We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions, and the coupling to the particle continuum is taken into account using a Berggren basis. The computed ground-state energies and the low-lying $J^{\pi }=2^{+}$ states for the isotopes ${}^{42,48,50,52}\mathrm{Ca}$ are in good agreement with data, and we predict the excitation energy of the first $J^{\pi }=2^{+}$ state in ${}^{54}\mathrm{Ca}$ at 1.9 MeV, displaying only a weak subshell closure. In the odd-mass nuclei ${}^{53,55,61}\mathrm{Ca}$ we find that the positive parity states deviate strongly from the naive shell model.

The shell model Monte Carlo method is a powerful technique to calculate thermal and ground-state properties of strongly correlated finite-size systems. However, its application to odd-particle-number systems has been hampered by the sign problem that originates from the projection on an odd number of particles. We circumvent this sign problem for the ground-state energy by extracting the ground-state energy of the odd-particle-number system from the asymptotic behavior of the imaginary-time single-particle Green’s function of the even-particle-number system. We apply this method to calculate pairing gaps of nuclei in the iron region. Our results are in good agreement with experimental pairing gaps.

Atomic masses of the neutron-rich isotopes ${}^{121–128}\mathrm{Cd}$, ${}^{129,131}\mathrm{In}$, ${}^{130–135}\mathrm{Sn}$, ${}^{131–136}\mathrm{Sb}$, and ${}^{132–140}\mathrm{Te}$ have been measured with high precision (10 ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four $r$-process nuclei ${}^{135}\mathrm{Sn}$, ${}^{136}\mathrm{Sb}$, and ${}^{139,140}\mathrm{Te}$ were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N=82$ for Sn, with a $Z$ dependence that is unexplainable by the current theoretical models.

The unbound excited states of the neutron drip-line isotope ${}^{24}\mathrm{O}$ have been investigated via the ${}^{24}\mathrm{O}(p,p^{\prime }){}^{23}\mathrm{O}+n$ reaction in inverse kinematics at a beam energy of $62\mathrm{MeV}/\mathrm{nucleon}$. The decay energy spectrum of ${}^{24}\mathrm{O}^{*}$ was reconstructed from the momenta of ${}^{23}\mathrm{O}$ and the neutron. The spin parity of the first excited state, observed at $E_x=4.65\pm 0.14\mathrm{MeV}$, was determined to be $J^{\pi }=2^{+}$ from the angular distribution of the cross section. Higher-lying states were also observed. The quadrupole transition parameter ${\beta }_2$ of the $2_1^{+}$ state was deduced, for the first time, to be $0.15\pm 0.04$. The relatively high excitation energy and small ${\beta }_2$ value are indicative of the $N=16$ shell closure in ${}^{24}\mathrm{O}$.

The azimuthal anisotropy of charged particles in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ is measured with the CMS detector at the LHC over an extended transverse momentum ($p_{\mathrm{T}}$) range up to approximately $60\mathrm{GeV}/c$. The data cover both the low-$p_{\mathrm{T}}$ region associated with hydrodynamic flow phenomena and the high-$p_{\mathrm{T}}$ region where the anisotropies may reflect the path-length dependence of parton energy loss in the created medium. The anisotropy parameter ($v_2$) of the particles is extracted by correlating charged tracks with respect to the event-plane reconstructed by using the energy deposited in forward-angle calorimeters. For the six bins of collision centrality studied, spanning the range of 0–60% most-central events, the observed $v_2$ values are found to first increase with $p_{\mathrm{T}}$, reaching a maximum around $p_{\mathrm{T}}=3\mathrm{GeV}/c$, and then to gradually decrease to almost zero, with the decline persisting up to at least $p_{\mathrm{T}}=40\mathrm{GeV}/c$ over the full centrality range measured.

The rotational band structure of the $Z=104$ nucleus ${}^{256}\mathrm{Rf}$ has been observed up to a tentative spin of $20\hslash$ using state-of-the-art $\gamma$-ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-$j$ orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at $Z=104$, which is predicted in a number of current self-consistent mean-field models.

The double-differential cross sections for the ${}^{208}\mathrm{Pb}$ and ${}^{90}\mathrm{Zr}(t,{}^3\mathrm{He})$ reactions at $300\mathrm{MeV}/u$ have been measured at the RI Beam Factory at RIKEN. This was the first physics experiment with the SHARAQ magnetic spectrometer. The combined analysis of the present $(t{,}^3\mathrm{He})$ data and previous ($n,p$) data provides the clearest identification for the ${\beta }^{+}$ isovector spin monopole resonance both in the ${}^{208}\mathrm{Tl}$ and ${}^{90}\mathrm{Y}$ nuclei, and puts the observations of this giant resonance on a firm foundation. The measured distributions of the ($t,{}^3\mathrm{He}$) monopole cross sections were well reproduced by the distorted-wave Born approximation calculation, where the target transition density was calculated with the self-consistent Hartree-Fock plus random-phase approximation using the T43 Skyrme interaction. A major part of the expected ${\beta }^{+}$ isovector spin monopole strength was found in the measured cross section spectra.

Material emitted as ejecta from ONe novae outbursts is observed to be rich in elements as heavy as Ca. The bottleneck for the synthesis of elements beyond sulphur is the ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ reaction. Its reaction rate is, however, not well determined due to uncertainties in the properties of key resonances in the burning regime. In the present study, gamma-ray transitions are reported for the first time from all key states in ${}^{31}\mathrm{S}$ relevant for the ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ reaction. The spins and parity of these resonances have been deduced, and energies have been measured with the highest precision to date. The uncertainty in the estimated ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ reaction rate has been drastically reduced. The rate using this new information is typically higher than previous estimates based on earlier experimental data, implying a higher flux of material processed to high-$Z$ elements in novae, but it is in good agreement with predictions using the Hauser-Feshbach approach at higher burning temperatures.

A high-resolution measurement of inelastic proton scattering off ${}^{90}\mathrm{Zr}$ near 0° was performed at 295 MeV with a focus on a pronounced strength previously reported in the low-energy tail of giant dipole resonance. A forest of fine structure was observed in the excitation energy region 7–12 MeV. A multipole decomposition analysis of the angular distribution for the forest was carried out using the ECIS95 distorted-wave Born approximation code with the Hartree-Fock plus random-phase approximation model of $E1$ and $M1$ transition densities and inclusion of $E1$ Coulomb excitation. The analysis separated pygmy dipole and $M1$ resonances in the forest at $E_{\mathrm{PDR}}=9.15\pm 0.18\mathrm{MeV}$ with ${\Gamma }_{\mathrm{PDR}}=2.91\pm 0.64\mathrm{MeV}$ and at $E_{M1}=9.53\pm 0.06\mathrm{MeV}$ with ${\Gamma }_{M1}=2.70\pm 0.17\mathrm{MeV}$ in the Lorentzian function, respectively. The $B(E1)\uparrow$ value for pygmy dipole resonance over 7–11 MeV is $0.75\pm 0.08e^2{\mathrm{fm}}^2$, which corresponds to $2.1\pm 0.2\%$ of the Thomas-Reiche-Kuhn sum rule.

It is shown that at sufficiently large $N_c$ for incident momenta which are much larger than the QCD scale, the total nucleon-nucleon cross section is independent of incident momentum and given by ${\sigma }^{\mathrm{total}}=2\pi {log}^2(N_c)/(m_{\pi }^2)$. This result is valid in the extreme large $N_c$ regime of $\log (N_c)\gg 1$ and has corrections of relative order $\log \mathbf{(}\log (N_c)\mathbf{)}/\log (N_c)$. A possible connection of this result to the Froissart-Martin bound is discussed.

We report on the single neutron and proton removal reactions from unstable nuclei with large asymmetry $\Delta S=S_n-S_p$ at incident energies below $80\mathrm{MeV}/\mathrm{nucleon}$. Strong nonsudden effects are observed in the case of deeply-bound-nucleon removal. The corresponding parallel momentum distributions exhibit an abrupt cutoff at high momentum that corresponds to an energy threshold occurring when the incident energy per particle is of comparable magnitude to the nucleon separation energy. A large low-momentum tail is related to both dissipative processes and the dynamics of the nucleon removal process. New limits for the applicability of the sudden and eikonal approximations in nucleon knockout are given.

We analyze published data from the ALICE Collaboration in order to obtain the first extraction of the recently proposed rapidity-even directed flow observable $v_1$. An accounting of the correlation due to the conservation of transverse momentum restores the factorization seen by ALICE in all other Fourier harmonics and thus indicates that the remaining correlation gives a reliable measurement of directed flow. We then carry out the first viscous hydrodynamic calculation of directed flow, and show that it is less sensitive to viscosity than higher harmonics. This allows for a direct extraction of the dipole asymmetry of the initial state, providing a strict constraint on the nonequilibrium dynamics of the early-time system. A prediction is then made for $v_1$ in Au-Au collisions at RHIC.

We compute initial conditions in heavy ion collisions within the color glass condensate framework by combining the impact parameter dependent saturation model with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this impact parameter dependent Glasma description includes quantum fluctuations of color charges on the length scale determined by the inverse nuclear saturation scale $Q_s$. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity ${\epsilon }_3/{\epsilon }_2$ is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and $v_{2,3,4}(p_T)$ of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.

We employ interactions from chiral effective field theory and compute binding energies, excited states, and radii for isotopes of oxygen with the coupled-cluster method. Our calculation includes the effects of three-nucleon forces and of the particle continuum, both of which are important for the description of neutron-rich isotopes in the vicinity of the nucleus ${}^{24}\mathrm{O}$. Our main results are the placement of the neutron drip line at ${}^{24}\mathrm{O}$, the assignment of spins, parities and resonance widths for several low-lying states of the drip line nucleus, and an efficient approximation that incorporates the effects of three-body interactions.

The ${}^{18}\mathrm{Ne}(\alpha ,p){}^{21}\mathrm{Na}$ reaction provides one of the main HCNO-breakout routes into the $rp$ process in x-ray bursts. The ${}^{18}\mathrm{Ne}(\alpha ,p_0){}^{21}\mathrm{Na}$ reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures $T\sim 2\mathrm{GK}$ by measuring its time-reversal reaction ${}^{21}\mathrm{Na}(p,\alpha ){}^{18}\mathrm{Ne}$ in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the ${}^{18}\mathrm{Ne}(\alpha ,p){}^{21}\mathrm{Na}$ reaction.

We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham’s formula is corrected, and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find $\delta M_{p\mathrm{\text{−}}n}^{\gamma }=1.30(03)(47)\mathrm{MeV}$. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input from lattice QCD to constrain this polarizability as: ${\beta }_{p-n}=-0.87(85)\times {10}^{-4}{\mathrm{fm}}^3$.

The reduced transition probability $B(E2;0_{gs}^{+}\to 2_1^{+})$ for ${}^{28}\mathrm{S}$ was obtained experimentally using Coulomb excitation at $53\mathrm{MeV}/\mathrm{nucleon}$. The resultant $B(E2)$ value $181(31)e^2{\mathrm{fm}}^4$ is smaller than the expectation based on empirical $B(E2)$ systematics. The double ratio $|M_n/M_p|/(N/Z)$ of the $0_{gs}^{+}\to 2_1^{+}$ transition in ${}^{28}\mathrm{S}$ was determined to be 1.9(2) by evaluating the $M_n$ value from the known $B(E2)$ value of the mirror nucleus ${}^{28}\mathrm{Mg}$, showing the hindrance of proton collectivity relative to that of neutrons. These results indicate the emergence of the magic number $Z=16$ in the $|T_z|=2$ nucleus ${}^{28}\mathrm{S}$.

Charge correlations in lattice gauge calculations suggest that up, down, and strange charges move independently in the quark-gluon plasma, and that the density of such charges is similar to what is expected from simple thermal arguments. Here, we show how specific elements of the charge-charge correlation matrix in the quark-gluon plasma survive hadronization and become manifest in final-state charge-charge correlation measurements.

Recent high-precision mass measurements of ${}^9\mathrm{Li}$ and ${}^9\mathrm{Be}$, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous isobaric mass multiplet equation behavior for the two $A=9$ quartets. The presence of a cubic $d=6.3(17)\mathrm{keV}$ term for the $J^{\pi }=3/2^{-}$ quartet and the vanishing cubic term for the excited $J^{\pi }=1/2^{-}$ multiplet depend upon the presence of a nearby $T=1/2$ state in ${}^9\mathrm{B}$ and ${}^9\mathrm{Be}$ that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. $T=1/2$ states have been observed near the calculated energy, above the $T=3/2$ state. However, an experimental confirmation of their $J^{\pi }$ is needed.

STAR’s measurements of directed flow ($v_1$) around midrapidity for ${\pi }^{\pm }$, $K^{\pm }$, $K_S^0$, $p$, and $\overline{p}$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ are presented. A negative $v_1(y)$ slope is observed for most of produced particles (${\pi }^{\pm }$, $K^{\pm }$, $K_S^0$, and $\overline{p}$). In 5%–30% central collisions, a sizable difference is present between the $v_1(y)$ slope of protons and antiprotons, with the former being consistent with zero within errors. The $v_1$ excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination, and a hydrodynamics model with a tilted source) are made. For those models which have calculations of $v_1$ for both pions and protons, none of them can describe $v_1(y)$ for pions and protons simultaneously. The hydrodynamics model with a tilted source as currently implemented cannot explain the centrality dependence of the difference between the $v_1(y)$ slopes of protons and antiprotons.