Coupled cluster theory is an attractive tool to solve the quantum many-body problem because its singles and doubles (CCSD) approximation is computationally affordable and yields about 90% of the correlation energy. Capturing the remaining 10%, e.g., via including triples, is numerically expensive. Here, we assume that short-range three-body correlations dominate and—following Lepage (arXiv:nucl-th/9706029)—that their effects can be included within CCSD by renormalizing the three-body contact interaction. We renormalize this contact in ${}^{16}\mathrm{O}$ and obtain systematically improved CCSD results for ${}^{24}\mathrm{O}, {}^{20–34}\mathrm{Ne}, {}^{40,48}\mathrm{Ca}, {}^{78}\mathrm{Ni}, {}^{90}\mathrm{Zr}$, and ${}^{100}\mathrm{Sn}$.

The ${}^9\mathrm{Be}({}^{25}\phantom{{}^{B}e}\mathrm{F}(5/2^{+}),{}^{24}\phantom{{}^{B}e}\mathrm{O}$)X proton-removal reaction was studied at the NSCL using the S800 spectrometer. The experimental spectroscopic factor for the ground-state to ground-state transition indicates a substantial depletion of the proton $d_{5/2}$ strength compared to shell-model expectations, similar to the findings of an inverse-kinematics $(p,2p)$ measurement performed at RIBF. The ${}^{25}\phantom{{}^{B}e}\mathrm{F}$ to ${}^{24}\phantom{{}^{B}e}\mathrm{O}$ ground-states overlap is considerably less than anticipated if the core nucleons behaved as rigid, doubly-magic ${}^{24}\phantom{{}^{B}e}\mathrm{O}$ within ${}^{25}\phantom{{}^{B}e}\mathrm{F}$. We interpret the new results within the framework of the Particle-Vibration Coupling (PVC) model, of a $d_{5/2}$ proton coupled to a quadrupole phonon of an effective core. This approach provides a good description of the experimental data, requiring an effective ${}^{24}\phantom{{}^{B}e}\mathrm{O}^{*}$ core with a phonon energy of $\hslash {\omega }_2$= 3.2 MeV and a $B\left(E2\right)\approx 2.7$ W.u. – softer and more collective than a bare ${}^{24}\phantom{{}^{B}e}\mathrm{O}$. Both the Nilsson deformed mean field and the PVC models appear to capture the properties of the effective core of ${}^{25}\phantom{{}^{B}e}\mathrm{F}$, suggesting that the additional proton polarizes ${}^{24}\phantom{{}^{B}e}\mathrm{O}$ in such a way that it becomes either slightly deformed or a quadrupole vibrator.

The nuclear structure of ${}^{248}\mathrm{Cf}$ was investigated at the Tokai Tandem Accelerator Laboratory of the Japan Atomic Energy Agency. ${}^{248}\mathrm{Cf}$ was one of the nuclei produced in the ${}^{18}\mathrm{O}+{}^{249}\mathrm{Cf}$ multinucleon transfer reaction. An array of Ge and ${\mathrm{LaBr}}_3$ detectors was used to detect the $\gamma$ rays emitted. More than ten new $\gamma$-ray transitions from ${}^{248}\mathrm{Cf}$ were observed and, for the first time, lifetimes of excited states in the nanosecond range were measured. For the previously known bandhead of the $2^{-}$ octupole vibrational band at 592 keV, a lifetime of 6.7(2) ns was found. Another, new isomeric state, with a lifetime of 16.8(5) ns, decays via a 48-keV $E1$ transition to a much longer-lived state lying at 0.9(3) MeV, for which a lifetime larger than $\approx 200$ ns is estimated. For this latter state, the unobserved decay points to $K⩾5$. Considering available theoretical models, possible spin-parity assignments of new states are discussed.

Largely enhanced parity-violating effects observed in compound resonances induced by epithermal neutrons are currently attributed to the mixing of parity-unfavored partial amplitudes in the entrance channel of the compound states. Furthermore, it is proposed that the same mechanism that enhances the parity violation also enhances the breaking of time-reversal invariance in the compound nucleus. The entrance-channel mixing induces energy-dependent spin-angular correlations of individual $\gamma$ rays emitted from the compound nuclear state. For a detailed study of the mixing model, the $\gamma$-ray yield in the reaction of ${}^{117}\mathrm{Sn}(n,\gamma ){}^{118}\mathrm{Sn}$ was measured using a pulsed beam of polarized epithermal neutrons and Ge detectors. An angular dependence of asymmetric $\gamma$-ray yields for the orientation of the neutron polarization was observed.

We explore the description of the bound ${}^{19}\mathrm{B}$ isotope in terms of a ${}^{17}\mathrm{B}+n+n$ three-body system where the two-body subsystems ${}^{17}\mathrm{B}+n$ and neutron-neutron ($nn$) have virtual states close to the continuum. Dimensionless scaling functions for the root-mean-square (rms) radii are defined and studied for different parameters of the neutron-core potential and considering three different models for neutron-neutron interaction. The scaling functions for the radii are rooted in the universal behavior of three-body systems close to the Efimov limit and depend only on dimensionless quantities formed by the two-neutron separation energies and scattering lengths. Our results show in practice the model independence of these scaling functions close to unitarity. We provide an estimation of the different rms relative separation distances between the constituents, as well as of the proton and matter radii.

The products of the ${}^{203,205}\mathrm{Tl}({}^{50}\mathrm{Ti},2n)$ fusion-evaporation reactions were studied using the recently commissioned Argonne Gas-Filled Analyzer at Argonne National Laboratory. Two $\alpha$-decay activities with energies of 9210(19) and 9246(19) keV and half-lives of ${42}_{-14}^{+42}$ and $24.4_{-4.5}^{+7.0}$ ms were observed which were followed by the known $\alpha$ decays of ${}^{247}\mathrm{Md}$ and ${}^{243}\mathrm{Es}$. They are interpreted as originating from the $1/2^{-}\left[521\right]$ and $7/2^{-}\left[514\right]$ single-proton Nilsson states in the hitherto unknown isotope ${}^{251}\mathrm{Lr}$. From the measured $Q_{\alpha }$ values the $1/2^{-}$ level was placed 117(27) keV above the $7/2^{-}$ level in ${}^{251}\mathrm{Lr}$ in contrast to ${}^{255}\mathrm{Lr}$ where the $1/2^{-}$ level is the lowest. Also, the $\alpha$ decay of ${}^{253}\mathrm{Lr}$ was studied in more detail and a new $\alpha$ line at 8660(20) keV was found and a new half-life value of 2.46(32) s for an isomeric state in ${}^{253}\mathrm{Lr}$ was measured. The ${}^{251,253,255}\mathrm{Lr}{Q}_{\alpha }$ values were compared with predictions of various mass models. The relative energies of the $1/2^{-}\left[521\right]$ and $7/2^{-}\left[514\right]$ single-proton Nilsson states in ${}^{251,253,255}\mathrm{Lr}$ isotopes were compared with results of the cranking shell model with pairing treated using the particle-number-conserving method. The level separation and, in particular, the level order change between ${}^{251}\mathrm{Lr}$ and ${}^{255}\mathrm{Lr}$ was reproduced only when the hexacontetrapole deformation ${\varepsilon }_6$ was included in the calculations.

We report the new level scheme of the ${}^{91}\mathrm{Nb}$ nucleus established by the reactions ${}^{82}\mathrm{Se}({}^{14}\mathrm{N},5n){}^{91}\mathrm{Nb}$ and ${}^{76}\mathrm{Ge}({}^{19}\mathrm{F},4n){}^{91}\mathrm{Nb}$. Thirty new transitions with energies up to about 12 MeV are assigned to the ${}^{91}\mathrm{Nb}$ nucleus and placed in the proposed level scheme. The excited levels are well reproduced by shell-model calculations with the GWBXG effective interaction. The obtained results, which conform to the most experimental data well, manifest that the high spins are construed as the proton excitations from $1p_{3/2}$, $0f_{5/2}$, and $1p_{1/2}$ orbitals, to the $0g_{9/2}$ orbital with the breakup of the $Z=38$ (40) core, as well as neutron excitations from the $0g_{9/2}$ orbital to the $1d_{5/2}$ or $0g_{7/2}$ orbital with the breakup of the $N=50$ core.

When two fragments are created in a fission decay, any torque due to nuclear and Coulomb interaction can change the fragment's angular momentum. This paper explores the character and magnitude of the angular momentum as a function of the initial conditions around the scission point using the time-dependent Hartree-Fock theory. To understand the torque acting on the fragments, the Frozen Hartree-Fock method is also used to determine the collective potential at scission. Two ${}^{240}\mathrm{Pu}$ fission channels $({}^{132}\mathrm{Sn}+{}^{108}\mathrm{Ru}$ and ${}^{144}\mathrm{Ba}+{}^{96}\mathrm{Sr})$ are studied. These two channels cover different shapes (spherical, quadrupole, and octupole deformation) of the fragments. It is found that the angular momentum generated by the Coulomb interaction after fission is mainly collective, while this is not the case for the angular momentum generated at scission. The competition between rotational modes (bending, wriggling, and twisting) is discussed and shows that the angular momentum is generated mainly perpendicular to the fission axis.

Background: Previously reported fusion-evaporation cross sections of residues in ${}^{45}\mathrm{Sc}$-induced reactions with lanthanide targets are much smaller than ${}^{48}\mathrm{Ca}$-induced reactions on the same targets. ${}^{44}\mathrm{Ca}$ is one proton removed from ${}^{45}\mathrm{Sc}$ and could be used to produce nuclei with a relative neutron content between those produced in the ${}^{45}\text{Sc-}$ and ${}^{48}\mathrm{Ca}$-induced reactions.

Purpose: Several experiments worldwide have attempted to discover elements beyond the currently heaviest known element, oganesson ($Z=118$). Due to a lack of appropriate targets, these efforts focused on projectiles other than ${}^{48}\mathrm{Ca}$, which has been widely used for a number of successful element discovery experiments. The present study continues our previous work to understand the influence of various projectiles on the compound nucleus in fusion-evaporation reactions, and addresses the influence of target neutron number on fusion-evaporation cross sections.

Methods: In experiments performed at the Cyclotron Institute at Texas A&M University, a beam of ${}^{44}\mathrm{Ca}^{6+}$ with an energy of $\approx 5\mathrm{MeV}/u$ was delivered by the K500 superconducting cyclotron to the Momentum Achromat Recoil Spectrometer (MARS). The ${}^{44}\mathrm{Ca}$ projectiles bombarded various isotopically enriched Gd targets in the MARS target chamber to create evaporation residues, which were spatially separated from unreacted projectiles by MARS and identified via their characteristic $\alpha \text{−}\mathrm{decay}$ energies. Excitation functions for the reactions of ${}^{44}\mathrm{Ca}$ with ${}^{154,156,157,160}\mathrm{Gd}$ were measured at several projectile energies each.

Results: The maximum $4n$ cross sections in the ${}^{44}\mathrm{Ca}{+}^{154,156,157,160}\mathrm{Gd}$ reactions were $0.038\pm 0.008, 0.83\pm 0.08, 3.8\pm 0.2$, and $3.0\pm 0.5$ mb, respectively. Production cross sections for the more neutron-rich targets were surprisingly constant even given the substantial changes in the difference in neutron binding energy and fission barrier of the compound nuclei.

Conclusions: Collective enhancements to level density caused a reduction in compound nucleus survivability for all targets. While this effect was required to obtain good agreement between theoretical calculations and experimental data, it was not sufficient to explain the cross sections for the reaction with the most neutron-deficient target studied $\left({}^{154}\mathrm{Gd}\right)$. Instead, it appears that the difference in the fission barrier and neutron binding energy is the dominant factor affecting the survival of the compound nucleus in this case.

Recently the splitting of elliptic flow $v_2$ at finite rapidities has been proposed as a result of the global vorticity in noncentral relativistic heavy ion collisions. In this study, we find that this left-right (i.e., on opposite sides of the impact parameter axis) splitting of the elliptic flow at finite rapidities is a result of the nonzero directed flow $v_1$, with the splitting magnitude $\approx 8v_1(1-3v_2)/\left(3\pi \right)$. We also use a multiphase transport model, which automatically includes the vorticity field and flow fluctuations, to confirm the $v_2$ splitting. In addition, we find that the analytical expectations for the $v_2$ splitting work for the raw $v_2$ and $v_1$ (i.e., before event plane resolutions are applied) measured relative to either the first- or second-order event plane. Since the $v_2$ splitting is mostly driven by $v_1$, it vanishes at zero transverse momentum $\left(p_{\mathrm{T}}\right)$, and its magnitude and sign may have nontrivial dependencies on $p_{\mathrm{T}}$, centrality, collision energy, and hadron species.

A new two-component model of the EMC effect based on light-front holographic QCD (LFHQCD) is presented. The model suggests the EMC effect is the result of the nuclear potential breaking SU(6) symmetry. The model separates the $F_2^A$ nuclear structure function into two parts: a free contribution, involving the addition of proton and neutron structure functions, weighted by the number of protons and neutrons respectively, and a nuclear/medium modified contribution that involves a nucleus-independent universal function. Further, the model displays a correlation between the size of the EMC effect and the SRC pair density $a_2$, extracted from kinematic plateaus at around $x>1$ in inclusive quasielastic (QE) scattering.

Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance mass-spectrometry technique, the atomic masses of ${}^{251}\mathrm{No}$ ($Z=102$), ${}^{254}\mathrm{Lr}$ ($Z=103$), and ${}^{257}\mathrm{Rf}$ ($Z=104$) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of ${}^{254}\mathrm{No}$ and ${}^{255,256}\mathrm{Lr}$ were improved by more than one order of magnitude. Relative statistical uncertainties as low as $\delta m/m\approx {10}^{-9}$ were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in ${}^{251,254}\mathrm{No}$ and ${}^{254,255}\mathrm{Lr}$. This provided an unambiguous determination of the binding energies for odd-$A$ and odd-odd nuclides previously determined only indirectly from decay spectroscopy.

We consider a spin-balanced degenerate gas of spin-1/2 fermions whose dynamics is governed by low-energy $P$-wave interactions characterized by the scattering volume $a_1$ and effective momentum $r_1$. The energy per particle $\overline{\mathcal{E}}$ in the many-body system is calculated by resumming the ladder diagrams comprising both particle-particle and hole-hole intermediate states, following the novel advances recently developed by us in Ann. Phys. (NY) 437, 168741 (2022). This allows us to obtain a renormalized result for $\overline{\mathcal{E}}$ within generic cutoff regularization schemes, with $\overline{\mathcal{E}}$ directly expressed in terms of the scattering parameters $a_1$ and $r_1$, once the cutoff is sent to infinity. The whole set of possible values of $a_1$ and $r_1$ is explored, looking for minima in the energy per particle with $\overline{\mathcal{E}}$ given as described. They are actually found, but a further inspection reveals that the associated scattering parameters give rise to resonance poles in the complex momentum plane with positive imaginary part, which is at odds with the Hermiticity of the Hamiltonian. We also determine that these conflictive poles, with a pole-position momentum that is smaller in absolute value than the Fermi momentum of the system, clearly impact the calculation of $\overline{\mathcal{E}}$. As a result, we conclude that unpolarized spin-1/2 fermionic normal matter interacting in $P$-wave is not stable. We also study three universal parameters around the unitary limit. Finally, the whole set of values for the parameters $a_1$, $r_1$ is characterized according to whether they give rise to unallowed poles and, if so, by attending to their pole positions relative to the Fermi momentum of the system explored.

An expression of partial-wave expansion of three-baryon interactions in chiral effective field theory is presented. The derivation follows the method by Hebeler et al. [Phys. Rev. C 91, 044001 (2015)], but the final expression is more general. That is, a systematic treatment of the higher-rank spin-momentum structure of the interaction becomes possible. Using the derived formula, a $\mathrm{\Lambda }$-deuteron folding potential is evaluated. This information is valuable for inferring the possible contribution of the $\mathrm{\Lambda }NN$ three-baryon forces to the hypertriton as the basis of further studies by sophisticated Faddeev calculations. A microscopic understanding of $\mathrm{\Lambda }NN$ three-baryon forces together with two-body $\mathrm{\Lambda }N$ interactions is essential for the description of hypernuclei and neutron-star matter.

Nucleon momentum distributions are crucial windows to probe nuclear structures. They provide valuable information not only on mean-field structures but also on short-range correlations. The $y$ scaling analysis generally serves as a tool to extract the nucleon momentum distribution from inclusive quasielastic electron cross sections. In this paper, we report new nucleon momentum distributions for deuteron, ${}^{3,4}\mathrm{He}$, ${}^9\mathrm{Be}$, and ${}^{12}\mathrm{C}$, extracted, based on ${\psi }^{\prime }$ scaling, directly from the latest high-precision experimental data. It is found that, for deuteron, ${}^{3,4}\mathrm{He}$, ${}^9\mathrm{Be}$, and ${}^{12}\mathrm{C}$, the ${\psi }^{\prime }$-scaling method provides reasonable results in agreement with state-of-the-art ab initio calculations up to 3.5 ${\mathrm{fm}}^{-1}$. These new nucleon momentum distributions can be helpful references for future studies of nuclear structures.

Cross sections of the ${}^{40}\mathrm{Ca}\left(n,{\alpha }_0\right){}^{37}\mathrm{Ar}$ and ${}^{40}\mathrm{Ca}\left(n,\alpha \right){}^{37}\mathrm{Ar}$ reactions at five neutron energy points in the $8.50–9.50$ MeV energy region were measured. The monoenergetic neutrons were produced through the ${}^2\mathrm{H}{\left(d,n\right)}^3\mathrm{He}$ reaction based on the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE). A twin gridded ionization chamber (GIC) was used as the charged particle detector. Detailed simulations were performed to determine the nuclear reaction events and detection efficiencies. Present results are compared with existing measurement and evaluation data, which shows that the evaluation data from all libraries are higher than the measurement data in the $8.50–9.50$ MeV region for the ${}^{40}\mathrm{Ca}\left(n,\alpha \right){}^{37}\mathrm{Ar}$ reaction. TALYS-1.9 code was used for theoretical calculations. Calculation results using the TALYS-1.9 code with the adjusted parameters are in agreement with the present measurements, which also show that the compound mechanism predominates the ${}^{40}\mathrm{Ca}\left(n,\alpha \right){}^{37}\mathrm{Ar}$ reaction in the $8.50–9.50$ MeV region. Both present measured forward/backward ratios and TALYS-1.9 calculations suggest that the direct and preequilibrium mechanisms are non-negligible for the ${}^{40}\mathrm{Ca}\left(n,\alpha \right){}^{37}\mathrm{Ar}$ reaction in the $8.50–9.50$ MeV region.

Background: Reaction channel coupling substantially modifies the real and imaginary nucleon-nucleus interactions for nuclei of $Z=20$ or less in ways that cannot be represented as uniform renormalizations of folding model potentials. For such nuclei coupling to inelastic channels also contributes. This raises the question of the effect of these couplings for heavier target nuclei.

Purpose: To establish and characterize the contribution to the proton-nucleus interaction generated by coupling to neutron pickup (outgoing deuteron) channels for 40 MeV protons on the heavy closed shell nucleus ${}^{208}\mathrm{Pb}$. To identify and evaluate the consequent dynamical non-locality.

Methods: Coupled reaction channel (CRC) calculations provide the elastic channel $S$-matrix $S_{lj}$ due to the included processes. Inversion of $S_{lj}$ will produce the local potential that would yield, in a single channel calculation, the elastic scattering observables from the CRC calculation. Subtracting the bare potential of the CRC calculations gives a local and $l$-independent representation of the dynamical polarization potential (DPP). From the DPPs due to various combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.

Results: Coupling to deuteron channels generates a repulsive component for the real potential and an absorptive component for the imaginary term. The radial shapes of both terms were modified in ways that could not be represented by uniform renormalization; the rms radius of the real part was substantially altered. Evidence of the dynamical nonlocality of the DPP due to pickup is provided by the nonadditivity of contributions of different couplings and other effects. For the doubly closed shell ${}^{208}\mathrm{Pb}$ coupling to low-lying (nongiant) collective states has a very small effect on elastic scattering, making a negligible contribution compared with pickup, and was not included.

Conclusions: The DPPs established here strongly challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of protons from heavy nuclei. Coupling to neutron pickup channels induces dynamical nonlocality in the proton optical model potential with implications for direct reactions.

A systematic analysis of the fusion cross sections around the Coulomb barrier energies with stable weakly bound (${}^6\mathrm{Li},{}^7\mathrm{Li},{}^9\mathrm{Be}$) and strongly bound ${}^{12}\mathrm{C}$ projectiles on various targets was performed by using the neutron flow model and coupled channels approach. The analysis shows that both models are successful in explaining the near barrier fusion data. Further, it is also observed that the collective degrees of freedom as well as the neutron flow influence the near barrier fusion process involving weakly bound projectiles.