Within the next-to-leading order (NLO) perturbative QCD (PQCD) parton model, suppression of away-side hadron spectra associated with a high $p_T$ photon due to parton energy loss is studied in high-energy heavy-ion collisions. Because of the sharp falloff of the $\gamma$-jet spectrum in momentum imbalance $p_T^{\mathrm{jet}}-p_T^{\gamma }>0$ in NLO PQCD, hadron spectra at large $z_T=p_T^h/p_T^{\gamma }\gtrsim 1$ are more susceptible to parton energy loss and therefore are dominated by surface emission of $\gamma$-associated jets with almost no energy loss, whereas small $z_T$ hadrons mainly come from the volume emission of jets with reduced energy. These lead to different centrality dependence of the $\gamma$-hadron suppression for different values of $z_T$. Therefore, a complete measurement of the suppression of $\gamma$-triggered hadron spectra allows a true tomographic study of the quark-gluon plasma in high-energy heavy-ion collisions.

We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $\eta /s$ from zero to infinity. We show that an $\eta /s$ ratio larger than 0.2 prevents the development of well-defined shock waves on time scales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.

We report on the first spectroscopic study of the $N=22$ nucleus ${}^{32}\mathrm{Ne}$ at the newly completed RIKEN Radioactive Ion Beam Factory. A single $\gamma$-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a $226\mathrm{MeV}/u$ ${}^{32}\mathrm{Ne}$ beam on a carbon target and proton removal from ${}^{33}\mathrm{Na}$ at $245\mathrm{MeV}/u$. This transition is assigned to the deexcitation of the first $J^{\pi }=2^{+}$ state in ${}^{32}\mathrm{Ne}$ to the $0^{+}$ ground state. Interpreted through comparison with state-of-the-art shell-model calculations, the low excitation energy demonstrates that the “island of inversion” extends to at least $N=22$ for the Ne isotopes.

We propose a new observable based on two-particle azimuth correlation to study the away-side medium response in midcentral $\mathrm{Au}+\mathrm{Au}$ collisions. We argue that a left-right asymmetry may appear at the away side by selecting triggers separately in the left and right sides of the reaction plane. A simple model estimation suggests that the magnitude of such asymmetry could reach 30% with details depending on the medium response mechanisms. This asymmetry, if observed, can help to distinguish competing theoretical models.

We report a measurement of the differential cross section for the $\gamma n\to {\pi }^{-}p$ process from the CLAS detector at Jefferson Laboratory in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles (${\theta }_{\mathrm{c}.\mathrm{m}.}$) between 50° and 115°. We confirm a previous indication of a broad enhancement around a c.m. energy ($\sqrt{s}$) of 2.1 GeV at ${\theta }_{\mathrm{c}.\mathrm{m}.}=90°$ in the scaled differential cross section $s^7\frac{d\sigma }{dt}$ and a rapid falloff in a center-of-mass energy region of about 400 MeV following the enhancement. Our data show an angular dependence of this enhancement as the suggested scaling region is approached for ${\theta }_{\mathrm{c}.\mathrm{m}.}$ from 70° to 105°.

We present the self-consistent, nonperturbative analysis of isospin mixing using the nuclear density functional approach and the rediagonalization of the Coulomb interaction in the good-isospin basis. The unphysical isospin violation on the mean-field level, caused by the neutron excess, is eliminated by the proposed method. We find a significant dependence of the magnitude of isospin breaking on the parametrization of the nuclear interaction. A rough correlation has been found between the isospin-mixing parameter and the difference of proton and neutron rms radii.

The double-differential cross sections for the ${}^{48}\mathrm{Ca}(p,n)$ and ${}^{48}\mathrm{Ti}(n,p)$ reactions were measured at 300 MeV. A multipole decomposition technique was applied to the spectra to extract the Gamow-Teller (GT) components. The integrated GT strengths up to an excitation energy of 30 MeV in ${}^{48}\mathrm{Sc}$ are $15.3\pm 2.2$ and $2.8\pm 0.3$ in the $(p,n)$ and $(n,p)$ spectra, respectively. In the $(n,p)$ spectra additional GT strengths were found above 8 MeV where shell models within the $fp$ shell-model space predict almost no GT strengths, suggesting that the present shell-model description of the nuclear matrix element of the two-neutrino double-$\beta$ decay is incomplete.

The 1789 keV state in ${}^{30}\mathrm{Mg}$ was identified as the first excited $0^{+}$ state via its electric monopole ($E0$) transition to the ground state. The measured small value of ${\rho }^2(E0,0_2^{+}\to 0_1^{+})=(26.2\pm 7.5)\times {10}^{-3}$ implies within a two-level model a small mixing of competing configurations with largely different intrinsic quadrupole deformation near the neutron shell closure at $N=20$. Axially symmetric configuration mixing calculations identify the ground state of ${}^{30}\mathrm{Mg}$ to be based on neutron configurations below the $N=20$ shell closure, while the excited $0^{+}$ state mainly consists of two neutrons excited into the $\nu$ $1f_{7/2}$ orbital. The experimental result represents the first case where an $E0$ back decay from a strongly deformed second to the normal deformed first nuclear potential minimum well has been unambiguously identified, thus directly proving shape coexistence at the borderline of the much-debated “island of inversion.”

A neutron or proton excess in nuclei leads to an isovector-vector mean field which, through its coupling to the quarks in a bound nucleon, implies a shift in the quark distributions with respect to the Bjorken scaling variable. We show that this result leads to an additional correction to the NuTeV measurement of ${sin}^2{\theta }_W$. The sign of this correction is largely model independent and acts to reduce their result. Explicit calculation in nuclear matter within a covariant and confining Nambu–Jona-Lasinio model predicts that this vector field correction may account for a substantial fraction of the NuTeV anomaly. We are therefore led to offer a new interpretation of the NuTeV measurement, namely, that it provides further evidence for the medium modification of the bound nucleon wave function.

The nuclides ${}^{104–108}\mathrm{Sn}$, ${}^{106–110}\mathrm{Sb}$, ${}^{108,109}\mathrm{Te}$, and ${}^{111}\mathrm{I}$ at the expected endpoint of the astrophysical $rp$ process have been produced in ${}^{58}\mathrm{Ni}+{}^{\mathrm{nat}}\mathrm{Ni}$ fusion-evaporation reactions at IGISOL and their mass values were precisely measured with the JYFLTRAP Penning trap mass spectrometer. For ${}^{106}\mathrm{Sb}$, ${}^{108}\mathrm{Sb}$, and ${}^{110}\mathrm{Sb}$ these are the first direct experimental mass results obtained. The related one-proton separation energies have been derived and the value for ${}^{106}\mathrm{Sb}$, $S_p=424(8)\mathrm{keV}$, shows that the branching into the closed SnSbTe cycle in the astrophysical $rp$ process is weaker than expected.

The lifetimes of the first excited states of the $N=30$ isotones ${}^{50}\mathrm{Ca}$ and ${}^{51}\mathrm{Sc}$ have been determined using the Recoil Distance Doppler Shift method in combination with the CLARA-PRISMA spectrometers. This is the first time such a method is applied to measure lifetimes of neutron-rich nuclei populated via a multinucleon transfer reaction. This extends the lifetime knowledge beyond the $f_{7/2}$ shell closure and allows us to derive the effective proton and neutron charges in the $fp$ shell near the doubly magic nucleus ${}^{48}\mathrm{Ca}$, using large-scale, shell-model calculations. These results indicate an orbital dependence of the core polarization along the $fp$ shell.

We present the first Gogny-Hartree-Fock-Bogoliubov (HFB) model which reproduces nuclear masses with an accuracy comparable with the best mass formulas. In contrast with the Skyrme-HFB nuclear-mass models, an explicit and self-consistent account of all the quadrupole correlation energies are included within the 5D collective Hamiltonian approach. The final rms deviation with respect to the 2149 measured masses is 798 keV. In addition, the new Gogny force is shown to predict nuclear and neutron matter properties in agreement with microscopic calculations based on realistic two- and three-body forces.

The ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction presently represents the largest nuclear uncertainty in the predicted solar neutrino flux and has important implications on the big bang nucleosynthesis, i.e., the production of primordial ${}^7\mathrm{Li}$. We present here the results of an experiment using the recoil separator ERNA (European Recoil separator for Nuclear Astrophysics) to detect directly the ${}^7\mathrm{Be}$ ejectiles. In addition, off-beam activation and coincidence $\gamma$-ray measurements were performed at selected energies. At energies above 1 MeV a large discrepancy compared to previous results is observed both in the absolute value and in the energy dependence of the cross section. Based on the available data and models, a robust estimate of the cross section at the astrophysical relevant energies is proposed.

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions ${}^9\mathrm{Be}({}^9\mathrm{C},{}^8\mathrm{B}+X)Y$ and ${}^9\mathrm{Be}({}^8\mathrm{B},{}^7\mathrm{Be}+X)Y$ are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

The effects of strong longitudinal color electric fields on the open charm production in nucleus-nucleus ($A+A$) collisions at $200A\mathrm{GeV}$ are investigated within the framework of the $\mathrm{HIJING}/B\overline{B}$ v2.0 model. A threefold increase of the effective string tension due to in-medium effects in $A+A$ collisions results in a sizable ($\approx 60\%–70\%$) enhancement of the total charm production cross sections (${\sigma }_{c\overline{c}}^{NN}$). The nuclear modification factor shows a suppression at moderate transverse momentum ($p_T$) consistent with BNL Relativistic Heavy Ion Collider data. At Large Hadron Collider energies the model predicts an increase of ${\sigma }_{c\overline{c}}^{NN}$ by approximately an order of magnitude.

Two particle correlation data from the BNL Relativistic Heavy Ion Collider have provided detailed femtoscopic information describing pion emission. In contrast with the success of hydrodynamics in reproducing other classes of observables, these data had avoided description with hydrodynamic-based approaches. This failure has inspired the term “HBT puzzle,” where HBT refers to femtoscopic studies which were originally based on Hanbury Brown–Twiss interferometry. Here, the puzzle is shown to originate not from a single shortcoming of hydrodynamic models, but the combination of several effects: mainly prethermalized acceleration, using a stiffer equation of state, and adding viscosity.

The NA60 experiment at the CERN Super Proton Synchrotron has studied dimuon production in $158A\mathrm{GeV}$ In-In collisions. The strong excess of pairs above the known sources found in the complete mass region $0.2<M<2.6\mathrm{GeV}$ has previously been interpreted as thermal radiation. We now present first results on the associated angular distributions. Using the Collins-Soper reference frame, the structure function parameters $\lambda$, $\mu$, and $\nu$ are measured to be zero, and the projected distributions in polar and azimuth angles are found to be uniform. The absence of any polarization is consistent with the interpretation of the excess dimuons as thermal radiation from a randomized system.

A new method of optical pumping in an ion beam cooler buncher has been developed to selectively enhance ionic metastable state populations. The technique permits the study of elements previously inaccessible to laser spectroscopy and has been applied here to the study of Nb. Model independent mean-square charge radii and nuclear moments have been studied for ${}^{90,90\mathrm{m},91,91\mathrm{m},92,93,99,101,103}\mathrm{Nb}$ to cover the region of the $N=50$ shell closure and $N\approx 60$ sudden onset of deformation. The increase in mean-square charge radius is observed to be less than that for Y, with a substantial degree of $\beta$ softness observed before and after $N=60$.

The rotational band structure of ${}^{255}\mathrm{Lr}$ has been investigated using advanced in-beam $\gamma$-ray spectroscopic techniques. To date, ${}^{255}\mathrm{Lr}$ is the heaviest nucleus to be studied in this manner. One rotational band has been unambiguously observed and strong evidence for a second rotational structure was found. The structures are tentatively assigned to be based on the $1/2^{-}[521]$ and $7/2^{-}[514]$ Nilsson states, consistent with assignments from recently obtained $\alpha$ decay data. The experimental rotational band dynamic moment of inertia is used to test self-consistent mean-field calculations using the Skyrme SLy4 interaction and a density-dependent pairing force.

The atomic masses of ${}^{130}\mathrm{Te}$ and ${}^{130}\mathrm{Xe}$ have been obtained by measuring cyclotron frequency ratios of pairs of triply charged ions simultaneously trapped in a Penning trap. The results, with 1 standard deviation uncertainty, are $M({}^{130}\mathrm{Te})=129.906222744(16)\mathrm{u}$ and $M({}^{130}\mathrm{Xe})=129.903509351(15)\mathrm{u}$. From the mass difference the double-$\beta$-decay $Q$ value of ${}^{130}\mathrm{Te}$ is determined to be $Q_{\beta \beta }({}^{130}\mathrm{Te})=2527.518(13)\mathrm{keV}$. This is a factor of 150 more precise than the result of the AME2003 [G. Audi et al., Nucl. Phys. A729, 337 (2003)].