We present predictions for the cross sections of coherent $J/\psi$ photoproduction in lead-lead and oxygen-oxygen ultraperipheral collisions (UPCs) as a function of the $J/\psi$ rapidity at the LHC in the framework of collinear factorization at next-to-leading order (NLO) in perturbative QCD. Taking generalized parton distribution functions in their forward limit and using the EPPS21, nNNPDF3.0, and nCTEQ15WZSIH nuclear parton distribution functions, we update our recent results for Pb-Pb collisions, make detailed predictions for O-O collisions for several beam energy configurations, and examine the ratio of O-O and Pb-Pb UPC cross sections. We show that the latter observable allows one to significantly reduce the scale uncertainty of NLO predictions for this process.

The nuclide ${}^{176}\mathrm{Lu}$ is one of the few naturally occurring isotopes that are potentially unstable with respect to electron capture (EC). Although experimental evidence for ${}^{176}\mathrm{Lu}$ EC decay is still missing, this isotope is instead well known to ${\beta }^{-}$ decay into ${}^{176}\mathrm{Hf}$ with a half-life of about 38 Gyr. The precise investigation of all possible decay modes for ${}^{176}\mathrm{Lu}$ is interesting because the Lu/Hf ratio is adopted as an isotopic clock. Previous searches for the ${}^{176}\mathrm{Lu}$ EC decay were performed by using a passive lutetium source coupled with a high-purity germanium (HPGe) spectrometer. Our approach uses a lutetium yttrium oxyorthosilicate (LYSO) crystal both as a lutetium source and as an active detector. Scintillation light from the LYSO crystal is acquired together with the signals from the HPGe detector, and this allows a powerful suppression of the background sourcing from the well-known ${\beta }^{-}$-decay branch. This approach led to an improvement on the ${}^{176}\mathrm{Lu}$ EC branching ratio limits by a factor of 3 to 30, depending on the considered EC channel.

Nuclear deformations and density profiles of neutron-rich even-even Zr isotopes are investigated by using the Skyrme-Hartree-Fock-Bogoliubov method. Large quadrupole and hexadecapole deformations are predicted along with large enhancement of the total reaction cross sections at the neutron number $N=60–74$. Strong nuclear deformation starting at $N=60$ is induced by the occupation of the intruder orbit with the asymptotic quantum number $\left[n{n}_z\mathrm{\Lambda }\right]\mathrm{\Omega }=\left[550\right]1/2$ originating from the spherical $0h_{11/2}$ orbit. The deformation region is further enlarged from $N=72$ to 74 owing to the occupation of the next intruder orbit with $\left[530\right]1/2$ originating from the spherical $1f_{7/2}$ orbit. This characteristic nuclear deformation is crucially reflected in a systematic behavior of the nuclear radii and the density profiles near the nuclear surface.

Background: Modeling nuclear reaction networks for nuclear science applications and for simulations of astrophysical environments relies on cross section data for a vast number of reactions, many of which have never been measured. Cross sections for neutron-induced reactions on unstable nuclei are particularly scarce, since they are the most difficult to measure. Consequently, we must rely on theoretical predictions or indirect measurements to obtain the requisite reaction data. For compound nuclear reactions, the surrogate reaction method can be used to determine many cross sections of interest.

Purpose: Earlier work has demonstrated that cross sections for neutron-induced fission and radiative neutron capture can be determined from a combination of surrogate reaction data and theory. For the fission case, it was shown that the Weisskopf-Ewing approximation, which significantly simplifies the implementation of the surrogate method, can be employed. Capture cross sections cannot be obtained, and require a detailed description of the surrogate reaction process. In this paper we examine the validity of the Weisskopf-Ewing approximation for determining unknown $(n,n^{\prime })$ and $(n,2n)$ cross sections from surrogate data.

Methods: Using statistical reaction calculations with realistic parametrizations, we investigate first whether the assumptions underlying the Weisskopf-Ewing approximation are valid for $(n,n^{\prime })$ and $(n,2n)$ reactions on representative target nuclei. We then produce simulated surrogate reaction data and assess the impact of applying the Weisskopf-Ewing approximation when extracting $(n,n^{\prime })$ and $(n,2n)$ cross sections in situations where the approximation is not strictly justified.

Results: We find that peak cross sections can be estimated using the Weisskopf-Ewing approximation, but the shape of the $(n,n^{\prime })$ and $(n,2n)$ cross sections, especially for low neutron energies, cannot be reliably determined without accounting for the angular-momentum differences between the neutron-induced and surrogate reaction.

Conclusions: To obtain reliable $(n,n^{\prime })$ and $(n,2n)$ cross sections from surrogate reaction data, a detailed description of the surrogate reaction mechanisms is required. To do so for the compound-nucleus energies and decay channels relevant to these reactions, it becomes necessary to extend current modeling capabilities.

Background: In low metallicity supermassive stars, the hot $pp$ chain can serve as an alternative to produce the CNO nuclei. In the astrophysical environment of high temperature, the proton capture of ${}^8\mathrm{B}$ can be faster than its $\beta$ decay, so that the ${}^8\mathrm{B}(p,\gamma ){}^9\mathrm{C}$ reaction plays an important role in the hot $pp$ chain. Due to the unstable nature of ${}^8\mathrm{B}$ and the unavailability of ${}^8\mathrm{B}$ beams, the study of the ${}^8\mathrm{B}(p,\gamma ){}^9\mathrm{C}$ reaction can only be achieved by indirect methods, so that large uncertainties exist.

Purpose: The Gamow shell model in the coupled-channel representation (GSM-CC) is applied to study the proton radiative capture reaction ${}^8\mathrm{B}(p,\gamma ){}^9\mathrm{C}$.

Method: The GSM-CC is a unified microscopic theory for the description of nuclear structure and nuclear reaction properties. A translationally invariant Hamiltonian is considered for that matter, making use of a finite-range two-body interaction, whose parameters are adjusted to reproduce the low-energy spectra of ${}^8\mathrm{B}$ and ${}^9\mathrm{C}$. The reaction channels are then built through the coupling of the wave functions of the ground state $2_1^{+}$, the first excited state $1_1^{+}$, and the second excited state $3_1^{+}$ in ${}^8\mathrm{B}$ to a projectile proton wave function in different partial waves. For the calculation of the ${}^8\mathrm{B}(p,\gamma ){}^9\mathrm{C}$ astrophysical factor, all $E1, M1$, and $E2$ transitions from the initial continuum states to the final bound states ${3/2}_1^{-}\mathrm{of}{}^9\mathrm{C}$ are considered. The resonant capture to the first resonant state ${1/2}_1^{-}$ of ${}^9\mathrm{C}$ is also calculated.

Results: The experimental low-energy levels and the proton emission threshold in ${}^9\mathrm{C}$ are reproduced by the GSM-CC. The calculated astrophysical factor agrees with experimental data obtained from indirect measurements. The reaction rates from the direct capture and resonant capture are calculated for the temperature range of astrophysical interest.

Conclusion: The calculated total astrophysical $S$ factor is dominated by the $E1$ transition to the ground state of ${}^9\mathrm{C}$. The GSM-CC calculations suggest that $S$ first increases with the energy of the center of mass $E_{\mathrm{c}.\mathrm{m}.}$, and then decrease with the energy. This agrees with existing data, which has smaller values around zero energy and larger values in the energy range of 0.2 MeV $\le E_{\mathrm{c}.\mathrm{m}.}\le$ 0.6 MeV.

There is no unique and widely accepted definition of the complexity measure (CM) of a many-fermion wave function in the presence of interactions. The simplest many-fermion wave function is a Slater determinant. In shell-model or configuration interaction (CI) and other related methods, the state is represented as a superposition of a large number of Slater determinants, which in the case of CI calculations reaches about 20 billion terms [Johnson, arXiv:1809.07869]. Although in practice this number has been used as a CM for decades, it is ill defined: it is not unique, and it depends on the particular type and the number of single-particle wave functions used to construct the Slater determinants. The canonical wave functions and/or natural orbitals [Löwdin, Adv. Phys. 5, 1 (1956); Löwdin and Shull, Phys. Rev. 101, 1730 (1956); Bardeen et al., Phys. Rev. 108, 1175 (1957); N. N. Bogoljubov, Il Nuovo Cimento 7, 794 (1958); Valatin, Il Nuovo Cimento 7, 843 (1958); de Gennes, Superconductivity of Metals and Alloys (CRC Press, Boca Raton, FL, 1999); Ring and Schuck, The Nuclear Many-Body Problem, 1st ed. (Springer-Verlag, Berlin, 2004)] and their corresponding occupation probabilities are intrinsic properties of any many-body wave function, irrespective of the representation, and they provide a unique solution to characterize the CM. The non-negative orbital entanglement entropy, which vanishes for a Slater determinant, provides the simplest CM, while a more complete measure of complexity is the entanglement spectrum. We illustrate these aspects in the case of a complex nonequilibrium time-dependent process, induced nuclear fission described within a real-time density functional theory framework extended to superfluid systems, which can describe simultaneously the long-range and the short-range correlations between fermions. The orbital entanglement entropy of the fissioning nucleus illustrates the localization mechanism of the many-body wave function in Fock and/or Hilbert space. The (minimal) number of Slater determinants required to represent such a complex many-body wave function with a well-defined number of particles in the case presented here is about ${10}^{500}$. The realistic case of the highly nonequilibrium nuclear fission process illustrated here is equivalent to a system of $23.328\times {10}^9$ interacting quantum spin-1/2 particles, a very large system for the study of quantum entanglement.

Infinite nuclear matter is studied by resuming the series of ladder diagrams based on the results developed by us [Ann. Phys. (NY) 437, 168741 (2022)]. The master formula for the energy density is explicitly solved for the case of contact interactions, within a pionless description of the nucleon-nucleon interactions. Renormalized results are obtained which are directly expressed in terms of the nucleon-nucleon phase shifts and mixing angles in partial-wave amplitudes up to and including $G$ waves, with convergence reached under the inclusion of higher partial waves. The energy per particle, density, and sound velocity resulting from the ladder series are given for symmetric and neutron matter. This resummation of the ladder diagrams provides a rigorous result that may be used as low-density reference for other parametrizations of $\overline{\mathcal{E}}$ for higher densities.

The dynamics of the rupture of the ternary system ${}^{70}\mathrm{Ni}+{}^{50}\mathrm{Ca}+{}^{132}\mathrm{Sn}$ formed at the spontaneous fission of ${}^{252}\mathrm{Cf}$ has been studied. The heaviest fragment ${}^{132}\mathrm{Sn}$ is separated first very easily and the behavior of the breakup of the ${}^{70}\mathrm{Ni}+{}^{50}\mathrm{Ca}$ system determines final directions of the angular distribution of the final products. The equations of motion with including microscopical friction forces between two contacting nuclei have been calculated. The friction force in the dynamical equations results in increase of decay time of the system only. The results of calculations show that the trajectory of the middle Ca nucleus is nearly perpendicular to the line connecting centers of two massive ${}^{70}\mathrm{Ni}$ and ${}^{132}\mathrm{Sn}$ nuclei if initial configuration is not collinear.

Isospin triggering allows to distinguish coalescence from thermal production of light clusters in heavy ion collisions. Triggering on $Y\left({\pi }^{-}\right)-Y\left({\pi }^{+}\right)$ allows to select very neutron or proton rich final states. The deuteron (cluster) production with coalescence ($d\propto n·p$) leads then to an inverse parabolic dependence of the deuteron yield on $\mathrm{\Delta }{Y}_{\pi }$. In contrast, in a thermal model, cluster production is independent on $\mathrm{\Delta }{Y}_{\pi }$. The observation of a maximum deuteron (cluster) yield as function of $\mathrm{\Delta }{Y}_{\pi }$ provides confirmation of the coalescence mechanism.

The stellar ($n,\gamma$) cross section data for the mass numbers around $A\approx 160$ are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occurs in the thermally pulsing asymptotic giant branch (TP-AGB). The new measurement of ($n,\gamma$) cross sections for ${}^{159}\mathrm{Tb}$ was performed using the ${\mathrm{C}}_6{\mathrm{D}}_6$ detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels are reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) are derived from the measured ${}^{159}\mathrm{Tb}(n,\gamma )$ cross sections at $kT=5$–100 keV and are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 significantly overestimate the present MACS up to $40\%$ and $20\%$, respectively. A sensitive test of the $s$-process nucleosynthesis is also performed with the stellar evolution code mesa. Significant changes in abundances around $A\approx 160$ are observed between the ENDF/B-VIII.0 and present measured rate of ${}^{159}\mathrm{Tb}(n,\gamma ){}^{160}\mathrm{Tb}$ in the mesa simulation.

The realizations of spin symmetry in the $\mathrm{\Lambda }$ hyperon spectra of hypernuclei ranging from light to heavy masses are investigated in the framework of the deformed Skyrme-Hartree-Fock approach. The effect of deformation on spin symmetry and its interplay with the required spin-orbit force is studied in detail. It is found that the spin symmetry prevails due to a small spin-orbit force. Moreover, for spin doublets with the same principal quantum number $n$, the reduced spin-orbit splitting $\mathrm{\Delta }{E}_{\text{s.o.}}$ shows a good linear relation with respect to the quantum number $l$, even for a large $\mathrm{\Lambda }N$ spin-orbit strength.

Understanding the phase diagram of QCD by measuring fluctuations of conserved charges in heavy-ion collision is one of the main goals of the beam energy scan program at the BNL Relativistic Heavy Ion Collider (RHIC). Within this work, we calculate the role of hadronic interactions and momentum cuts on cumulants of conserved charges up to fourth order in a system in equilibrium within a hadronic transport approach (smash). In our model the net baryon, net charge, and net strangeness are perfectly conserved on an event-by-event basis and the cumulants are calculated as a function of subvolume sizes and compared to analytic expectations. We find a modification of the kurtosis due to charge annihilation processes in systems with simplified degrees of freedom. Furthermore the result of the full smash hadron gas for the net baryon and net proton number fluctuations is presented for systems with zero and finite values of baryon chemical potential. Additionally we find that due to dynamical correlations the cumulants of the net baryon number cannot easily be recovered from the net protons. Finally the influence of deuteron cluster formation on the net proton and net baryon fluctuations in a simplified system is shown. This analysis is important to better understand the relation between measurements of fluctuations in heavy-ion collisions and theoretical calculations which are often performed in a grand canonical ensemble.

We employed the isobar model for investigating the $K^{+}\mathrm{\Lambda }$ photoproduction process. We paid special attention to the recent CLAS polarization data and enhanced the ${\chi }^2$ minimization by adding a penalty term. Without changing the set of included resonances used by the model, this technique known as Ridge regression leads to reduced couplings that in previous studies acquired unreasonably large values. As a result, we have arrived at a much more robust model with hyperon couplings which are reduced to more physical values. This model serves us to extract valuable information on the background to the $K^{+}\mathrm{\Lambda }$ photoproduction and particularly on the role of various hyperon resonances. The set of the nucleon resonances is the same with respect to previous fits but their role may have changed due to different couplings which they acquire in the present fit.

The elastic $\alpha \text{−}{}^{12}\mathrm{C}$ scattering at low energies for $l=0,1,2,3,4,5,6$ is studied in effective field theory. I discuss the construction of the $S$ matrices of elastic $\alpha \text{−}{}^{12}\mathrm{C}$ scattering in terms of the amplitudes of subthreshold bound and resonant states of ${}^{16}\mathrm{O}$, which are calculated from the effective Lagrangian. The parameters appearing in the $S$ matrices are fitted to the phase shift data below the $p\text{−}{}^{15}\mathrm{N}$ breakup threshold energy, and one finds that the phase shifts are well described within the theory.

We explore the relation between the nuclear matrix elements of neutrinoless double-beta ($0\nu \beta \beta$) decay and two other processes: double Gamow-Teller (DGT) and double-magnetic-dipole ($M1M1$) transitions, with focus on medium-mass to heavy nuclei studied with the proton-neutron quasiparticle random-phase approximation ($pn$QRPA) framework. We explore a wide span of isoscalar proton-neutron pairing strengths covering the typical range of values that describe well $\beta$- and two-neutrino $\beta \beta$-decay data. Our results indicate good linear correlations between $0\nu \beta \beta$ and both DGT and $M1M1$ matrix elements. Together with future measurements of DGT and $M1M1$ transitions, these correlations could help constrain the values of the $0\nu \beta \beta$-decay nuclear matrix elements.

The presence of $\alpha$-clustered structure in the light nuclei produces different exotic shapes in nuclear structure studies at low energies. Recent phenomenological studies suggest that collision of heavy nuclei with $\alpha$-clustered carbon (${}^{12}\mathrm{C}$) at relativistic energies can lead to large initial state anisotropies. This is expected to impact the final momentum anisotropies of the produced particles significantly. The emission of electromagnetic radiations is considered to be more sensitive to the initial state compared to hadronic observables and thus photon observables are expected to be affected by the initial clustered structure profoundly. In this work we estimate the production and anisotropic flow of photons from most-central collisions of triangular $\alpha$-clustered carbon and gold at $\sqrt{s_{NN}}=200$ GeV using an event-by-event hydrodynamic framework and compare the results with those obtained from unclustered carbon and gold collisions. We show that the thermal photon $v_3$ for most central collisions is significantly large for the clustered case compared to the case with unclustered carbon, whereas the elliptic flow parameter does not show much difference for the two cases. In addition, the ratio of anisotropic flow coefficients is found to be a potential observable to constrain the initial state produced in relativistic heavy-ion collisions and also to know more about the $\alpha$-clustered structure in carbon nucleus.

We employ the transport model coupled with hydrodynamic equations to study the charmonium dissociation and regeneration in the quark-gluon plasma (QGP) with the large baryon chemical potential in Au-Au collisions at the energies of $\sqrt{s_{NN}}=$ 39, 14.5, and 7.7 GeV. The baryon chemical potential ${\mu }_B$ is encoded in both Debye mass characterizing the heavy-quark potential and also the equation of state of the bulk medium. After considering ${\mu }_B$ corrections in both heavy quarkonium and the QGP medium, we calculate the nuclear modification factor $R_{AA}$ of charmonium. We find the ${\mu }_B$ influence on charmonium production at $\sqrt{s_{NN}}$ = 39 and 14.5 GeV is negligible, while the $R_{AA}$ of charmonium is reduced considering ${\mu }_B$ influence at $\sqrt{s_{NN}}=7.7$ GeV Au-Au collisions, which is crucial for studying charmonium production in low energy and also fixed-target heavy-ion collisions.

$P$-type point contact (PPC) high-purity germanium detectors are an important technology in astroparticle and nuclear physics due to their superb energy resolution, low noise, and pulse shape discrimination capabilities. Analysis of data from the Majorana Demonstrator, a neutrinoless double-$\beta$ decay experiment deploying PPC detectors enriched in ${}^{76}\mathrm{Ge}$, has led to several novel improvements in the analysis of PPC signals. In this work we discuss charge trapping in PPC detectors and its effect on energy resolution. Small dislocations or impurities in the crystal lattice result in trapping of charge carriers from an ionization event of interest, attenuating the signal, and degrading the measured energy. We present a modified digital pole-zero correction to the signal energy estimation that counters the effects of charge trapping and improves the energy resolution

of the Majorana Demonstrator by approximately $30\%$ to around 2.4 keV full width at half-maximum at 2039 keV, the ${}^{76}\mathrm{Ge} Q$ value. An alternative approach achieving similar resolution enhancement is also presented.

Neutron star constraints and ab initio perturbative quantum chromodynamics (pQCD) evaluations require the equation of state (EoS) representing cold quark matter to be stiff at intermediate baryonic densities and soft at high$n_B$. Here, I suggest that the three flavor Nambu–Jona-Lasinio model with a density dependent repulsive coupling, $G_V\left(\mu \right)$, can generate an EoS which interpolates between these two regimes. Such an interpolation requires repulsion to start decreasing with the chemical potential just after chiral transition takes place. The conjecture behind this mechanism is that repulsion should be necessary only as long as the quark condensates, which dress the effective masses, have nonvanishing values. This assumption guarantees that an initially hard EoS suffers a conspicuous change of slope at $\mathcal{E}\simeq 0.7\mathrm{GeV}{\mathrm{fm}}^{-3}$ converging to the pQCD results at higher energy densities. Then, the speed of sound naturally reaches a nonconformal maximum at $n_B=3.23n_0=0.52{\mathrm{fm}}^{-3}$ while the trace anomaly remains positive for all densities, in agreement with recent investigations. These nontrivial results cannot be simultaneously obtained when $G_V$ vanishes or has a fixed value. Therefore, the simple model proposed here is able to link the (nonperturbative) region of intermediate densities to the region where pQCD becomes reliable.