In this work, we perform a study of nucleon resonance production in the $\gamma p\to p\eta \varphi$ reaction within an effective Lagrangian approach. In our model, we consider the excitation of the $N^{*}\left(1535\right)$, $N^{*}\left(1650\right)$, $N^{*}\left(1710\right)$, and $N^{*}\left(1720\right)$ in the intermediate state and the background term. We find that this reaction is dominated by the excitation of the $N^{*}\left(1535\right)$ in the near threshold region. Especially, we study the possible role of the scalar meson exchange in this reaction. It is found that the $f_0\left(980\right)$ exchange may give a significant contribution and the parity asymmetry can be used to identify its role in this reaction.

The factorization scheme, based on the impulse approximation and the spectral function formalism, has been recently generalized to allow the description of electromagnetic nuclear interactions driven by two-nucleon currents. We have extended this framework to the case of weakly charged and neutral currents, and carried out calculations of the double-differential neutrino-carbon and neutrino-oxygen cross sections using two different models of the target spectral functions. The results, showing a moderate dependence on the input spectral function, confirm that our approach provides a consistent treatment of all reaction mechanisms contributing to the signals detected by accelerator-based neutrino experiments.

The photodisintegration cross sections for the ${}^{94}\mathrm{Mo}(\gamma ,n)$ and ${}^{90}\mathrm{Zr}(\gamma ,n)$ reactions have been experimentally investigated with quasi-monochromatic photon beams at the High Intensity $\gamma$-ray Source $\left(\mathrm{HI}\gamma \mathrm{S}\right)$ facility of the Triangle Universities Nuclear Laboratory (TUNL). The energy dependence of the photoneutron reaction cross sections was measured with high precision from the respective neutron emission thresholds up to 13.5 MeV. These measurements contribute to a broader investigation of nuclear reactions relevant to the understanding of the $p$-process nucleosynthesis. The results are compared with the predictions of Hauser-Feshbach statistical model calculations using two different models for the dipole $\gamma$-ray strength function. The resulting ${}^{94}\mathrm{Mo}(\gamma ,n)$ and ${}^{90}\mathrm{Zr}(\gamma ,n)$ photoneutron stellar reaction rates as a function of temperature in the typical range of interest for the $p$-process nucleosynthesis show how sensitive the photoneutron stellar reaction rate can be to the experimental data in the vicinity of the neutron threshold.

We construct a new class of phenomenological equations of state for homogeneous matter for use in simulations of hot and dense matter in local thermodynamic equilibrium. We construct a functional form which respects experimental, observational, and theoretical constraints on the nature of matter in various density and temperature regimes. Our equation of state (EOS) matches (i) the virial coefficients expected from nucleon-nucleon scattering phase shifts, (ii) experimental measurements of nuclear masses and charge radii, (iii) observations of neutron star radii, (iv) theory results on the equation of state of neutron matter near the saturation density, and (v) theory results on the evolution of the EOS at finite temperatures near the saturation density. Our analytical model allows one to compute the variation in the thermodynamic quantities based on the uncertainties in the nature of the nucleon-nucleon interaction. Finally, we perform a correction to ensure the equation of state is causal at all densities, temperatures, and electron fractions.

We analyze a generic model where wounded quarks are amended with strings in which both endpoint positions fluctuate in spatial rapidity. With the assumption that the strings emit particles independently of one another and with a uniform distribution in rapidity, we are able to analyze the model semianalytically, which allows for its detailed understanding. Using as a constraint the one-body string emission functions obtained from the experimental data for collisions at $\sqrt{s_{NN}}=200$ GeV, we explore the two-body correlations for various scenarios of string fluctuations. We find that the popular measures used to quantify the longitudinal fluctuations ($a_{nm}$ coefficients) are limited with upper and lower bounds. These measures can be significantly larger in the model where both endpoints are allowed to fluctuate, compared to the model with single endpoint fluctuations.

The production yield of the $\mathrm{\Lambda }\left(1520\right)$ baryon resonance is measured at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathit{NN}}}$ = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is performed in the $\mathrm{\Lambda }\left(1520\right)\to \mathrm{p}{\mathrm{K}}^{-}$ (and charge conjugate) hadronic decay channel as a function of the transverse momentum ($p_{\mathrm{T}}$) and collision centrality. The ratio of the $p_{\mathrm{T}}$-integrated production of $\mathrm{\Lambda }\left(1520\right)$ baryons relative to $\mathrm{\Lambda }$ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first $3\sigma$ evidence of $\mathrm{\Lambda }\left(1520\right)$ suppression within a single collision system. The measured $\mathrm{\Lambda }\left(1520\right)/\mathrm{\Lambda }$ ratio in central collisions is smaller than the value predicted by the statistical hadronization model calculations. The shape of the measured $p_{\mathrm{T}}$ distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances.

Comprehensive results on the production of unidentified charged particles, ${\pi }^{\pm }, {\mathrm{K}}^{\pm }, {\mathrm{K}}_{\mathrm{S}}^0, {\mathrm{K}}^{*}{\left(892\right)}^0, p, \overline{p}, \varphi$(1020), $\mathrm{\Lambda }, \overline{\mathrm{\Lambda }}, {\mathrm{\Xi }}^{-}, {\overline{\mathrm{\Xi }}}^{+}, {\mathrm{\Omega }}^{-}$, and ${\overline{\mathrm{\Omega }}}^{+}$ hadrons in proton-proton ($pp$) collisions at $\sqrt{s}=7$ TeV at midrapidity ($\left|y\right|<0.5$) as a function of charged-particle multiplicity density are presented. In order to avoid autocorrelation biases, the actual transverse momentum ($p_{\mathrm{T}}$) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately constant as a function of multiplicity, the corresponding ratios of strange hadrons to pions show a significant enhancement that increases with increasing strangeness content. Furthermore, all identified particle-to-pion ratios are shown to depend solely on charged-particle multiplicity density, regardless of system type and collision energy. The evolution of the spectral shapes with multiplicity and hadron mass shows patterns that are similar to those observed in $p$-Pb and Pb-Pb collisions at Large Hadron Collider energies. The obtained $p_{\mathrm{T}}$ distributions and yields are compared to expectations from QCD-based $pp$ event generators as well as to predictions from thermal and hydrodynamic models. These comparisons indicate that traces of a collective, equilibrated system are already present in high-multiplicity $pp$ collisions.

We compute the matrix elements for elastic scattering of dark matter (DM) particles off light nuclei (${}^2\mathrm{H}, {}^3\mathrm{H}, {}^3\mathrm{He}, {}^4\mathrm{He}$, and ${}^6\mathrm{Li}$) using quantum Monte Carlo methods. We focus on scalar-mediated DM-nucleus interactions and use scalar currents obtained to next-to-leading order in chiral effective theory. The nuclear ground states are obtained from a phenomenological nuclear Hamiltonian that includes the Argonne $v_{18}$ two-body interaction and the three-body Urbana IX interaction. Within this approach, we study the impact of one- and two-body currents and discuss the size of nuclear uncertainties, including for the first time two-body effects in $A=4$ and $A=6$ systems. Our results provide the nuclear structure input needed to assess the sensitivity of future experimental searches of (light) dark matter using light nuclei, such as ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$.

Background: The nuclear kinetic density is one of many fundamental, nonobservable quantities in density functional theory (DFT) dependent on the nonlocal nuclear density. Often, approximations may be made when computing the density that may result in spurious contributions in other DFT quantities. With the ability to compute the nonlocal nuclear density from ab initio wave functions, it is now possible to estimate effects of such spurious contributions.

Purpose: We derive the kinetic density using ab initio nonlocal scalar one-body nuclear densities computed within the no-core shell model (NCSM) approach, utilizing two- and three-nucleon chiral interactions as the sole input. The ability to compute translationally invariant nonlocal densities allows us to gauge the impact of the spurious center-of-mass (c.m.) contributions in DFT quantities, such as the kinetic density, and provide ab initio insight into refining energy density functionals.

Methods: The nonlocal nuclear densities are derived from the NCSM one-body densities calculated in second quantization. We present a review of c.m. contaminated and translationally invariant nuclear densities. We then derive an analytic expression for the kinetic density using these nonlocal densities, producing an ab initio kinetic density.

Results: The ground-state nonlocal densities of ${}^{4,6,8}\mathrm{He},{}^{12}\mathrm{C}$, and ${}^{16}\mathrm{O}$ are used to compute the kinetic densities of the aforementioned nuclei. The impact of c.m. removal techniques in the density are discussed and compared to a procedure applied in DFT. The results of this work can be extended to other fundamental quantities in DFT.

Conclusions: The use of a general nonlocal density allows for the calculation of fundamental quantities taken as input in theories such as DFT. This allows benchmarking c.m. removal procedures and provides a bridge for comparison between ab initio and DFT many-body techniques.

Background: Relativistic treatments of quantum mechanical systems are important for understanding hadronic structure and dynamics at subnucleon scales. Relativistic invariance of a quantum system means that there is an underlying unitary representation of the Poincaré group. This is equivalent to the requirement that the quantum observables (probabilities, expectation values, and ensemble averages) for equivalent measurements performed in different inertial reference frames are identical. Different representations are used in practice, including Poincaré covariant forms of dynamics, representations based on Lorentz covariant wave functions, Euclidean covariant representations, and representations generated by Lorentz covariant fields.

Purpose: The purpose of this work is to illustrate the relation between the different equivalent representations of states in relativistic quantum mechanics.

Method: The starting point is a description of a particle of mass $m$ and spin $j$ using irreducible representations of the Poincaré group. Since any unitary representation of the Poincaré group can be decomposed into a direct integral of irreducible representations, these are the basic building blocks of any relativistically invariant quantum theory. The equivalence is established by constructing equivalent Lorentz covariant irreducible representations from Poincaré covariant irreducible representations and constructing equivalent Euclidean covariant irreducible representations from Lorentz covariant irreducible representations.

Results: Equivalent descriptions for positive mass representations of arbitrary spin are presented in each of these frameworks. Dynamical realizations of the different representations are briefly discussed.

Conclusion: Poincaré covariant, Lorentz covariant, and Euclidean covariant realizations of relativistic dynamics are shown to be equivalent by explicitly relating the positive-mass positive-energy irreducible representations of the Poincaré group that appear in the direct integral.

We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity $1<\left|\eta \right|<3$ in Au + Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients $v_2\left\{2\right\},v_2\left\{4\right\},v_2\left\{6\right\}$, and $v_2\left\{8\right\}$, and triangular flow coefficients $v_3\left\{2\right\}$ and $v_3\left\{4\right\}$. Using the small-variance limit, we estimate the mean and variance of the event-by-event $v_2$ distribution from $v_2\left\{2\right\}$ and $v_2\left\{4\right\}$. In a complementary analysis, we also use a folding procedure to study the distributions of $v_2$ and $v_3$ directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed.

Excited states in ${}^{133}\mathrm{Sn}$ were investigated through the $\beta$ decay of ${}^{133}\mathrm{In}$ at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for ${}^{133}\mathrm{In}$, allowing us to study separately, and in detail, the $\beta$-decay branch of ${}^{133}\mathrm{In}{\mathrm{J}}^{\pi }=(9/2^{+}$) ground state and its ${\mathrm{J}}^{\pi }=(1/2^{-}$) isomer. Thanks to the large spin difference of the two $\beta$-decaying states of ${}^{133}\mathrm{In}$, it is possible to investigate separately the lower and higher spin states in the daughter, ${}^{133}\mathrm{Sn}$, and thus to probe independently different single-particle and single-hole levels. We report here new $\gamma$ transitions observed in the decay of ${}^{133}\mathrm{In}$, including those assigned to the deexcitation of the neutron-unbound states.

Background: Significant yield discrepancies (500%–600%) were reported recently between experimental results and predictions (from the gef model) and evaluations (from the JEFF-3.1.1 and ENDF/B-VII.1 libraries) for Mo and Sn fission-fragment yields in fast-neutron-induced reactions on ${}^{238}\mathrm{U}$ using $\gamma -\gamma -\gamma$ coincidence spectroscopy. The model and evaluations also predict Mo and Sn fragments that are on average $\sim 1$ to 2 neutrons richer than the experimental results.

Purpose: $\gamma -\gamma -\gamma$ coincidence spectroscopy favors detection of higher-multiplicity $\gamma$-ray cascades. An alternative approach is determining the fragment yields using single-$\gamma$-ray spectroscopy, as it was attempted here for selected cases where it was feasible. Advantages and drawbacks in both approaches need to be understood and potential systematic errors in the experimental results should be addressed using theoretical models.

Methods: Fast neutrons from the LANSCE WNR facility were used to induce fission on ${}^{238}\mathrm{U}$. The emitted $\gamma$ rays were measured with the GEANIE spectrometer.

Results: The yield of selected even-even fission fragments was determined. The selection was based on the ability to reliably determine excitation functions for the detected $\gamma$ rays.

Conclusions: Our single-$\gamma$-ray results provide better agreement between experiment and predictions and evaluations.

Background: In heavy-ion induced reactions, the sub-barrier fusion cross sections are found to be higher as compared to the predictions of the one-dimensional barrier penetration model. Attempts have been made to explain sub-barrier fusion enhancement by including the static deformations, the couplings to inelastic excitations, and non-fusion channels.

Purpose: To investigate factors which influence the sub-barrier fusion in the ${}^{37}\mathrm{Cl}+{}^{130}\mathrm{Te}$ system and to understand the interplay of couplings, the fusion excitation function was measured at energies from $10\%$ below to $15\%$ above the Bass barrier.

Method: The fusion excitation function was measured by employing a recoil mass spectrometer, the Heavy-Ion Reaction Analyser (HIRA), at the Inter-University Accelerator Centre, New Delhi. To study the behavior of the fusion excitation function and the effect of couplings at sub-barrier energies, the excitation function was analyzed in the framework of the coupled-channels code ccfull.

Results: In the present work, the fusion cross section was measured down to 1 $\mu \mathrm{b}$ at the lowest measured energy, i.e., $10\%$ below the barrier. It was found that the inclusion of couplings of low-lying excited states along with the modified barrier between interacting nuclei satisfactorily reproduces the fusion excitation function of the ${}^{37}\mathrm{Cl}+{}^{130}\mathrm{Te}$ system. For better insight into the sub-barrier fusion, the fusion barrier distribution, the logarithmic derivative L(E) factor, and the astrophysical S factor were extracted from the analysis of the experimentally measured fusion excitation function.

Conclusions: The analysis of the fusion excitation function in terms of the astrophysical S factor and the L(E) factor suggests the absence of fusion hindrance in the ${}^{37}\mathrm{Cl}+{}^{130}\mathrm{Te}$ system down to a 1 $\mu \mathrm{b}$ cross section achieved at the lowest measured energy. The excitation function of the present system is compared with the existing measurements in which ${}^{37}\mathrm{Cl}$ has been used as a projectile to understand the interplay of entrance-channel parameters in sub-barrier fusion enhancement.

The effect of inverse magnetic catalysis (IMC) has been observed on the conserved charge fluctuations and the correlations along the chemical freeze-out curve in a hadron resonance gas model. The fluctuations and the correlations have been compared with and without charge conservations. The charge conservation plays an important role in the calculation of the fluctuations at nonzero magnetic field and for the fluctuations in the strange charge at zero magnetic field. The charge conservation diminishes the correlations ${\chi }_{\mathrm{BS}}$ and ${\chi }_{\mathrm{QB}}$, but enhances the correlation ${\chi }_{\mathrm{QS}}$. The baryonic fluctuations (second order) at $B=0.25{\mathrm{GeV}}^2$ increases more than two times compared to $B=0$ at higher ${\mu }_B$. The fluctuations have been compared at nonzero magnetic field along the freeze-out curve, i.e., along fitted parameters of the chemical freeze-out temperature and chemical potentials, with the fluctuations at nonzero magnetic field along the freeze-out curve with the IMC effect, and the results are very different with the IMC effect. This is clearly seen in the products of different moments ${\sigma }^2/M$ and $S\sigma$ of net-kaon distribution.

The exotic Borromean nucleus ${}^{20}\mathrm{Mg}$ with $N=8$, located at the proton drip line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in ${}^{20}\mathrm{Mg}$ from the ${}^{20}\mathrm{Mg}(d,d^{\prime })$ reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and ab initio calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of ${\beta }_n=0.46\pm 0.21$. This provides the first indication of a possible weakening of the $N=8$ shell closure at the proton drip line.

The half-life of the $4_2^{+}$ state of the $2\mathrm{p}-2\mathrm{h}$ proton intruder band of ${}^{116}\mathrm{Sn}$ has been measured with the fast-timing technique. The lifetime of $T_{1/2}=29\left(10\right)$ ps leads to a transition probability $B\left(E2;4_2^{+}\to 2_2^{+}\right)=40\left(13\right)$ Weisskopf units, which is in very good agreement with the large $B\left(E2;2_2^{+}\to 0_3^{+}\right)$ value measured previously and provides strong support for the $0_3^{+}$ state as the bandhead of the intruder configuration and for the shape coexistence in the semimagic ${}^{116}\mathrm{Sn}$ nucleus. IBM-2 calculations with mixing reproduce the experimental data very well, giving insight into the degree of mixing between the different states.

The quasifree $pp\to pp{\pi }^{+}{\pi }^{-}$ reaction has been measured by means of $pd$ collisions at $T_p=1.2\mathrm{GeV}$ using the WASA detector setup at COSY enabling exclusive and kinematically complete measurements. Total and differential cross sections have been extracted for the energy region $T_p=1.08–1.36$ GeV ($\sqrt{s}=2.35–2.46\mathrm{GeV}$) covering thus the regions of $N^{*}\left(1440\right)$ and $\mathrm{\Delta }\left(1232\right)\mathrm{\Delta }\left(1232\right)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange as well as isospin relations based on the $pp\to pp{\pi }^0{\pi }^0$ data underpredict substantially the measured total cross section. The calculations are also at variance with specific experimental differential cross sections. An isotensor $\mathrm{\Delta }N$ dibaryon resonance with $I\left(J^P\right)=2\left(1^{+}\right)$ produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong [Phys. Rev. Lett. 13, 815 (1964)] and more recently calculated by A. Gal and H. Garcilazo [Nucl. Phys. A 928, 73 (2014)].

Several phenomena occurring in neutron stars are affected by the elementary excitations that characterize the stellar matter. In particular, low-energy excitations can play a major role in the emission and propagation of neutrinos, neutron star cooling, and transport processes. In this paper, we consider the elementary modes in the star region where both proton and neutron components are superfluid. We study the overall spectral functions of protons, neutrons, and electrons on the basis of the Coulomb and nuclear interactions. This paper is performed in the framework of the random-phase approximation, generalized to superfluid systems. The formalism we use ensures that the generalized Ward's identities are satisfied. We focus on the coupling between neutrons and protons. On one hand, this coupling results in collective modes that involve simultaneously neutrons and protons; on the other hand, it produces a damping of the excitations. Both effects are especially visible in the spectral functions of the different components of the matter. At high densities while the neutrons and protons tend to develop independent excitations as indicated by the spectral functions, the neutron-proton coupling still produces a strong damping of the modes.

Features of a new phenomenon—so-called collinear cluster tri-partition—are analyzed from various viewpoints. First, limitations on the angular distributions which are imposed by the general principles of quantum mechanics are considered. Second, these limitations together with the experimental data published earlier are used to estimate the effect as a whole. Third, some confirmation of the large yield of the lightest component of the tri-partition arising from geochemical data is presented.