We simulate top-energy $\mathrm{Au}+\mathrm{Au}$ collisions using ideal hydrodynamics in order to make the first comparison to the complete set of midrapidity flow measurements made by the PHENIX Collaboration. A simultaneous calculation of $v_2$, $v_3$, $v_4$, and the first event-by-event calculation of quadrangular flow defined with respect to the $v_2$ event plane ($v_4\{{\Psi }_2\}$) gives good agreement with measured values, including the dependence on both transverse momentum and centrality. This provides confirmation that the collision system is indeed well described as a quark-gluon plasma with an extremely small viscosity and that correlations are dominantly generated from collective effects. In addition, we present a prediction for $v_5$.

We present a parameter-free postdiction of the high-$p_T$ charged-hadron nuclear modification factor ($R_{AA}$) in two centralities, measured by the CMS Collaboration in Pb-Pb collisions at the LHC. The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the $R_{AA}$ using a perturbative QCD-based formalism, the higher twist scheme. The transverse momentum diffusion coefficient $\widehat{q}$ is assumed to scale with the entropy density and is normalized by fitting the $R_{AA}$ in the most central Au-Au collisions at the Relativistic Heavy-Ion Collider. This setup is validated in noncentral Au-Au collisions at the Relativistic Heavy-Ion Collider and then extrapolated to Pb-Pb collisions at the LHC, keeping the relation between $\widehat{q}$ and entropy density unchanged. We obtain a satisfactory description of the CMS $R_{AA}$ over the $p_T$ range from 10 to 100 GeV.

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive ${}^{18}\mathrm{F}$, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes, but its reaction rate is not well determined because of the lack of experimental data at energies relevant to novae explosions. In this study, the reaction cross section has been measured directly for the first time in a wide energy range $E_{\mathrm{c}.\mathrm{m}.}\simeq 200–370\mathrm{keV}$ appropriate to hydrogen burning in classical novae. In addition, the $E_{\mathrm{c}.\mathrm{m}.}=183\mathrm{keV}$ resonance strength, $\omega \gamma =1.67\pm 0.12\mu \mathrm{eV}$, has been measured with the highest precision to date. The uncertainty on the ${}^{17}\mathrm{O}(p,\gamma ){}^{18}\mathrm{F}$ reaction rate has been reduced by a factor of 4, thus leading to firmer constraints on accurate models of novae nucleosynthesis.

The interaction of an $E/A=70$-MeV ${}^7\mathrm{Be}$ beam with a Be target was used to populate levels in ${}^6\mathrm{Be}$ following neutron knockout reactions. The three-body decay of the ground and first excited states into the $\alpha +p+p$ exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

We report on direct time-of-flight based mass measurements of 16 light neutron-rich nuclei. These include the first determination of the masses of the Borromean drip-line nuclei ${}^{19}\mathrm{B}$, ${}^{22}\mathrm{C}$, and ${}^{29}\mathrm{F}$ as well as that of ${}^{34}\mathrm{Na}$. In addition, the most precise determinations to date for ${}^{23}\mathrm{N}$ and ${}^{31}\mathrm{Ne}$ are reported. Coupled with recent interaction cross-section measurements, the present results support the occurrence of a two-neutron halo in ${}^{22}\mathrm{C}$, with a dominant $\nu 2s_{1/2}^2$ configuration, and a single-neutron halo in ${}^{31}\mathrm{Ne}$ with the valence neutron occupying predominantly the $2p_{3/2}$ orbital. Despite a very low two-neutron separation energy the development of a halo in ${}^{19}\mathrm{B}$ is hindered by the $1d_{5/2}^2$ character of the valence neutrons.

In this Letter, we study the impact of the inclusion of the recently measured beta decay properties of the ${}^{102;104;105;106;107}\mathrm{Tc}$, ${}^{105}\mathrm{Mo}$, and ${}^{101}\mathrm{Nb}$ nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes ${}^{235,238}\mathrm{U}$ and ${}^{239,241}\mathrm{Pu}$. These actinides are the main contributors to the fission processes in pressurized water reactors. The beta feeding probabilities of the above-mentioned Tc, Mo, and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of ${}^{239}\mathrm{Pu}$, solving a large part of the $\gamma$ discrepancy in the 4–3000 s range. They have been measured by using the total absorption technique, insensitive to the pandemonium effect. The calculations are performed by using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of ${}^{235}\mathrm{U}$, ${}^{239,241}\mathrm{Pu}$, and, in particular, ${}^{238}\mathrm{U}$ for which no measurement has been published yet. We conclude that new total absorption technique measurements are mandatory to improve the reliability of the predicted spectra.

We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range $150\mathrm{MeV}\le T\le 170\mathrm{MeV}$ the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%–15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.

Expansion dynamics at the yoctosecond time scale affect the evolution of the quark gluon plasma (QGP) created in heavy ion collisions. We show how these dynamics are accessible through Hanbury Brown–Twiss (HBT) intensity interferometry of direct photons emitted from the interior of the QGP. A detector placed close to the beam axis is particularly sensitive to early polar momentum anisotropies of the QGP. Observing a modification of the HBT signal at the proposed FoCal detector of the LHC ALICE experiment would allow us to measure the isotropization time of the plasma and could provide first experimental evidence for photon double pulses at the yoctosecond time scale.

We have measured the beam-normal single-spin asymmetry $A_n$ in the elastic scattering of 1–3 GeV transversely polarized electrons from ${}^1\mathrm{H}$ and for the first time from ${}^4\mathrm{He}$, ${}^{12}\mathrm{C}$, and ${}^{208}\mathrm{Pb}$. For ${}^1\mathrm{H}$, ${}^4\mathrm{He}$, and ${}^{12}\mathrm{C}$, the measurements are in agreement with calculations that relate $A_n$ to the imaginary part of the two-photon exchange amplitude including inelastic intermediate states. Surprisingly, the ${}^{208}\mathrm{Pb}$ result is significantly smaller than the corresponding prediction using the same formalism. These results suggest that a systematic set of new $A_n$ measurements might emerge as a new and sensitive probe of the structure of heavy nuclei.

Excited states in ${}^{38,40,42}\mathrm{Si}$ nuclei have been studied via in-beam $\gamma$-ray spectroscopy with multinucleon removal reactions. Intense radioactive beams of ${}^{40}\mathrm{S}$ and ${}^{44}\mathrm{S}$ provided at the new facility of the RIKEN Radioactive Isotope Beam Factory enabled $\gamma \mathrm{\text{−}}\gamma$ coincidence measurements. A prominent $\gamma$ line observed with an energy of 742(8) keV in ${}^{42}\mathrm{Si}$ confirms the $2^{+}$ state reported in an earlier study. Among the $\gamma$ lines observed in coincidence with the $2^{+}\to 0^{+}$ transition, the most probable candidate for the transition from the yrast $4^{+}$ state was identified, leading to a $4_1^{+}$ energy of 2173(14) keV. The energy ratio of 2.93(5) between the $2_1^{+}$ and $4_1^{+}$ states indicates well-developed deformation in ${}^{42}\mathrm{Si}$ at $N=28$ and $Z=14$. Also for ${}^{38,40}\mathrm{Si}$ energy ratios with values of 2.09(5) and 2.56(5) were obtained. Together with the ratio for ${}^{42}\mathrm{Si}$, the results show a rapid deformation development of Si isotopes from $N=24$ to $N=28$.

Isospin-dependent nuclear forces play a fundamental role in nuclear structure. In relativistic models of nuclear structure constructed at the quark level these isovector nuclear forces affect the $u$ and $d$ quarks differently, leading to nontrivial flavor-dependent modifications of the nuclear parton distributions. We explore the effect of isospin dependent forces for parity-violating deep inelastic scattering on nuclear targets and demonstrate that the cross sections for nuclei with $N\ne Z$ are sensitive to the flavor dependence of the EMC effect. Indeed, for nuclei like lead and gold we find that these flavor-dependent effects are large.

Recent calculations suggest that the rate of neutron capture by ${}^{130}\mathrm{Sn}$ has a significant impact on late-time nucleosynthesis in the $r$ process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the $N=82$ closed shell, so $r$-process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the ($d$,$p$) reaction has been studied in inverse kinematics using a 630 MeV beam of ${}^{130}\mathrm{Sn}$ ($4.8\mathrm{MeV}/\mathrm{u}$) and a $({\mathrm{CD}}_2{)}_n$ target. An array of Si strip detectors, including the Silicon Detector Array and an early implementation of the Oak Ridge Rutgers University Barrel Array, was used to detect reaction products. Results for the ${}^{130}\mathrm{Sn}(d,\text{}p){}^{131}\mathrm{Sn}$ reaction are found to be very similar to those from the previously reported ${}^{132}\mathrm{Sn}(d,\text{}p){}^{133}\mathrm{Sn}$ reaction. Direct-semidirect ($n$,$\gamma$) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates.

The orbital $M1$ scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-$\gamma$ coincidences are recorded with deuteron and ${}^3\mathrm{He}$-induced reactions on ${}^{232}\mathrm{Th}$. The residual nuclei ${}^{231,232,233}\mathrm{Th}$ and ${}^{232,233}\mathrm{Pa}$ show an unexpectedly strong integrated strength of $B_{M1}=11–15{\mu }_n^2$ in the $E_{\gamma }=1.0–3.5\mathrm{MeV}$ region. The increased $\gamma$-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis.

The neutron-rich lead isotopes, up to ${}^{216}\mathrm{Pb}$, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond ${}^{208}\mathrm{Pb}$.

Two years after the discovery of element 117, we undertook a second campaign using the ${}^{249}\mathrm{Bk}+{}^{48}\mathrm{Ca}$ reaction for further investigations of the production and decay properties of the isotopes of element 117 on a larger number of events. The experiments were started in the end of April 2012 and are still under way. This Letter presents the results obtained in 1200 hours of an experimental run with the beam dose of ${}^{48}\mathrm{Ca}$ of about $1.5\times {10}^{19}$ particles. The ${}^{249}\mathrm{Bk}$ target was irradiated at two energies of ${}^{48}\mathrm{Ca}$ that correspond to the maximum probability of the reaction channels with evaporation of three and four neutrons from the excited ${}^{297}117$. In this experiment, two decay chains of ${}^{294}117$ ($3n$) and five decay chains of ${}^{293}117$ ($4n$) were detected. In the course of the long-term work, ${}^{249}\mathrm{Cf}$—the product of decay of ${}^{249}\mathrm{Bk}$ (330 d)—is being accumulated in the target. Consequently, in the present experiment, we also detected a single decay of the known isotope ${}^{294}118$ that was produced during 2002–2005 in the reaction ${}^{249}\mathrm{Cf}({}^{48}\mathrm{Ca},3n){}^{294}118$. The obtained results are compared with the data from previous experiments. The experiments are carried out in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, using the heavy-ion cyclotron U400.

The passage of muons through matter is dominated by the Coulomb interaction with electrons and nuclei. The interaction with the electrons leads to continuous energy loss and stopping of the muons. The interaction with nuclei leads to angle “diffusion.” Two muon-imaging methods that use flux attenuation and multiple Coulomb scattering of cosmic-ray muons are being studied as tools for diagnosing the damaged cores of the Fukushima reactors. Here, we compare these two methods. We conclude that the scattering method can provide detailed information about the core. Attenuation has low contrast and little sensitivity to the core.

Neutral-pion ${\pi }^0$ spectra were measured at midrapidity ($|y|<0.35$) in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=39$ and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of $1<p_T<10\mathrm{GeV}/c$. The high-$p_T$ tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for $p+p$ collisions. The nuclear modification factors ($R_{AA}$) show significant suppression, with a distinct energy, centrality, and $p_T$ dependence. Above $p_T=7\mathrm{GeV}/c$, $R_{AA}$ is similar for $\sqrt{s_{\mathrm{NN}}}=62.4$ and 200 GeV at all centralities. Perturbative-quantum-chromodynamics calculations that describe $R_{AA}$ well at 200 GeV fail to describe the 39 GeV data, raising the possibility that, for the same $p_T$ region, the relative importance of initial-state effects and soft processes increases at lower energies. The $p_T$ range where ${\pi }^0$ spectra in central $\mathrm{Au}+\mathrm{Au}$ collisions have the same power as in $p+p$ collisions is $\approx 5$ and $7\mathrm{GeV}/c$ for $\sqrt{s_{\mathrm{NN}}}=200$ and 62.4 GeV, respectively. For the $\sqrt{s_{\mathrm{NN}}}=39\mathrm{GeV}$ data, it is not clear whether such a region is reached, and the $x_T$ dependence of the $x_T$-scaling power-law exponent is very different from that observed in the $\sqrt{s_{\mathrm{NN}}}=62$ and 200 GeV data, providing further evidence that initial-state effects and soft processes mask the in-medium suppression of hard-scattered partons to higher $p_T$ as the collision energy decreases.

We report the measurement of direct photons at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The direct photon signal was extracted for the transverse momentum range of $4\mathrm{GeV}/c<p_T<22\mathrm{GeV}/c$, using a statistical method to subtract decay photons from the inclusive photon sample. The direct photon nuclear modification factor $R_{\mathrm{AA}}$ was calculated as a function of $p_T$ for different $\mathrm{Au}+\mathrm{Au}$ collision centralities using the measured $p+p$ direct photon spectrum and compared to theoretical predictions. $R_{\mathrm{AA}}$ was found to be consistent with unity for all centralities over the entire measured $p_T$ range. Theoretical models that account for modifications of initial direct photon production due to modified parton distribution functions in Au and the different isospin composition of the nuclei predict a modest change of $R_{\mathrm{AA}}$ from unity. They are consistent with the data. Models with compensating effects of the quark-gluon plasma on high-energy photons, such as suppression of jet-fragmentation photons and induced-photon bremsstrahlung from partons traversing the medium, are also consistent with this measurement.

The transverse energy ($E_{\mathrm{T}}$) in Pb-Pb collisions at 2.76 TeV nucleon-nucleon center-of-mass energy ($\sqrt{s_{\mathrm{NN}}}$) has been measured over a broad range of pseudorapidity ($\eta$) and collision centrality by using the CMS detector at the LHC. The transverse energy density per unit pseudorapidity ($d{E}_{\mathrm{T}}/d\eta$) increases faster with collision energy than the charged particle multiplicity. This implies that the mean energy per particle is increasing with collision energy. At all pseudorapidities, the transverse energy per participating nucleon increases with the centrality of the collision. The ratio of transverse energy per unit pseudorapidity in peripheral to central collisions varies significantly as the pseudorapidity increases from $\eta =0$ to $|\eta |=5.0$. For the 5% most central collisions, the energy density per unit volume is estimated to be about $14\mathrm{GeV}/{\mathrm{fm}}^3$ at a time of $1\mathrm{fm}/c$ after the collision. This is about 100 times larger than normal nuclear matter density and a factor of 2.6 times higher than the energy density reported at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ at the Relativistic Heavy Ion Collider.

The $E1\mathrm{\text{−}}E2$ interference sign between the $E_{\mathrm{c}.\mathrm{m}.}=2.68-\mathrm{MeV}$ $E2$ resonance and an underlying $E1$ strength has been measured for the first time. An $E1\mathrm{\text{−}}E2$ asymmetry parameter of $a=0.07\pm 0.05$ was extracted from the thick-target $\gamma$-ray yields of the narrow resonance at angles of 45° and 135°. The positive sign of $a$ corresponded to constructive interference at forward angles and, further, allowed the interference between the resonance and an $E2$ background to be identified as constructive below the resonance energy. The $E2\mathrm{\text{−}}E2$ interference was then used to evaluate the global $S_{E2}$ data within the vicinity of the resonance $2.5\le E_{\mathrm{c}.\mathrm{m}.}\le 3.0\mathrm{MeV}$. An analysis of the global $S_{E2}$ data that agreed with the interference scenario has determined the $E2\mathrm{\text{−}}E2$ interference scheme of the 4.34-MeV resonance and background, resulting in a value of $S_{E2}(300)={62}_{-6}^{+9}\mathrm{keV}\mathrm{b}$.