Signatures of order and collectivity appear in a broad range of one- and two-level boson systems. Toy systems of $N$ particles on a single $j=3,4,\cdots ,7$ level, and on two levels $(j_1,j_2)$ with $j_1+j_2\le 6$ were studied. Surprising novel features in the yrast lines were consistent with boson condensates. Strong signatures of order and collectivity were the norm. These included the usual energy ratios and quadropole transition strengths for vibrational and rotational bands. There were pronounced correlations in energy ratios, sharp peaks in the Alaga ratios, and fractional collectivity across all the one-level systems, as well as signatures of triaxiality. Yrast lines consistent with a deformed rotating core were common.

Background: For several decades, it was believed that while the fission fragment mass distributions of actinides nuclei are asymmetric, the distributions gradually become symmetric for pre-actinide nuclei. Earlier measurements suggested that the transition from asymmetric to symmetric mass distributions occurs for ${}^{201}\mathrm{Tl}$, where the contribution of the asymmetric component appears to vanish. However, a recent reanalysis of the previously measured fission data has indicated the possible presence of asymmetric fission modes in ${}^{201}\mathrm{Tl}$ as well.

Purpose: To search for the fission modes in ${}^{201}\mathrm{Tl}$, the measurement of the fission fragment mass and total kinetic energy distribution (TKE) in the reaction ${}^4\mathrm{He}+{}^{197}\mathrm{Au}$ was carried out at various excitation energies. To check the predictive powers of theoretical models, the measured mass distributions were compared with the general description of fission observables (GEF) model. To investigate the origin of fission modes, state-of-the-art density functional theory (DFT) calculations were performed to generate the potential energy surface.

Methods: Two multiwire proportional counter detectors were employed to detect fission fragments. These detectors were positioned at the folding angles calculated using Viola's systematic. The mass of the fission fragments was determined using the time-of-flight difference method. By measuring the flight time, the velocities of the fission fragments were calculated, and these velocities were subsequently used to determine the total kinetic energy (TKE).

Results: The mass distributions analyzed across all excitation energies exhibited asymmetry. This asymmetry was evident in the mass-mean TKE correlations, which deviated from the parabolic pattern predicted by the liquid drop model (LDM). To account for the unique features of the mass and energy distributions, two asymmetric modes and one symmetric mode were required. The asymmetric modes are associated with the stabilizing effects of proton shells at $Z_L\approx 36$ (A1) and $Z_H\approx 52$ (A2), whereas the symmetric mode aligns with the predictions of the LDM.

Conclusion: The decomposition of mass and energy distributions suggests multimodal fission in the pre-actnide nucleus ${}^{201}\mathrm{Tl}$, which was earlier envisaged as a transitional nucleus with unimodal fission. DFT calculations also support the existence of asymmetric modes in this nucleus. The experimental findings align qualitatively with the semi-empirical GEF code, although they were unable to reproduce the experimental data accurately.

Electromagnetic fields produced in noncentral heavy ion collisions play a crucial role in phenomena such as chiral anomalous effects, directed flow of mesons, and splitting of spin polarization of $\mathrm{\Lambda }/\overline{\mathrm{\Lambda }}$. A precise description of these fields is essential for quantitatively studying these effects. We investigate the space-time evolution of the electromagnetic fields by numerically solving Maxwell's equations using the results from the ultrarelativistic quantum molecular ynamics (UrQMD) model, rather than relying on an ansatz. We present the space-averaged dynamic electromagnetic fields, weighted by energy density, in the central region of heavy ion collisions. These measurements can help us evaluate the effects caused by magnetic fields. Compared to the fields at geometric center of the collisions, the space-averaged dynamical fields weighted by the energy density are smaller at the early stage but damp much slower at the later stage. We further discuss the impact of these space-averaged dynamical magnetic fields on the spin polarization and spin alignment in heavy ion collisions. Additionally, we explore the opportunity to study the nonperturbative regime of quantum electrodynamics (QED) by presenting the simulation results for the space-averaged dynamical electric field at intermediate collision energies. Finally, the space-averaged dynamical electromagnetic anomaly $\mathbf{\text{E}}·\mathbf{B}$ weighted by energy density is also calculated and compared with experimentally measured slope parameter $r$.

We present a study of the transverse size of parton showers and their diminishing interaction with the medium in the high virtuality stage of jet evolution. We consider the process of a hard quark produced in deep inelastic scattering off a large nucleus. Single gluon radiation from this quark, in the absence of scattering, is rederived using wave packets. This allows for a derivation of the quantum uncertainty size of the hard quark, at the point of splitting. This uncertainty size is then incorporated within a Monte Carlo shower routine yielding transverse shower sizes noticeably larger than the classical antenna size of the shower. No clear relation is found between the full uncertainty size of the shower and the virtuality of the originating parton. The single gluon emission from the hard quark is then reanalyzed for the case of single rescattering off the remainder of the nucleus. A relation is derived between the jet transport coefficient $\widehat{q}$ and the gluon Transverse momentum-dependent parton distribution function (gTMDPDF). Solving this relation, for a simple case, clearly demonstrates the weakening of $\widehat{q}$ with the virtuality of the hard splitting parton.

The operator product expansion (OPE) is applied in conjunction with Pionless effective field theory to study the short-range structure of nuclei. By matching the OPE with the selected nuclear potentials for nucleon-nucleon scattering states, we obtain the Wilson coefficients. The nucleon momentum distribution in the deuteron is then used to test the OPE against the predictions of these nuclear potentials. In order to achieve a systematic separation of short-range and long-range interactions, we discuss how the OPE approximation can be improved by including higher-order EFT potentials and higher-dimension local operators.

We extend the spherical coupled-cluster ab initio method for open-shell nuclei where two nucleons are removed from a shell subclosure. Following the recent implementation of the two-particle-attached approach [Phys. Rev. C 110, 044306 (2024)], we focus on the two-particle-removed method. Using the equations-of-motion framework, we address both nuclear structure and dipole response functions by coupling coupled-cluster theory with the Lorentz integral transform technique. We perform calculations using chiral interactions, including three-nucleon forces, and estimate many-body uncertainties by comparing different coupled-cluster truncation schemes. We validate our approach by studying ground-state energies, excited states, and electric dipole polarizabilities in the oxygen and calcium isotopic chains. For binding energies and selected low-lying excited states, we achieve an accuracy comparable to that of the established closed-shell coupled-cluster theory and generally agree with experiment. Finally, we underestimate experimental data for electric dipole polarizabilities, particularly in calcium isotopes.

Excited levels in ${}^{111-121}\mathrm{Ag}$, odd-$A$ isotopes populated following spontaneous fission of ${}^{252}\mathrm{Cf}$ have been studied using high-fold $\gamma$ coincidences measured with Gammasphere array of Compton-suppressed Ge spectrometers at Argonne National Laboratory. The experimental information on these nuclei reported before has been corrected and extended. In the work we discuss the evolution of triaxiality in odd-Ag nuclei. Relative positions of the $\pi p_{1/2}$ and $\pi g_{9/2}$ shells defining the $Z=40$ gap when approaching the $N=82$ closure, the $\pi 1/2^{+}\left[431\right]$ intruder bands, the three-quasiparticle configurations, and the so called $j-1$ anomaly in odd-Ag nuclei are also discussed.

Nuclear energy density-functional theory (DFT) provides a microscopic framework for predicting nuclear masses with sub-MeV accuracy by incorporating pairing correlations and deformation effects. A key ingredient for reaching this precision is the inclusion of dynamical correlation energies (DCEs), comprising rotational correction energy (RCE) and vibrational correction energy (VCE). These quantities are typically estimated at the mean-field level using phenomenological formulas based on the cranking approximation. In this work, we benchmark these phenomenological approximations of the DCEs against quantum-number projected-generator coordinate method (PGCM) calculations based on covariant DFT for odd-mass chromium isotopes, including even-even counterparts for comparison. We find that the phenomenological RCEs generally agree with exact angular-momentum projection (AMP) results, except in cases where symmetry restoration significantly shifts the energy minimum, leading to large deviations. The phenomenological VCEs typically range from 0.7 to 1.1 MeV and are consistent with PGCM results, but tend to be overestimated by up to 0.6 MeV for some odd-mass isotopes. These findings highlight the limitations of phenomenological formulas, particularly for odd-mass systems, and underscore the need for more accurate treatments to improve the predictive power of DFT for nuclear masses beyond the sub-MeV level.

A new framework, called x-scape, for the combined study of both hard and soft transverse momentum sectors in high-energy proton-proton ($p\text{−}p$) and proton-nucleus ($p\text{−}A$) collisions is set up. A dynamical initial state is set up using the 3d-Glauber model with transverse locations of hotspots within each incoming nucleon. A hard scattering that emanates from two colliding hotspots is carried out using the Pythia generator. Initial state radiation from the incoming hard partons is carried out in a new module called I-matter, which includes the longitudinal location of initial splits. The energy-momentum of both the initial hard partons and their associated beam remnants is removed from the hot spots, depleting the energy-momentum available for the formation of the bulk medium. Outgoing showers are simulated using the matter generator, and results are presented for both cases, allowing for and not allowing for energy loss. First comparisons between this hard-soft model and single inclusive hadron and jet data from $p\text{−}p$ and minimum bias $p\text{−}\text{Pb}$ collisions are presented. Single hadron spectra in $p\text{−}p$ are used to carry out a limited (in number of parameters) Bayesian calibration of the model. Fair comparisons with data are indicative of the utility of this new framework. Theoretical studies of the correlation between jet $p_T$ and event activity at mid and forward rapidity are carried out.

We study the stability of bound antiprotons in close proximity to the atomic nucleus. Using experimental data from x-ray spectroscopy measurements of antiprotonic atom transitions, we tune a minimal theoretical framework and estimate parameter ranges where the strong or electromagnetic decay channels govern the stability of the deepest bound states. In this way, we present an overview of the dominant decay mechanism of antiprotonic orbits for a given principle quantum number, to assist future spectroscopic experiments on antiprotonic atoms.

The astrophysical direct nuclear capture reaction ${}^{12}\mathrm{C}(p,\gamma ){}^{13}\mathrm{N}$ is studied within the framework of a potential model. Parameters of the nuclear $p\text{−}{}^{12}\mathrm{C}$ interaction potentials of the Woods-Saxon form are adjusted to reproduce experimental $p\text{−}{}^{12}\mathrm{C}$ scattering phase shifts, as well as the binding energies and empirical values of the asymptotic normalization coefficient (ANC) for the ${}^{13}\mathrm{N}$($1/2^{-}$) ground state from the literature. The reaction rates are found to be very sensitive to the description of the value of the ANC of the ${}^{13}\mathrm{N}$($1/2^{-}$) ground state. The potential model, which yields the ANC value of 1.63 ${\mathrm{fm}}^{-1/2}$ for the ${}^{13}\mathrm{N}$($1/2^{-}$) ground state and a value of $\mathrm{\Gamma }=39$ keV for the ${}^{13}\mathrm{N}$($1/2^{+}$) resonance width, is able to reproduce the astrophysical $S$ factor in the energy interval up to 2 MeV, the empirical values of the reaction rates in the temperature region up to $T={10}^{10}\mathrm{K}$ of the LUNA Collaboration [J. Skowronski et al., Phys. Rev. Lett. 131, 162701 (2023)], and the results of the $R$-matrix fit. The astrophysical factor $S\left(0\right)=1.35$ keV b is found using the asymptotic expansion method of Baye and Brainis [Phys. Rev. C 61, 025801 (2000)]. The obtained value is in good agreement with the Solar Fusion II result. At the same time, the calculated value of 1.44 keV b of the astrophysical $S$ factor at the solar Gamow energy is consistent with the result of the $R$-matrix fit of $S\left(25\mathrm{keV}\right)=1.48\pm 0.09$ keV b by Kettner et al. [Phys. Rev. C 108, 035805 (2023)], but slightly less than the result of $S\left(25\mathrm{keV}\right)=1.53\pm 0.06$ keV b from the LUNA Collaboration [B. Acharya, M. Aliotta, A. B. Balantekin et al., arXiv:2405.06470].

We report the measurement of the parity-violating asymmetry in the $N\to \mathrm{\Delta }$ transition via the $e^{-}+p\to e^{-}+{\mathrm{\Delta }}^{+}$ reaction at two different kinematic points with low four-momentum transfer $Q^2$. Measurements were made with incident electron beam energies of 0.877 and 1.16 GeV, corresponding to $Q^2$ values of 0.0111 and 0.0208 (${\mathrm{GeV}/\mathrm{c})}^2$, respectively. These measurements put constraints on a low-energy constant in the weak Lagrangian, $d_{\mathrm{\Delta }}$, corresponding to a parity-violating electric-dipole transition matrix element. This matrix element has been shown to be large in the strangeness-changing channel, via weak hyperon decays such as ${\mathrm{\Sigma }}^{+}\to p\gamma$. The measurements reported here constrain $d_{\mathrm{\Delta }}$ in the strangeness-conserving channel. The final asymmetries were $-0.65\pm 1.00\left(\mathrm{stat}.\right)\pm 1.02\left(\mathrm{syst}.\right)$ ppm (parts per million) for 0.877 GeV and $-3.59\pm 0.82\left(\mathrm{stat}.\right)\pm 1.33\left(\mathrm{syst}.\right)$ ppm for 1.16 GeV. With these results we deduce a small value for $d_{\mathrm{\Delta }}$, consistent with zero, in the strangeness-conserving channel, in contrast to the large value for $d_{\mathrm{\Delta }}$ previously reported in the strangeness-changing channel.

In this paper we calculate the structure functions and event rates of spin-dependent elastic and inelastic WIMP-nucleus scattering off the odd-$A$ thallium nuclei ${}^{203,205}\mathrm{Tl}$. These nuclei are used as active dopants in sodium and cesium iodide scintillators in many dark-matter experiments. We begin by presenting nuclear shell-model calculations of the nuclei, then compare the calculated energy spectra, nuclear moments and electromagnetic transitions to their experimental values to establish the validity of our nuclear model. Then, we proceed to calculate the structure functions for both elastic and inelastic WIMP scattering, and after that we calculate the differential event rates for WIMPs of various masses (100, 200, 500, and 1000 GeV). We employ a state-of-the-art WIMP-nucleus-scattering formalism that takes into account all pion-exchange, pion-pole, and contact currents. The present work is the first time that two-body currents have been taken into account for ${}^{203,205}\mathrm{Tl}$ in WIMP-scattering calculations. The results show that elastic scattering is at least an order of magnitude more important than inelastic scattering in all the cases studied. Elastic scattering structure functions were found to be of similar magnitude to other nuclei.

In relativistic heavy-ion collisions, charged particles are accelerated to nearly the speed of light, and their external electromagnetic fields can be effectively approximated as quasireal photons. These photons interact with another nucleus via photon-nuclear interactions, producing vector mesons. These vector mesons possess extremely low transverse momentum ($p_T\sim 0.1\mathrm{GeV}/c$), distinguishing them from particles produced via hadronic interactions. STAR and ALICE have observed $J/\psi$, ${\rho }^0$ and other vector mesons with very low $p_T$, which are well described by photoproduction models. This unique characteristic of having extremely low transverse momentum allows them to serve as a novel experimental probe. Recent STAR results show that the equivalent photons in photoproduction processes are fully linearly polarized, affecting the azimuthal distribution of final-state particles like ${\rho }^0\to {\pi }^{+}{\pi }^{-}$. Since the polarization links to the initial collision geometry, the ${\rho }^0$ azimuthal modulation can probe nuclear structure. However, the post-collision magnetic field may deflect these particles, distorting the azimuthal distribution and complicating structure measurements. We simulated the distribution of residual magnetic fields over time under different collision conditions using ultrarelativistic quantum molecular dynamics for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV and calculated their effects on the azimuthal modulation ($\langle cos2\varphi \rangle$) of photoproduced ${\rho }^0$. Our results show that in peripheral collisions, the field significantly alters the $\langle cos2\varphi \rangle$ for photoproduced ${\rho }^0$ with $p_T\approx 0.1$ $\mathrm{GeV}/c$. This provides key insights for future nuclear structure studies via photoproduction in peripheral collisions.

We report the first measurement of the azimuthal anisotropy of $J/\psi$ at forward rapidity ($1.2<\left|\eta \right|<2.2$) in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV at the BNL Relativistic Heavy Ion Collider. The data were collected by the PHENIX experiment in 2014 and 2016 with integrated luminosity of 14.5 ${\mathrm{nb}}^{-1}$. The second Fourier coefficient ($v_2$) of the azimuthal distribution of $J/\psi$ is determined as a function of the transverse momentum ($p_T$) using the event-plane method. The measurements were performed for several selections of collision centrality: 0%–50%, 10%–60%, and 10%–40%. We find that in all cases the values of $v_2\left(p_T\right)$, which quantify the elliptic flow of $J/\psi$, are consistent with zero. Within uncertainties, the results are consistent with measurements at midrapidity, indicating no significant elliptic flow of the $J/\psi$ within the quark-gluon-plasma medium at collision energies of $\sqrt{s_{{}_{NN}}}=200$ GeV.

In this work, the weak interaction rates of $sd$-shell nuclei in the hot and dense stellar environment are calculated using the shell model. The ab initio effective interactions are employed for the calculation of Gamow-Teller strengths and weak rates in addition to the phenomenological interaction. The weak rates are evaluated in a fine grid of density and temperature. The electron capture and ${\beta }^{-}$-decay rates of Urca pairs of nuclei with $A=23,25,29,31\text{and}33$ are evaluated as a function of ${log}_{10}\rho Y_e$ and the corresponding Urca density is obtained. The screening effects are also included for the evaluation of these stellar weak rates. In addition, the intrinsic cooling strength is evaluated for $A=29,31\text{and}33$ Urca pairs in neutron star crusts. The stellar weak rates, along with the neutrino energy emitted and the gamma heat production, are tabulated for $A=29\text{–}39$ nuclei.

The lifetime of free neutrons measured in the laboratory has a longstanding disparity of $\approx 9$ s. A space-based technique has recently been proposed to independently measure the neutron lifetime using interactions between the galactic cosmic rays and a low atmosphere planetary body. This technique has not produced competitive results yet due to constraints of nonoptimized data that contain large systematic errors. We use data from the neutron spectrometer on-board NASA's Lunar Prospector, and study two large systematics in the measurement of neutron lifetime: the lunar subsurface temperature and the lunar surface composition. We use the HeCd and HeSn neutron spectrometer data when the spacecraft was in a highly elliptical orbit during the orbit insertion period. We report the neutron lifetime using four different models that each have different choices of surface temperature and composition. The $5^{\circ }$ [Prettyman et al., J. Geophys. Res.: Planets 111, 2005JE002656 (2006)] and $2^{\circ }$ [Wilson et al., Phys. Rev. C 104, 045501 (2021)] rebinned maps result in $777.6\pm 11.7$ s and $739.6\pm 10.8$ s, respectively. For the ${20}^{\circ }$ map (Prettyman et al., 2006), constant equatorial and a latitude-dependent temperature model result in $738.6\pm 10.8$ s and $767.3\pm 11.2$ s, respectively. Increasing the complexities of the models accounting for the systematic effects increase the measured lifetime. However, the reported measurements are not competitive with the laboratory results due to large unaccounted systematics resulting from nonoptimized measurements and modeling assumptions. This work serves as a study of systematic uncertainties for future neutron lifetime measurements using the space-based technique. We estimate the effect on the lifetime from the choice of temperature model to be to be $28.7\pm 15.5$ s, and choice of compositional map (for ${20}^{\circ }$ and $5^{\circ }$ maps) to be $10.3\pm 12.2$ s.

I perform a further study regarding a renormalization-group (RG) issue—which concerns a wide variety of the so-called perturbative power counting under effective field theories (EFTs)—as pointed out by Gasparyan and Epelbaum [A. M. Gasparyan and E. Epelbaum, Phys. Rev. C 107, 034001 (2023)]. I show that the issue could originate from a wrong power counting, or from treating those incomplete, truncated amplitudes beyond the degree to which they should be trusted. Meanwhile, under EFT principles, one should always associate the result with an uncertainty that is adequate to its EFT order. One way to accommodate this is to encode its effect in a more general form of contact terms. In this regard, no RG issue is found in the ${}^3\mathrm{P}_0$ nucleon-nucleon scattering under the Long and Yang power counting. In contrast, the RG issue under Weinberg's pragmatic proposal remains a problem even with uncertainty taken into account.

We employ a specific U(5)-O(6) Hamiltonian of the interacting boson model (IBM) to describe even-even nuclei near the O(6) limit. Our analysis identifies a zero generalized boson pairing mode, where the generalized pairing energy vanishes exactly. Within this zero mode, excitation energies remain invariant under variations in the control parameters. Exact solutions for this zero mode are derived from the zeros of the corresponding Jacobi polynomials, while solutions for the nonzero mode are obtained from the more complex extended Heine-Stieltjes polynomials. We fit some low-lying positive-parity energy levels and associated $B$($E2$) values for ${}^{194,196}\mathrm{Pt}$. The results demonstrate that ${}^{194}\mathrm{Pt}$ lies closer to the O(6) limit as evidenced by the available experimental $B$($E2$) values.

Measurements of the ${}^{182}\mathrm{W}(n,2n){}^{181}\mathrm{W}$ cross section have been performed in the neutron energy range between 8 and 15 MeV using the activation technique. Such data are needed to help interpret results of laser shots at the National Ignition Facility using a new deuterium-tritium capsule design, featuring a high-$Z$ inner shell, with tungsten as the favored material, and an outer shell made of a low-$Z$ material. Our data are in very good agreement with the previous data of Frehaut et al. (Technical Report No. 6447, Centre d'Etudes Nucleaires, Saclay, 2016), which are based on a different technique, and are in fair agreement with the ENDF/B-VIII.0 and the JEFF-3.3 evaluations.