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.

Effectively charged neutrons involved in one- and two-nucleon tunneling processes in heavy-ion collisions between superfluid nuclei are expected to emit photons. Although the centroid, width, and integrated energy area characterizing the associated $\gamma$-strength functions are rather similar, the corresponding line shapes reflect the thermal equilibrated-like character of the quasiparticle transfer ($1n$ channel, blackbody spectral functional dependence) and the quantal coherent character of the Cooper pair transfer ($2n$ channel, and Gaussian functional dependence), respectively. The predicted angular distributions, polarizations, and analyzing powers provide further insight into the profoundly different physics to be found at the basis of what can be considered transient Joule-like and (ac) Josephson-like nuclear processes.

Population of the 8 eV ${}^{229m}\mathrm{Th}$ isomer via the second nuclear excited state at 29.19 keV by means of coherent x-ray pulses is investigated theoretically. We focus on two nuclear coherent population transfer schemes using partially overlapping x-ray pulses known from quantum optics: stimulated Raman adiabatic passage, and successive $\pi$ pulses. Numerical results are presented for three possible experimental setups. Our results identify the Gamma Factory as the most promising scenario, where two ultraviolet pulses combined with relativistically accelerated ions deliver the required intensities for efficient isomer population. Our simulations require knowledge of the in-band and cross-band nuclear transition probabilities. We give theoretically predicted values for the latter and discuss them in the context of recent experiments.

Within the improved quantum molecular dynamics (ImQMD) model we follow the evolution of nuclear matter for planar Couette flow in a periodic box. We focus on the region of liquid-gas phase transition and extract the shear viscosity coefficient from the local stress tensor, directly following the viscosity definition. By switching on and off the mean field and thus inducing the phase transition, we are able to observe the impact of clumping in the phase transition region on the viscosity.

The Baksan Experiment on Sterile Transitions (BEST) probes the gallium anomaly and its possible connections to oscillations between active and sterile neutrinos. Based on the Gallium-Germanium Neutrino Telescope (GGNT) technology of the SAGE experiment, BEST employs two zones of liquid Ga target to explore neutrino oscillations on the meter scale. Oscillations on this short scale could produce deficits in the ${}^{71}\mathrm{Ge}$ production rates within the two zones, as well as a possible rate difference between the zones. From July 5th to October 13th 2019, the two-zone target was exposed to a primarily monoenergetic, 3.4-MCi ${}^{51}\mathrm{Cr}$ neutrino source 10 times for a total of 20 independent ${}^{71}\mathrm{Ge}$ extractions from the two Ga targets. The ${}^{71}\mathrm{Ge}$ production rates from the neutrino source were measured from July 2019 to March 2020. At the end of these measurements, the counters were filled with ${}^{71}\mathrm{Ge}$ doped gas and calibrated during November 2020. In this paper, results from the BEST sterile neutrino oscillation experiment are presented in details. The ratio of the measured ${}^{71}\mathrm{Ge}$ production rates to the predicted rates for the inner and the outer target volumes are calculated from the known neutrino capture cross section. Comparable deficits in the measured ratios relative to predicted values are found for both zones, with the $4\sigma$ deviations from unity consistent with the previously reported gallium anomaly. If interpreted in the context of neutrino oscillations, the deficits give best-fit oscillation parameters of $\mathrm{\Delta }{m}^2=3.3_{-2.3}^{+\infty }{\mathrm{eV}}^2$ and ${\sin }^{2}2\theta =0.{42}_{-0.17}^{+0.15}$, consistent with ${\nu }_e\to {\nu }_s$ oscillations governed by a surprisingly large mixing angle.

The structure of the unbound ${}^{15}\mathrm{F}$ nucleus is investigated using the inverse kinematics resonant scattering of a radioactive ${}^{14}\mathrm{O}$ beam impinging on a ${\mathrm{CH}}_2$ target. The analysis of ${}^1\mathrm{H}({}^{14}\mathrm{O},\mathrm{p}){}^{14}\mathrm{O}$ and ${}^1\mathrm{H}({}^{14}\mathrm{O},2\mathrm{p}){}^{13}\mathrm{N}$ reactions allowed the confirmation of the previously observed narrow $1/2^{-}$ resonance, near the two-proton decay threshold, and the identification of two new narrow $5/2^{-}$ and $3/2^{-}$ resonances. The newly observed levels decay by 1p emission to the ground of ${}^{14}\mathrm{O}$, and by sequential 2p emission to the ground state of ${}^{13}\mathrm{N}$ via the $1^{-}$ resonance of ${}^{14}\mathrm{O}$. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the $5/2^{-}$ and $3/2^{-}$ resonances may be collectivized by the continuum coupling to nearby 2p- and 1p-decay channels. The observed excitation function ${}^1\mathrm{H}({}^{14}\mathrm{O},\mathrm{p}){}^{14}\mathrm{O}$ and resonance spectrum in ${}^{15}\mathrm{F}$ are well reproduced in the unified framework of the GSM.

The temperature dependence of stellar electron-capture (EC) rates is investigated, with a focus on nuclei near $N=50$, just above $Z=28$, which play an important role during the collapse phase of core-collapse supernovae (CCSN). Two new microscopic calculations of stellar EC rates are obtained from relativistic and nonrelativistic finite-temperature quasiparticle random-phase approximation approaches, for a conventional grid of temperatures and densities. In both approaches, EC rates due to Gamow-Teller transitions are included. In the relativistic calculation, contributions from first-forbidden transitions are also included and add strongly to the EC rates. The new EC rates are compared with large-scale shell-model calculations for the specific case of ${}^{86}\mathrm{Kr}$, providing insight into the finite-temperature effects on the EC rates. At relevant thermodynamic conditions for core collapse, the discrepancies between the different calculations of this paper are within about one order of magnitude. Numerical simulations of CCSN are performed with the spherically symmetric gr1d simulation code to quantify the impact of such differences on the dynamics of the collapse. These simulations also include EC rates based on two parametrized approximations. A comparison of the neutrino luminosities and enclosed mass at core bounce shows that differences between simulations with different sets of EC rates are relatively small ($\approx 5\%$), suggesting that the EC rates used as inputs for these simulations have become well constrained.

The electromagnetic response of hot QCD matter to decaying external magnetic fields is investigated. We examine the validity of Ohm's law and find that the induced electric current increases from zero and relaxes towards the value from Ohm's law. The relaxation time is larger than the lifetime of the external magnetic field for the QCD matter in relativistic heavy-ion collisions. The lower-than-expected electric current significantly suppresses the induced magnetic field and makes the electromagnetic response incomplete. We demonstrate the incomplete electromagnetic response of hot QCD matter by calculations employing the parton transport model combined with the solution of Maxwell's equations. Our results show a strong suppression by two orders of magnitude in the magnetic field relative to calculations assuming the validity of Ohm's law. This may undermine experimental efforts to measure magnetic-field-related effects in heavy-ion collisions.

Collective phenomena in quantum many-body systems are often described in terms of hydrodynamics, an appropriate framework when the involved particle numbers are effectively macroscopic. We propose to use experiments on expanding clouds of few and many interacting cold atoms to investigate the emergence of hydrodynamics as a function of particle number. We consider gases confined in two-dimensional elliptically deformed traps, and we employ the manifestation of elliptic flow as an indicator of collective behavior. We quantify the response of the gas to the deformation of the trapping potential, and show how such information can be used to establish how many atoms are needed for the system to develop a degree of collectivity comparable to that expected in the hydrodynamic limit. This method permits one, in particular, to exploit observations made in expanding atomic gases to shed light on the apparent hydrodynamic behavior of mesoscopic systems of quarks and gluons formed in the scattering of light ions in high-energy collider experiments.

Pairing rotations are the low-energy excitations of finite superfluid systems, connecting systems that differ in their number of Cooper pairs. This paper presents a model-independent derivation of pairing rotations within an effective theory that exploits the emergent breaking of $\text{U}\left(1\right)$ phase symmetries. The symmetries are realized nonlinearly and the Nambu-Goldstone modes depend only on time because the system is finite. Semimagic nuclei exhibit pairing rotational bands while the pairing spectrum becomes an elliptical paraboloid for open-shell nuclei. Model-independent relations between double charge-exchange reactions and $\alpha$ particle capture or knockout in open-shell nuclei are in analogy to the pair transfer reactions in a single superfluid. Odd semimagic nuclei are described by coupling a fermion to the superfluid. The leading-order theories reproduce data for pairing rotational bands within uncertainty estimates.

The STAR collaboration presents jet substructure measurements related to both the momentum fraction and the opening angle within jets in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}} =200\mathrm{GeV}$. The substructure observables include SoftDrop groomed momentum fraction ($z_g$), groomed jet radius ($R_g$), and subjet momentum fraction ($z_{\mathrm{SJ}}$) and opening angle (${\theta }_{\mathrm{SJ}}$). The latter observable is introduced for the first time. Fully corrected subjet measurements are presented for $p+p$ collisions and are compared to leading-order Monte Carlo models. The subjet ${\theta }_{\mathrm{SJ}}$ distributions reflect the jets leading opening angle and are utilized as a proxy for the resolution scale of the medium in $\mathrm{Au}+\mathrm{Au}$ collisions. We compare data from $\mathrm{Au}+\mathrm{Au}$ collisions to those from $p+p$ which are embedded in minimum-bias $\mathrm{Au}+\mathrm{Au}$ events in order to include the effects of detector smearing and the heavy-ion collision underlying event. The subjet observables are shown to be more robust to the background than $z_g$ and $R_g$. We observe no significant modifications of the subjet observables within the two highest-energy, back-to-back jets, resulting in a distribution of opening angles and the splittings that are vacuumlike. We also report measurements of the differential dijet momentum imbalance ($A_J$) for jets of varying ${\theta }_{\mathrm{SJ}}$. We find no qualitative differences in energy loss signatures for varying angular scales in the range $0.1< {\theta }_{\mathrm{SJ}}<0.3$, leading to the possible interpretation that energy loss in this population of high-momentum dijet pairs, is due to soft medium-induced gluon radiation from a single color charge as it traverses the medium.