The second $J^{\pi }=2^{+}$ state of ${}^{12}\mathrm{C}$, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the ${}^{12}\mathrm{C}(\gamma ,{\alpha }_0){}^8\mathrm{Be}$ reaction. The alpha particles produced by the photodisintegration of ${}^{12}\mathrm{C}$ were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the $\mathrm{HI}\gamma \mathrm{S}$ facility. The measured angular distributions determine the cross section and the $E1\mathrm{\text{−}}E2$ relative phases as a function of energy leading to an unambiguous identification of the second $2^{+}$ state in ${}^{12}\mathrm{C}$ at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; $B(E2:2_2^{+}\to 0_1^{+})=0.73(13)e^2{\mathrm{fm}}^4$ [or 0.45(8) W.u.]. The Hoyle state and its rotational $2^{+}$ state that are more extended than the ground state of ${}^{12}\mathrm{C}$ presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in ${}^{12}\mathrm{C}$. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state.

A new technique was developed to measure the lifetimes of neutron unbound nuclei in the picosecond range. The decay of ${}^{26}\mathrm{O}\to {}^{24}\mathrm{O}+n+n$ was examined as it had been predicted to have an appreciable lifetime due to the unique structure of the neutron-rich oxygen isotopes. The half-life of ${}^{26}\mathrm{O}$ was extracted as ${4.5}_{-1.5}^{+1.1}(\mathrm{stat})\pm 3(\mathrm{syst})\mathrm{ps}$. This corresponds to ${}^{26}\mathrm{O}$ having a finite lifetime at an 82% confidence level and, thus, suggests the possibility of two-neutron radioactivity.

The inclusive breakup for the ${}^{11}\mathrm{Li}+{}^{208}\mathrm{Pb}$ reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of ${}^9\mathrm{Li}$ following the ${}^{11}\mathrm{Li}$ dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of $B(E1)$ distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the ${}^{11}\mathrm{Li}$ continuum at low excitation energy.

Elliptic flow ($v_2$) values for identified particles at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions, measured by the STAR experiment in the beam energy scan at RHIC at $\sqrt{s_{NN}}=7.7–62.4\mathrm{GeV}$, are presented. A beam-energy-dependent difference of the values of $v_2$ between particles and corresponding antiparticles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and antiparticles are not consistent with the universal number-of-constituent-quark scaling of $v_2$ that was observed at $\sqrt{s_{NN}}=200\mathrm{GeV}$.

Single nucleon pickup reactions were performed with a $18.1\mathrm{MeV}/\mathrm{nucleon}$ ${}^{14}\mathrm{O}$ beam on a deuterium target. Within the coupled reaction channel framework, the measured cross sections were compared to theoretical predictions and analyzed using both phenomenological and microscopic overlap functions. The missing strength due to correlations does not show significant dependence on the nucleon separation energy asymmetry over a wide range of 37 MeV, in contrast with nucleon removal data analyzed within the sudden-eikonal formalism.

Long-lived isomers in ${}^{212}\mathrm{Bi}$ have been studied following ${}^{238}\mathrm{U}$ projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of ${}^{212}\mathrm{Bi}$ was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of $>1910\mathrm{keV}$. It was also found to have an extended Lorentz-corrected in-ring half-life $>30\min$, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

The effect of the tensor force on $\beta$ decay is studied in the framework of the proton-neutron random phase approximation with the Skyrme force. The investigation is performed for even-even semimagic and magic nuclei, ${}^{34}\mathrm{Si}$, ${}^{68,78}\mathrm{Ni}$, and ${}^{132}\mathrm{Sn}$. The tensor correlation induces strong impact on the low-lying Gamow-Teller state. In particular, it improves the $\beta$-decay half-lives. $Q$ and $ft$ values are also investigated and compared with experimental data.

The Hoyle state plays a crucial role in the helium burning of stars that have reached the red giant stage. The close proximity of this state to the triple-alpha threshold is needed for the production of carbon, oxygen, and other elements necessary for life. We investigate whether this life-essential condition is robust or delicately fine-tuned by measuring its dependence on the fundamental constants of nature, specifically the light quark mass and the strength of the electromagnetic interaction. We show that there exist strong correlations between the alpha-particle binding energy and the various energies relevant to the triple-alpha process. We derive limits on the variation of these fundamental parameters from the requirement that sufficient amounts of carbon and oxygen be generated in stars. We also discuss the implications of our results for an anthropic view of the Universe.

We propose a new method for the analysis of deuteron stripping reactions, $A(d,p)B$, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by $\sim 40\mathrm{MeV}$ from the “$E_d/2$” value frequently used in the analysis of experimental data, where $E_d$ is the incident deuteron energy. The “$E_d/2$” rule lies at the heart of all three-body analyses of ($d$, $p$) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the $n+p+A$ wave function that dominate the ($d$, $p$) reaction amplitude. The large shift reduces the effective $d-A$ potentials and leads to a change in predicted ($d$, $p$) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure.

The modifications of $D_s$-meson spectra in ultrarelativistic heavy-ion collisions are identified as a quantitative probe of key properties of the hot nuclear medium. The unique valence-quark content of the $D_s=c\overline{s}$ couples the well-known strangeness enhancement with the collective-flow pattern of primordially produced charm quarks. This idea is illustrated utilizing a consistent strong-coupling treatment with hydrodynamic bulk evolution and nonperturbative $T$-matrix interactions for both heavy-quark diffusion and hadronization in the quark-gluon plasma (QGP). A large enhancement of the $D_s$ nuclear modification factor at Relativistic Heavy Ion Collider is predicted, with a maximum of $\sim 1.5–1.8$ at transverse momenta around $2\mathrm{GeV}/c$. This is a direct consequence of the strong coupling of the heavy quarks to the QGP and their hadronization via coalescence with strange quarks. We furthermore introduce the effects of diffusion in the hadronic phase and suggest that an increase of the $D$-meson elliptic flow compared to the $D_s$ can disentangle the transport properties of hadronic and QGP liquids.

Low-lying collective excitations in even-even vibrational and transitional nuclei may be described semiclassically as quadrupole running waves on the surface of the nucleus (“tidal waves”), and the observed vibrational-rotational behavior can be thought of as resulting from a rotating condensate of interacting $d$ bosons. These concepts have been investigated by measuring lifetimes of the levels in the yrast band of the ${}^{102}\mathrm{Pd}$ nucleus with the Doppler shift attenuation method. The extracted $B(E2)$ reduced transition probabilities for the yrast band display a monotonic increase with spin, in agreement with the interpretation based on rotation-induced condensation of aligned $d$ bosons.

A measurement of the $\alpha \mathrm{\text{−}}\beta \mathrm{\text{−}}\overline{\nu }$ angular correlation in the Gamow-Teller decay ${}^8\mathrm{Li}\to {}^8\mathrm{Be}^{*}+\overline{\nu }+\beta$, ${}^8\mathrm{Be}^{*}\to \alpha +\alpha$ has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the $\alpha$ particles emitted along and opposite the direction of the $\beta$ particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component $C_T$ relative to that of the dominant axial-vector component $C_A$ of the electroweak interaction is limited to $|C_T/C_A|<0.18$ (95.5% confidence level). This experimental approach is facilitated by several favorable features of the ${}^8\mathrm{Li}$ $\beta$ decay and has different systematic effects than the previous $\beta \mathrm{\text{−}}\overline{\nu }$ correlation results for a pure Gamow-Teller transition obtained from studying ${}^6\mathrm{He}$ $\beta$ decay.

A novel technique for $\beta$-delayed neutron spectroscopy has been demonstrated using trapped ions. The neutron-energy spectrum is reconstructed by measuring the time of flight of the nuclear recoil following neutron emission, thereby avoiding all the challenges associated with neutron detection, such as backgrounds from scattered neutrons and $\gamma$ rays and complicated detector-response functions. ${}^{137}\mathrm{I}^{+}$ ions delivered from a ${}^{252}\mathrm{Cf}$ source were confined in a linear Paul trap surrounded by radiation detectors, and the $\beta$-delayed neutron-energy spectrum and branching ratio were determined by detecting the ${\beta }^{-}$ and recoil ions in coincidence. Systematic effects were explored by determining the branching ratio three ways. Improvements to achieve higher detection efficiency, better energy resolution, and a lower neutron-energy threshold are proposed.

The transverse momentum ($p_T$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) $p+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ with the ALICE detector at the LHC. The $p_T$ spectra measured near central rapidity in the range $0.5<p_T<20\mathrm{GeV}/c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{p\mathrm{Pb}}$ is consistent with unity for $p_T$ above $2\mathrm{GeV}/c$. This measurement indicates that the strong suppression of hadron production at high $p_T$ observed in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.

Through an explicit calculation of massive scalar particle (e.g., Higgs boson) production in high energy $pA$ collisions up to one-loop order, we demonstrate, for the first time, that the Sudakov-type logarithms in hard processes in the small-$x$ saturation formalism can be systematically separated from the small-$x$ logarithms. The generic feature of the Sudakov logarithms and all order resummation is derived. This calculation shall provide us deep insights into the understanding of factorizations in the saturation formalism. We further comment on the phenomenological implications in the LHC energy regime and extension to other hard processes in small-$x$ calculations.

A novel approach based on the projection of the Penning-trap ion motion onto a position-sensitive detector opens the door to very accurate mass measurements on the ppb level even for short-lived nuclides with half-lives well below a second. In addition to the accuracy boost, the new method provides a superior resolving power by which low-lying isomeric states with excitation energy on the 10-keV level can be easily separated from the ground state. A measurement of the mass difference of ${}^{130}\mathrm{Xe}$ and ${}^{129}\mathrm{Xe}$ has demonstrated the great potential of the new approach.

A long-lived $J^{\pi }=4_1^{+}$ isomer, $T_{1/2}=2.2(1)\mathrm{ms}$, has been discovered at 643.4(1) keV in the weakly bound ${}_9{}^{26}\mathrm{F}$ nucleus. It was populated at Grand Accélérateur National d’Ions Lourds in the fragmentation of a ${}^{36}\mathrm{S}$ beam. It decays by an internal transition to the $J^{\pi }=1_1^{+}$ ground state [82(14)%], by $\beta$ decay to ${}^{26}\mathrm{Ne}$, or $\beta$-delayed neutron emission to ${}^{25}\mathrm{Ne}$. From the $\beta$-decay studies of the $J^{\pi }=1_1^{+}$ and $J^{\pi }=4_1^{+}$ states, new excited states have been discovered in ${}^{25,26}\mathrm{Ne}$. Gathering the measured binding energies of the $J^{\pi }=1_1^{+}-4_1^{+}$ multiplet in ${}_9{}^{26}\mathrm{F}$, we find that the proton-neutron $\pi 0d_{5/2}\nu 0d_{3/2}$ effective force used in shell-model calculations should be reduced to properly account for the weak binding of ${}_9{}^{26}\mathrm{F}$. Microscopic coupled cluster theory calculations using interactions derived from chiral effective field theory are in very good agreement with the energy of the low-lying $1_1^{+}$, $2_1^{+}$, $4_1^{+}$ states in ${}^{26}\mathrm{F}$. Including three-body forces and coupling to the continuum effects improve the agreement between experiment and theory as compared to the use of two-body forces only.

Previous explanations for the resonance behavior of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion at low energies were based on a nonresonant compound-nucleus background and an additional contribution from a series of resonances. This separation into “resonance” and “background” contributions of the cross section is artificial. We propose to explain this phenomenon through the impact on the cross section of the relatively large spacings and the narrow widths of ${}^{24}\mathrm{Mg}$ compound levels in the corresponding excitation-energy region.

We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of ${}^{136}\mathrm{Xe}$. We obtain a lower limit for the neutrinoless double-beta decay half-life of $T_{1/2}^{0\nu }>1.9\times {10}^{25}\mathrm{yr}$ at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give $T_{1/2}^{0\nu }>3.4\times {10}^{25}\mathrm{yr}$ at 90% C.L., which corresponds to a Majorana neutrino mass limit of $⟨m_{\beta \beta }⟩<(120–250)\mathrm{meV}$ based on a representative range of available matrix element calculations. Using those calculations, this result excludes the Majorana neutrino mass range expected from the neutrinoless double-beta decay detection claim in ${}^{76}\mathrm{Ge}$, reported by a part of the Heidelberg-Moscow Collaboration, at more than 97.5% C.L.

The damping of the nuclear shell effect with excitation energy has been measured through an analysis of the neutron spectra following the triton transfer in the ${}^7\mathrm{Li}$ induced reaction on ${}^{205}\mathrm{Tl}$. The measured neutron spectra demonstrate the expected large shell correction energy for the nuclei in the vicinity of doubly magic ${}^{208}\mathrm{Pb}$ and a small value around ${}^{184}\mathrm{W}$. A quantitative extraction of the allowed values of the damping parameter $\gamma$, along with those for the asymptotic nuclear level density parameter $\tilde{a}$, has been made for the first time.