The extended radius of a halo nuclide is very sensitive to the minute binding energy of its valence nucleons. The binding energy of ${}^{11}\mathrm{Li}$ has been measured with high precision by using the radio-frequency spectrometer MISTRAL at CERN’s ISOLDE facility. The new two-neutron separation energy of $378\pm 5\mathrm{keV}$ is 25% higher than the previously accepted value with an uncertainty 5 times smaller.

We measure the hyperfine splitting of the $9S_{1/2}$ level of ${}^{210}\mathrm{Fr}$, and find a magnetic dipole hyperfine constant $A=622.25(36)\mathrm{MHz}$. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of $4.38(5){\mu }_N$ for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.

The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio $\eta /s$ for a gluon gas, which involves elastic $gg\to gg$ perturbative QCD (PQCD) scatterings as well as inelastic $gg\leftrightarrow ggg$ PQCD bremsstrahlung. For ${\alpha }_s=0.3$ we find $\eta /s=0.13$ and for ${\alpha }_s=0.6$, $\eta /s=0.076$. The small $\eta /s$ values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.

Inclusive inelastic electron scattering off the deuteron under 180° has been studied at the S-DALINAC close to the breakup threshold at momentum transfers $q=0.27{\mathrm{fm}}^{-1}$ and $0.74{\mathrm{fm}}^{-1}$ with good energy resolution sufficient to map in detail the spin flip $M1$ response, which governs the starting reaction $pn\to d\gamma$ of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for $q=0.27{\mathrm{fm}}^{-1}$) from pionless nuclear effective field theory are in excellent agreement with the data.

A detailed analysis of the effect of short-range and tensor correlations on one- and two-nucleon momentum distributions of medium-weight nuclei ($12\le A\le 40$) is carried out. Although our Letter is primarily aimed at understanding the role of the tensor force on nucleon momentum distributions of medium-weight nuclei, the possible relevance of our results for the interpretation of $(e,e^{\prime }N)$ and $(e,e^{\prime }2N)$ processes at high $Q^2$, aimed at investigating nucleon-nucleon correlations, is discussed.

Photoneutron cross sections were measured for ${}^{91}\mathrm{Zr}$, ${}^{92}\mathrm{Zr}$, and ${}^{94}\mathrm{Zr}$ near the neutron separation energy with quasimonochromatic $\gamma$ rays. The data exhibit some extra components around the neutron threshold. A coherent analysis of the photoneutron data for ${}^{92}\mathrm{Zr}$ together with the neutron capture on ${}^{91}\mathrm{Zr}$ based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation model for the $E1$ strength has revealed the presence of an $M1$ resonance at 9 MeV. The microscopic approach systematically shows the same $M1$ strength in the photoneutron cross section for ${}^{91}\mathrm{Zr}$ and ${}^{94}\mathrm{Zr}$. The total $M1$ strength is about 75% larger than the strength predicted by the systematics, being qualitatively consistent with the giant $M1$ resonance observed in the inelastic proton scattering.

An ensemble with random $n$-body interactions is investigated in the presence of symmetries. A striking emergence of regularities in the spectra, ground state spins, and isospins is discovered. In even-particle systems the strong preponderance of spin zero ground states is observed with three, four, and higher-order random many-body interactions, and similar trends are discovered in systems that possess both rotational and isospin symmetry. Various types of correlations from pairing to spectral sequences and correlations across different masses are explored. A search for an interpretation is presented.

The NA60 experiment has measured low mass muon pair production in In-In collisions at $158A\mathrm{GeV}$ with unprecedented precision. We show that these data are reproduced very well by a dynamical model with parameters scaled from fits to measurements of hadronic transverse mass spectra and Hanbury Brown–Twiss correlations in Pb-Pb and Pb-Au collisions at the same energy. The data are consistent with in-medium properties of $\rho$ and $\omega$ mesons at finite temperature and density as deduced from empirical forward-scattering amplitudes. Inclusion of the vacuum decay of the $\rho$ meson after freeze-out is necessary for an understanding of the mass and transverse momentum spectrum of dimuons with $M\lesssim 0.9\mathrm{GeV}/c^2$.

In high-energy collisions, massive heavy quarks are produced back to back initially and they are sensitive to early dynamical conditions. The strong collective partonic wind from the fast expanding quark-gluon plasma created in high-energy nuclear collisions modifies the correlation pattern significantly. While the hot and dense medium in collisions at the BNL Relativistic Heavy Ion Collider ($\sqrt{s_{NN}}=200\mathrm{GeV}$) can only smear the initial back-to-back $D\overline{D}$ correlation, a clear and strong near side $D\overline{D}$ correlation is expected at the CERN Large Hadron Collider ($\sqrt{s_{NN}}=5500\mathrm{GeV}$). This is considered as a signature for the strongly coupled quark-gluon plasma.

The neutron unbound ground state of ${}^{25}\mathrm{O}$ ($Z=8$, $N=17$) was observed for the first time in a proton knockout reaction from a ${}^{26}\mathrm{F}$ beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of ${770}_{-10}^{+20}\mathrm{keV}$ with a total width of 172(30) keV. The $N=16$ shell gap was established to be 4.86(13) MeV by the energy difference between the $\nu 1s_{1/2}$ and $\nu 0d_{3/2}$ orbitals. The neutron separation energies for ${}^{25}\mathrm{O}$ agree with the calculations of the universal $sd$ shell model interaction. This interaction incorrectly predicts an ${}^{26}\mathrm{O}$ ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of ${}^{26}\mathrm{O}$. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.

The lifetime of the $2_1^{+}$ state in ${}^{16}\mathrm{C}$ has been measured with the recoil distance method using the ${}^9\mathrm{Be}({}^9\mathrm{Be},2p)$ fusion-evaporation reaction at a beam energy of 40 MeV. The mean lifetime was measured to be 11.7(20) ps corresponding to a $B(E2;2_1^{+}\to 0^{+})$ value of $4.15(73)e^2{\mathrm{fm}}^4$ [1.73(30) W.u.], consistent with other even-even closed shell nuclei. Our result does not support an interpretation for “decoupled” valence neutrons.

A simple, empirical, easy-to-measure effective order parameter of a first-order phase transition in atomic nuclei is presented, namely, the ratio of the energies of the first excited $6^{+}$ and $0^{+}$ states, distinguishing between first- and second-order transitions, and taking on a special value in the critical region, as data in Nd-Dy show. In the large $N_B$ limit of the interacting boson approximation model, a repeating degeneracy between alternate yrast and successive $0^{+}$ states is found in the critical region around the line of a first-order phase transition, pointing to a possible underlying symmetry.

The analysis of a large body of heavy ion fusion reaction data with medium-heavy projectiles ($6\le Z\le 18$) and actinide targets suggests a disappearance of the $3n$ exit channel with increasing atomic number of the projectile. Here, we report a measurement of the excitation function of the reaction ${}^{248}\mathrm{Cm}({}^{26}\mathrm{Mg},xn){}^{274\mathrm{\text{−}}x}\mathrm{Hs}$ and the observation of the new nuclide ${}^{271}\mathrm{Hs}$ produced in the $3n$ evaporation channel at a beam energy well below the Bass fusion barrier with a cross section comparable to the maxima of the $4n$ and $5n$ channels. This indicates the possible discovery of new neutron-rich transactinide nuclei using relatively light heavy ion beams of the most neutron-rich stable isotopes and actinide targets.

Using a new fast cleaning procedure to prepare isomerically pure ion samples, we have measured the beta-decay $Q_{\mathrm{EC}}$ values of the superallowed $\beta$ emitters ${}^{50}\mathrm{Mn}$ and ${}^{54}\mathrm{Co}$ to be 7634.48(7) and 8244.54(10) keV, respectively, results which differ significantly from the previously accepted values. The corrected $\mathcal{F}t$ values derived from our results strongly support new isospin-symmetry-breaking corrections that lead to a higher value of the up-down quark mixing element $V_{ud}$ and improved confirmation of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The ${}^{12}\mathrm{C}(\gamma ,{\pi }^0){}^{12}\mathrm{C}_{4.4\mathrm{MeV}}^{*}$ reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a ${\pi }^0$ spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the $\Delta$ in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a $\Delta$-hole model.

A new long-lived isomeric state in ${}^{65}\mathrm{Fe}$ has been discovered with Penning trap mass spectrometry and high-precision mass measurements of the neutron-rich isotopes ${}^{63–65}\mathrm{Fe}$ and ${}^{64–66}\mathrm{Co}$ have been performed with the Low-Energy Beam and Ion Trap Facility at the NSCL. For the new isomer in ${}^{65}\mathrm{Fe}$ an excitation energy of 402(5) keV has been determined from the measured mass difference between the isomeric and ground states. The mass uncertainties of all isotopes have been reduced by a factor of 10–100 compared to previous results. In the case of ${}^{64}\mathrm{Co}$ the previous mass value was found to deviate by about 5 standard deviations from the new measurement.

The exclusive process ${}^3\mathrm{He}(e,e^{\prime }p{)}^2\mathrm{H}$ has been analyzed by a nonfactorized and parameter-free approach based upon realistic few-body wave functions corresponding to the AV18 interaction and treating the rescattering of the struck nucleon within a generalized eikonal approximation. The results of our calculations, compared with recent JLab experimental data, show that the left-right asymmetry exhibits a clear dependence upon the final state interaction demonstrating the breaking down of the factorization approximation at “negative” and large ($\gtrsim 300\mathrm{MeV}/c$) values of the missing momentum.

Collective properties of the low-lying levels in the odd-$A$ ${}^{67–73}\mathrm{Cu}$ were investigated by Coulomb excitation with radioactive beams. The beams were produced at ISOLDE and postaccelerated by REX-ISOLDE up to $2.99\mathrm{MeV}/\mathrm{u}$. In ${}^{67,69}\mathrm{Cu}$, low-lying $1/2^{-}$, $5/2^{-}$, and $7/2^{-}$ states were populated. In ${}^{71,73}\mathrm{Cu}$, besides the known transitions deexciting the single-particle-like $5/2^{-}$ and core-coupled $7/2^{-}$ levels, $\gamma$ rays of 454 and 135 keV, respectively, were observed for the first time. Based on a reanalysis of $\beta$-decay work and comparison with the systematics, a spin $1/2^{-}$ is suggested for these excited states. Three $B(E2)$ values were determined in each of the four isotopes. The results indicate a significant change in the structure of the odd-$A$ Cu isotopes beyond $N=40$ where single-particle-like and collective levels are suggested to coexist at very low excitation energies.

The possibility of observing neutrinoless double $\beta$ decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of ${}^{76}\mathrm{Ge}$ (a candidate for such decay) and ${}^{76}\mathrm{Se}$ (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit.

The $E_{\gamma }\mathrm{\text{−}}{E}_{\gamma }$ coincidence spectra from the electromagnetic decay of excited superdeformed states in ${}^{194}\mathrm{Hg}$ reveal surprisingly narrow ridges, parallel to the diagonal. A total of 100–150 excited bands are found to contribute to these ridges, which account for nearly all the unresolved $E2$ decay strength. Comparison with theory suggests that these excited bands have many components in their wave functions, yet they display remarkable rotational coherence. This phenomenon can be explained in terms of the combination of shell effects and motional narrowing.