A formalism for the study of charge-symmetry-breaking (CSB) effects is discussed and used to analyze the effects of charge-symmetry breaking on neutron $\beta$ decay. The effect of including CSB reduces the $\beta$-decay matrix element by an amount on the order of ${10}^{-4}$, a value much larger than the previous estimate. The earlier calculation used the neutron-proton mass difference as the CSB operator instead of the matrix element of the sum of the individual terms between the ground and excited states. The electromagnetic and dynamic effects of the up-down quark mass difference oppose the up-down quark mass difference leading to a small $n-p$ mass difference, but add coherently in computing the excitation matrix elements causing large enhancements. The current uncertainty in the value of $V_{ud}$ is also on the order of ${10}^{-4}$. An improvement of that uncertainty by an order of magnitude would require that charge-symmetry-breaking effects should be included in future analyses.

Employing the ${}^{11}\mathrm{B}(p,\gamma ){}^{12}\mathrm{C}$ nuclear reaction, the angular correlation of $e^{+}{e}^{-}$ pairs was investigated in the angular range of ${40}^{\circ }\le \mathrm{\Theta }\le {175}^{\circ }$ for five different proton energies between $E_p=1.50$–2.5 MeV. At small angles ($\mathrm{\Theta }\le {120}^{\circ }$), the results can be well interpreted by the internal pair creation process of electromagnetic radiations with $E1$ and $M1$ multipolarities and by the external pair creation in the target backing. However, at angles greater than ${120}^{\circ }$, additional count excesses and anomalies were observed, which could be well accounted for by the existence of the previously suggested hypothetical X17 particle. Our results suggest that the X17 particle was generated mainly in $E1$ radiation. The derived mass of the particle is $m_{\mathrm{X}}{c}^2=17.03\pm 0.11\left(\mathrm{stat}\right)\pm 0.20\left(\mathrm{syst}\right)$ MeV. According to the mass, and to the derived branching ratio [$B_x=3.6\left(3\right)\times {10}^{-6}$], this is likely the same X17 particle that we recently suggested for describing the anomaly observed in the decay of ${}^8\mathrm{Be}$ and ${}^4\mathrm{He}$.

The influence of nucleon-nucleon short-ranged correlations (SRC) on nuclear superallowed $\beta$ decay is examined. The need for this is driven by the observed depletion of spectroscopic strength obtained in studies of $(e,e^{\prime })$ and $(d,{}^3\mathrm{He})$ reactions on a wide variety of nuclei. We show that the influence of SRC is model dependent, but may be very substantial. The ${}^{46}\mathrm{V}$ nucleus is used as an example. The resulting impact on studies of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element is discussed.

The available data on some actinide nuclei point to certain significant features of the rotational yrast band and other excited bands. The rotational properties of plutonium isotopes (${}^{236–346}\mathrm{Pu}$) were studied via projected shell model (PSM). Calculations are based on the Hamiltonian of the PSM which includes the formed part of a single particle, the $Q-Q$ force, and the residual interaction of monopole and quadrupole pairings. The results of the calculated energy levels of the yrast band are then compared with available experimental data and a good agreement has been found. The crossing between two-quasiparticle (2qp) excited bands and the ground state band (g band) in the high-spin regions has been analyzed in terms of band diagrams. The upbendings observed in the kinematic moments of inertia ($j^{\left(1\right)}$ MOI) curves for ${}^{236–346}\mathrm{Pu}$ isotopes are due to the effect of two aligning nucleons that occupy excited bands and the $\nu (j_{15/2}$), $\pi (i_{13/2}$) high-$j$ intruder orbits. The PSM successfully reproduces the observed upbending in $j^{\left(1\right)}$ as well as the upturning and downturning in $j^{\left(2\right)}$. For the ${}^{240}\mathrm{Pu}$ isotope, the PSM predicts a simultaneous alignment of neutrons ${\nu }^2 [1/2,-7/2] K^{\pi }$ = $4^{+}$ and protons ${\pi }^2 [-3/2,5/2] K^{\pi }$ = $1^{+}$ bands cross the g band at spin $I=22$. We expect it to be mainly responsible for the disagreement at $I=22$. Furthermore, electric quadrupole transition probabilities $B\left(E2\right)$ and the gyromagnetic factor ($g$ factor) for the yrast band energy levels are also studied.

We study the quasifission barriers of different fusion reactions leading to synthesis of the superheavy element $Z=120$ using the dinuclear system approach. In particular, the influence of the projectile-target orientation and angular momentum on quasifission barriers has been investigated. The quasifission barrier height is observed to be maximum when the angle of orientation of projectile-target is about ${90}^{\circ }$ (tip-tip orientation). The role of entrance channel effects on quasifission barriers is investigated, and also suggested are suitable empirical formulas for the same. The striking results leading to larger quasifission barriers, whose cross sections are $>10$ fb, are also mentioned. As a result, the current research might be valuable in developing corrective techniques for future experimental attempts to synthesize superheavy nuclei with $Z=120$.

The recent discovery of carbon enhanced metal poor (CEMP) stars leaves open questions as to how carbon, nitrogen, and oxygen (CNO) elements were enriched through the nucleosynthesis of primordial elements in the first stars. It has been proposed that the reaction sequence ${}^6\mathrm{Li}(\alpha ,\gamma ){}^{10}\mathrm{B}(\alpha ,d){}^{12}\mathrm{C}$ may offer an alternative path to the traditional triple-$\alpha$ process, taking advantage of $\alpha$ cluster configurations in the ${}^{10}\mathrm{B}$ and ${}^{14}\mathrm{N}$ compound nuclei. In the present study, an investigation of the low-energy ${}^6\mathrm{Li}(\alpha ,\gamma ){}^{10}\mathrm{B}$ cross section is performed using a combination of different $\gamma$ ray detectors. The discrepancies in the literature of the width of the broad resonance ($E_{\text{c.m.}}=1200$ keV, $1_3^{+}$) are resolved. A consistent and much more precise width, ${\mathrm{\Gamma }}_{\alpha }=125\left(8\right)$ keV, is obtained via a simultaneous $R$-matrix fit of the data from the present study and that reported previously in the literature. The uncertainty in the tail contribution of the broad resonance indicates that a substantial increase in the low temperature reaction rate is possible compared to that adopted by the REACLIB compilation.

The Coulomb excitation of ${}^{102}\mathrm{Ru}$ was performed with beams of ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ ions. The beam particles scattered at forward angles were momentum analyzed with a magnetic spectrograph. The resolution achieved enabled the populations of the $2_1^{+}$ state, the unresolved $2_2^{+}/4_1^{+}$, and $2_4^{+}/3_1^{-}$, doublets of states, and the $3_2^{-}$ state to be determined as a function of the scattering angle. These populations are compared with gosia calculations, yielding $B(E2;2_1^{+}\to 0_1^{+})=41.5\pm 2.3$ W.u., $B(E2;2_2^{+}\to 0_1^{+})=1.75\pm 0.11$ W.u., $B(E3;3_1^{-}\to 0_1^{+})=31.5\pm 3.5$ W.u., and $B(E3;3_2^{-}\to 0_1^{+})=6.8\pm 0.5$ W.u. The $B(E3;3_1^{-}\to 0_1^{+})$ value is significantly larger than previously measured. The weakly populated $2_3^{+}$ state, presumed to be a member of the band built on the $0_2^{+}$ state, was observed clearly for a single angle only, and a fit to its population results in $B(E2;2_3^{+}\to 0_1^{+})=0.053\pm 0.011$ W.u. Using the known $\gamma$-ray branching ratios for the $2_3^{+}$ level, the $B(E2;2_3^{+}\to 0_2^{+})$ value is calculated to be $18\pm 4$ W.u., substantially less than the $B(E2;2_1^{+}\to 0_1^{+})$. This suggests that the deformation of the $0_2^{+}$ state is lower than that of the $0_1^{+}$ state. The results are compared with beyond-mean-field calculations with the Gogny-D1S interaction using the symmetry-conserving configuration-mixing method.

A measurement of the ${}^{54}\mathrm{Fe}(d,p){}^{55}\mathrm{Fe}$ reaction at 16 MeV was performed using the Florida State University Super-Enge Split-Pole Spectrograph to determine single-neutron energies for the $2p_{3/2}, 2p_{1/2}, 1f_{5/2}, 1g_{9/2}$, and $2d_{5/2}$ orbits. Two states were observed that had not been observed in previous ($d,p$) measurements. In addition, we made angular momentum transfer, $L$, assignments to four states and changed $L$ assignments from previous ($d,p$) measurements for nine more states. The spin-orbit splitting between the $2p_{3/2}$ and $2p_{1/2}$ orbits is similar to that in the other $N=29$ isotones and not close to zero as a previous measurement suggested. While the $1f_{5/2}$ single neutron energy is significantly lower in ${}^{55}\mathrm{Fe}$ than in ${}^{51}\mathrm{Ti}$, as predicted by a covariant density functional theory calculation, the single-neutron energy for this orbit in ${}^{55}\mathrm{Fe}$ is more than 1 MeV higher than the calculation suggests, although it is only 400 keV above the $2p_{1/2}$ orbit. The summed spectroscopic strength we observed for the $1g_{9/2}$ orbit up to the single-neutron separation energy of 9.3 MeV is only 0.3. This is surprising because the $1g_{9/2}$ orbit is predicted by Togashi et al. to be located only 5.5 MeV above the $2p_{3/2}$ orbit.

Cross sections of the ${}^{91}\mathrm{Zr}(n,\alpha ){}^{88}\mathrm{Sr}$ reaction were measured at four incident neutron energies in the range of 3.9 to 5.3 MeV. The experiment was carried out on the Van de Graaff accelerator EG-5 at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Russia. Fast neutrons were produced via the ${}^2\mathrm{H}(d,n){}^3\mathrm{He}$ reaction with a deuterium gas target. A twin gridded ionization chamber (GIC) was used as the charged particle detector, in which ${}^{91}\mathrm{Zr}$ back-to-back samples on a tantalum backing were placed at the common cathode. The relative and absolute neutron fluxes were measured using two ${}^{238}\mathrm{U}_3{\mathrm{O}}_8$ samples inside the GIC. Cross-section data obtained in this measurement were compared with those in existing data library and from theoretical calculations using talys code. The present data for the ${}^{91}\mathrm{Zr}(n,\alpha ){}^{88}\mathrm{Sr}$ reaction should be helpful in clarifying the discrepancies in various published nuclear evaluation data. An alpha clustering factor is calculated using the statistical model and knock-on mechanism.

The neutron-deficient Ca isotopes continue to attract attention due to their importance for testing isospin symmetry and their relevance in capture reactions of interest for nova nucleosynthesis and the shape of light curves in Type I x-ray bursts. To date, spectroscopic information on ${}^{38,39}\mathrm{Ca}$ is largely limited to data on lower-spin excited states. Here, we report in-beam $\gamma$-ray spectroscopy of complementary higher-spin, complex-structure states in ${}^{39}\mathrm{Ca}$ populated in fast-beam-induced, momentum-dissipative processes leading to neutron pickup onto excited configurations of the projectile, ${}^9\mathrm{Be}({}^{38}\mathrm{Ca}^{*},{}^{39}\mathrm{Ca}+\gamma )X$. Such a dissipative reaction was recently characterized for the case of inelastic scattering of ${}^{38}\mathrm{Ca}$ off ${}^9\mathrm{Be}, {}^9\mathrm{Be}({}^{38}\mathrm{Ca}, {}^{38}\mathrm{Ca}+\gamma )X$. Additional data and discussion on the nuclear structure of ${}^{38}\mathrm{Ca}$ is also presented. An explanation for the more-complex-structure states, populated with small cross sections in one-nucleon knockout reactions, and observed in the tails of their longitudinal momentum distributions, is also offered.

The low-energy structure and $\beta$-decay properties of neutron-rich even- and odd-mass Pd and Rh nuclei are studied using a mapping framework based on the nuclear density-functional theory and the particle-boson coupling scheme. Constrained Hartree-Fock-Bogoliubov calculations using the Gogny-D1M energy density functional are performed to obtain microscopic inputs to determine the interacting-boson Hamiltonian employed to describe the even-even core Pd nuclei. The mean-field calculations also provide single-particle energies for the odd systems, which are used to determine essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. The potential-energy surfaces obtained for even-even Pd isotopes as well as the spectroscopic properties for the even- and odd-mass systems suggest a transition from prolate deformed to $\gamma$-unstable and to nearly spherical shapes. The predicted $\beta$-decay $logft$ values are shown to be sensitive to the details of the wave functions for the parent and daughter nuclei and therefore serve as a stringent test of the employed theoretical approach.

The lifetimes of the first excited $4^{+}$ and $6^{+}$ states in ${}^{212}\mathrm{Po}$ were measured using the recoil-distance Doppler shift method. The nucleus of interest was populated in the ${}^{208}\mathrm{Pb}({}^{18}\mathrm{O},{}^{14}\mathrm{C}){}^{212}\mathrm{Po}$ reaction. The experimental results are compared to large-scale shell model calculations performed using the recently developed H208 effective interaction. The calculations describe well the low-lying structure of ${}^{212}\mathrm{Po}$ with an exception of the $2_1^{+}\to 0_1^{+}$ transition rate which is strongly overestimated. This has been attributed to additional components in the wave function of the ground state.

In this paper, we present results of the second experiment on the synthesis of Mc isotopes in the ${}^{243}\mathrm{Am}+{}^{48}\mathrm{Ca}$ reaction performed at the gas-filled separator DGFRS-2 of the SHE Factory at JINR. The new isotope ${}^{286}\mathrm{Mc}$ was synthesized, and its half-life of $20\begin{array}{c}+98\\ -9\end{array}$ ms and α-particle energy of $10.71\pm 0.02$ MeV were determined. A ${}^{286}\mathrm{Mc} \alpha \text{−}\mathrm{decay}$ chain was recorded down to the spontaneous fission of ${}^{266}\mathrm{Db}$. The spontaneous fission of ${}^{279}\mathrm{Rg}$ was observed for the first time in one of four new decay chains of ${}^{287}\mathrm{Mc}$. The excitation function of the reaction was measured at three ${}^{48}\mathrm{Ca}$ energies of 242, 250, and 259 MeV; the latter resulted in the first observation of the $5n\text{−}\mathrm{evaporation}$ channel with a cross section of $0.5_{-0.4}^{+1.3}$ pb. The decay properties of 21 previously known $\mathrm{odd}\text{−}Z$ isotopes were improved. The potential for an electron-capture decay mode is discussed for ${}^{288}\mathrm{Mc}$ and ${}^{284}\mathrm{Nh}$ isotopes. The half-lives of spontaneously fissioning nuclei produced in the ${}^{48}\mathrm{Ca}\text{−}\mathrm{induced}$ reactions with actinide targets are compared with several theoretical predictions.

Energetic partons traveling in a strongly interacting medium lose energy by emitting radiation and through collisions with medium constituents. Nonperturbative, next-to-leading-order and leading-order collision kernels are implemented within AMY-McGill formalism. The resulting gluon emission rates are then evaluated and compared by considering scattering occurring in a brick of quark-gluon plasma, as well as in a realistic simulation of $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s}=2.76$ ATeV using martini. We find that the variations in quenching of hard partons resulting from using different kernels can be important, depending on the overall value of the strong-coupling constant ${\alpha }_{\mathrm{s}}$.

Strong interaction energy shifts and widths in kaonic atoms are calculated for the first time using microscopic $K^{-}N+K^{-}NN$ potentials derived from $K^{-}N$ scattering amplitudes constructed within SU(3) chiral coupled-channels models of meson-baryon interactions. The in-medium modifications of the free-space amplitudes due to the Pauli correlations are taken into account. The $K^{-}N+K^{-}NN$ potentials evaluated for 23 nuclear species are confronted with kaonic atoms data. The description of the data significantly improves when the $K^{-}NN$ absorption is included. To get ${\chi }^2$ as low as for the $K^{-}N+$ phenomenological multinucleon potential an additional phenomenological term, accounting for $K^{-}-3N\left(4N\right)$ processes, is still needed. However, density dependence of this phenomenological term points out some deficiencies in the microscopic potentials, and further improvements of the applied model are thus desirable. The calculated branching ratios for $K^{-}N$ and $K^{-}NN$ absorption channels in the ${}^{12}\mathrm{C}+K^{-}$ atom are in reasonable agreement with the old bubble chamber data, as well as with the latest data from the AMADEUS Collaboration.

Neutrinoless double beta decay searches can determine the Majorana nature of neutrinos, the absolute neutrino mass, and provide invaluable insights on the matter dominance of the universe. However, the uncertainty in the nuclear matrix elements that govern the decay limits the physics reach of these experiments. We devise a novel framework based on the generalized contact formalism that combines the nuclear shell model and quantum Monte Carlo methods and compute the neutrinoless double-beta decay of nuclei used in the most advanced experiments, including ${}^{76}\mathrm{Ge}, {}^{130}\mathrm{Te}$, and ${}^{136}\mathrm{Xe}$. Our results cover all relevant terms, including the leading-order short-range operator recognized recently. We validate our method in light nuclei by comparing against accurate variational Monte Carlo results. On heavy systems we obtain reduced nuclear matrix elements compared with previous calculations due to additional correlations captured by quantum Monte Carlo and introduced within the generalized contact formalism, suggesting longer decay half-lives than previously considered. On the other hand, we find an enhancement of the nuclear matrix elements due to the new short-range operator.

We present a comprehensive investigation of few-nucleon systems as well as light and medium-mass nuclei up to $A=48$ using the current Low Energy Nuclear Physics International Collaboration two-nucleon interactions in combination with the third-order (${\mathrm{N}}^2\mathrm{LO}$) three-nucleon forces. To address the systematic overbinding of nuclei starting from $A\approx 10$ found in our earlier study utilizing the ${\mathrm{N}}^2\mathrm{LO}$ two- and three-nucleon forces, we take into account higher-order corrections to the two-nucleon potentials up through fifth order in chiral effective field theory. The resulting Hamiltonian can be completely determined using the $A=3$ binding energies and selected nucleon-deuteron cross sections as input. It is then shown to predict other nucleon-deuteron scattering observables and spectra of light $p$-shell nuclei, for which a detailed correlated truncation error analysis is performed, in agreement with experimental data. Moreover, the predicted ground state energies of nuclei in the oxygen isotopic chain from ${}^{14}\mathrm{O}$ to ${}^{26}\mathrm{O}$ as well as ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$ show a remarkably good agreement with experimental values, given that the Hamiltonian is fixed completely from the $A\le 3$ data, once the fourth-order (${\mathrm{N}}^3\mathrm{LO}$) corrections to the two-nucleon interactions are taken into account. On the other hand, the charge radii are found to be underpredicted by $\approx 10\%$ for the oxygen isotopes and by almost $20\%$ for ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$.

High-spin states in ${}^{74}\mathrm{As}$ were studied using the ${}^{74}\mathrm{Ge}({}^4\mathrm{He},1p3n)$ reaction at beam energies of 58.6 and 62.6 MeV. Two positive- and one negative-parity bands have been identified in ${}^{74}\mathrm{As}$. The two positive-parity bands are interpreted as chiral doublet bands, which is supported by the triaxial particle rotor model. Three electric dipole transitions linking the yrast positive- and negative-parity bands were also observed in this work, suggesting the existence of octupole correlations in ${}^{74}\mathrm{As}$.

We use a Bayesian-calibrated multistage viscous hydrodynamic model to explore deuteron yield, mean transverse momentum and flow observables in Pb-Pb collisions at the Large Hadron Collider. We explore theoretical uncertainty in the production of deuterons, including (i) the contribution of thermal deuterons, (ii) models for the subsequent formation of deuterons (hadronic transport vs coalescence), and (iii) the overall sensitivity of the results to the hydrodynamic model, in particular to bulk viscosity, which is often neglected in studies of deuteron production. Using physical parameters set by a comparison to only light hadron observables, we find good agreement with measurements of the mean transverse momentum $\langle p_T\rangle$ and elliptic flow $v_2$ of deuterons; however, tension is observed with experimental data for the deuteron multiplicity in central collisions. The results are found to be sensitive to each of the mentioned theoretical uncertainties, with a particular sensitivity to bulk viscosity, indicating that the latter is an important ingredient for an accurate treatment of deuteron production.