We develop a theory of ultracold and very cold neutron scattering on viscoelastic surface waves up to second-order perturbation theory. The results are applied to reanalyze the 1989 neutron-lifetime experiment using ultracold neutron storage in a Fomblin-coated vessel by Mampe et al. [Phys. Rev. Lett. 63, 593 (1989)]. Inclusion of this theory of the quasielastic scattering process in the data analysis shifts the neutron lifetime value from $887.6\pm 3$ to $882.5\pm 2.1$ s.

Deformations of Ne isotopes in the island of inversion are determined by the folding model description of the interaction cross sections measured for ${}^{28-32}$Ne isotopes incident on a ${}^{12}$C target at 240 MeV/nucleon, using the Melbourne g-matrix interaction and the nuclear densities calculated by antisymmetrized molecular dynamics (AMD). The double folding model with the AMD density well reproduces the measured interaction cross sections, if the tail correction is made to the AMD density for ${}^{31}$Ne. The quadrupole deformation determined is around 0.4 in the island of inversion and ${}^{31}$Ne is a halo nucleus with large deformation. We propose the Woods-Saxon model with the AMD deformation and a suitably chosen parametrization set as an approximate but simple method to reproduce the AMD density with the tail correction. The angular momentum projection is essential to obtain the large deformation in the island of inversion. Effects of the pairing correlation are investigated.

We present results of the application of the anisotropic hydrodynamics (aHydro) framework to (2+1)-dimensional boost-invariant systems. The necessary aHydro dynamical equations are derived by taking moments of the Boltzmann equation using a momentum-space anisotropic one-particle distribution function. We present a derivation of the necessary equations and then proceed to numerical solutions of the resulting partial differential equations using both realistic smooth Glauber initial conditions and fluctuating Monte Carlo Glauber initial conditions. For this purpose we have developed two numerical implementations: one that is based on straightforward integration of the resulting partial differential equations supplemented by a two-dimensional weighted Lax-Friedrichs smoothing in the case of fluctuating initial conditions and another that is based on the application of the Kurganov-Tadmor central scheme. For our final results we compute the collective flow of the matter via the laboratory-frame energy-momentum tensor eccentricity as a function of the assumed shear viscosity-to-entropy ratio, proper time, and impact parameter.

One goal of contemporary particle physics is to determine the mixing angles and mass-squared differences that constitute the phenomenological constants that describe neutrino oscillations. Of great interest are not only the best-fit values of these constants but also their errors. Some of the neutrino oscillation data is statistically poor and cannot be treated by normal (Gaussian) statistics. To extract confidence intervals when the statistics are not normal, one should not utilize the value for $\Delta {\chi }^2$ versus confidence level taken from normal statistics. Instead, we propose that one should use the normalized likelihood function as a probability distribution; the relationship between the correct $\Delta {\chi }^2$ and a given confidence level can be computed by integrating over the likelihood function. This allows for a definition of confidence level independent of the functional form of the ${\chi }^2$ function; it is particularly useful for cases in which the minimum of the ${\chi }^2$ function is near a boundary. We point out that the question of what is the probability that a parameter is not zero is more precisely worded as what is the maximum confidence level at which the value of zero is not included. We present two pedagogic examples and find that the proposed method yields confidence intervals that can differ significantly from those obtained by using the value of $\Delta {\chi }^2$ from normal statistics. For example, we find that for the T2K experiment the value of $\Delta {\chi }^2$ corresponding to a confidence level of 90$\%$ is 3.57 rather than the normal statistics value of 2.71.

A simple coalescence model is employed to investigate the production of light (anti)nuclei and (anti)hypertriton as well as di-$\Lambda$ in the most central Au+Au collisions. The invariant yields of ${}^3$He(${}^3\overline{\mathrm{He}}$), ${}_{\Lambda }^{3}H$(${}_{\overline{\Lambda }}^3\overline{\mathrm{H}}$), and ${}^4$He(${}^4\overline{\mathrm{He}}$) obtained within current framework are found to be consistent with the measurements of the solenoidal tracker at the BNL Relativistic Heavy Ion Collider (STAR) detector. We also investigate the coalescence parameters $B_A$ ($A=2,3,4$) as a function of transverse momentum for $d$($\overline{d}$), ${}^3$He(${}^3\overline{\mathrm{He}}$), ${}_{\Lambda }^{3}H$(${}_{\overline{\Lambda }}^3\overline{\mathrm{H}}$), and ${}^4$He(${}^4\overline{\mathrm{He}}$), respectively. $B_2$ for $d$($\overline{d}$) and $B_3$ for ${}^3$He(${}^3\overline{\mathrm{He}}$) are comparable with the STAR measurement within statistical uncertainties. The $p_T$ integrated yields for di-$\Lambda$ $d{N}_{\Lambda \Lambda }/dy\sim 2.23\times {10}^{-5}$, and is not strongly dependent on the parameter employed for the coalescence process. Combining the data points extracted by the PHENIX Collaboration, the coalescence parameters exhibit a strong centrality dependence. An exponential behavior is shown for the differential invariant yields versus baryon number distribution. The production rate reduces by a factor of 1692 (1285) for each additional antinucleon (nucleon) added to antinuclei (nuclei), and the production rate of ${}^6\overline{\mathrm{Li}}$ is about ${10}^{-16}$ which is consistent with results extracted by the STAR experiment. The relative abundance of light anti(nuclei) and (anti)hypertriton are explored with particle ratios, and agree with experimental data as well as thermal model predictions.

We propose a simple quartet condensation model (QCM) which describes with very high accuracy the isovector pairing correlations in self-conjugate nuclei. The quartets have an $\alpha$-like structure and are formed by collective isovector pairs. The accuracy of the QCM is tested for $N=Z$ nuclei for which exact shell model diagonalizations can be performed. The calculations are done with two isovector pairing forces, one extracted from standard shell model interactions and the other of seniority type, acting, respectively, upon spherical and axially deformed single-particle states. It is shown that for all calculated nuclei the QCM gives very accurate values for the pairing correlations energies, with errors which do not exceed 1$\%$. These results show clearly that the correlations induced by the isovector pairing in self-conjugate nuclei are of quartet type and also indicate that QCM is the proper tool to calculate the isovector proton-neutron correlations in mean field pairing models.

Five $N=82$ isotones have been produced in two fusion-fission reactions and their $\gamma$ rays studied with the Euroball array. The high-spin states of ${}^{139}$La have been identified, while the high-spin yrast and near-to-yrast structures of the four others have been greatly extended. From angular correlation analysis, spin values have been assigned to some states of ${}^{136}$Xe and ${}^{137}$Cs. Several cascades involving $\gamma$ rays of ${}^{139}$La have been found to be delayed; they deexcite an isomeric state with $T_{1/2}=315\left(35\right)$ ns located at 1800 keV excitation energy. The excited states of these five $N=82$ isotones are expected to be due to various proton excitations involving the three high-$j$ subshells located above the $Z=50$ shell closure. This is confirmed by the results of shell-model calculations performed in this work. In addition, high-spin states corresponding to the excitation of the neutron core have been unambiguously identified in ${}^{136}$Xe, ${}^{137}$Cs, and ${}^{138}$Ba.

The cross sections for single-nucleon knockout from ${}^{36}$Ca on a ${}^9$Be target at 70 MeV/nucleon were measured to be ${\sigma }_{\exp }(-p)=51.1\pm 2.6$ mb for proton knockout and ${\sigma }_{\exp }(-n)=5.03\pm 0.46$ mb for neutron knockout. The spectroscopic factors and orbital angular momenta of the neutrons and protons removed from ${}^{36}$Ca, leading to bound $A=35$ residues, were deduced by comparison of the experimental cross sections and longitudinal-momentum distributions to those calculated in an eikonal reaction theory, and found to be $S(p,1d_{3/2})=0.79\pm 0.04$ and $S(n,2s_{1/2})=0.23\pm 0.02$ (relative to independent-particle-model values and only including experimental contributions to the uncertainties). As found in previous knockout studies, the spectroscopic factor deduced for the deeply bound neutron was significantly reduced relative to shell-model calculations, a result at variance with dispersive optical model (DOM) extrapolations, which suggest a spectroscopic factor closer to $60\%$ of the independent-particle-model value.

Fluctuations in the initial QCD matter density distribution are found to enhance the production of thermal photons significantly in the range $2⩽p_T⩽4$ GeV/$c$ compared to a smooth initial state averaged profile in ideal hydrodynamic calculation for $200A$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and $2.76A$ TeV Pb+Pb collisions at the Large Hadron Collider (LHC). The thermal emission of photons is strongly dependent on the initial temperature of the system where the presence of “hot spots” in the initial state translates into enhanced production of photons compared to a smooth profile. The effect of fluctuations in the initial state is found to be stronger for peripheral collisions and for lower beam energies. The $p_T$ spectra are found to be quite sensitive to the value of the initial formation time of the plasma which is not known unambiguously and which may vary with collision centralities at a particular beam energy. Increase in the value of the formation time lowers the production of thermal photons compared to the results from a shorter formation time. However, the relative enhancement from fluctuating initial states (compared to a smooth initial state) is found to be stronger for the larger values of formation time. The $p_T$ spectra alone are found to be insufficient to quantify the fluctuations in the initial density distribution due to the uncertainties in the initial conditions. A suitably normalized ratio of central-to-peripheral yield as a function of collision centrality and $p_T$ can be a useful measure of the fluctuation size scale.

We have examined the available latest super proton synchrotron (SPS) data on $J/\psi$ suppression in Pb+Pb and In+In collisions at 158 A GeV. Our employed model, with parameters fixed by $p$-$p$ and $p$-nucleus collisions, gives excellent description of NA50 and NA60 data on the centrality dependence of $J/\psi$ suppression. The model is then applied to predict the centrality dependence of $J/\psi$ production in Au+Au collisions in the facility for anti-proton and ion research (FAIR) energy domain. A much larger suppression of $J/\psi$ is predicted. In addition the possible effects of a baryon-rich medium on $J/\psi$ production is also investigated.

We attempted to determine the possible models for the neutron star PSR J1614-2230 in the framework of the relativistic mean field theory considering the baryon octet. It was found that the maximum mass of the neutron star will increase as the $x_{\omega }$ increases, with the $x_{\rho \Lambda },x_{\rho \Sigma },x_{\rho \Xi }$, and the $x_{\sigma }$ being fixed. By successively adopting the approximate methods, we can obtain four of the possible models: (i) $x_{\sigma }=0.33$ and $x_{\omega }=0.6964$, (ii) $x_{\sigma }=0.4$ and $x_{\omega }=0.7435$, (iii) $x_{\sigma }=0.5$ and $x_{\omega }=0.8106$, and (iv) $x_{\sigma }=0.6$ and $x_{\omega }=0.8772$. Here, the hyperon coupling constants $x_{\rho }$ are $x_{\rho \Lambda }=0$, $x_{\rho \Sigma }=2$, $x_{\rho \Xi }=1,$ and the nucleon coupling constants are chosen as GL97. Further, the possible value range of $x_{\sigma }$ and $x_{\omega }$, which corresponds to the mass of the neutron star PSR J1614-2230, is also determined through the four values of hyperon coupling constants determined in this paper. Our results may prove that the hadronic theory model can describe the mass of the neutron star PSR J1614-2230.

The phase diagram of the superfluid phase coupled to spin singlet ($S=0$) and isospin triplet ($T=1$) states in infinite nuclear matter is analyzed within the nonrelativistic Skyrme model. We use an approach that allows a unified and consistent treatment of the particle-hole and particle-particle channels. The gap equation is solved for the full range of accessible densities, isospin asymmetries, and temperatures. The characteristic features of each of the components $T_z=0,\pm 1$ are emphasized. The search for signatures of a BCS-BEC crossover yields negative results within the scheme proposed.

Background: The pygmy dipole resonance (PDR) is an interesting nuclear structure phenomenon with an impact in predicting different astrophysics scenarios, for example, specific properties of neutron stars that can be determined from the thickness of the neutron skin which is directly connected to the strength of the PDR. Various collective and microscopic models were employed in order to account for the observed properties of the PDR.

Purpose: Determine for the first time whether it is possible to use the interacting boson approximation (IBA) to reproduce the general characteristics of the PDR.

Methods: The PDR properties of the stable even-even $N=82$ isotones are calculated in the IBA-$spdf$ model based on the assumption that many effects of the mixing caused by the shell structure can be simulated by considering the number of bosons as an effective value.

Results: The IBA calculations indicate a resonance-like structure of the $E1$ strength in the energy region 5–8 MeV, thus confirming the experimental results for this mass region. The distribution and fragmentation of the $J^{\pi }=1^{-}$ states and of the $E1$ strength are in good agreement with the experimental data. By employing the same procedure as for the $N=82$ isotones, the model is used to predict the PDR strength for a nucleus in a different mass region, i.e., for the ${}^{94}$Mo nucleus.

Conclusions: The calculations confirm a good agreement for the distribution and fragmentation of the $E1$ strength.

When a jet collides coherently with many parton scatterers at very high energies, the Bose-Einstein symmetry with respect to the interchange of the virtual bosons leads to a destructive interference of the Feynman amplitudes in most regions of the momentum transfer phase space, but a constructive interference in some other regions of the momentum transfer phase space. As a consequence, the recoiling scatterers have a tendency to come out collectively along the incident jet direction, each carrying a substantial fraction of the incident jet longitudinal momentum. The manifestation of the Bose-Einstein interference as collective recoils of the scatterers along the jet direction may have been observed in angular correlations of hadrons associated with a high-$p_T$ trigger in high-energy heavy-nuclei collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).

We study the existence of third, hyperdeformed minima in a number of even-even Th, U, and Pu nuclei using the Woods-Saxon microscopic-macroscopic model that very well reproduces first and second minima and fission barriers in actinides. Deep (3–4 MeV) minima found previously by Ćwiok et al. are found spurious after sufficiently general shapes are included. Shallow third wells may exist in ${}^{230,232}$Th, with IIIrd barriers $⩽$ 200 and 330 keV (respectively). Thus, a problem of qualitative discrepancy between microscopic-macroscopic and self-consistent predictions is resolved. Now, an understanding of experimental results on the apparent third minima in uranium becomes an issue.

The $\gamma p\to {\pi }^0{\pi }^{0}p$ reaction has been measured from threshold to 1.4 GeV using the Crystal Ball and TAPS photon spectrometers together with the photon tagging facility at the Mainz Microtron. The experimental results include total and differential cross sections as well as specific angular distributions, which were used to extract partial-wave amplitudes. In particular, the energy region below the $D_{13}\left(1520\right)$ resonance was studied.

Structures observed in heavy-ion fusion cross sections at energies above the Coulomb barrier are interpreted as caused by the penetration of centrifugal barriers that are well separated in energy. The structures are most pronounced in the fusion of lighter, symmetric systems, where the separation in energy between successive angular momentum barriers is relatively large. It is shown that the structures or peaks can be revealed by plotting the first derivative of the energy weighted cross section. It is also shown how an orbital angular momentum can be assign to the observed peaks by comparing to coupled-channels calculations. This is illustrated by analyzing high-energy fusion data for ${}^{12}$C+${}^{16}$O and ${}^{16}$O+${}^{16}$O, and the possibility of observing similar structures in the fusion of heavier systems is discussed.

The appearance of monojets is among the most striking signatures of jet quenching in the context of ultrarelativistic heavy-ion collisions. Experimentally, the disappearance of jets has been quantified by the ATLAS and CMS Collaborations in terms of the dijet asymmetry observable $A_J$. While the experimental findings initially gave rise to claims that the measured $A_J$ would challenge the radiative energy loss paradigm, the results of a systematic investigation of $A_J$ in different models for the medium evolution and for the shower-medium interaction presented here suggest that the observed properties of $A_J$ arise fairly generically and independent of specific model assumptions for a large class of reasonable models. This would imply that, rather than posing a challenge to any particular model, the observable prompts the question of which model dynamics is incompatible with the data.