The $\alpha$ decays of naturally occurring platinum isotopes, which are accompanied by the emission of $\gamma$ quanta, have been searched for deep underground (3600 m water equivalent) at the Gran Sasso National Laboratories of the INFN (Italy). A sample of Pt with a mass of 42.5 g and a natural isotopic composition has been measured with a low background HP Ge detector (468 cm${}^3$) during 1815 h. The $\alpha$ decay of ${}^{190}\mathrm{Pt}$ to the first excited level of ${}^{186}\mathrm{Os}$ ($J^{\pi }=2^{+}$, $E_{\mathrm{exc}}=137.2$ keV) has been observed for the first time, with the half-life determined as $T_{1/2}=2.6_{-0.3}^{+0.4}(\mathrm{stat}.)\pm 0.6(\mathrm{syst}.)\times {10}^{14}$ yr. The $T_{1/2}$ limits for the $\alpha$ decays of other Pt isotopes have been determined at the level of $T_{1/2}\simeq {10}^{16}$–10${}^{20}$ yr. These limits have been set for the first time or they are better than those known from earlier experiments.

Nuclear effective field theory (NEFT) including pions in the two-nucleon sector is examined from the Wilsonian renormalization group point of view. The pion exchange is cut off at the floating cutoff scale, $\Lambda$, with the short-distance part being represented as contact interactions in accordance with the general principle of renormalization. We derive the nonperturbative renormalization group equations in the leading order of the nonrelativistic approximation in the operator space up to including $\mathcal{O}(p^2)$, and find the nontrivial fixed points in the ${}^1{S}_0$ and ${}^3{S}_1$-${}^3{D}_1$ channels which are identified with those in the pionless NEFT. The scaling dimensions, which determine the power counting, of the contact interactions at the nontrivial fixed points are also identified with those in the pionless NEFT. We emphasize the importance of the separation of the pion exchange into the short-distance and the long-distance parts, since a part of the former is nonperturbative while the latter is perturbative.

A new measurement of $\alpha$ resonant scattering on ${}^7\mathrm{Li}$ was performed over the excitation energy of 10.2–13.0 MeV in ${}^{11}\mathrm{B}$ at the low-energy RI beam facility CNS Radioactive Ion Beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo. The excitation function of ${}^7\mathrm{Li}$$+$$\alpha$ at 180${}^{ˆ}$ in the center-of-mass system was successfully measured for the first time with the inverse kinematics method, providing important information on the $\alpha$ cluster structure in ${}^{11}\mathrm{B}$ and the reaction rate of ${}^7\mathrm{Li}$($\alpha ,\gamma$), which is relevant to the ${}^{11}\mathrm{B}$ production in the $\nu$ process in core-collapse supernovae. The excitation function of the ${}^7\mathrm{Li}$($\alpha ,p$) reaction cross section for 11.7–13.1 MeV was also measured.

The two-fluid interacting vector boson model (IVBM) with $\mathrm{U}(6)$ as a dynamical group possesses a rich algebraic structure of physically interesting subgroups that define its distinct exactly solvable dynamical limits. The classical images corresponding to different dynamical symmetries are obtained by means of the coherent state method. The phase structure of the IVBM is investigated and the following basic phase shapes, connected to specific geometric configurations of the ground state, are determined: spherical, ${\mathrm{U}}_p(3)\otimes {\mathrm{U}}_n(3)$, $\gamma$-unstable, $\mathrm{O}(6)$, and axially deformed, $\mathrm{SU}(3)\otimes {\mathrm{U}}_T(2)$. The ground-state quantum phase transitions between different phase shapes, corresponding to the different dynamical symmetries and mixed symmetry case, are investigated.

We present nuclear matter calculations based on low-momentum interactions derived from chiral effective field theory potentials. The current calculations use an improved treatment of the three-nucleon force (3NF) contribution that includes a corrected combinatorial factor beyond Hartree-Fock that was omitted in previous nuclear matter calculations. We find realistic saturation properties using parameters fit only to few-body data, but with larger uncertainty estimates from cutoff dependence and the 3NF parametrization than in previous calculations.

The dipole-strength distribution in the semimagic nucleus ${}^{44}\mathrm{Ca}$ has been measured up to 10 MeV excitation energy in photon-scattering experiments using bremsstrahlung and monoenergetic 100% linearly polarized photon beams. The combination of both measurements allows a clear determination of spin and parity quantum numbers of the excited states as well as absolute cross sections and transition probabilities. The results show that the majority of the dipole strength in ${}^{44}\mathrm{Ca}$ below 10 MeV is due to $E1$ transitions while $M1$ strength plays only a minor role. The experimental results are compared to the strength in the neighboring doubly magic nuclei ${}^{40,48}\mathrm{Ca}$ and to microscopic calculations within the extended theory of finite Fermi systems in order to investigate the evolution of the low-lying $E1$ strength in this isotopic chain. Both, experiment and calculations, show a nontrivial dependence of the total $E1$ strength as a function of the neutron number.

We study the bulk deformation properties of the Skyrme nuclear energy density functionals (EDFs). Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band heads in Hg and Pb isotopes and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear EDFs. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

Mean-field calculations can now provide all the nuclear ingredients required to describe the fission path from the equilibrium deformation up to the nuclear scission point. The information obtained from microscopic mean-field models has been included in the TALYS reaction code to improve the predictions of neutron-induced fission cross sections. The nuclear inputs concern not only the details of the energy surface along the fission path, but also the coherent estimate of the nuclear level density derived within the combinatorial approach on the basis of the same single-particle properties, in particular at the fission saddle points. The predictive power of such a microscopic approach is tested on the experimental data available for the uranium isotopic chain. It is also shown that the various inputs can be tuned to reproduce, at best, experimental data in one unique coherent framework, so that in a close future it should become possible to make, on the basis of such models, accurate fission-cross-section calculations and the corresponding estimates for nuclei, energy ranges, or reaction channels for which no data exist. Such model uncertainties are usually not taken into account in data evaluations.

Excited states in ${}^{213}\mathrm{Po}$ have been populated using the ${}^{18}\mathrm{O}$$+$ ${}^{208}\mathrm{Pb}$ reaction at 85 MeV beam energy and studied with the Euroball IV $\gamma$ multidetector array. The level scheme has been built up to $~2.0$ MeV excitation energy and spin $I~25/2\hslash$ from the triple $\gamma$ coincidence data. Spin and parity values of several yrast states have been assigned from the $\gamma$ angular properties. The configurations of the yrast states are discussed using results of empirical shell-model calculations and by analogy with the neighboring nuclei. The spin and parity values of several low-spin states of ${}^{213}\mathrm{Po}$ previously identified from the $\beta$ decay of ${}^{213}\mathrm{Bi}$ are revised.

By adopting the fully quantal triaxial particle-rotor model, the candidate chiral doublet bands in odd-$A$ nuclei ${}^{103}\mathrm{Rh}$ and ${}^{105}\mathrm{Rh}$ with $\pi g_{9/2}^{-1}\otimes \nu h_{11/2}^2$ configuration are studied. For the doublet bands in both nuclei, agreement is excellent for the observed energies over the entire spin range and $B(M1)/B(E2)$ at higher spin range. The evolution of the chiral geometry with angular momentum is discussed in detail by using the angular momentum components and their probability distributions. Chirality is found to change from chiral vibration to nearly static chirality at spin $I=37/2$ and back to another type of chiral vibration at higher spin. The influence of the triaxial deformation $\gamma$ is also studied.

We consider multipole amplitudes for low-energy pion photoproduction, constructed with minimal model dependence, at single energies. A previous fit making minimal use of Watson’s theorem has been reexamined in light of more recent measurements. Problems associated with the choice of a unique solution are discussed. Comparisons with more recent fits to the full resonance region are made. Explanations are suggested for the discrepancies and more precise measurements of the recoil polarization, $P$, are motivated.

We have measured the differential cross section for the $\gamma$${}^3\mathrm{He}$$\to \pi {}^{+}t$ reaction. This reaction was studied using the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid ${}^3\mathrm{He}$ target. The differential cross sections for the $\gamma$${}^3\mathrm{He}$$\to \pi {}^{+}t$ reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.

We develop a framework for event-by-event ideal hydrodynamics to study the differential elliptic flow, which is measured at different centralities in Au $+$ Au collisions at the Relativistic Heavy Ion Collider (RHIC). Fluctuating initial energy density profiles, which here are the event-by-event analogs of the wounded nucleon profiles, are created using a Monte Carlo Glauber model. Using the same event plane method for obtaining $v_2$ as in the data analysis, we can reproduce both the measured centrality dependence and the $p_T$ shape of charged-particle elliptic flow up to $p_T~2$ GeV. We also consider the relation of elliptic flow to the initial-state eccentricity using different reference planes and discuss the correlation between the physical event plane and the initial participant plane. Our results demonstrate that event-by-event hydrodynamics with initial-state fluctuations must be accounted for before a meaningful lower limit for viscosity can be obtained from elliptic flow data.

Electroweak bosons produced in conjunction with jets in high-energy collider experiments is one of the principal final-state channels that can be used to test the accuracy of perturbative quantum chromodynamics calculations and to assess the potential to uncover new physics through comparison between data and theory. In this article we present results for the $Z^0/\gamma {}^{*}$$+$jet production cross sections at the CERN Large Hadron Collider (LHC) at leading and next-to-leading orders. In proton-proton reactions we elucidate up to $\mathcal{O}(G_F{\alpha }_s^2)$ the constraints that jet tagging via the $Z^0/\gamma {}^{*}$ decay dileptons provides on the momentum distribution of jets. In nucleus-nucleus reactions we demonstrate that tagged jets can probe important aspects of the dynamics of quark and gluon propagation in hot and dense nuclear matter and characterize the properties of the medium-induced parton showers in ways not possible with more inclusive measurements. Finally, we present specific predictions for the anticipated suppression of the $Z^0/\gamma {}^{*}$$+$jet production cross section in the quark-gluon plasma that is expected to be created in central lead-lead collisions at the LHC relative to the naive superposition of independent nucleon-nucleon scatterings.

The unbiased spectra of fragments from large-angle-scattered partons (midrapidity parton fragment distributions) in 200 GeV Au-Au collisions can be accurately described by perturbative QCD (pQCD) methods, revealing that a substantial population of parton fragments is present in hadron spectra at low transverse momentum ($p_t$). Angular correlations including all accepted hadron pairs above some low threshold $p_t$ (minimum-bias correlations) contain jetlike structures with most-probable hadron momentum $~$1 GeV/c. In this study, we convert minimum-bias jetlike angular correlations to single-particle hadron yields and compare them with parton fragment yields inferred from differential spectrum analysis (spectrum hard components). We find that jetlike correlations in central 200 GeV Au-Au collisions correspond quantitatively to pQCD predictions, and the jet-correlated hadron yield comprises one third of the Au-Au final state in central collisions.

We study gluon condensate in a pion superfluid by calculating the equation of state of the system in the Nambu–Jona-Lasinio model. While in mean-field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate, and the broken scalar symmetry can be smoothly restored at finite isospin density.

We combine heavy-quark renormalization group arguments with our understanding of the nucleon’s wave function to deduce a bound on the gluon polarization $\Delta g$ in the proton. The bound is consistent with the values extracted from spin experiments at COMPASS and RHIC.

In recent years, the Similarity Renormalization Group has provided a powerful and versatile means to soften interactions for ab initio nuclear calculations. The substantial contribution of both induced and initial three-body forces to the nuclear interaction has required the consistent evolution of free-space Hamiltonians in the three-particle space. We present the most recent progress on this work, extending the calculational capability to the $p$-shell nuclei and showing that the hierarchy of induced many-body forces is consistent with previous estimates. Calculations over a range of the flow parameter for ${}^6\mathrm{Li}$, including fully evolved $\mathit{NN}$ $+$ 3$N$ interactions, show moderate contributions due to induced four-body forces and display the same improved convergence properties as in lighter nuclei. A systematic analysis provides further evidence that the hierarchy of many-body forces is preserved.

Experimental reaction cross sections for ${}^6\mathrm{He}$ and ${}^4\mathrm{He}$ projectiles are reduced and are shown to follow well-defined trajectories that can be characterized by respective Wong-type curves. The strong enhancement observed for the ${}^6\mathrm{He}$ data is interpreted as caused by two separate halo effects: a size effect, which affects the whole energy region, and a dynamic effect, important only near and below the barrier. Evidence for a core-halo decoupling is presented for the ${}^6\mathrm{He}+{}^{64}\mathrm{Zn}$ system, which further supports the hypothesis that the decoupling is a characteristic feature of true halo systems.