A puzzle has long existed for the $\alpha$-cluster content in the near-threshold 7.54-MeV state of ${}^{10}\mathrm{Be}$. A new measurement was conducted to measure the cluster-decay partial width of this state using the reaction ${}^9\mathrm{Be}({}^9\mathrm{Be},{}^{10}\mathrm{Be}^{*}\to \alpha +{}^6\mathrm{He}){}^8\mathrm{Be}$ at 45-MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-decay strength was also obtained based on the threefold coincident measurement. A cluster-decay branching ratio of $(4.04\pm 1.26)\times {10}^{-4}$ is obtained, resulting in a reasonably large $\alpha$-cluster spectroscopic factor. The present Rapid Communication confirms the formation of the $\sigma$-bond molecular rotational band headed by the 6.18-MeV state in ${}^{10}\mathrm{Be}$.

To probe the role of the intrinsic structure of the projectile on subbarrier fusion, measurement of fusion cross sections has been carried out in a ${}^9\mathrm{Be} + {}^{197}\mathrm{Au}$ system in the energy range $E_{\mathrm{c}.\mathrm{m}.}/V_B\approx$ 0.82 to 1.16 using off-beam $\gamma$-counting method. Measured fusion excitation function has been analyzed in the framework of the coupled-channel approach using CCFULL code. It is observed that the coupled-channel calculations, including couplings to the inelastic state of the target and the first two states of the rotational band built on the ground state of the projectile, provide a very good description of the subbarrier fusion data. At above-barrier energies, the fusion cross section is found to be suppressed by $\approx 39\left(2\right)\%$ as compared to the coupled-channel prediction. A comparison of reduced excitation function of ${}^9\mathrm{Be} + {}^{197}\mathrm{Au}$ with other $x + {}^{197}\mathrm{Au}$ shows a larger enhancement for ${}^9\mathrm{Be}$ in the subbarrier region amongst $Z=2–5$ weakly and tightly bound projectiles, which indicates the prominent role of the projectile deformation in addition to the weak binding.

A systematic search for a critical point in the phase diagram of QCD matter is under way at the Relativistic Heavy Ion Collider (RHIC) and is planned at several future facilities. Its existence, if confirmed, and its location will greatly enhance our understanding of QCD. In this article, we emphasize several important issues that are often not fully recognized in theoretical interpretations of experimental results relevant to the critical point search. We discuss ways in which our understanding on these issues can be improved.

We reinvestigated the neutron multiplicity yields of Ba-Mo, Ce-Zr, Te-Pd, and Nd-Sr from the spontaneous fission of ${}^{252}\mathrm{Cf}$ by (i) using both $\gamma -\gamma -\gamma -\gamma$ and $\gamma -\gamma -\gamma$ coincidence data, (ii) using up to date level scheme structures, and (iii) crosschecking analogous energy transitions in multiple isotopes, we have achieved higher precision than previous analyses. Particular attention was given to the Ba-Mo pairs where our results clearly confirm that the Ba-Mo yield data have a second hot fission mode where 8–10, and now 11 neutron evaporation channels are observed. These are the first observations of the 11 neutron channel. These 8–11 neutron channels are observed for the first time in the Ce-Zr pairs, but are not observed in other fission pairs. The measured intensities of the second mode in Ba-Mo and Ce-Zr pairs are $\sim 1.5\left(4\right)\%$ and $\sim 1.0\left(3\right)\%$, respectively. These high neutron number evaporation modes can be an indication of hyperdeformation and/or octupole deformation in ${}^{143–145}\mathrm{Ba}$ and in ${}^{146,148}\mathrm{Ce}$ at scission to give rise to such high neutron multiplicities.

Background: For the description of many astrophysical processes, precise knowledge of cross sections and reaction rates is necessary. In particular, the exact nucleosynthesis mechanisms of the $p$ nuclei—a group of 30 to 35 neutron deficient nuclei—are still unknown. Since many reactions of astrophysical relevance are not accessible in the laboratory, one has to rely on theoretical calculations based on Hauser-Feshbach codes. The calculated values depend strongly on nuclear physics input parameters like nuclear level densities (NLDs), $\gamma$-ray strength functions ($\gamma$-SFs) and $\text{particle}+\text{nucleus}$ optical model potentials (OMPs).

Purpose: Measuring the ${}^{107}\mathrm{Ag}(p,\gamma ){}^{108}\mathrm{Cd}$ reaction cross section at sub-Coulomb energies extends the scarce experimental database. In particular, partial cross sections yield important information about the $\gamma$-SF in ${}^{108}\mathrm{Cd}$. Via the comparison of total ($p,\gamma$) cross sections to theoretical calculations, a locally adopted NLD model was found.

Method: Highly enriched ${}^{107}\mathrm{Ag}$ targets were bombarded with protons at six different beam energies between 2.0 and 5.0 MeV. The reaction yield and thus the reaction cross section were determined via in-beam $\gamma$-ray spectroscopy using the HORUS $\gamma$-ray spectrometer. Total ($p,\gamma$) cross sections were obtained by the observation of ground-state transitions in ${}^{108}\mathrm{Cd}$ and partial cross sections via the analysis of primary $\gamma$-ray transitions into different excited states in ${}^{108}\mathrm{Cd}$.

Results: Cross-section values at six energies close to the astrophysical relevant energy region were determined. The slight adjustment of microscopic models for the NLD to the total ($p,\gamma$) cross sections, respectively the dipole strength function to the partial cross sections, yielded an excellent agreement between the experimentally determined results and statistical model calculations.

Conclusion: The obtained results help to constrain the nuclear physics input for statistical model calculations and hence to improve the precision of the theoretical determination of reaction rates. In particular, information about the $p$ nucleus ${}^{108}\mathrm{Cd}$ helps us to understand the mechanisms of the $p$ process.

The $\beta$ decay of ${}^{57}\mathrm{Zn}$ and ${}^{58}\mathrm{Zn}$ was investigated in an experiment at the National Superconducting Cyclotron Laboratory of Michigan State University. For the first time $\beta$-delayed proton emission from ${}^{58}\mathrm{Zn}$ was observed with a branching ratio of 0.7(1)%. The proton-energy spectrum allowed for probing the Gamow-Teller strength distribution above the proton-separation energy in the daughter nucleus. Moreover, the absolute branching ration for delayed-proton emission from ${}^{57}\mathrm{Zn}$ was found to be compatible with 100%.

The rotation of a triaxial nucleus can be represented (in a semiclassical description) as a precession of the total angular momentum around a certain axis and at a given tilt, producing tilted precession (TiP) bands. Such bands are described by rotational models and can in principle be approximated with wobbling. We studied for which TiP bands such an approximation is justified. It was found that TiP bands become approximately similar to wobbling bands at high spins for both zero-seniority bands in even-even nuclei, and one-quasiparticle bands with longitudinal coupling of the angular momenta in odd-mass nuclei. Contrary to that, the precession for transverse coupling of the angular momenta in one-quasiparticle configurations giving rise to TiP bands cannot be approximated with wobbling either at low or at high spins. This suggests that the interpretation of a band in terms of transverse wobbling cannot be justified only by particle-rotor-type model, as this model implies a different, TiP, nature. Contrary to TiP bands, the transverse wobbling bands exhibit quantized excitation energies and transition probabilities which is typical for bands involving phonon excitations.

The Royer formulas are often used to calculate the $\alpha$-decay half-lives [G. Royer, J. Phys. G 26, 1149 (2000); Nucl. Phys. A 848, 279 (2010)]. In recent years, the amount of experimental data on $\alpha$ decay has increased and these formulas have been examined again. They describe precisely the favored $\alpha$ decays. For unfavored decays, they are less accurate and important deviations may occur between the calculations and experimental data. The underlying physics of this phenomenon has been revealed and an improved formula with only eight parameters is proposed. This formula takes into account both the blocking effect of unpaired nucleons and the contribution of centrifugal potential. Compared with the original formulas and other improvements, our new formula is more simple to use and more accurate. Encouraged by this, the $\alpha$-decay half-lives of even-even nuclei and odd-$A$ nuclei with $Z=117$, 118, 119, and 120 are predicted using our improved formula and the universal decay law [C. Qi et al., Phys. Rev. Lett. 103, 072501 (2009)] with the extrapolated $Q_{\alpha }$ of the WS3+ mass model [N. Wang and M. Liu, Phys. Rev. C 84, 051303(R) (2011)]. The predictions of these two formulas are consistent. However, for ${}^{293}\mathrm{Ts}$ and ${}^{294}\mathrm{Og}$, predicted $\alpha$-decay half-lives by our improved formula show better agreement with experimental data, indicating that predictions by our improved formula are more reliable and useful for future new superheavy elements and isotopes experimental assignments and identifications. Meanwhile, the features of predicted $\alpha$-decay energy and half-lives imply that $N=184$ is the next neutron magic number after $N=126$.

The adopted level densities (LD) for the nuclei produced through different reaction mechanisms significantly impact the accurate calculation of cross sections for the different reaction channels. Many common LD models make simplified assumptions regarding the overall behavior of the total LD and the intrinsic spin and parity distributions of the excited states. However, very few experimental constraints are taken into account in these models: LD at neutron separation energy coming from average spacings of $s$- and $p$-wave resonances ($D_0$ and $D_1$, respectively) whenever they have been previously measured, and the sometimes subjective extrapolation of discrete levels. These, however, constrain the LD only in very specific regions of excitation energy, and for specific spins and parities. This work aims to establish additional experimental constraints on LD through quantitative correlations between cross sections and LD. This allows for fitting and the determination of detailed structures in LD. For this we use the microscopic Hartree-Fock-Bogoliubov (HFB) LD as a starting point as the HFB LD provide a more realistic spin and parity distributions than phenomenological models such as Gilbert-Cameron (GC). We then associate variations predicted by the HFB model with the structure observed in double-differential cross sections at low outgoing neutron energy, a region that is dominated by the LD input. We also use ($n,p$) on ${}^{56}\mathrm{Fe}$, as an example case where angle-integrated cross sections are extremely sensitive to LD. For comparison purposes we also perform calculations with the GC model. With this approach we are able to perform fits of the LD based on actual experimental data, constraining the model and ensuring its consistency. This approach can be particularly useful in extrapolating the LD to nuclei for which high-excited discrete levels and/or values of $D_0$ or $D_1$ are unknown. It also predicts neutron-induced inelastic $\gamma$ cross sections that in some cases can differ significantly from more standard phenomenological LD models such as GC.

The simultaneous measurement of the isotopic fission-fragment yields and fission-fragment velocities of ${}^{239}\mathrm{U}$ has been performed for the first time. The ${}^{239}\mathrm{U}$ fissioning system was produced in one-neutron transfer reactions between a ${}^{238}\mathrm{U}$ beam at 5.88 MeV/nucleon and a ${}^9\mathrm{Be}$ target. The combination of inverse kinematics at low energy and the use of the $\mathrm{VAMOS}++$ spectrometer at the GANIL facility allows the isotopic identification of the full fission-fragment distribution and their velocity in the reference frame of the fissioning system. The proton and neutron content of the fragments at scission, their total kinetic and total excitation energy, as well as the neutron multiplicity were determined. Information from the scission point configuration is obtained from these observables and the correlation between them. The role of the octupole-deformed proton and neutron shells in the fission-fragment production is discussed.

Proton number fluctuation is sensitive observable to search for the QCD critical point in heavy-ion collisions. In this paper, we studied rapidity acceptance dependence of the proton cumulants and correlation functions in most central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=5\mathrm{GeV}$ from a microscopic hadronic transport model [the jet AA microscopic transportation model (JAM)]. At midrapidity, we found the effects of resonance weak decays and hadronic rescattering on the proton cumulants and correlation functions are small, but those effects get larger when further increasing the rapidity acceptance. On the other hand, we found the baryon number conservation is a dominant background effect on the rapidity acceptance dependence of proton number fluctuations. It leads to a strong suppression of cumulants and cumulant ratios as well as the negative proton correlation functions. We also studied those two effects on the energy dependence of cumulant ratios of net-proton distributions in most central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=5-200\mathrm{GeV}$ from the JAM model. This paper can serve as a noncritical baseline for a future QCD critical point search in heavy-ion collisions at the high baryon density region.

The PHENIX experiment has studied nuclear effects in $p+\mathrm{Al}$ and $p+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$ on charged hadron production at forward rapidity ($1.4<\eta <2.4$, $p$-going direction) and backward rapidity ($-2.2<\eta <-1.2$, $A$-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central $p+\mathrm{Al}$ and $p+\mathrm{Au}$ collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in $p+p$ collisions. The magnitude of enhancement at backward rapidity is larger in $p+\mathrm{Au}$ collisions than in $p+\mathrm{Al}$ collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.

This article reports measurements of the $p_{\mathrm{T}}$-differential inclusive jet cross section in $pp$ collisions at $\sqrt{s}=5.02\mathrm{TeV}$ and the $p_{\mathrm{T}}$-differential inclusive jet yield in $\text{Pb-Pb}$ 0–10% central collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$. Jets were reconstructed at midrapidity with the ALICE tracking detectors and electromagnetic calorimeter using the anti-$k_{\mathrm{T}}$ algorithm. For $pp$ collisions, we report jet cross sections for jet resolution parameters $R=0.1–0.6$ over the range $20<p_{\mathrm{T},\mathrm{jet}}<140$ $\mathrm{GeV}/c$, as well as the jet cross-section ratios of different $R$ and comparisons to two next-to-leading-order (NLO)–based theoretical predictions. For $\text{Pb-Pb}$ collisions, we report the $R=0.2$ and $R=0.4$ jet spectra for $40<p_{\mathrm{T},\mathrm{jet}}<140$ $\mathrm{GeV}/c$ and $60<p_{\mathrm{T},\mathrm{jet}}<140$ $\mathrm{GeV}/c$, respectively. The scaled ratio of jet yields observed in $\text{Pb-Pb}$ to $pp$ collisions, $R_{\mathrm{AA}}$, is constructed, and exhibits strong jet quenching and a clear $p_{\mathrm{T}}$ dependence for $R=0.2$. No significant $R$ dependence of the jet $R_{\mathrm{AA}}$ is observed within the uncertainties of the measurement. These results are compared to several theoretical predictions.

The experimentally measured charge-dependent correlations in heavy-ion collisions have been suggested as a signature of the chiral magnetic effect (CME). Early model studies could not reproduce the measurement. For example, the hijing model yielded far smaller magnitude for the charge-dependent correlation than observed in data. This led to the conclusion that the CME had to be invoked to explain the observed correlations in heavy-ion collisions. In this paper we show that this conclusion of the CME interpretation is premature. We show that the reason that hijing predicts a far smaller correlation than data is because the elliptic anisotropy ($v_2$) parameter in hijing is too small. When properly scaled, the hijing model can reproduce in entirety the measured correlations. We also employ the AMPT model, which has a large enough $v_2$, to demonstrate that the measured data can be easily accommodated by models without invoking the CME.

The nuclear liquid-gas transition at normal nuclear densities, $n\approx n_0=0.16{\mathrm{fm}}^{-3}$, and small temperatures, $T\approx 20\mathrm{MeV}$, has a large influence on analytic properties of the QCD grand-canonical thermodynamic potential. A classical van der Waals equation is used to determine qualitatively these unexpected features due to dense cold matter. The existence of the nuclear matter critical point results in thermodynamic branch points, which are located at complex chemical potential values, for $T>T_c\simeq 20\mathrm{MeV}$, and exhibit a moderate model dependence up to rather large temperatures $T\lesssim 100\mathrm{MeV}$. The behavior at higher temperatures is studied using the van der Waals hadron resonance gas (vdW-HRG) model. The baryon-baryon interactions have a decisive influence on the QCD thermodynamics close to ${\mu }_B=0$. In particular, nuclear matter singularities limit the radius of convergence $r_{{\mu }_B/T}$ of the Taylor expansion in ${\mu }_B/T$, with $r_{{\mu }_B/T}\approx 2–3$ values at $T\approx 140–170\mathrm{MeV}$ obtained in the vdW-HRG model.

The ratio of the electric to magnetic form factors of the proton, ${\mu }_p{G}_E^p/G_M^p$, has been measured for elastic electron-proton scattering with polarized beam and target up to four-momentum transfer squared $Q^2=5.66{\left(\mathrm{GeV}/c\right)}^2$ using double spin asymmetry for target spin orientation aligned nearly perpendicular to the beam momentum direction. This measurement of ${\mu }_p{G}_E^p/G_M^p$ agrees with the $Q^2$ dependence of previous recoil polarization data and reconfirms the discrepancy at high $Q^2$ between the Rosenbluth and the polarization-transfer method with a different measurement technique and systematic uncertainties uncorrelated to those of the recoil-polarization measurements. The form factor ratio at $Q^2=2.06{\left(\mathrm{GeV}/c\right)}^2$ has been measured as ${\mu }_p{G}_E^p/G_M^p=0.720\pm 0.{176}_{\mathrm{stat}}\pm 0.{039}_{\mathrm{sys}}$, which is in agreement with an earlier measurement using the polarized target technique at similar kinematics. The form factor ratio at $Q^2=5.66{\left(\mathrm{GeV}/c\right)}^2$ has been determined as ${\mu }_p{G}_E^p/G_M^p=0.244\pm 0.{353}_{\mathrm{stat}}\pm 0.{013}_{\mathrm{sys}}$, which represents the highest $Q^2$ measurement reached using double spin asymmetries with polarized target to date.

The first experimental investigation of the near-threshold cross section for incoherent ${\pi }^{-}$ photoproduction on the deuteron $\gamma d\to {\pi }^{-}pp$ is presented. The experimental technique involved detection of the $\approx 131$ MeV $\gamma$ ray resulting from the radiative capture of photoproduced ${\pi }^{-}$ in the target. The total cross section was measured using an unpolarized tagged-photon beam, a liquid-deuterium target, and three very large NaI(Tl) spectrometers. The data are compared to theoretical models that give insight into the elementary reaction $\gamma n\to {\pi }^{-}p$ and pion-nucleon and nucleon-nucleon final-state interactions.

By means of Monte Carlo methods, we perform a full error analysis on the Duflo-Zucker mass model. In particular, we study the presence of correlations in the residuals to obtain a more realistic estimate of the error bars on the predicted binding energies. To further reduce the discrepancies between model prediction and experimental data we also apply a multilayer perceptron neural network. We show that the root mean square of the model further reduces by roughly 40%. We then use the resulting models to predict the composition of the outer crust of a nonaccreting neutron star. We provide a first estimate of the impact of error propagation on the resulting equation of state of the system.