We propose a new kind of two-particle correlation of identified hadrons in longitudinal rapidity space which can reflect directly the conserved charge correlations of a hot quark system produced in $AA$ collisions at Large Hadron Collider (LHC) energies. It is derived from the basic scenario of quark combination mechanism of hadron production. Like the elliptic flow of identified hadrons at intermediate transverse momentum, this correlation is independent of the absolute hadronic yields but depends only on the flavor compositions of hadrons and thus exhibits interesting properties for different kinds of hadrons. We suggest the measurement of this correlation function in $AA$ collisions at the LHC to gain more insight into the charge-correlation properties of the produced hot quark matter.

Thermodynamic properties of hot and dense hadronic systems with a hard-sphere interaction are calculated in the Boltzmann approximation. Two parametrizations of pressure as a function of density are considered: the first one, used in the excluded-volume model and the second one, suggested earlier by Carnahan and Starling. The results are given for one-component systems containing only nucleons or pions, as well as for chemically equilibrated mixtures of different hadronic species. It is shown that the Carnahan–Starling approach can be used in a much broader range of hadronic densities as compared to the excluded-volume model. In this case the superluminal sound velocities appear only at very high densities, in the region where the deconfinement effects should be already important.

Background: The rate ${\lambda }_{pp\mu }^{}$ characterizes the formation of $pp\mu$ molecules in collisions of muonic $p\mu$ atoms with hydrogen. In measurements of the basic weak muon capture reaction on the proton to determine the pseudoscalar coupling $g_P^{}$, capture occurs from both atomic and molecular states. Thus knowledge of ${\lambda }_{pp\mu }^{}$ is required for a correct interpretation of these experiments.

Purpose: Recently the MuCap experiment has measured the capture rate ${\mathrm{\Lambda }}_{\mathrm{S}}^{}$ from the singlet $p\mu$ atom, employing a low-density active target to suppress $pp\mu$ formation [V. Andreev et al. (MuCap Collaboration), Phys. Rev. Lett. 110, 012504 (2013)]. Nevertheless, given the unprecedented precision of this experiment, the existing experimental knowledge in ${\lambda }_{pp\mu }^{}$ had to be improved.

Method: The MuCap experiment derived the weak capture rate from the muon disappearance rate in ultrapure hydrogen. By doping the hydrogen with 20 ppm of argon, a competing process to $pp\mu$ formation was introduced, which allowed the extraction of ${\lambda }_{pp\mu }^{}$ from the observed time distribution of decay electrons.

Results: The $pp\mu$ formation rate was measured as ${\lambda }_{pp\mu }^{}=(2.01\pm 0.{06}_{\mathrm{stat}}\pm 0.{03}_{\mathrm{sys}})\times {10}^6{\text{s}}^{-1}$. This result updates the ${\lambda }_{pp\mu }^{}$ value used in the abovementioned MuCap publication.

Conclusions: The $2.5\times$ higher precision compared to earlier experiments, and the fact that the measurement was performed under nearly identical conditions as the main data taking, reduces the uncertainty induced by ${\lambda }_{pp\mu }^{}$ to a minor contribution to the overall uncertainty of ${\mathrm{\Lambda }}_{\mathrm{S}}^{}$ and $g_P^{}$, as determined in the MuCap experiment. Our final value for ${\lambda }_{pp\mu }^{}$ shifts ${\mathrm{\Lambda }}_{\mathrm{S}}^{}$ and $g_P^{}$ by less than one-tenth of their respective uncertainties compared to our results published earlier.

The effects of charge symmetry breaking in nucleon electromagnetic form factors on parity-violating elastic electron-${}^{12}\mathrm{C}$ scattering is studied and found to be much smaller than other known effects. The analysis of a planned experiment is discussed. Nuclear isospin violation is likely to provide the largest correction term.

Low-energy proton capture reactions have been studied in a statistical model using the semimicroscopic optical potential in the mass range $A=110-125$. Nuclear density obtained from relativistic mean-field calculations has been folded with nucleon-nucleon interactions to obtain the optical potential. Theoretical results have been compared with experimental measurements to normalize the potential. Results have also been compared with a standard calculation available in the literature.

Excited states in ${}^{99}\mathrm{Tc}$ with energies up to 6 MeV have been populated using the ${}^{96}\mathrm{Zr}({}^7\mathrm{Li},4n){}^{99}\mathrm{Tc}$ reaction with a laboratory beam energy of 35 MeV. Coincident $\gamma$ rays from excited nuclei produced in the reactions were detected using an array of coaxial, planar, and clover-type high-purity germanium detectors. A total of 60 new $\gamma$-ray transitions and 21 new levels are identified and placed into a new level scheme. Two collective bands assigned to be built on the $\pi g_{9/2}\left[422\right]5/2{}^{+}$ and $\pi p_{1/2}\left[301\right]1/2{}^{-}$ Nilsson configurations have been extended with spins up to 35/2 and $33/2 \hslash$, respectively. Backbending and signature inversion have been observed in the yrast band. The large signature splitting of the positive-parity band in ${}^{99}\mathrm{Tc}$ may be caused by a triaxial deformation, which agrees well with the electromagnetic properties, theoretical calculations based on total Routhian surface, and triaxial particle-rotor model calculations.

High-energy giant dipole resonance (GDR) $\gamma$ rays were measured following the decay of the hot, rotating compound nucleus of ${}^{88}\mathrm{Mo}$, produced at excitation energies of 124 and 261 MeV. The reaction ${}^{48}\mathrm{Ti}$ + ${}^{40}\mathrm{Ca}$ at 300 and 600 MeV bombarding energies has been used. The data were analyzed using the statistical model Monte Carlo code gemini++. It allowed extracting the giant dipole resonance parameters by fitting the high-energy $\gamma$-ray spectra. The extracted GDR widths were compared with the available data at lower excitation energy and with theoretical predictions based on (i) The Lublin-Strasbourg drop macroscopic model, supplemented with thermal shape fluctuations analysis, and (ii) The phonon damping model. The theoretical predictions were convoluted with the population matrices of evaporated nuclei from the statistical model gemini++. Also a comparison with the results of a phenomenological expression based on the existing systematics, mainly for lower temperature data, is presented and discussed. A possible onset of a saturation of the GDR width was observed around $T=3$ MeV.

$\varphi$ and ${\mathrm{K}}^{-}$ mesons from Ni+Ni collisions at the beam energy of $1.91A$ GeV have been measured by the FOPI spectrometer, with a trigger selecting central and semicentral events amounting to 52% of the total cross section. The phase-space distributions, and the total yield of ${\mathrm{K}}^{-}$, as well as the kinetic energy distribution and the total yield of $\varphi$ mesons are presented. The $\varphi /$ ${\mathrm{K}}^{-}$ ratio is found to be $0.44\pm 0.07{\left(\text{stat}\right)}_{-0.10}^{+0.16}\left(\text{syst}\right)$, meaning that about 22% of ${\mathrm{K}}^{-}$ mesons originate from the decays of $\varphi$ mesons, occurring mostly in vacuum. The inverse slopes of direct kaons are up to about 15 MeV larger than the ones extracted within the one-source model, signaling that a considerable share of gap between the slopes of ${\mathrm{K}}^{+}$ and ${\mathrm{K}}^{-}$ could be explained by the contribution of $\varphi$ mesons to negative kaons.

The beam-spin asymmetry, $\Sigma$, for the reaction $\gamma d\to pn$ has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins, between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, ${\theta }_{\mathrm{c}.\mathrm{m}.}$, between ${25}^{\circ }$ and ${160}^{\circ }$. These are the first measurements of beam-spin asymmetries at ${\theta }_{\mathrm{c}.\mathrm{m}.}={90}^{\circ }$ for photon-beam energies above 1.6 GeV, and the first measurements for angles other than ${\theta }_{\mathrm{c}.\mathrm{m}.}={90}^{\circ }$. The angular and energy dependence of $\Sigma$ is expected to aid in the development of QCD-based models to understand the mechanisms of deuteron photodisintegration in the transition region between hadronic and partonic degrees of freedom, where both effective field theories and perturbative QCD cannot make reliable predictions.

We calculate the nuclear and neutron matter equations of state from microscopic nuclear forces at different orders in chiral effective field theory and with varying momentum-space cutoff scales. We focus attention on how the order-by-order convergence depends on the choice of resolution scale and the implications for theoretical uncertainty estimates on the isospin asymmetry energy. Specifically we study the equations of state using consistent NLO and ${\mathrm{N}}^2\mathrm{LO}$ (next-to-next-to-leading order) chiral potentials where the low-energy constants $c_D$ and $c_E$ associated with contact vertices in the ${\mathrm{N}}^2\mathrm{LO}$ chiral three-nucleon force are fitted to reproduce the binding energies of ${}^3\text{H}$ and ${}^3\text{He}$ as well as the beta-decay lifetime of ${}^3\text{H}$. At these low orders in the chiral expansion there is little sign of convergence, while an exploratory study employing the ${\mathrm{N}}^3\mathrm{LO}$ two-nucleon force together with the ${\mathrm{N}}^2\mathrm{LO}$ three-nucleon force give first indications for (slow) convergence with low-cutoff potentials and poor convergence with higher-cutoff potentials. The consistent NLO and ${\mathrm{N}}^2\mathrm{LO}$ potentials described in the present work provide the basis for estimating theoretical uncertainties associated with the order-by-order convergence of nuclear many-body calculations in chiral effective field theory.

Background: The neutron-rich Ba isotopes with only six valence protons represent the beginning of the collective rotation-vibration band structure. The sharp shape phase transition at $N=88\text{–}90$ observed in Ce-Gd isotones is not exhibited in ${}^{144\text{–}146}\mathrm{Ba}$, which renders their analysis interesting. Also there are ambiguities in the spin and band assignments.

Purpose: To study their spectra empirically and to compare with predictions from an interacting boson model and microscopic dynamic pairing plus quadrupole model to explain the smooth shape transition at $N=88\text{–}90$.

Method: We compare the results of the calculation in the interacting boson models (IBM-1) and IBM-2 and the dynamic pairing plus quadrupole model with experiment and illustrate the variation in level structure of the Ba isotopes with N. The absence of sharp phase transition at $N=88\text{–}90$ is examined.

Results: The ambiguous spin and parity of levels of the vibrational bands are assigned on the basis of calculated K components and the decay characteristics.

Conclusion: The second $I^{\pi }=2^{+}$ states in ${}^{144,146}\mathrm{Ba}$ have $K=0$ predominance, and $I^{\pi }=2_3^{+}$ states are $K=2$. The smooth transition at $N=88\text{–}90$ is explained.

An approach based on combined solutions of the Bethe-Salpeter (BS) and Dyson-Schwinger (DS) equations within the ladder-rainbow approximation in the presence of singularities is proposed to describe the meson spectrum as quark-antiquark bound states. We consistently implement in the BS equation the quark propagator functions from the DS equation, with and without pole-like singularities, and show that, by knowing the precise positions of the poles and their residues, one is able to develop reliable methods of obtaining finite interaction BS kernels and to solve the BS equation numerically. We show that, for bound states with masses $M<1$ GeV, there are no singularities in the propagator functions when employing the infrared part of the Maris-Tandy kernel in truncated BS-DS equations. For $M>1$ GeV, however, the propagator functions reveal pole-like structures. Consequently, for each type of meson (unflavored, strange, and charmed) we analyze the relevant intervals of $M$ where the pole-like singularities of the corresponding quark propagator influence the solution of the BS equation and develop a framework within which they can be consistently accounted for. The BS equation is solved for pseudoscalar and vector mesons. Results are in good agreement with experimental data. Our analysis is directly related to the future physics program at FAIR with respect to open charm degrees of freedom.

A brief outline of the Lorentz integral transform (LIT) method is given. The method is well established and allows treatment of reactions into the many-body continuum with bound-state-like techniques. The energy resolution that can be achieved is studied by means of a simple two-body reaction. From the discussion it will become clear that the LIT method is an approach with a controlled resolution and that there is no principle problem to even resolve narrow resonances in the many-body continuum. As an example, the isoscalar monopole resonance of ${}^4\mathrm{He}$ is considered. The importance of the choice of a proper basis for the expansion of the LIT states is pointed out. By employing such a basis, a width of 180(70) keV is found for the ${}^4\mathrm{He}$ isoscalar monopole resonance when using a simple central nucleon-nucleon potential model.

We present a new phenomenological nucleon-nucleon $\left(NN\right)$ chiral potential fitted to $925 pp$ and $1743 np$ scattering data selected from the Granada-$2013 NN$ database up to a laboratory energy of 125 MeV with 20 short-distance parameters and three chiral constants $c_1,c_3$, and $c_4$ with ${\chi }^2/\nu =1.02$. Special attention is given to testing the normality of the residuals which allows for a sound propagation of statistical errors from the experimental data to the potential parameters, phase shifts, scattering amplitudes, and counterterms. This fit allows for a new determination of the chiral constants $c_1,c_3$, and $c_4$ compatible with previous determinations from $NN$ data. This new interaction is found to be softer than other high-quality potentials by undertaking a Weinberg eigenvalue analysis. We further explore the interplay between the error analysis and the assumed form of the short-distance interaction. The present work shows that it is possible to fit $NN$ scattering with a two-pion exchange (TPE) chiral potential fulfilling all necessary statistical requirements up to 125 MeV and shows unequivocal nonvanishing $D$-wave short-distance pieces.

Magnetic properties of deformed odd-mass nuclei are studied within a nonrelativistic mean-field-plus-pairing approach, namely the Skyrme-Hartree-Fock-BCS approach with self-consistent blocking. For an odd number of nucleons these approaches lead to the breaking of the time-reversal invariance. The deviation from the Schmidt values of the isoscalar magnetic dipole moment is known to result from a subtle balance between core-polarization effects and meson-exchange current effects. However, the former are usually calculated in the random phase approximation without time-reversal symmetry breaking at the mean-field level. In this work we show that if one takes into account this symmetry breaking already in the mean-field solution, the correction from core polarization yields a significant contribution to the empirical quenching of the spin gyromagnetic ratios as compared to the free values in deformed odd-mass nuclei. Moreover, we calculate magnetic dipole moments in the Bohr and Mottelson unified-model description with self-consistent blocked mean-field intrinsic states. The obtained results in the $A\sim 100$ and $A\sim 180$ mass regions as well as for three actinide nuclei compare favorably with experimental data.

A recursive method for the efficient computation of two-body matrix elements is presented. The method consists of a set of recursion relations for the computationally demanding radial integral and adds one more tool to the set of computational methods introduced by Horie and Sasaki [H. Horie and K. Sasaki, Prog. Theor. Phys. 25, 475 (1961)]. The neutrinoless double-$\beta$ decay will serve as the primary application and example, but the method is general and can be applied equally well to other kinds of nuclear structure calculations involving matrix elements of two-body interactions.

In this work we perform a systematic study of pairs of single-$\beta$-decaying nuclei in the mass region $A=100–136$ to extract information on the effective value of the axial-vector coupling constant $g_{\mathrm{A}}$. As the many-body framework we use the quasiparticle random-phase approximation (QRPA) and its proton-neutron variant (pnQRPA) in single-particle valence bases with Woods-Saxon-calculated single-particle energies. It is found that, to a reasonable approximation, $g_{\mathrm{A}}$ is a linear function of the mass number $A$, with a slightly different parametrization below and above the mass $A=121$. Using the values of $g_{\mathrm{A}}$ extracted from the linear fit, as well as an average constant value of $g_{\mathrm{A}}$, we calculate the two-neutrino double-$\beta$ ($2\nu \beta \beta$) decay half-lives of 11 ${\beta }^{-}{\beta }^{-}$ decays and 10 mixed ${\beta }^{+}$ and electron-capture (EC) decays, ${\beta }^{+}{\beta }^{+}/{\beta }^{+}\mathrm{EC}/\mathrm{ECEC}$, to both the ground state and the lowest three excited states.

The scissors mode, a magnetic dipole excitation-mainly orbital, is usually discussed in terms of a transition from a $J=0^{+}$ ground state to a $J=1^{+}$ excited state. This is understandable because it follows from the way the experiment is performed, e.g., inelastic electron scattering. Here, however, we start with the excited $1^{+}$ state and consider all possible transitions to $J=0^{+},1^{+},$ and $2^{+}$ states with final isospins. There is a larger transition to the $0_2^{+}$ state than to ground. This has a much richer structure. We note that the “sum of sums” is independent of the interaction.

A systematic theoretical study of $\alpha$-decay half-lives in the superheavy mass region of the periodic table of elements is carried out by extending the quantum-mechanical fragmentation theory based on the preformed cluster model (PCM) to include temperature $\left(T\right)$ dependence in its built-in preformation and penetration probabilities of decay fragments. Earlier, the $\alpha$-decay chains of the isotopes of $Z=115$ were investigated by using the standard PCM for spontaneous decays, with“hot-optimum” orientation effects included, which required a constant scaling factor of ${10}^4$ to approach the available experimental data. In the present approach of the PCM $\left(T\ne 0\right)$, the temperature effects are included via the recoil energy of the residual superheavy nucleus (SHN) left after $x$-neutron emission from the superheavy compound nucleus. The important result is that the $\alpha$-decay half-lives calculated by the PCM $\left(T\ne 0\right)$ match the experimental data nearly exactly, without using any scaling factor of the type used in the PCM. Note that the PCM $\left(T\ne 0\right)$ is an equivalent of the dynamical cluster-decay model for heavy-ion collisions at angular momentum $\ell =0$. The only parameter of model is the neck-length parameter $\Delta R$, which for the calculated half-lives of $\alpha$-decay chains of various isotopes of $Z=113$ to 118 nuclei formed in “hot-fusion” reactions is found to be nearly constant, i.e., $\Delta R\approx 0.95\pm 0.05$ fm for all the $\alpha$-decay chains studied. The use of recoiled residue nucleus as a secondary heavy-ion beam for nuclear reactions has also been suggested in the past.