Rare event searches allow us to search for new physics at energy scales inaccessible with other means by leveraging specialized large-mass detectors. Machine learning provides a new tool to maximize the information provided by these detectors. The information is sparse, which forces these algorithms to start from the lowest level data and exploit all symmetries in the detector to produce results. In this work we present KamNet, which harnesses breakthroughs in geometric deep learning and spatiotemporal data analysis to maximize the physics reach of KamLAND-Zen, a kiloton scale spherical liquid scintillator detector searching for $0\nu \beta \beta$. Using a simplified background model for KamLAND, we show that KamNet outperforms a conventional convolutional neural network (CNN) on benchmarking Monte Carlo simulations with an increasing level of robustness. Using simulated data, we then demonstrate KamNet's ability to increase KamLAND-Zen's sensitivity to $0\nu \beta \beta$ and $2\nu \beta \beta$ decay to excited states. A key component of this work is the addition of an attention mechanism to elucidate the underlying physics KamNet is using for the background rejection.

Measurements of the dynamical correlations between neutral and charged kaons in central Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV by the ALICE Collaboration display anomalous behavior relative to conventional heavy-ion collision simulators such as AMPT, EPOS, and HIJING. We consider other conventional statistical models, none of which can reproduce the magnitude and centrality dependence of the correlations. The data can be reproduced by coherent emission from domains, which grow in number and volume with increasing centrality. We show that the energy released by condensation of strange quarks may be sufficient to explain the anomaly.

We calculate the $\beta$ spectrum in the decay of ${}^6\mathrm{He}$ using quantum Monte Carlo methods with nuclear interactions derived from chiral effective field theory and consistent weak vector and axial currents. We work at second order in the multipole expansion, retaining terms suppressed by $\mathcal{O}(q^2/m_{\pi }^2)$, where $q$ denotes low-energy scales such as the reaction's $\mathcal{Q}$ value or the electron energy, and $m_{\pi }$ is the pion mass. We go beyond the impulse approximation by including the effects of two-body vector and axial currents. We estimate the theoretical error on the spectrum by using four potential models in the Norfolk family of local two- and three-nucleon interactions, which have different cutoffs, fit two-nucleon data up to different energies, and use different observables to determine the couplings in the three-body force. We find the theoretical uncertainty on the $\beta$ spectrum, normalized by the total rate, to be well below the permille level, and to receive contributions of comparable size from first- and second-order corrections in the multipole expansion. We consider corrections to the $\beta$ decay spectrum induced by beyond-standard-model charged-current interactions in the standard model effective field theory, with and without sterile neutrinos, and discuss the sensitivity of the next generation of experiments to these interactions.

Current and future electron and neutrino scattering experiments will be greatly aided by a better understanding of the role played by short-range correlations in nuclei. Two-body physics, including nucleon-nucleon correlations and two-body electroweak currents, is required to explain the body of experimental data for both static and dynamical nuclear properties. In this work, we focus on examining nucleon-nucleon correlations from a chiral effective field theory perspective and provide a comprehensive set of new variational Monte Carlo calculations of one- and two-body densities and momentum distributions based on the Norfolk many-body nuclear Hamiltonians for $A\le 12$ systems. Online access to detailed tables and figures is available.

Production cross sections of heavy neutron-rich isotopes are calculated by employing quantal transport description in ${}^{250}\mathrm{Cf}+{}^{232}\mathrm{Th}$ collisions. This quantal transport description is based on the stochastic mean-field approach, and it provides a microscopic approach beyond time-dependent Hartree-Fock theory to include mean-field fluctuations. Deexcitation of primary fragments is determined by employing the statistical $\mathrm{GEMINI}++$ code. Calculations provide predictions for production cross sections of neutron rich transfermium isotopes without any adjustable parameters.

Background: The nuclear energy density functional method at finite temperature is a useful tool for studies of nuclear structure at high excitation, and also for researches of nuclear matter involved in explosive stellar phenomena and neutron stars. However, its unrestricted calculation requires large computational costs for the three-dimensional coordinate-space solvers, especially for the Hamiltonian matrix diagonalization and (or) the Gram-Schmidt orthonormalization of the single-particle wave functions.

Purpose: I test numerical performance of a numerical method, that requires neither the diagonalization nor the Gram-Schmidt orthonormalization, for finite nuclei and inhomogeneous nuclear matter. I examine its advantageous features in future applications.

Methods: The Fermi operator expansion method, which approximates the Fermi-Dirac distribution in terms of the Chebyshev polynomials, is used to construct the one-body density matrix for the energy density functional calculations at finite temperature. The modified Broyden's mixing method is adopted for the self-consistent iteration process.

Results: The method is applied to isolated finite $N=Z$ nuclei and to nonuniform symmetric nuclear matter at finite temperature, and it turns out be very effective with the three-dimensional coordinate-space representation, especially at high temperature. The liquid-gas transition is clearly observed in the calculations.

Conclusions: The Fermi operator expansion method is a useful tool for studies of various nuclear phases at finite temperature with the energy density functional calculations. The method is suitable for massively parallel computing with distributed memory. Furthermore, when the space size is large, the calculation may benefit from its order-$N$ scaling property.

We present a microscopic study on the fusion reactions ${}^{14,15}\mathrm{C}+{}^{232}\mathrm{Th}$ by emphasizing the effect of deformed halo structure on reaction dynamics within the framework of time-dependent density functional theory. The internuclear potentials are obtained by using the density-constraint frozen Hartree-Fock approach and then are adopted to calculate the fusion cross sections of ${}^{14,15}\mathrm{C}+{}^{232}\mathrm{Th}$, taking all the orientations of deformed reactants into account. Our microscopic calculations not only reproduce the enhancement of fusion cross sections at sub-barrier energies without any adjustable parameters, but also reveal the underlying mechanism of this enhancement, which is driven by the deformed halo structure of ${}^{15}\mathrm{C}$. More interestingly, by performing particle number projection based on the wave functions from time-dependent Hartree-Fock simulation, we find that the one-neutron transfer probabilities are more sensitive to the orientations of ${}^{15}\mathrm{C}$ than ${}^{232}\mathrm{Th}$, indicating the notable effects of halo structure on the reaction dynamics.

The paper is devoted to the $\overline{K}NNN$ system, which is an exotic system consisting of an antikaon and three nucleons. Dynamically exact four-body Faddeev-type equations were solved, and characteristics of the quasibound state in the $K^{-}ppn$ system caused by strong interactions were evaluated. Three antikaon-nucleon and three nucleon-nucleon potentials were used, so the dependence of the four-body pole positions on the two-body interaction models was studied. The resulting binding energies $B_{K^{-}ppn}^{\mathrm{Chiral}}\approx 30.5–34.5$ MeV obtained with the chirally motivated and $B_{K^{-}ppn}^{\mathrm{SIDD}}\approx 46.4–52.0$ MeV obtained with the phenomenological antikaon-nucleon potentials are close to those obtained for the $K^{-}pp$ system with the same $\overline{K}N$ and $NN$ potentials, while the four-body widths ${\mathrm{\Gamma }}_{K^{-}ppn}\approx 38.2–50.9$ MeV are smaller.

We introduce a novel set of observables associated to the rapidly developing field of persistent homology for the quantitative characterization of nuclear collisions and their evolution. Persistent homology allows for the identification of topological and homological characteristics of distributions in multidimensional spaces. We demonstrate here how to apply the tool kit of persistent homology to the extraction of novel clustering signatures and the identification of long-range flow correlations in the particle production process of nuclear collisions.

We analyze $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=2.76$ TeV with a novel framework based on the dynamical core-corona picture that describes particle productions from both equilibrium and nonequilibrium components. We remark on the possibility of the contribution from nonequilibrium components in the very low transverse momentum $\left(p_T\right)$ region and show that such contributions significantly affect $p_T$-integrated four-particle cumulants. These results strongly suggest the necessity of nonequilibrium components when one extracts properties of the quark-gluon plasma from experimental data using sophisticated dynamical models based on relativistic hydrodynamics.

Despite recent advances and focus on rigorous uncertainty quantification for microscopic models of quantum many-body systems, the uncertainty on the dynamics of those systems has been underexplored. To address this, we have used time-dependent Hartree-Fock to examine the model uncertainty for a collection of low-energy, heavy-ion fusion reactions. Fusion reactions at near-barrier energies represent a rich test-bed for the dynamics of quantum many-body systems owing to the complex interplay of collective excitation, transfer, and static effects that determine the fusion probability of a given system. The model uncertainty is sizable for many of the systems studied and the primary contribution arises from static properties that are ill-constrained, such as the neutron radius of neutron-rich nuclei. These large uncertainties motivate the use of information from reactions to better constrain existing models and to infer static properties from reaction data.

We present results of the first experiment aimed at the synthesis of Mc isotopes in the ${}^{243}\mathrm{Am}+{}^{48}\mathrm{Ca}$ reaction performed at the new gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the Super Heavy Element Factory at JINR. Fifty-five new decay chains of ${}^{288}\mathrm{Mc}$ and six chains assigned to ${}^{289}\mathrm{Mc}$ were detected. The $\alpha$ decay of ${}^{268}\mathrm{Db}$ with an energy of 7.6–8.0 MeV, half-life of ${16}_{-4}^{+6}\mathrm{h}$, and a branch of ${55}_{-15}^{+20}\%$ was registered for the first time, and a new spontaneously fissioning isotope ${}^{264}\mathrm{Lr}$ with a half-life of $4.9_{-1.3}^{+2.1}\mathrm{h}$ was identified. The cross section for the ${}^{243}\mathrm{Am}({}^{48}\mathrm{Ca},3n){}^{288}\mathrm{Mc}$ reaction was measured to be $17.1_{-4.7}^{+6.3}$ pb, which is the largest value for the known superheavy nuclei at the island of stability.

A new density-dependent point-coupling covariant density functional PCF-PK1 is proposed, where the exchange terms of the four-fermion terms are local and are taken into account with the Fierz transformation. The coupling constants of the PCF-PK1 functional are determined by empirical saturation properties and ab initio equation of state and proton-neutron Dirac mass splittings for nuclear matter as well as the ground-state properties of selected spherical nuclei. The success of the PCF-PK1 is illustrated with properties of the infinite nuclear matter and finite nuclei including the ground-state properties and the Gamow-Teller resonances. In particular, the PCF-PK1 eliminates the spurious shell closures at $Z=58$ and $Z=92$, which exist commonly in many covariant density functionals without exchange terms. Moreover, the Gamow-Teller resonances are nicely reproduced without any adjustable parameters, and this demonstrates that a self-consistent description for the Gamow-Teller resonances can be achieved with the localized exchange terms in the PCF-PK1.

The $\mathrm{\Lambda }$ separation energies in the mirror hypernuclei ${}_{\mathrm{\Lambda }}^4\mathrm{H}\text{−}{}_{\mathrm{\Lambda }}^4\mathrm{He}$ exhibit large charge symmetry breaking (CSB). Analyzing this CSB within pionless effective field theory while using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a $\mathrm{\Lambda }\text{−}{\mathrm{\Sigma }}^0$ induced in-medium admixture amplitude ${\mathcal{A}}_{I=1}\approx 1.5\%$ in the dominantly isospin $I=0\mathrm{\Lambda }$ hyperon. Our results confirm the free-space value ${\mathcal{A}}_{I=1}^{\left(0\right)}$ inferred directly within the SU(3) baryon octet by Dalitz and von Hippel in 1964 and reaffirmed in a recent $\mathrm{QCD}+$QED lattice calculation. Furthermore, exploring the consequences of SU(3) flavor symmetry on the $\mathrm{\Lambda }$-nucleon interaction, we find that CSB is expected to impact the $S=1$ and $S=0$ spin channels in opposite directions, with the latter dominating by an order of magnitude. These observations explain a recent deduction of $\mathrm{\Lambda }$-nucleon CSB strengths.

Strong magnetic fields can modify the microscopic composition of matter with consequences on stellar macroscopic properties. Within this context, we study, for the first time, the possibility of the appearance of spin-3/2 $\mathrm{\Delta }$ baryons in magnetars. We make use of two different relativistic models for the equation of state of dense matter under the influence of strong magnetic fields considering the effects of Landau levels and the anomalous magnetic moment (AMM) proportional to the spin of all baryons and leptons. In particular, we analyze the effects of the AMM of $\mathrm{\Delta }$ baryons in dense matter for the first time. We also obtain global properties corresponding to the EoS models numerically and study the corresponding role of the $\mathrm{\Delta }$ baryons. We find that they are favored over hyperons, which causes an increase in isopin asymmetry and a decrease in spin polarization. We also find that, contrary to what generally occurs when new degrees of freedom are introduced, the $\mathrm{\Delta }$'s do not make the EoS significantly softer and magnetars less massive. Finally, the magnetic field distribution inside a given star is not affected by the presence of $\mathrm{\Delta }$'s.

We present results on the search for two-neutrino double-electron capture ($2\nu \text{ECEC}$) of ${}^{124}\mathrm{Xe}$ and neutrinoless double-$\beta$ decay ($0\nu \beta \beta$) of ${}^{136}\mathrm{Xe}$ in XENON1T. We consider captures from the $K$ shell up to the $N$ shell in the $2\nu \text{ECEC}$ signal model and measure a total half-life of $T_{1/2}^{2\nu \text{ECEC}}=(1.1\pm 0.2_{\text{stat}}\pm 0.1_{\text{sys}})\times {10}^{22}\text{yr}$ with a $0.87\text{kg}\text{yr}$ isotope exposure. The statistical significance of the signal is $7.0\sigma$. We use XENON1T data with $36.16\text{kg}\text{yr}$ of ${}^{136}\mathrm{Xe}$ exposure to search for $0\nu \beta \beta$. We find no evidence of a signal and set a lower limit on the half-life of $T_{1/2}^{0\nu \beta \beta }>1.2\times {10}^{24}\text{yr}\text{at}90\%\text{CL}$. This is the best result from a dark matter detector without an enriched target to date. We also report projections on the sensitivity of XENONnT to $0\nu \beta \beta$. Assuming a $275\text{kg}\text{yr} {}^{136}\mathrm{Xe}$ exposure, the expected sensitivity is $T_{1/2}^{0\nu \beta \beta }>2.1\times {10}^{25}\text{yr}\text{at}90\%\text{CL}$, corresponding to an effective Majorana mass range of $\langle m_{\beta \beta }\rangle <(0.19–0.59)\mathrm{eV}/c^2$.

We consider the case, in QCD, of a single jet propagating within a strongly interacting fluid of a finite extent. Interactions lead to the appearance of a source of energy-momentum within the fluid. The remnant jet that escapes the container is analyzed along with portions of the medium excited by the jet. We study the effect of a static versus a semirealistic expanding medium, with jets traveling inward versus outward. We consider the medium response via recoils in partonic scatterings based on a weakly coupled description and its combination with hydrodynamical medium response based on a strongly coupled description, followed by incorporation into a jet. The effects of these limits on the reconstructed energy, momentum, and mass of the jet, as a function of the angle away from the original parton direction, are studied. It is demonstrated that different flow velocity configurations in the medium produce considerable differences in jet observables. This work highlights the importance of accurate dynamical modeling of the soft medium as a foundation on which to calculate jet modification and casts skepticism on results obtained without such modeling.

In this work we present a framework that allows one to solve the Faddeev equations for three-nucleon scattering using the wave-packet continuum-discretization method. We perform systematic benchmarks using results in the literature and study in detail the convergence of this method with respect to the number of wave packets. We compute several different elastic neutron-deuteron scattering cross-section observables for a variety of energies using chiral nucleon-nucleon interactions. For the optimized next-to-next-to-leading order interaction ${\text{N2LO}}_{\text{opt}}$ we find good agreement with data for nucleon scattering-energies $E_{\text{Lab}}\le 70$ MeV and a slightly larger maximum of the neutron analyzing power $A_y\left(n\right)$ at $E_{\text{Lab}}=10$ and 21 MeV compared with other interactions. This work represents a first step towards a systematic inclusion of three-nucleon scattering observables in the construction of next-generation nuclear interactions.

Machine learning methods and uncertainty quantification have been gaining interest throughout the last several years in low-energy nuclear physics. In particular, Gaussian processes and Bayesian neural networks have increasingly been applied to improve mass model predictions while providing well-quantified uncertainties. In this work, we use the probabilistic Mixture Density Network (MDN) to directly predict the mass excess of the 2016 Atomic Mass Evaluation within the range of measured data, and we extrapolate the inferred models beyond available experimental data. The MDN provides not only mean values but also full posterior distributions both within the training set and extrapolated testing set. We show that the addition of physical information to the feature space increases the accuracy of the match to the training data as well as provides for more physically meaningful extrapolations beyond the the limits of experimental data.

Suppression of the $J/\psi$ nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the $\psi \left(2S\right)$ state in $p+A$ and $d+A$ collisions suggested the presence of final-state effects. Results of $J/\psi$ and $\psi \left(2S\right)$ measurements in the dimuon decay channel are presented here for $p+p$, $p+\mathrm{Al}$, and $p+\mathrm{Au}$ collision systems at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The results are predominantly shown in the form of the nuclear-modification factor, $R_{pA}$, the ratio of the $\psi \left(2S\right)$ invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in $p+p$ collisions. Measurements of the $J/\psi$ and $\psi \left(2S\right)$ nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large Hadron Collider energies.