The transfer of neutrons onto ${}^{24}\mathrm{Ne}$ has been measured using a reaccelerated radioactive beam of ${}^{24}\mathrm{Ne}$ to study the $(d,p)$ reaction in inverse kinematics. The unusual raising of the first $3/2^{+}$ level in ${}^{25}\mathrm{Ne}$ and its significance in terms of the migration of the neutron magic number from $N=20$ to $N=16$ is put on a firm footing by confirmation of this state’s identity. The raised $3/2^{+}$ level is observed simultaneously with the intruder negative parity $7/2^{-}$ and $3/2^{-}$ levels, providing evidence for the reduction in the $N=20$ gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the $3/2^{+}$ state shows that the established USD shell model breaks down well within the $sd$ model space and requires a revised treatment of the proton-neutron monopole interaction.

We perform coupled-cluster calculations of the energies and lifetimes of single-particle states around the doubly magic nucleus ${}^{16}\mathrm{O}$ based on chiral nucleon-nucleon interactions at next-to-next-to-next-to-leading order. To incorporate effects from the scattering continuum, we employ a Gamow-Hartree-Fock basis. Our calculations for the $J^{\pi }=1/2^{+}$ proton halo state in ${}^{17}\mathrm{F}$ and the $1/2^{+}$ state in ${}^{17}\mathrm{O}$ agree well with experiment, while the calculated spin-orbit splitting between $5/2^{+}$ and $3/2^{+}$ states is too small due to the lack of three-nucleon forces. Continuum effects yield a significant amount of additional binding energy for the $1/2^{+}$ and $3/2^{+}$ states in ${}^{17}\mathrm{O}$ and ${}^{17}\mathrm{F}$.

We show that a heavy quark moving sufficiently fast through a quark-gluon plasma may lose energy by Cherenkov-radiating mesons. We demonstrate that this takes place in all strongly coupled, large-$N_c$ plasmas with a gravity dual. The energy loss is exactly calculable in these models despite being an $\mathcal{O}(1/N_c)$ effect. We discuss implications for heavy-ion collision experiments.

A measurement of the energy and spin of superdeformed states in ${}^{190}\mathrm{Hg}$, obtained through the observation of transitions directly linking superdeformed and normal states, expands the number of isotopes in which binding energies at superdeformation are known. Comparison with neighboring nuclei shows that two-proton separation energies are higher in the superdeformed state than in the normal state, despite the lower Coulomb barrier and lower total binding energy. This unexpected result provides a critical test for nuclear models.

The discovery of a new chemical element with atomic number $Z=117$ is reported. The isotopes ${}^{293}117$ and ${}^{294}117$ were produced in fusion reactions between ${}^{48}\mathrm{Ca}$ and ${}^{249}\mathrm{Bk}$. Decay chains involving 11 new nuclei were identified by means of the Dubna gas-filled recoil separator. The measured decay properties show a strong rise of stability for heavier isotopes with $Z\ge 111$, validating the concept of the long sought island of enhanced stability for superheavy nuclei.

An unusual but effective way to determine at threshold the $d\pi \leftrightarrow NN$ transition strength $\alpha$ is to exploit the hadronic ground-state broadening ${\Gamma }_{1s}$ in pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated by the true absorption channel $d{\pi }^{-}\to nn$, which is related to $s$-wave pion production $pp\to d{\pi }^{+}$ by charge symmetry and detailed balance. Using the exotic atom circumvents the problem of Coulomb corrections to the cross section as necessary in the production experiments. Our dedicated measurement finds ${\Gamma }_{1s}=({1171}_{-49}^{+23})\mathrm{meV}$ yielding $\alpha =({252}_{-11}^{+5})\mu \mathrm{b}$.

This Letter presents the first measurement of event-by-event fluctuations of the elliptic flow parameter $v_2$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ as a function of collision centrality. The relative nonstatistical fluctuations of the $v_2$ parameter are found to be approximately 40%. The results, including contributions from event-by-event elliptic flow fluctuations and from azimuthal correlations that are unrelated to the reaction plane (nonflow correlations), establish an upper limit on the magnitude of underlying elliptic flow fluctuations. This limit is consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. These results provide important constraints on models of the initial state and hydrodynamic evolution of relativistic heavy ion collisions.

We present lattice results for the ground state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our analysis includes isospin breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.

We have analyzed data of the DISTO experiment on the exclusive $pp\to p\Lambda K^{+}$ reaction at 2.85 GeV to search for a strongly bound compact $K^{-}pp(\equiv X)$ state to be formed in the $pp\to K^{+}+X$ reaction. The observed spectra of the $K^{+}$ missing mass and the $p\Lambda$ invariant-mass with high transverse momenta of $p$ and $K^{+}$ revealed a broad distinct peak of $26\mathrm{\text{−}}\sigma$ confidence with a mass $M_X=2267\pm 3(\mathrm{stat})\pm 5(\mathrm{syst})\mathrm{MeV}/c^2$ and a width ${\Gamma }_X=118\pm 8(\mathrm{stat})\pm 10(\mathrm{syst})\mathrm{MeV}$. The enormously large cross section indicates formation of a compact $K^{-}pp$ with a large binding energy of $B_K=103\mathrm{MeV}$, which can be a possible gateway toward cold and dense kaonic nuclear matter.

A first experiment is reported that makes use of a new kind of spectrometer uniquely suited to the study of reactions with radioactive beams in inverse kinematics, the helical orbit spectrometer, HELIOS. The properties of some low-lying states in the neutron-rich $N=8$ nucleus ${}^{13}\mathrm{B}$ were studied with good resolution. From the measured angular distributions of the $(d,\text{}p)$ reaction and the relative spectroscopic factors, spin and configuration assignments of the first- and third-excited states of this nucleus can be constrained.

The production of $e^{+}{e}^{-}$ pairs for $m_{e^{+}{e}^{-}}<0.3\mathrm{GeV}/c^2$ and $1<p_T<5\mathrm{GeV}/c$ is measured in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central $\mathrm{Au}+\mathrm{Au}$ collisions, the excess of the direct photon yield over $p+p$ is exponential in transverse momentum, with an inverse slope $T=221\pm {19}^{\mathrm{stat}}\pm {19}^{\mathrm{syst}}\mathrm{MeV}$. Hydrodynamical models with initial temperatures ranging from $T_{\mathrm{init}}\sim 300–600\mathrm{MeV}$ at times of $\sim 0.6–0.15\mathrm{fm}/c$ after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at $\sim 170\mathrm{MeV}$.

Spectroscopic factors have been extracted for proton-rich ${}^{34}\mathrm{Ar}$ and neutron-rich ${}^{46}\mathrm{Ar}$ using the ($p$, $d$) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton-rich nucleus ${}^{34}\mathrm{Ar}$ compared to that of ${}^{46}\mathrm{Ar}$. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements.

Elliptic flow is a hallmark of collectivity in hadronic collisions. Its measurement relies on analysis techniques which require high event multiplicity and so far can only be applied to heavy ion collisions. Here, we delineate the conditions under which elliptic flow becomes measurable in the samples of high-multiplicity ($d{N}_{\mathrm{ch}}/dy\ge 50$) $p\mathrm{\text{−}}p$ collisions, which will soon be collected at the LHC. We observe that fluctuations in the $p\mathrm{\text{−}}p$ interaction region can result in a sizable spatial eccentricity even for the most central $p\mathrm{\text{−}}p$ collisions. Under relatively mild assumptions on the nature of such fluctuations and on the eccentricity scaling of elliptic flow, we find that the resulting elliptic flow signal in high-multiplicity $p\mathrm{\text{−}}p$ collisions at the LHC becomes measurable with standard techniques.

High-sensitivity studies of $E1$ and $M1$ transitions observed in the reaction ${}^{138}\mathrm{Ba}(\overrightarrow{\gamma },{\gamma }^{\prime })$ at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the $\mathrm{HI}\overrightarrow{\gamma }\mathrm{S}$ facility. The electric dipole character of the so-called “pygmy” dipole resonance was experimentally verified for excitations from 4.0 to 8.6 MeV. The fine structure of the $M1$ “spin-flip” mode was observed for the first time in $N=82$ nuclei.

A measurement of two-particle correlations with a high transverse momentum trigger particle ($p_T^{\mathrm{trig}}>2.5\mathrm{GeV}/c$) is presented for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ over the uniquely broad longitudinal acceptance of the PHOBOS detector ($-4<\Delta \eta <2$). A broadening of the away-side azimuthal correlation compared to elementary collisions is observed at all $\Delta \eta$. As in $p+p$ collisions, the near side is characterized by a peak of correlated partners at small angle relative to the trigger particle. However, in central $\mathrm{Au}+\mathrm{Au}$ collisions an additional correlation extended in $\Delta \eta$ and known as the “ridge” is found to reach at least $|\Delta \eta |\approx 4$. The ridge yield is largely independent of $\Delta \eta$ over the measured range, and it decreases towards more peripheral collisions. For the chosen $p_T^{\mathrm{trig}}$ cut, the ridge yield is consistent with zero for events with less than roughly 100 participating nucleons.

Reaction cross sections (${\sigma }_R$) for ${}^{19}\mathrm{C}$, ${}^{20}\mathrm{C}$ and the drip-line nucleus ${}^{22}\mathrm{C}$ on a liquid hydrogen target have been measured at around $40A\mathrm{MeV}$ by a transmission method. A large enhancement of ${\sigma }_R$ for ${}^{22}\mathrm{C}$ compared to those for neighboring C isotopes was observed. Using a finite-range Glauber calculation under an optical-limit approximation the rms matter radius of ${}^{22}\mathrm{C}$ was deduced to be $5.4\pm 0.9\mathrm{fm}$. It does not follow the systematic behavior of radii in carbon isotopes with $N\le 14$, suggesting a neutron halo. It was found by an analysis based on a few-body Glauber calculation that the two-valence neutrons in ${}^{22}\mathrm{C}$ preferentially occupy the $1s_{1/2}$ orbital.

We show that two almost degenerate poles near the $\pi \Delta$ threshold and the next higher mass pole in the $P_{11}$ partial wave of $\pi N$ scattering evolve from a single bare state through its coupling with $\pi N$, $\eta N$, and $\pi \pi N$ reaction channels. This finding provides new information on understanding the dynamical origins of the Roper $N^{*}(1440)$ and $N^{*}(1710)$ resonances listed by Particle Data Group. Our results for the resonance poles in other $\pi N$ partial waves are also presented.

We compare the azimuthal correlations arising from three and two hadron production in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$. We show that in $\mathrm{Au}+\mathrm{Au}$, the two away side partons in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Since in average the particle with the shortest path length in two-to-three processes loses less energy, with respect to the away-side particle in two-to-two processes, this effect leads to a relative enhancement of the ratio of two-to-three to two-to-two processes in $\mathrm{Au}+\mathrm{Au}$ compared to $p+p$ collisions. We argue that this phenomenon may be responsible for the shape of the away side in azimuthal correlations at the Relativistic Heavy-Ion Collider.

Excited states in ${}^{212}\mathrm{Po}$ were populated by $\alpha$ transfer using the ${}^{208}\mathrm{Pb}({}^{18}\mathrm{O},{}^{14}\mathrm{C})$ reaction, and their deexcitation $\gamma$ rays were studied with the Euroball array. Several levels were found to decay by a unique $E1$ transition ($E_{\gamma }<1\mathrm{MeV}$) populating the yrast state with the same spin value. Their lifetimes were measured by the Doppler-shift attenuation method. The values, found in the range 0.1–1.4 ps, lead to very enhanced transitions, $B(E1)=2\times {10}^{-2}–1\times {10}^{-3}\mathrm{W}.\mathrm{u}.$ These results are discussed in terms of an $\alpha$-cluster structure which gives rise to states with non-natural-parity values, provided that the composite system cannot rotate collectively, as expected in the “$\alpha +{}^{208}\mathrm{Pb}$” case. Such states due to the oscillatory motion of the $\alpha$-core distance are observed for the first time.

The first example of an empirically manifested quasidynamical symmetry trajectory in the interior of the symmetry triangle of the interacting boson approximation model is identified for large boson numbers. Along this curve, extending from SU(3) to near the critical line of the first order phase transition, spectra exhibit nearly the same degeneracies that characterize the low energy levels of SU(3). This trajectory also lies close to the Alhassid-Whelan arc of regularity, the unique interior region of regular behavior connecting the SU(3) and U(5) vertices, thus offering a possible symmetry-based interpretation of that narrow zone of regularity amidst regions of more chaotic spectra.