive dependence of the internal part of the nuclear potential on the nuclear equation of state determines a reduction of the classically allowed region for overlapping configurations and consequently a decrease in the fusion cross sections at bombarding energies far below the barrier. Within the coupled-channels method, including couplings to the low-lying $2^{+}$ and $3^{-}$ states in both target and projectile as well as mutual and two-phonon excitations of these states, we calculate and compare with the experimental data the fusion cross sections, $S$ factors, and logarithmic derivatives for the above-mentioned systems and find good agreement with the data even at the lowest energies. We predict, in particular, a distinct double peaking in the $S$ factor for the far sub-barrier fusion of ${}^{58}\mathrm{Ni}+{}^{58}\mathrm{Ni}$, which should be tested experimentally.

We calculate contributions of hadron resonances to two-photon exchange effects in electron-proton scattering. In addition to the nucleon and $P33$ resonance, the following heavier resonances are included as intermediate states in the two-photon exchange diagrams: $D13,D33,P11,S11$, and $S31$. We show that the corrections due to the heavier resonances are smaller than the dominant nucleon and $P33$ contributions. We also find that there is a partial cancellation between the contributions from the spin 1/2 and spin 3/2 resonances, which results in a further suppression of their aggregate two-photon exchange effect.

The neutron-proton bremsstrahlung process $(\mathit{np}\to \mathit{np}\gamma )$ is known to be sensitive to meson exchange currents in the nucleon-nucleon interaction. The triply differential cross section for this reaction has been measured for the first time at the Los Alamos Neutron Science Center, using an intense, pulsed beam of up to 700-MeV neutrons to bombard a liquid hydrogen target. Scattered neutrons were observed at six angles between ${12}^{°}$ and ${32}^{°}$, and the recoil protons were observed in coincidence at ${12}^{°},{20}^{°}$, and ${28}^{°}$ on the opposite side of the beam. Measurement of the neutron and proton energies at known angles allows full kinematic reconstruction of each event. The data are compared with predictions of two theoretical calculations, based on relativistic soft-photon and nonrelativistic potential models.

High-spin states in the odd-odd ${}^{138}\mathrm{Pr}$ nucleus were reinvestigated with the reaction ${}^{128}\mathrm{Te}$(${}^{14}\mathrm{N}$,$4n)$ at a beam energy of 64 MeV. Six collective bands were observed, and two of them were newly identified. For the $\pi h_{11/2}\otimes \nu h_{11/2}$ band, high-spin states are followed up to $I^{\pi }={16}^{+}$. The spin values for this band have been reassigned based on the systematical comparison with the neighboring nuclei. The observed band crossing is proposed to be due to the alignment of protons, and the signature inversion with the neutron number changing in La and Pr isotopes has been discussed. The other five collective bands are proposed to be based on oblate deformation with $\gamma ~-{60}^{°}$.

Rapidity/pseudorapidity densities for charged particles and their centrality, rapidity, and energy dependence in Au+Au collisions at the Relativistic Heavy Ion Collider are studied in a quark combination model. Using a Gaussian-type rapidity distribution for constituent quarks as a result of Landau hydrodynamic evolution, the data at $\sqrt{s_{\mathit{NN}}}=130,200$ GeV at various centralities in full pseudorapidity range are well described, and the charged-particle multiplicities are reproduced as functions of the number of participants. The energy dependence of the shape of the ${\mathit{dN}}_{\mathit{ch}}/d\eta$ distribution is also described at various collision energies $\sqrt{s_{\mathit{NN}}}=200,130,62.4$ GeV in central collisions with same value of parameters except 19.6 GeV. The calculated rapidity distributions and yields for the charged pions and kaons in central Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV are compared with experimental data of the BRAHMS Collaboration.

We introduce a modified form of the Kharzeev-Levin-Nardi (KLN) approach for nuclear collisions. The new ansatz for the unintegrated gluon distribution function preserves factorization, and the saturation scale is bound from below by that for a single nucleon. It also reproduces the correct scaling with the number of collisions at high transverse momentum. The corresponding Monte Carlo implementation allows us to account for fluctuations of the hard sources (nucleons) in the transverse plane. We compute various definitions of the eccentricity within the new approach, which are relevant for the interpretation of the elliptic flow. Our approach predicts breaking of the scaling of the eccentricity with the Glauber eccentricity at the level of about 30%.