Recently the NA60 Collaboration has reported the transverse mass spectra of dimuons coming from In-In collisions at 158 GeV/nucleon. The measured yields display a strong invariant mass dependence not typical of radial flow, suggesting that different sources contribute in different mass regions. We interpret the dimuon transverse mass spectra from an early thermalized partonic phase and hadronic phase constrained by the strictures of broken chiral symmetry. Each phase develops a specific transverse momentum dependence by hydrodynamical expansion. We show that a measurement of the momentum anisotropy at NA60 could provide information on the dominant emission source (hadronic or partonic) in the intermediate mass region $1.5⩽M⩽3.0$ GeV.

We calculate pseudorapidity (η) asymmetry in $\mathit{pA}$ and $\mathit{dA}$ collisions in a pQCD-improved parton model. With the calculations tuned to describe existing spectra from $\mathit{pp}$ collisions and asymmetric systems at midrapidity and large rapidities at Fermi National Accelerator Laboratory and Relativistic Heavy Ion Collider energies, we investigate the roles of nuclear shadowing and multiple scattering on the observed asymmetry. Using this framework, we make predictions for pseudorapidity asymmetries at high $p_T$ and large η in a wide range of energies up to those of the Large Hadron Collider.

We present a relativistic calculation of the saturation properties of nuclear matter which contains the correlation energy. Pion loops are incorporated on top of a relativistic Hartree-Fock (RHF) approach based on a chiral theory. It includes the effect of nucleon structure through its response to the background chiral invariant scalar field. All the parameters which enter the RHF calculation are fixed or strongly constrained by hadron phenomenology or lattice data. The new input for the correlation energy is the Landau-Migdal parameter $g^{\text{'}}$ governing the short-range part of the spin-isospin interaction. We find that the inclusion of the correlation energy improves the description of the saturation properties of nuclear matter.

Analysis of presolar grains in primitive meteorites has shown isotopic ratios largely characteristic of the conditions thought to prevail in various astrophysical environments. A possible indicator for a grain of ONe nova origin is a large ${}^{33}\mathrm{S}$ abundance: nucleosynthesis calculations predict as much as 150 times the solar abundance of ${}^{33}\mathrm{S}$ in the ejecta of nova explosions on massive ONe white dwarfs. This overproduction factor may, however, vary by factors of at least 0.01–3 because of uncertainties of several orders of magnitude in the ${}^{33}\mathrm{S}$$(p,\gamma )$${}^{34}\mathrm{Cl}$ reaction rate at nova peak temperatures ($T_{\mathrm{peak}}~0.1\text{−}0.4$ GK). These uncertainties arise due to the lack of nuclear physics information for states within $~600$ keV of the ${}^{33}\mathrm{S}$$+p$ threshold in ${}^{34}\mathrm{Cl}$ (S${}_p$(${}^{34}\mathrm{Cl}$) = 5143 keV). To better constrain this rate we have measured, for the first time, the ${}^{34}\mathrm{S}$(${}^3\mathrm{He}$,$t$)${}^{34}\mathrm{Cl}$ reaction over the region $E_x$(${}^{34}\mathrm{Cl}$) = 4.9–6 MeV. We confirm previous states and find 15 new states in this energy region. New ${}^{33}\mathrm{S}$$(p,\gamma )$${}^{34}\mathrm{Cl}$ resonances at $E_R=281(2)$, 301(2), and 342(2) keV may dominate this rate at relevant nova temperatures. Our results could affect predictions of sulphur isotopic ratios in nova ejecta (e.g., ${}^{32}\mathrm{S}$/${}^{33}\mathrm{S}$) that may be used as diagnostic tools for the nova paternity of grains.

A systematic study of fission-barrier dependence on excitation energy has been performed using the self-consistent finite-temperature Hartree-Fock + BCS (FT-HF + BCS) formalism with the SkM${}^{*}$ Skyrme energy density functional. The calculations have been carried out for even-even superheavy nuclei with $Z$ ranging between 110 and 124. For an accurate description of fission pathways, the effects of triaxial and reflection-asymmetric degrees of freedom have been fully incorporated. Our survey demonstrates that the dependence of isentropic fission barriers on excitation energy changes rapidly with particle number, pointing to the importance of shell effects even at large excitation energies characteristic of compound nuclei. The fastest decrease of fission barriers with excitation energy is predicted for deformed nuclei around $N=164$ and spherical nuclei around $N=184$ that are strongly stabilized by ground-state shell effects. For the nuclei ${}^{240}\mathrm{Pu}$ and ${}^{256}\mathrm{Fm}$, which exhibit asymmetric spontaneous fission, our calculations predict a transition to symmetric fission at high excitation energies owing to the thermal quenching of static reflection asymmetric deformations.

Yrast states in ${}^{34}\mathrm{P}$ were investigated using the ${}^{18}\mathrm{O}$(${}^{18}\mathrm{O}$,$\mathit{pn})$ reaction at energies of 20, 24, 25, 30, and 44 MeV at Florida State University and at Lawrence Berkeley National Laboratory. The level scheme was expanded, γ-ray angular distributions were measured, and lifetimes were inferred with the Doppler-shift attenuation method by detecting decay protons in coincidence with one or more γ rays. The results provide a clearer picture of the evolution of structure approaching the “island of inversion,” particularly how the one- and two-particle-hole (ph) states fall in energy with increasing neutron number approaching inversion. However, the agreement of the lowest few states with pure $\mathit{sd}$ shell model predictions shows that the level scheme of ${}^{34}\mathrm{P}$ is not itself inverted. Rather, the accumulated evidence indicates that the 1-ph states start at 2.3 MeV. A good candidate for the lowest 2-ph state lies at 6236 keV, just below the neutron separation energy of 6291 keV. Shell model calculations made using a small modification of the WBP interaction reproduce the negative-parity, 1-ph states rather well.

We present a new extension of the random-phase approximation method: the quasiboson approximation is avoided and correlations are included in the ground state without resorting to renormalized operators or renormalized matrix elements; the configuration space is enlarged by considering also elementary excitations corresponding to the annihilation of a particle (hole) and the creation of another particle (hole) on the correlated ground state, together with the particle-hole ones. Two new and relevant advantages of this method with respect to the existing extensions of random-phase approximation are highlighted: (i) the energy weighted sum rules are completely satisfied; (ii) the problem of the existence of nonphysical states in the spectrum, related to the inclusion of particle-particle and hole-hole configurations, is solved: a way to unambiguously disentangle physical from nonphysical states in the excitation spectrum is presented. The method is applied here to a three-level Lipkin model where its quality can be judged by comparing with the exact results. Both advantages (i) and (ii) shall lead to feasible future applications of this extended RPA to several realistic cases.

Four-, six-, and eight-quasiparticle isomers with $K^{\pi }={14}^{-}$, (${21}^{+}$) and (${26}^{-}$) have been identified in the deformed nucleus ${}^{174}\mathrm{Lu}$, in addition to the previously reported $K^{\pi }={13}^{{}^{+}}$, four-quasiparticle isomeric state. Analysis of alignments and in-band crossover-to-cascade branching ratios lead to the characterization of the configurations associated with the $K^{\pi }={14}^{-}$ and (${21}^{+}$) isomers. The excitation energies of the observed states are compared with results from multi-quasiparticle calculations that include effects of blocking and residual nucleon-nucleon interactions. Good agreement is found for medium-spin ($I=13\text{−}14\hslash$) and the highest spin ($I>20\hslash$) states observed, but there remain ambiguities in assigning configurations in the $I=15\text{−}19\hslash$ region.

The excited states in ${}^{22}\mathrm{Mg}$ have been investigated by the resonant elastic scattering of ${}^{21}\mathrm{Na}$$+p$. A 4.0 MeV/nucleon ${}^{21}\mathrm{Na}$ beam was separated by the Center for Nuclear Study (CNS) radioactive ion beam separator (CRIB) and then used to bombard a thick (CH${}_2$)${}_n$ target. The energy spectra of recoiled protons were measured at scattering angles of ${\theta }_{\mathrm{c}.\mathrm{m}.}\approx 172{}^{\circ },146{}^{\circ }$, and ${134}^{\circ }$, respectively. A wide energy-range of excitation function in ${}^{22}\mathrm{Mg}$ (up to $E_x~8.9$ MeV) was obtained simultaneously with a thick-target method, and a state at 7.06 MeV was newly observed. The resonant parameters were deduced from an $R$-matrix analysis of the center-of-mass (c.m.) differential cross-section data with a SAMMY-M6-BETA code. The astrophysical resonant reaction rate for the ${}^{18}\mathrm{Ne}$($\alpha ,p$)${}^{21}\mathrm{Na}$ reaction was recalculated based on the present parameters. Generally speaking, the present rates are much smaller than the previous ones.

The fission probability of ${}^{232}\mathrm{U}$ has been measured using the ${}^{231}\mathrm{Pa}$(${}^3\mathrm{He}$,df) reaction with an energy resolution of 11 keV in the excitation energy region of $E^{*}=4.0\text{−}6.4$ MeV. A number of sub-barrier fission resonances have been observed for the first time in the excitation energy range below $E^{*}=4.8$ MeV and interpreted as rotational bands with a rotational parameter characteristic to a hyperdeformed nuclear shape ($\hslash {}^2/2\Theta =1.96\pm 0.11$ keV). The angular distribution of the associated fission fragments was measured to deduce the $K$ value of the rotational bands. The fission barrier parameters of ${}^{232}\mathrm{U}$ have been determined by analyzing the overall features of the fission probability. A deep third minimum with an excitation energy of $E_{\mathrm{III}}=3.2(2)$ MeV and rather low inner barrier height of $E_A=4.0(3)$ MeV could be established.

The nonlinear σ model that includes vector meson contributions is utilized for the study of nuclear matter. Here, the σ meson degree of freedom is eliminated by the condition that ${\sigma }^2+{\mathit{\pi }}^2$ is invariant under both chiral transformation and isospin rotation. The nuclear matter consists of nucleons, pions, and vector (ω) mesons. In the model, there are only three free parameters, and the minimum energy and desired incompressibility at the normal nuclear density for the pion pair condensed nuclear matter can be obtained by adjusting these parameters.

High transverse momentum ($P_T$) $\gamma$-hadron correlations are currently being regarded as the “golden channel” for the study of the medium produced in ultrarelativistic heavy-ion collisions by means of hard probes. This is for several reasons, all linked to the fact that because of the smallness of the electromagnetic coupling $\alpha$, the photon does not substantially interact with the medium and is expected to escape unmodified. Thus, a high $P_T$ photon indicates a hard process in the collision independent of the position of the hard vertex. In contrast, there may not be a clear signal for a hard process involving strongly interacting partons if the production vertex is deep in the medium as both partons undergo substantial final state interaction. Equally important, if photon production by fragmentation can be separated experimentally, the photon provides almost full knowledge of the initial kinematics. In the present paper, these properties are used to demonstrate a distinguishing feature between two assumptions made in modeling the medium modifications of strongly interacting high $P_T$ processes: loss of energy into the medium vs medium modification of the partonic shower. It is shown that $\gamma$-hadron correlations provide a very clean signature for distinguishing the two scenarios.

The nucleus ${}^{77}\mathrm{Ge}$ was studied through the ${}^{76}\mathrm{Ge}({}^{13}\mathrm{C},{}^{12}\mathrm{C}){}^{77}\mathrm{Ge}$ reaction at a sub-Coulomb energy. The angular distributions of $\gamma$ rays depopulating excited states in ${}^{77}\mathrm{Ge}$ were measured in order to constrain spin and parity assignments. Some of these assignments are of use in connection with neutrinoless double beta decay, where the population of states near the Fermi surface of ${}^{76}\mathrm{Ge}$ was recently explored using transfer reactions.

Modern experiments with heavy ion-leptons collisions open the possibility to measure the deviation of a cross section of small angles electron(positron)-ion elastic scattering from the Rutherford formula due to multiple virtual photons exchange. The charge asymmetry and the polarization of the scattered leptons are calculated and numerical predictions are given. A generalization to elastic proton-nucleus scattering is discussed.

We investigate the connection between the Breit and infinite momentum frames and show that when the nucleon matrix element of the time component of the electromagnetic current, which yields $G_E$ in the Breit frame, is boosted to the infinite momentum (or light-front) frame, the quantity $F_1$ is obtained.

The stellar $(n,\gamma )$ cross section of ${}^{40}\mathrm{Ca}$ at $\mathit{kT}=25$ keV has been measured with a combination of the activation technique and accelerator mass spectrometry (AMS). This combination is required when direct off-line counting of the produced activity is compromised by the long half-life and/or missing $\gamma$-ray transitions. The neutron activations were performed at the Karlsruhe Van de Graaff accelerator using the quasistellar neutron spectrum of $\mathit{kT}=25$ keV produced by the ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ reaction. The subsequent AMS measurements were carried out at the Vienna Environmental Research Accelerator (VERA) with a 3 MV tandem accelerator. The doubly magic ${}^{40}\mathrm{Ca}$ is a bottle-neck isotope in incomplete silicon burning, and its neutron capture cross section determines the amount of leakage, thus impacting on the eventual production of iron group elements. Because of its high abundance, ${}^{40}\mathrm{Ca}$ can also play a secondary role as “neutron poison” for the $s$-process. Previous determinations of this value at stellar energies were based on time-of-flight measurements. Our method uses an independent approach, and yields for the Maxwellian-averaged cross section at $\mathit{kT}=30$ keV a value of $\langle \sigma \rangle {}_{3}0\hspace{0.5em}\mathrm{keV}=5.73\pm 0.34$ mb.

Two high-lying states in ${}^{15}\mathrm{F}$ and ${}^{16}\mathrm{Ne}$, unbound with respect to one-proton ($1p$) and two-proton ($2p$) emissions, have been observed in the fragmentation of ${}^{17}\mathrm{Ne}$ at intermediate energies. They undergo mainly sequential emissions of protons via intermediate states in ${}^{14}\mathrm{O}$ and ${}^{15}\mathrm{F}$ and have decay energies of 7.8(2) and 7.6(2) MeV, respectively. The widths of the newly observed states in ${}^{15}\mathrm{F}$ and ${}^{16}\mathrm{Ne}$ are much smaller than the Wigner limits for single-particle configurations, of 0.4(4) and $0.8($${}_{+8}^{-4})$ MeV, respectively. In addition, narrow widths of 0.2(2) MeV are derived for two other high-lying states in ${}^{15}\mathrm{F}$ with $Q_p$ of 4.9 and 6.4 MeV, which match features of the recently predicted narrow odd-parity ${}^{15}\mathrm{F}$ states with two valence protons in the $\mathit{sd}$ shell. All energies and widths have been obtained by analyzing angular correlations of the decay products, $p\text{−}p\text{−}{}^{14}\mathrm{O}$ and $p\text{−}p\text{−}{}^{13}\mathrm{N}$, whose trajectories have been measured by a tracking technique with silicon microstrip detectors.

Photoabsorption cross sections ${\sigma }_{\gamma }$ up to the neutron-separation energy $S_n$ were measured for the stable even-mass isotopes ${}^{92-100}\mathrm{Mo}$ in photon-scattering experiments. The photon-scattering data were analyzed in a novel way by taking into account the intensity of unresolved levels at high excitation energy and high level density. Simulations of $\gamma$-ray cascades were performed to estimate the intensity distribution of inelastic transitions to low-lying levels and, hence, to deduce intensities and branching ratios of the ground-state transitions needed for the determination of ${\sigma }_{\gamma }$. The present $(\gamma ,{\gamma }^{\text{'}})$ data can be combined for the first time with $(\gamma ,n)$ data, which allows us to obtain ${\sigma }_{\gamma }$ in the energy range from about 4 MeV up to the giant dipole resonance for a series of isotopes. The ${\sigma }_{\gamma }$ values below $S_n$ increase with the number of neutrons above the neutron shell closure at $N=50$. Calculations using a quasiparticle random-phase approximation in a deformed Woods-Saxon potential describe this effect as a consequence of the increasing nuclear deformation.

Chopped-beam techniques and $\gamma$-ray spectroscopy with Gammasphere have been used to measure the lifetime of the 1112-keV $8^{-}$ isomeric state in ${}^{174}\mathrm{Er}$. The value obtained of $\tau =5.8(4)$ s corresponds to a reduced hindrance of $f_{\nu }=98$ for the 163-keV $E1$ transition to the $8^{+}$ state of the ground-state band, in good agreement with the systematics of the corresponding $E1$ strengths in the $N=106$ isotones. The $K$-mixing in the $8^{-}$ states is calculated in the context of the particle-rotor model and used to extract the underlying reduced hindrances.