We calculate the baryon factorial cumulants assuming arbitrary short-range correlations and the global baryon number conservation. The general factorial cumulant generating function is derived. Various relations between factorial cumulants subjected to baryon number conservation and the factorial cumulants without this constraint are presented. We observe that for $n\mathrm{th}$ factorial cumulant the short-range correlations of more than $n$ particles are suppressed with increasing number of particles. The recently published [V. Vovchenko et al., Phys. Lett. B 811, 135868 (2020)] relations between the cumulants in a finite acceptance with global baryon conservation and the grand-canonical susceptibilities are reproduced.

We study the reaction of pion photoproduction on the nucleon in the framework of chiral perturbation theory with explicit $\mathrm{\Delta }\left(1232\right)$ degrees of freedom. In the covariant approach, we give results up to order ${\epsilon }^3$ in the small scale expansion scheme. Furthermore, we provide $\mathrm{\Delta }$-less and $\mathrm{\Delta }$-full results obtained in the heavy-baryon scheme to analyze the differences from the covariant approach. Low-energy constants are fitted to multipole amplitudes using theoretical truncation errors estimated by a Bayesian approach. We also compare our findings to data of neutral pion production cross sections and polarization asymmetries. The description of the reaction is clearly improved by the explicit treatment of the $\mathrm{\Delta }\left(1232\right)$ resonance.

We consider the total and longitudinal cross sections by using the color dipole model according to the known Kharzeev-Levin-Nardi model in nuclei. Our calculations can predict the low-$x$ electron-nucleus cross sections, the saturation effect, and the ratio between the structure functions for different nuclei and energies of colliding particles. The results indicate the differences between two perturbative and nonperturbative regions at low $x$, which are compared with the H1, ZEUS, New Muon, and E665 Collaborations.

In the framework of the quark delocalization color screening model, we investigate the meson-meson interaction in the four-quark system with the three flavors $u, d$, and $s$. The calculation of the effective potentials of all the $S$-wave states shows that for most states the interaction between two vector mesons is attractive, the one between a pseudoscalar meson and a vector meson is repulsive or weakly attractive, and the one between two pseudoscalar mesons is always repulsive. However, there are still some exceptions. The interaction of the $IJ=00\pi \pi$ channel is attractive, while the one of the $IJ=02\varphi \varphi$ channel is repulsive. So it is difficult to use the $S$-wave $\varphi \varphi$ state to explain the $X\left(2239\right)$ at present calculation. The $S$-wave $\rho \rho$ states are more likely to be resonance states, which are worthy of investigating in future work. The study of the contribution of each interaction term shows that both the one-gluon exchange and the kinetic energy interaction are important in the interaction between two mesons. The study of the variation of the delocalization parameter indicates that the contribution of the kinetic energy relates to the intermediate-range attraction mechanism in the quark delocalization color screening model (QDCSM), which is achieved by the quark delocalization.

The reaction ${}^{96}\mathrm{Zr}(\alpha ,\mathrm{n}){}^{99}\mathrm{Mo}$ plays an important role in $\nu$-driven wind nucleosynthesis in core-collapse supernovae and is a possible avenue for medical isotope production. Cross-section measurements were performed using the activation technique at the Edwards Accelerator Laboratory. Results were analyzed along with world data on the ${}^{96}\mathrm{Zr}(\alpha ,n)$ cross section and ${}^{96}\mathrm{Zr}(\alpha ,\alpha )$ differential cross section using large-scale Hauser-Feshbach calculations. We compare our data, previous measurements, and a statistical description of the reaction. We find a larger cross section at low energies compared to prior experimental results, allowing for a larger astrophysical reaction rate. This may impact results of core-collapse supernova $\nu$-driven wind nucleosynthesis calculations but does not significantly alter prior conclusions about ${}^{99}\mathrm{Mo}$ production for medical physics applications. The results from our large-scale Hauser-Feshbach calculations demonstrate that phenomenological optical potentials may yet be adequate to describe $(\alpha ,n)$ reactions of interest for $\nu$-driven wind nucleosynthesis, albeit with regionally adjusted model parameters.

The ${}^{22}\mathrm{Ne}(\alpha ,\gamma ){}^{26}\mathrm{Mg}$ is an important reaction in stellar helium burning environments as it competes directly with one of the main neutron sources for the s-process, the ${}^{22}\mathrm{Ne}(\alpha ,n){}^{25}\mathrm{Mg}$ reaction. The reaction rate of the ${}^{22}\mathrm{Ne}(\alpha ,\gamma ){}^{26}\mathrm{Mg}$ is dominated by the low-energy resonances at $E_{\alpha }^{\mathrm{lab}}=650$ and 830 keV, respectively. The $E_{\alpha }^{\mathrm{lab}}=830$-keV resonance has been measured previously, but there are some uncertainties in the previous measurements. We confirmed the measurement of the $E_{\alpha }^{\mathrm{lab}}=830$-keV resonance using implanted ${}^{22}\mathrm{Ne}$ targets. We obtained a resonance strength of $\omega \gamma =35\pm 4 \mu \mathrm{eV}$ and provide a weighted average of the present and previous measurements of $\omega \gamma =35\pm 2 \mu \mathrm{eV}$ with reduced uncertainties compared to previous studies. We also attempted to measure the strength of the predicted resonance at $E_{\alpha }^{\mathrm{lab}}=650$ keV directly for the first time and found an upper limit of $\omega \gamma <0.15 \mu \mathrm{eV}$ for the strength of this resonance. In addition, we also studied the $E_P^{\mathrm{lab}}=851$-keV resonance in ${}^{22}\mathrm{Ne}(p,\gamma ){}^{23}\mathrm{Na}$ and obtained a resonance strength of $\omega \gamma =9.2\pm 0.7$ eV with significantly lower uncertainties compared to previous measurements.

We demonstrate that Bayesian machine learning can be used to treat the vast amount of experimental fission data which are noisy, incomplete, discrepant, and correlated. To supply the application needs, the two-dimensional cumulative fission yields (CFY) of neutron-induced fission of ${}^{238}\mathrm{U}$ are evaluated for energy dependencies and uncertainty qualifications by cross-experiment data fusion. For independent fission yields (IFY) with very few experimental data, the heterogeneous data fusion of CFY and IFY is employed to interpolate the energy dependence. This work shows that Bayesian data fusion can facilitate the maximum utilization of imperfect raw nuclear data.

In this Letter, we consider strong and electromagnetic (ultraperipheral) mechanisms in proton-nucleus coherent diffraction at the CERN Large Hadron Collider. We explicitly demonstrate the dominance of the latter and explain the CMS data on the forward rapidity gap distribution in $p\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=8.16$ TeV. In particular, we provide simple estimates, which give a good, semiquantitative description of both magnitude and shape of the $\mathrm{\Delta }{\eta }^F$ distribution in the Pomeron-proton topology. We also make predictions for the proton-oxygen run.

Excited states of ${}^{89}\mathrm{Zr}$ and ${}^{91}\mathrm{Mo}$ have been investigated using the fusion reaction ${}^6\mathrm{Li}+{}^{89}\mathrm{Y}$ at beam energy of 34 MeV. Based on new experimental data, about 16 (13) new transitions have been added to the level scheme of ${}^{89}\mathrm{Zr}$ (${}^{91}\mathrm{Mo}$). The level structures are investigated in the framework of the spherical-basis shell model using the effective interactions JUN45 and GWBXG. Reasonable agreement is obtained between the experimental results and the calculations. The calculated results indicate the newly proposed states are characterized by proton excitations from the $1f_{5/2}, 2p_{3/2}, 2p_{1/2}$ orbits to the high-$j 1g_{9/2}$ orbit. The systematic features of low lying states in the $N=49$ isotones are discussed.

Background: The quasi-deuteron model introduced by Levinger is used to explain cross sections for knocking out high-momentum protons in photoabsorption on nuclei. This is within a framework we characterize as exhibiting high renormalization group (RG) resolution. Assuming a one-body reaction operator, the nuclear wave function must include two-body short-range correlations (SRCs) with deuteronlike quantum numbers. In Phys. Rev. C 104, 034311 (2021), we showed that SRC physics can be naturally accounted for at low RG resolution.

Purpose: Here we describe the quasi-deuteron model at low RG resolution and determine the Levinger constant, which is proportional to the ratio of nuclear photoabsorption to that for photodisintegration of a deuteron.

Method: We extract the Levinger constant based on the ratio of momentum distributions at high relative momentum. We compute momentum distributions evolved under similarity RG (SRG) transformations where the SRC physics is shifted into the operator as a universal two-body term. The short-range nature of this operator motivates using local-density approximations with uncorrelated wave functions in evaluating nuclear matrix elements, which greatly simplifies the analysis. The operator must be consistently matched to the RG scale and scheme of the interaction for a reliable extraction. We apply SRG transformations to different nucleon-nucleon (NN) interactions and use the deuteron wave functions and Weinberg eigenvalues to determine approximate matching scales.

Results: We predict the Levinger constant for several NN interactions and a wide range of nuclei comparing to experimental extractions.

Conclusions: The predictions at low RG resolution are in good agreement with experiment when starting with a hard NN interaction and the initial operator. Similar agreement is found using soft NN interactions when the additional two-body operator induced by evolution from hard to soft is included.

We investigate the hidden strange $\varphi$ meson production in heavy-ion collisions from subthreshold ($E_{\text{kin}}\approx 1A$ GeV) to relativistic ($E_{\text{kin}}\approx 21A$ TeV) energies as well as its coupling to the open strange mesons (kaons, antikaons) and their productions. Our study is based on the off-shell microscopic parton-hadron-string dynamics (PHSD) transport approach which is applicable for the dynamical description of strongly interacting hadronic and partonic degrees-of-freedom created in heavy-ion collisions. Implementing novel meson-baryon and meson-hyperon production channels for $\varphi$ mesons, calculated within a $T$-matrix coupled-channel approach based on the extended SU(6) chiral effective Lagrangian model, along with the collisional broadening of the $\varphi$-meson in-medium spectral function, we find a substantial enhancement of $\varphi$ meson production in heavy-ion collisions, especially at sub- and near-thresholds. This allows us to describe the experimentally observed strong enhancement of the $\varphi /K^{-}$ ratio at low energies without including hypothetical decays of heavy baryonic resonances to $\varphi$ as in alternative approaches. Moreover, we show that in spite of a stronger contribution from enhanced $\varphi$ to $K^{-}$ production, the majority of the experimental data for different $A+A$ systems at low energies favor the scenario with in-medium modifications of the kaon and antikaon properties in the hot and dense environment. Moreover, we study the influence of the final-state interactions of $K,\overline{K}$ mesons on the reconstruction of $\varphi \text{'}\mathrm{s}$ by the invariant-mass method.

In this work, we show that the eigenvalue continuation approach introduced recently by Frame et al. [Phys. Rev. Lett. 121, 032501 (2018)], despite its many advantages, has some fundamental limitations which cannot be overcome when strongly correlated many-body systems are considered. Taking as a working example a very simple system of several fermionic particles confined in a harmonic trap we show that the eigenvector continuation is not able to go beyond the accuracy of the sampling states. We support this observation within a very simple three-level model capturing directly this obstacle. Since mentioned inaccuracy cannot be determined self-consistently within the eigenvalue continuation approach, support from other complementary methods is needed.

The paper contains new results for the $T_{20}$ component of the tensor analyzing power measured for the incoherent photoproduction of neutral pions on a deuteron, $\gamma d\to {\pi }^{0}pn$. The results are presented for photon energies $E_{\gamma }$ in the range from 300 to 600 MeV. The experimental statistics accumulated at the VEPP-3 accelerator complex in 2013 was used. To identify the events, the proton and two $\gamma$'s from the ${\pi }^0\to 2\gamma$ decay were registered in coincidence. For determination of $T_{20}$, the asymmetry of the reaction yield associated with the sign change of the tensor polarization of the deuterium target was measured. The experimental results are compared with theoretical calculations based on the spectator model, including interaction of the final state particles.

We simulate the excited states of the Lipkin model using the recently proposed quantum equation of motion (qEOM) method. The qEOM generalizes the EOM on classical computers and gives access to collective excitations based on quasiboson operators ${\widehat{O}}_n^{†}\left(\alpha \right)$ of increasing configuration complexity $\alpha$. We show, in particular, that the accuracy strongly depends on the fermion to qubit encoding. Standard encoding leads to large errors, but the use of symmetries and the Gray code reduces the quantum resources and improves significantly the results on current noisy quantum devices. With this encoding scheme, we use IBM quantum machines to compute the energy spectrum for a system of $N=2$, 3, and 4 particles, and compare the accuracy against the exact solution. We found that the results of the approach with $\alpha =2$, an analog of the second random phase approximation (SRPA), are, in principle, more accurate than with $\alpha =1$, which corresponds to the random phase approximation (RPA), but the SRPA is more amenable to noise for large coupling strengths. Thus, the proposed scheme shows potential for achieving higher spectroscopic accuracy by implementations with higher configuration complexity, if a proper error mitigation method is applied.

It was recently observed that chiral two-body interactions can be efficiently represented using matrix factorization techniques such as the singular value decomposition. However, the exploitation of these low-rank structures in a few- or many-body framework is nontrivial and requires reformulations that explicitly utilize the decomposition format. In this work, we present a general least-square approach that is applicable to different few- and many-body frameworks and allows for an efficient reduction to a low number of singular values in the least-square iteration. We verify the feasibility of the least-square approach by solving the Lippmann-Schwinger equation in a factorized form. The resulting low-rank approximations of the $T$ matrix are found to fully capture scattering observables. Potential applications of the least-square approach to other frameworks with the goal of employing tensor factorization techniques are discussed.

The detailed investigation of microscopic mechanisms leading to the formation of bubble structures in nuclei is performed in the framework of covariant density functional theory. The main emphasis of this study is on the role of single-particle degrees of freedom and Coulomb interaction. In general, the formation of bubbles lowers the Coulomb energy. However, in nuclei this trend is counteracted by the quantum nature of the single-particle states: only specific single-particle states with specific density profiles can be occupied with increasing proton and neutron numbers. A significant role of the central classically forbidden region at the bottom of the wine bottle potentials in the formation of nuclear bubbles (via primarily the reduction of the densities of the $s$ states at $r=0$) is revealed for the first time. Their formation also depends on the availability of low-$l$ single-particle states for occupation since single-particle densities represent the basic building blocks of total densities. Nucleonic potentials disfavor the occupation of such states in hyperheavy nuclei and this contributes to the formation of bubbles in such nuclei. Existing bubble indicators are strongly affected by single-particle properties and thus they cannot be reliable measures of bulk properties (such as the Coulomb interaction). An additivity rule for densities is proposed for the first time. It was shown that the differences in the densities of bubble and flat density nuclei follow this rule in the $A\approx 40$ mass region and in superheavy nuclei with comparable accuracy. This strongly suggests the same mechanism of the formation of central depression in bubble nuclei of these two mass regions. Nuclear saturation mechanisms and self-consistency effects also affect the formation of bubble structures. The detailed analysis of different aspects of bubble physics strongly suggests that the formation of bubble structures in superheavy nuclei is dominated by single-particle effects. The role of the Coulomb interaction increases in hyperheavy nuclei but even for such systems we do not find strong arguments that the formation of bubble structures is dominated by it.

Low-spin, excited states of the ${}^{89}\mathrm{Br}$ nucleus, populated in ${\beta }^{-}$ decay of ${}^{89}\mathrm{Se}$ have been studied for the first time. The ${}^{89}\mathrm{Se}$ nuclei were produced in proton-induced fission of natural thorium using the IGISOL facility and separated using a dipole magnet and the coupled JYFLTRAP Penning trap. Gamma radiation following the ${\beta }^{-}$ decay of ${}^{89}\mathrm{Se}$ was measured with an array of high-resolution germanium detectors. Levels scheme of ${}^{89}\mathrm{Br}$ was extended by 12 new levels and 31 new $\gamma$ transitions. Spin-parity (3/$2^{+}$) has been proposed for the ground state of the ${}^{89}\mathrm{Se}$ mother nucleus, replacing the (5/$2^{+}$) assignment reported in data bases. The observed Gamow-Teller ${\beta }^{-}$ transition to the 1754.5-keV level indicates a $\pi g_{9/2}$-based configuration. The level scheme of ${}^{89}\mathrm{Br}$ has been compared to large scale shell-model calculations. Excitations based on $\pi p_{3/2}$ and $\pi f_{5/2}$ single-particle levels as well as their anomalous coupling are proposed to explain the low-energy excitation scheme of ${}^{89}\mathrm{Br}$.

The eigenvector continuation $R$-matrix theory is an algorithm to emulate the nuclear reaction observables at different coupling constants. It exploits the analytic properties of eigensolutions in coupling constants. In this work, several extensions of the eigenvector continuation $R$-matrix theory are proposed by utilizing the analytic properties of regular eigensolutions in momentum and angular momentum. Taking a two-body scattering problem as the proof of concept, the specific extension based on analyticity in momentum is shown to be particularly useful, resulting in new phase-shift emulators with good extrapolation and interpolation properties with respect to momentum. It can be further hybridized with the original eigenvector continuation $R$-matrix theory to give an emulator that predicts the phase shifts at different coupling constants and different momenta simultaneously.

The neutron-deficient ${}^{188}\mathrm{Bi}$ and ${}^{188}\mathrm{Po}$ isotopes have been studied by $\gamma$-ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-$\mu \mathrm{s}$ isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV $\gamma$ rays have been established on top of the (${10}^{-}$) $\alpha$-decaying isomer in ${}^{188}\mathrm{Bi}$. The first excited ($2^{+}$) state in ${}^{188}\mathrm{Po}$ was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first $2^{+}$ states in ${}^{190,192,194}\mathrm{Po}$. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at $N=104$. In this mass region, a reduction in the prompt $\gamma$-ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.

The nuclear mass evaluations have been brought into quite an accurate level with the advent of machine learning, while their extrapolations are in great debate as manifested by the large discrepancies between themselves. Here, we present a possible way to heal these existing differences and raise the predictive ability of mass formulas through performing the multi-objective optimization aimed at both the binding energy and the $\alpha$ decay energy. As exemplified by the microscopically inspired Dulfo-Zuker model, the Pareto optimal solutions are found to guarantee the robust mass predictions especially towards the extreme neutron-rich nuclei plus the coherent statistical analysis. Besides effectively avoiding the overfitting problem, our results shed new light on narrowing the window of symmetry energy in nuclear mass formulas serving not only the reliable nuclear dripline but also the stringent equation of state in asymmetric nuclear matter.