We point out that the quartic cumulant (and kurtosis) of the order parameter fluctuations is universally negative when the critical point is approached on the crossover side of the phase separation line. As a consequence, the kurtosis of a fluctuating observable, such as, e.g., proton multiplicity, may become smaller than the value given by independent Poisson statistics. We discuss implications for the beam energy scan program at RHIC at BNL.

One of the most promising probes to study deconfined matter created in high energy nuclear collisions is the energy loss of (heavy) quarks. It has been shown in experiments at the Relativistic Heavy Ion Collider that even charm and bottom quarks, despite their high mass, experience a remarkable medium suppression in the quark gluon plasma. In this exploratory investigation we study the energy loss of heavy quarks in high multiplicity proton-proton collisions at LHC energies. Although the colliding systems are smaller than compared to those at the Relativistic Heavy Ion Collider ($p+p$ vs $\mathrm{Au}+\mathrm{Au}$), the higher energy might lead to multiplicities comparable to $\mathrm{Cu}+\mathrm{Cu}$ collisions at the Relativistic Heavy Ion Collider. The interaction of charm quarks with this environment gives rise to a non-negligible suppression of high momentum heavy quarks in elementary collisions.

Charge-changing cross sections ${\sigma }_{\mathrm{cc}}$ of stable and unstable nuclei (${}^{9–11}\mathrm{Be}$, ${}^{14–16}\mathrm{C}$, and ${}^{16–18}\mathrm{O}$) on a carbon target were investigated at $300\mathrm{MeV}/\mathrm{nucleon}$. A phenomenological analysis based on the Glauber theory indicates an approximate, but universal, scaling of ${\sigma }_{\mathrm{cc}}$ over a wide range of $A/Z$. This allows the determination of the density distributions of protons tightly bound in the nuclei. An application to ${}^{16}\mathrm{C}$, which is considered to be an anomalously deformed nucleus, indicates a systematic evolution of proton root-mean-square radii and has revealed for the first time a neutron skin effect in carbon isotopes. Being complementary to isotope-shift and electron-scattering experiments, the present method can open up a new approach to explore the structure of exotic nuclei.

We report on the first measurement of the triangular $v_3$, quadrangular $v_4$, and pentagonal $v_5$ charged particle flow in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow $v_2$ and $v_3$ have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.

We present microscopic coupled-cluster calculations of the spectroscopic factors for proton removal from the closed-shell oxygen isotopes ${}^{14,16,22,24,28}\mathrm{O}$ with a chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order. We include coupling-to-continuum degrees of freedom by using a Hartree-Fock basis built from a Woods-Saxon single-particle basis. This basis treats bound and continuum states on an equal footing. We find a significant quenching of spectroscopic factors in the neutron-rich oxygen isotopes, pointing to enhanced many-body correlations induced by strong coupling to the scattering continuum above the neutron emission thresholds.

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for $Q^2=0.22{\mathrm{GeV}}^2/c^2$ and $0.63{\mathrm{GeV}}^2/c^2$ at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic ($\pi N$) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.

A formula for the relationship between the $\alpha$-decay energies ($Q$ values) of superheavy nuclei (SHN) is presented, which is composed of the effects of Coulomb energy and symmetry energy. It can be employed not only to validate the experimental observations and measurements to a large extent, but also to predict the $Q$ values of heaviest SHN with a high accuracy generally which will be very useful for future experiments. Furthermore, the shell closures in superheavy region and the effect of the symmetry energy on the stability of SHN against $\alpha$ decay are discussed with the help of this formula.

We report on the first direct measurement of the proton separation energy for the proton-unbound nucleus ${}^{69}\mathrm{Br}$. Bypassing the ${}^{68}\mathrm{Se}$ waiting point in the rp process is directly related to the $2p$-capture rate through ${}^{69}\mathrm{Br}$, which depends exponentially on the proton separation energy. We find a proton separation energy for ${}^{69}\mathrm{Br}$ of $S_p({}^{69}\mathrm{Br})=-{785}_{-40}^{+34}\mathrm{keV}$; this is less bound compared to previous predictions which have relied on uncertain theoretical calculations. The influence of the extracted proton separation energy on the rp process occurring in type I x-ray bursts is examined within the context of a one-zone burst model.

We show that the Bogoliubov–de Gennes equations for nuclear ground-state wave functions support solutions in which the condensate has a mixture of spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates do not occur when there are equal numbers of neutrons and protons, but only when there is an isospin imbalance. Using a phenomenological Hamiltonian, we predict that such nuclei may occur in the physical region within the proton dripline. We also solve the Bogoliubov–de Gennes equations with variable constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei that exhibit this new pairing behavior, the resulting energy surface can be rather soft, suggesting that there may be low-lying excitations associated with the spin mixing.

A precise determination of the neutron skin $\Delta r_{np}$ of a heavy nucleus sets a basic constraint on the nuclear symmetry energy ($\Delta r_{np}$ is the difference of the neutron and proton rms radii of the nucleus). The parity radius experiment (PREX) may achieve it by electroweak parity-violating electron scattering (PVES) on ${}^{208}\mathrm{Pb}$. We investigate PVES in nuclear mean field approach to allow the accurate extraction of $\Delta r_{np}$ of ${}^{208}\mathrm{Pb}$ from the parity-violating asymmetry $A_{\mathrm{PV}}$ probed in the experiment. We demonstrate a high linear correlation between $A_{\mathrm{PV}}$ and $\Delta r_{np}$ in successful mean field forces as the best means to constrain the neutron skin of ${}^{208}\mathrm{Pb}$ from PREX, without assumptions on the neutron density shape. Continuation of the experiment with higher precision in $A_{\mathrm{PV}}$ is motivated since the present method can support it to constrain the density slope of the nuclear symmetry energy to new accuracy.

We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction $pn\to d{\pi }^0{\pi }^0$ over the full energy region of the ABC effect, a pronounced low-mass enhancement in the $\pi \pi$-invariant mass spectrum. The measurements, which cover also the transition region to the conventional $t$-channel $\Delta \Delta$ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with $m=2.37\mathrm{GeV}$, $\Gamma \approx 70\mathrm{MeV}$ and $I(J^P)=0(3^{+})$ in both $pn$ and $\Delta \Delta$ systems. Necessary further tests of the resonance interpretation are discussed.

We investigate photon production in a scenario of quark-gluon plasma formation in proton-proton scattering at 7 TeV. It is shown that thermal photon yields increase quadratically with the charged particle multiplicity. This gives an enhanced weight to high multiplicity events, and leads to an important photon production even in minimum-bias events, where the thermal photons largely dominate over the prompt ones at transverse momentum values smaller than $10\mathrm{GeV}/c$.

We present a new ab initio method that uses similarity renormalization group (SRG) techniques to continuously diagonalize nuclear many-body Hamiltonians. In contrast with applications of the SRG to two- and three-nucleon interactions in free space, we perform the SRG evolution “in medium” directly in the $A$-body system of interest. The in-medium approach has the advantage that one can approximately evolve $3,\dots ,A$-body operators using only two-body machinery based on normal-ordering techniques. The method is nonperturbative and can be tailored to problems ranging from the diagonalization of closed-shell nuclei to the construction of effective valence-shell Hamiltonians and operators. We present first results for the energies of ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$, which have accuracies comparable to coupled-cluster calculations.

The radiative neutron capture on lithium-7 is calculated model independently using a low-energy halo effective field theory. The cross section is expressed in terms of scattering parameters directly related to the $S$-matrix elements. It depends on the poorly known $p$-wave effective range parameter $r_1$. This constitutes the largest uncertainty in traditional model calculations. It is explicitly demonstrated by comparing with potential model calculations. A single parameter fit describes the low-energy data extremely well and yields $r_1\approx -1.47{\mathrm{fm}}^{-1}$.

We investigate the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta /s$ on the transverse momentum spectra and elliptic flow of hadrons in ultrarelativistic heavy-ion collisions. We find that the elliptic flow in $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC is dominated by the viscosity in the hadronic phase and in the phase transition region, but largely insensitive to the viscosity of the quark-gluon plasma (QGP). At the highest LHC energy, the elliptic flow becomes sensitive to the QGP viscosity and insensitive to the hadronic viscosity.

A search for $Z$ bosons in the ${\mu }^{+}{\mu }^{-}$ decay channel has been performed in PbPb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ with the CMS detector at the LHC, in a $7.2\mu {\mathrm{b}}^{-1}$ data sample. The number of opposite-sign muon pairs observed in the $60–120\mathrm{GeV}/c^2$ invariant mass range is 39, corresponding to a yield per unit of rapidity ($y$) and per minimum bias event of $[33.8\pm 5.5(\mathrm{stat})\pm 4.4(\mathrm{syst})]\times {10}^{-8}$, in the $|y|<2.0$ range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.

We report the microscopic origins of the anomalously suppressed beta decay of ${}^{14}\mathrm{C}$ to ${}^{14}\mathrm{N}$ using the ab initio no-core shell model with the Hamiltonian from the chiral effective field theory including three-nucleon force terms. The three-nucleon force induces unexpectedly large cancellations within the $p$ shell between contributions to beta decay, which reduce the traditionally large contributions from the nucleon-nucleon interactions by an order of magnitude, leading to the long lifetime of ${}^{14}\mathrm{C}$.

The low-lying states in ${}^{106}\mathrm{Zr}$ and ${}^{108}\mathrm{Zr}$ have been investigated by means of $\beta \mathrm{\text{−}}\gamma$ and isomer spectroscopy at the radioactive isotope beam factory (RIBF), respectively. A new isomer with a half-life of $620\pm 150\mathrm{ns}$ has been identified in ${}^{108}\mathrm{Zr}$. For the sequence of even-even Zr isotopes, the excitation energies of the first $2^{+}$ states reach a minimum at $N=64$ and gradually increase as the neutron number increases up to $N=68$, suggesting a deformed subshell closure at $N=64$. The deformed ground state of ${}^{108}\mathrm{Zr}$ indicates that a spherical subshell gap predicted at $N=70$ is not large enough to change the ground state of ${}^{108}\mathrm{Zr}$ to the spherical shape. The possibility of a tetrahedral shape isomer in ${}^{108}\mathrm{Zr}$ is also discussed.

A new robust method to extract the specific shear viscosity $(\eta /s{)}_{\mathrm{QGP}}$ of a quark-gluon plasma (QGP) at temperatures $T_c<T\lesssim 2T_c$ from the centrality dependence of the eccentricity-scaled elliptic flow $v_2/\epsilon$ measured in ultrarelativistic heavy-ion collisions is presented. Coupling viscous fluid dynamics for the QGP with a microscopic transport model for hadronic freeze-out we find for 200 $A$ GeV $\mathrm{Au}+\mathrm{Au}$ collisions that $v_2/\epsilon$ is a universal function of multiplicity density $(1/S)(d{N}_{\mathrm{ch}}/dy)$ that depends only on the viscosity but not on the model used for computing the initial fireball eccentricity $\epsilon$. Comparing with measurements we find $1<4\pi (\eta /s{)}_{\mathrm{QGP}}<2.5$ where the uncertainty range is dominated by model uncertainties for the values of $\epsilon$ used to normalize the measured $v_2$.

The Hoyle state plays a crucial role in the helium burning of stars heavier than our Sun and in the production of carbon and other elements necessary for life. This excited state of the carbon-12 nucleus was postulated by Hoyle as a necessary ingredient for the fusion of three alpha particles to produce carbon at stellar temperatures. Although the Hoyle state was seen experimentally more than a half century ago nuclear theorists have not yet uncovered the nature of this state from first principles. In this Letter we report the first ab initio calculation of the low-lying states of carbon-12 using supercomputer lattice simulations and a theoretical framework known as effective field theory. In addition to the ground state and excited spin-2 state, we find a resonance at $-85(3)\mathrm{MeV}$ with all of the properties of the Hoyle state and in agreement with the experimentally observed energy.