We extend effective field theory to the case of spontaneous symmetry breaking in genuinely finite quantum systems such as small superfluid systems, molecules, or atomic nuclei and focus on deformed nuclei. In finite superfluids, symmetry arguments alone relate the spectra of systems with different particle numbers. For systems with nonspherical intrinsic ground states such as atomic nuclei or molecules, symmetry arguments alone yield the universal features of the low-lying excitations as vibrations that are the heads of rotational bands. The low-lying excitations in deformed nuclei differ from those in molecules because of symmetry properties caused by pairing.

We report on an improved measurement of the $2\nu \beta \beta$ half-life of ${}^{136}$Xe performed by EXO-200. The use of a large and homogeneous time-projection chamber allows for the precise estimate of the fiducial mass used for the measurement, resulting in a small systematic uncertainty. We also discuss in detail the data-analysis methods used for double-$\beta$ decay searches with EXO-200, while emphasizing those directly related to the present measurement. The ${}^{136}$Xe $2\nu \beta \beta$ half-life is found to be $T_{1/2}^{2\nu \beta \beta }$ = $2.165\pm 0.016\left(\mathrm{stat}\right)\pm 0.059\left(\mathrm{sys}\right)\times {10}^{21}$ yr. This is the most precisely measured half-life of any $2\nu \beta \beta$ decay to date.

Background: The ${}^{17}O(p,\gamma ){}^{18}F$ reaction affects the production of key isotopes (e.g., ${}^{18}F$ and ${}^{18}O$) in the explosive hydrogen burning that powers classical novae. Under these explosive conditions, the reaction rate is dominated by contributions from a narrow resonance at $E_{\mathrm{c}.\mathrm{m}.}=183\mathrm{keV}$ and by the combined contributions of direct capture and low-energy tails of broad resonances. At present, the astrophysical reaction rate is not well constrained because of the lack of data in the energy region appropriate to classical novae.

Purpose: This study aims at the measurement of the ${}^{17}O$$(p,\gamma ){}^{18}F$ reaction cross section in order to determine its reaction rate in the temperature region appropriate to explosive hydrogen burning in novae.

Method: The ${}^{17}O$$(p,\gamma ){}^{18}F$ reaction cross section was measured using both the prompt detection of the emitted $\gamma$ rays and an activation technique. Measurements were carried out at the Laboratory for Underground Nuclear Astrophysics (Gran Sasso, Italy) where the strongly reduced cosmic-ray-induced background allows for improved sensitivity compared to previous studies.

Results: The ${}^{17}O$$(p,\gamma ){}^{18}F$ reaction cross section was measured in the range $E_{\mathrm{c}.\mathrm{m}.}=160$ to $370\mathrm{keV}$. The strength of the $E_{\mathrm{c}.\mathrm{m}.}=183\mathrm{keV}$ resonance, $\omega \gamma =1.67\pm 0.12\mu \mathrm{eV}$, was determined with unprecedented precision. The total $S$ factor was obtained through a combined fit of prompt $\gamma$-ray and activation results. An overall global fit including other existing data sets was also carried out and a recommended astrophysical reaction rate is presented.

Conclusions: The reaction rate uncertainty attained in this work is now below the required precision for nova models. We verified, following a full set of hydrodynamic nova models, that the abundances of oxygen and fluorine isotopes obtained with the present reaction rate are determined with 10% precision and put firmer constraints on observational signatures of novae events.

Background: The Po, Pb, Hg, and Pt region is known for the presence of coexisting structures that correspond to different particle-hole configurations in the shell model language or equivalently to nuclear shapes with different deformation.

Purpose: We intend to study the configuration mixing phenomenon in the Hg isotopes and to understand how different observables are influenced by it.

Method: We study in detail a long chain of mercury isotopes, ${}^{172--200}$Hg, using the interacting boson model with configuration mixing. The parameters of the Hamiltonians are fixed through a least-squares fit to the known energies and absolute $B\left(E2\right)$ transition rates of states up to 3 MeV.

Results: We obtained the IBM-CM Hamiltonians and we calculate excitation energies, $B\left(E2\right)$'s, quadrupole shape invariants, wave functions, isotopic shifts, and mean-field energy surfaces.

Conclusions: We obtain a fairly good agreement with the experimental data for all the studied observables and we conclude that the Hamiltonian and the states we obtain constitute a good approximation to the Hg isotopes.

We carry out a combined analysis of elliptic and triangular flow data using viscous relativistic hydrodynamics. We show that these data allow us to put tight constraints on models of the early dynamics of a nucleus-nucleus collision. Specifically, the rms values of the initial ellipticity ${\varepsilon }_2$ and the initial triangularity ${\varepsilon }_3$ are constrained to lie within a narrow band for each centrality. We use these constraints as a filter for existing Monte Carlo models of initial state, and provide a simple test that can be performed on any candidate model to determine its compatibility with data.

Using the $\delta$-shell representation we present a successful fit to neutron-proton and proton-proton scattering data below the pion production threshold. A detailed overview of the theory necessary to calculate observables with this potential is presented. A new data selection process is used to obtain the largest mutually consistent data base. The analysis includes data within the years 1950 to 2013. Using 46 parameters we obtain ${\chi }^2/N_{\mathrm{data}}=1.04$ with $N_{\mathrm{data}}=6713$ including normalization data. Phase shifts with error bars are provided.

We investigate the effects of finite baryon chemical potential on the transport properties of a hadron resonance gas. We find that a hadron resonance gas with large baryon number density is closer to the ideal fluid limit than the corresponding gas with zero baryon number. This suggests that the system created at the Relativistic Heavy Ion Collider (RHIC) at lower collision energies may behave as a fluid, with an effective fluidity close to the one found at RHIC's highest energy near phase transition. This might explain why the differential elliptic flow coefficient measured at lower collisional energies at RHIC is similar to the one observed at high energies.

We study the nonperturbative renormalization of the nucleon-nucleon ($NN$) interaction at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of chiral effective field theory. A systematic variation of the cutoff parameter is performed for values below the chiral symmetry breaking scale of about 1 GeV. The accuracy of the predictions is determined by calculating the ${\chi }^2$ for the reproduction of the $NN$ data for energy intervals below pion-production threshold. At NLO, $NN$ data are described well up to about 100 MeV laboratory energy and, at NNLO, up to about 200 MeV—with, essentially, cutoff independence for cutoffs between about 450 and 850 MeV.

We analyze the mixing nature of the low-lying scalar resonance consisting of the $\pi \pi$ composite and the elementary particle within the $\sigma$ model. A method to disentangle the mixing is formulated in the scattering theory with the concept of the two-level problem. We investigate the composite and elementary components of the $\sigma$ meson by changing a mixing parameter. We also study the dependence of the results on model parameters such as the cut-off value and the mass of the elementary $\sigma$ meson.

Proton emission from deformed nuclei near the drip line is regarded as a versatile tool in nuclear structure physics and such a study in odd-odd nuclei provides us with an excellent opportunity to understand several interesting features including the interaction between the valence proton and the valence neutron. We present a detailed formalism for a full microscopic calculation of such proton emitters, where the nuclear structure and decay aspects are taken into account exactly. This formalism is based on the nonadiabatic approach for the two quasiparticle plus rotor model, where the residual neutron-proton interactions are considered in the mean field represented by a deformed Woods-Saxon potential. We demonstrate a systematic way of unambiguously identifying several parameters involved in the calculations with the aid of the experimental data. The quality of results in the case of ${}^{180}$Ta justifies the approach which is further extended to discuss in detail the proton emission from ${}^{130}$Eu. $I^{\pi }=1^{+}$ state in ${}^{130}$Eu still remains to be the proton emitting state irrespective of the choice of several parameters. We also note that the decay widths could be quite sensitive to the residual $np$ interaction in case of proton emission from isomeric states.

A new implementation of the finite amplitude method (FAM) for the solution of the relativistic quasiparticle random-phase approximation (RQRPA) is presented, based on the relativistic Hartree-Bogoliubov (RHB) model for deformed nuclei. The numerical accuracy and stability of the FAM–RQRPA is tested in a calculation of the monopole response of ${}^{22}$O. As an illustrative example, the model is applied to a study of the evolution of monopole strength in the chain of Sm isotopes, including the splitting of the giant monopole resonance in axially deformed systems.

The low-spin level scheme of ${}^{68}$Ni was investigated following two-neutron-knockout and multinucleon-transfer reactions. The energy of the first excited state was determined to be $E_x\left(0_2^{+}\right)=1603.5\left(3\right)$ keV. Relative $B\left(E2\right)$ transition probabilities were deduced and compared with shell-model calculations using several modern effective interactions. Theory reproduces the data well, but indicates substantial mixing of multi-particle, multi-hole configurations for the lowest observed $0^{+}$ and $2^{+}$ states.

We report the exclusive photoproduction cross sections for the ${\Sigma }^0\left(1385\right)$, $\Lambda \left(1405\right)$, and $\Lambda \left(1520\right)$ in the reactions $\gamma +p\to K^{+}+Y^{*}$ using the CLAS detector for energies from near the respective production thresholds up to a center-of-mass energy $W$ of $2.85$ GeV. The differential cross sections are integrated to give the total exclusive cross sections for each hyperon. Comparisons are made to current theoretical models based on the effective-Lagrangian approach and fit to previous data. The accuracy of these models is seen to vary widely. The cross sections for the $\Lambda \left(1405\right)$ region are strikingly different for the ${\Sigma }^{+}{\pi }^{-}$, ${\Sigma }^0{\pi }^0$, and ${\Sigma }^{-}{\pi }^{+}$ decay channels, indicating the effect of isospin interference, especially at $W$ values close to the threshold.