The energy levels and $\gamma$-ray decay scheme of the positive-parity states in the $T_z=\frac{1}{2}$ nucleus ${}^{67}\mathrm{As}$ have been studied by using the ${}^{40}\mathrm{Ca}({}^{36}\mathrm{Ar},2\alpha p){}^{67}\mathrm{As}$ reaction at a beam energy of 145 MeV. Two new band structures have been identified which can be connected to the previously known levels. The results for these bands are compared with configuration-dependent cranked Nilsson–Strutinsky calculations. The good level of agreement between theory and experiment suggests that these structures can be interpreted in terms of configurations that involve three ${\mathrm{g}}_{\frac{9}{2}}$ particles and that both possess noncollective terminating states.

We study pairing in low-density neutron matter including the screening interaction due to the exchange of particle-hole and RPA excitations. As bare force, we employ the effective low-momentum interaction $V_{\text{low}k}$, while the Fermi-liquid parameters are taken from a phenomenological energy density functional (SLy4) which correctly reproduces the equation of state of neutron matter. At low density, we find screening, i.e., pairing is reduced, while at higher densities, we find antiscreening, i.e., pairing is enhanced. This enhancement is mostly due to the strongly attractive Landau parameter $f_0$. We discuss in detail the critical temperature $T_c$ in the limit of low densities and show that the suppression of $T_c$ predicted by Gor'kov and Melik-Barkhudarov can only be reproduced if the cutoff of the $V_{\text{low}k}$ interaction is scaled with the Fermi momentum. We also discuss the effect of noncondensed pairs on the density dependence of $T_c$ in the framework of the Nozières-Schmitt-Rink theory.

Background: With the possibility to measure the isoscalar giant monopole resonance (ISGMR) in the short-lived nuclei, the compressibility of the open-shell and exotic nuclei has attracted much attention.

Purpose: The present work is an attempt to develop a semiclassical model to describe the ISGMR and the compressibility of the finite nuclei.

Method: The fluid dynamical reduction of the Boltzmann-Langevin equation was carried out to describe the collective motion of the nucleus [Z. Phys. A 337, 413 (1990); Z. Phys. A 349, 119 (1994)]. In this work, by including the Skyrme energy density functional, we develop the model and apply it to the ISGMR. Both the self-consistent and linearized methods are used to solve the corresponding Langevin equation.

Results: It is shown that the calculations of the ISGMR energies in this work agree with those by the relativistic mean-field theory and the random phase approximation, and reproduce the general trend of the data. The model only includes the two-body dissipation, and underestimates the width of the ISGMR. Twelve sets of the Skyrme interactions are applied to perform the calculations and study the incompressibility parameters in the leptodermous expansion. The calculated surface parameter $K_S$ within the model is smaller than the extracted value, and decreases linearly over mass number of the nucleus. The calculated values of the symmetry parameter $K_{\tau }$ and the Coulomb parameter $K_C$ agree with the extracted values by fitting the available data for the nuclei from ${}^{12}\mathrm{C}$ to ${}^{238}\mathrm{U}$.

Conclusions: The Bohr-Mottelson model provides a reasonable method to understand the ISGMR in a macroscopic approach.

We investigate different formulations of the transmission coefficient $T_c$, including the form implied by Moldauer's “sum rule for resonance reactions” [P. A. Moldauer, Phys. Rev. Lett. 19, 1047 (1967)], the SPRT method [G. Noguere et al., EPJ Web Conf. 146, 02036 (2017)] and the Moldauer-Simonius form [M. Simonius, Phys. Lett. B 52, 279 (1974); P. A. Moldauer, Phys. Rev. 157, 907 (1967)]. Within these different formulations, we compute the neutron transmission coefficients in the resolved and unresolved resonance regions, allowing a direct comparison with the transmission coefficients computed using an optical model potential. For nuclei for which there are no measured resonances, these approaches allow one to predict the average neutron resonance parameters directly from the optical model and level densities. Some of the approaches are valid in both the strong and weak coupling limits (i.e., any value of the average width and mean level spacing). Finally, both the Moldauer-Simonius and Moldauer's sum rule forms approaches suggest that superradiance, that is, the quantum chaotic enhancement of certain channels, may be a common phenomena in nuclear collisions. Our results suggest why superradiance has been previously overlooked. We apply our approach to neutron reactions on the closed shell ${}^{90}\mathrm{Zr}$ nucleus and the midshell ${}^{197}\mathrm{Au}$ nucleus.

Background: Experimental data from heavy-ion experiments at RHIC-BNL and LHC-CERN are quantitatively described using relativistic fluid dynamics. Even $p+A$ and $p+p$ collisions show signs of collective behavior describable in the same manner. Nevertheless, small system sizes and large gradients strain the limits of applicability of fluid-dynamical methods.

Purpose: The range of applicability of fluid dynamics for the description of the collective behavior, and in particular of the elliptic flow, of small systems needs to be explored.

Method: Results of relativistic fluid-dynamical simulations are compared with solutions of the Boltzmann equation in a longitudinally boost-invariant picture. As the initial condition, several different transverse energy-density profiles for equilibrated matter are investigated.

Results: While there is overall a fair agreement of energy- and particle-density profiles, components of the shear-stress tensor are more sensitive to details of the implementation. The highest sensitivity is exhibited by quantities influenced by properties of the medium at freeze-out.

Conclusions: For some quantities, like the shear-stress tensor, agreement between fluid dynamics and transport theory extends into regions of Knudsen numbers and inverse Reynolds numbers where relativistic fluid dynamics is believed to fail.

New results on the single-differential and fully integrated cross sections for the process ${\gamma }_{v}p\to p^{\prime }{\pi }^{+}{\pi }^{-}$ are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass $W$ from 1.3 to 1.825 GeV and the photon virtuality $Q^2$ from 0.4 to 1.0 ${\mathrm{GeV}}^2$. The cross sections were obtained in narrow $Q^2$ bins (0.05 ${\mathrm{GeV}}^2$) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the $Q^2$ evolution of the electrocouplings of most resonances with masses up to $\sim 1.8$ GeV.

Background: Extracting the proton charge radius from electron scattering data requires determining the slope of the charge form factor at $Q^2$ of zero. As experimental data cannot reach that limit, numerous methods for making the extraction have been proposed.

Purpose: In this study, we seek to find functional forms that will allow a robust extraction of the proton radius from a wide variety of functional forms. The primary motivation of this study is to have confidence in the extraction of upcoming low-$Q^2$ experimental data.

Method: We create a general framework for studying various form-factor functions along with various fitting functions. The input form factors are used to generate pseudodata with fluctuations mimicking the binning and random uncertainty of a set of real data. All combinations of input functions and fit functions can then be tested repeatedly against regenerated pseudodata. Since the input radius is known, this allows us to find fitting functions that are robust for proton radius extractions in an objective fashion.

Results: For the range and uncertainty of the PRad data, we find that a two-parameter rational function, a two-parameter continued fraction, and the second-order polynomial expansion of $z$ can extract the input radius regardless of the input charge form factor function that is used.

Conclusions: We have created a framework to determine which functional forms allow a robust extraction of the radius from pseudodata generated from a wide variety of trial functions. By taking into account both bias and variance, the optimal functions for extracting the proton radius can be determined.

$\beta$-decay properties of neutron-rich Ca, Ti, and Cr isotopes are studied within a deformed proton-neutron quasiparticle random-phase approximation. The underlying mean field is described self-consistently from deformed Skyrme Hartree-Fock calculations with pairing correlations. Residual spin-isospin interactions in the particle-hole and particle-particle channels are also included in the formalism. The energy distributions of the Gamow-Teller strength, the $\beta$-decay feedings, the $\beta$-decay half-lives, and the $\beta$-delayed neutron emission probabilities are discussed and compared with other theoretical results, as well as with the available experimental information. The evolution of these nuclear $\beta$-decay properties is investigated in isotopic chains in a search for structural changes. A reliable estimate of the $\beta$-decay properties in this mass region is valuable information for evaluating decay rates in astrophysical scenarios.

We study the mechanism of the weak decay process of ${\mathrm{\Xi }}_b^0$ into $D^0$ with a meson-baryon pair. It is shown that the dominant component of the prompt weak decay produces the meson-baryon pair with the spectator strange quark being transferred to the baryon, so that the $\overline{K}N$ channel is absent. Subsequent final state interaction then reflects the $\pi \mathrm{\Sigma }$ originated $\mathrm{\Lambda }\left(1405\right)$ formation amplitude, which has been difficult to access in previous experimental studies. We predict the line shapes of the $\pi \mathrm{\Sigma }$ invariant mass distribution using a realistic chiral meson-baryon amplitude for the final state interaction. It is shown that the interference between the direct and the rescattering contributions can strongly distort the peak structure of the $\mathrm{\Lambda }\left(1405\right)$ in the mass distribution. This indicates the necessity of a detailed investigation of the reaction mechanism in order to extract the $\mathrm{\Lambda }\left(1405\right)$ property in the $\pi \mathrm{\Sigma }$ mass distribution.

The new version of the Liège intranuclear-cascade model (INCL), recently extended to the production of strange particles and hypernuclei, is used to investigate the $\mathrm{\Lambda }$-nucleus potential in a broad range of nuclear masses from Si to Pb. The combination of the INCL calculation results with experimental cross sections of $\mathrm{\Lambda }$ hypernuclei, obtained from (${\pi }^{+},K^{+}$) reaction studies, allows us to constrain the $\mathrm{\Lambda }$-nucleus potential depth with an accuracy of about 0.9 MeV. Our results show that the potential depth increases with the mass number ($A$) from 28 MeV in the region of medium-mass hypernuclei up to a maximum of 39.6 MeV in the region of heavy hypernuclei around $A=208$. This deviation could be related to the nucleon-isospin dependence of the three-body $\mathrm{\Lambda }$-nucleon-nucleon force in asymmetry matter whose contribution is more relevant in hyperneutron matter due to a strong contribution from $\mathrm{\Lambda }nn$ interactions.

This paper presents a measurement of jet fragmentation functions in 0.49 ${\mathrm{nb}}^{-1}$ of Pb+Pb collisions and 25 ${\mathrm{pb}}^{-1}$ of $pp$ collisions at $\sqrt{s_{\mathit{\text{NN}}}}=5.02 \text{TeV}$ collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultrarelativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in $pp$ collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 and 398 $\text{GeV}$ and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet transverse momentum. Yields of particles carrying a very large fraction of the jet momentum are also observed to be enhanced. Between these two enhancements of the fragmentation functions a suppression of particles carrying an intermediate fraction of the jet momentum is observed in Pb+Pb collisions. A small dependence of the modifications on jet rapidity is observed.

We calculate the production of prompt and thermal photons from $\text{Pb}+\text{Pb}$ collisions at $5.02A$ TeV at the Large Hadron Collider (LHC) and at $39A$ TeV at the proposed Future Circular Collider (FCC) facility. The photon spectra and anisotropic flow at these energies are compared with the results obtained from $2.76A$ TeV $\text{Pb}+\text{Pb}$ collisions at the LHC for three different centrality bins. The prompt photons originating from initial hard scatterings are found to increase by a factor of 1.5 to 2 at $5.02A$ TeV in the $p_T$ region 2 to 15 GeV and the enhancement is found to be about 5 to 15 times at FCC energies compared with $2.76A$ TeV in the same $p_T$ region. The evolution of the quark-gluon plasma (QGP) formed in $\text{Pb}+\text{Pb}$ collisions at LHC and FCC energies are studied by using a hydrodynamical model and the $p_T$ spectra and elliptic flow of thermal photons are calculated using state-of-the-art photon rates. The relative enhancement in the production of thermal photons is found to be more compared with prompt photons at FCC than at the LHC energies. Although the production of direct (prompt + thermal) photons is found to enhance significantly with increase in beam energy, the photon elliptic flow increases only marginally and does not show strong sensitivity to the collision energy.

We present a novel and simple algorithm in the variation after projection (VAP) approach for the non-yrast nuclear states. It is the first time that the yrast state and non-yrast states can be varied on the same footing. The orthogonality among the calculated states is automatically fulfilled by solving the Hill-Wheeler equation. This avoids the complexity of the frequently used Gram-Schmidt orthogonalization, as adopted by the excited VAMPIR method. Thanks to Cauchy's interlacing theorem in matrix theory, the sum of the calculated lowest projected energies with the same quantum numbers can be safely minimized. Once such minimization is converged, all the calculated energies and corresponding states can be obtained, simultaneously. The present VAP calculations are performed with time-odd Hartree-Fock Slater determinants. It is shown that the calculated VAP energies (both yrast and non-yrast) are very close to the corresponding ones from the full shell model calculations. It appears the present algorithm is not limited to the VAP, but should be universal, i.e., one can do the variation with different forms of the many-body wave functions to calculate the excited states in different quantum many-body systems.

I have used a simple model to compute matter radii for ${}^{16–23}\mathrm{N}$, paying special attention to the configurations of the valence neutron(s). I compare results with recent predictions and with earlier matter radii extracted from measurements of interaction cross sections. The present calculations are closer to the experimental radii than any of the results from the other procedures.

We have identified the most probable projectile-target combination by studying the fusion cross section, evaporation residue cross section, compound nucleus formation probability ($P_{\mathrm{CN}}$), and survival probability ($P_{\mathrm{Surv}}$) of different projectile target combinations to synthesize the superheavy element $Z=122$. The selected most probable projectile-target combinations to synthesize the superheavy element $Z=122$ are $\mathrm{Cr}+\mathrm{Cf}$, $\mathrm{Fe}+\mathrm{Cm}$, $\mathrm{Se}+\mathrm{Ra}$, and $\mathrm{As}+\mathrm{Ac}$. Superheavy nuclei may decay through the different decay modes such as spontaneous fission, ternary fission, and cluster decay. We have also studied the half-lives of spontaneous fission, ternary fission, and cluster decay of the predicted nuclei for $Z=122$ and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay, and alpha decay in the superheavy nuclei of $Z=122$. The comparision of half lives for different decay modes reveals that alpha decay is having smaller half lives than the other studied decay modes. A detail study of branching ratio of alpha decay with respect to other decay modes also confirms that alpha decay is most dominant decay mode for the isotopes superheavy nuclei ${}^{307–314}122$ and hence these nuclei can be detected through the alpha decay mode only. We hope that our predictions may be guide for the future experiments in the synthesis of more isotopes of superheavy nuclei $\mathrm{Z}=122$.

Background: ${}^{32}\mathrm{Cl}$ is a neutron-deficient isotope with a $\beta$-decay half-life of 298 ms and a spin and parity of $J^{\pi }=1^{+}$. Previous measurements of ${}^{32}\mathrm{Cl} \beta$-delayed $\gamma$ rays have yielded a $\beta$-decay scheme with twelve $\beta$-decay transitions, contributing to studies of nuclear structure and fundamental symmetries. Those experiments have been limited to the observation of ${}^{32}\mathrm{S}$ states with $J^{\pi }=0^{+},1^{+},2^{+}$.

Purpose: Our goal is to search for new $\beta$-delayed $\gamma$ rays and $\beta$-decay transitions of ${}^{32}\mathrm{Cl}$ to ${}^{32}\mathrm{S}$.

Methods: A measurement of ${}^{32}\mathrm{Cl} \beta$-delayed $\gamma$ decay has been performed using the Clovershare array of high-purity germanium detectors at the National Superconducting Cyclotron Laboratory.

Results: By acquiring the highest-statistics ${}^{32}\mathrm{Cl} \beta$-delayed $\gamma$-ray spectrum to date and exploiting a new sensitivity to $\gamma -\gamma$ coincidences, this experiment has enabled the observation of nine previously unobserved $\beta$-delayed $\gamma$-ray transitions, leading to the inference of five $\beta$-decay transitions never before observed in ${}^{32}\mathrm{Cl} \beta$-delayed $\gamma$ decay. The set of observed states includes negative-parity states for the first time. By combining the new information with data from previous work, the lifetimes and partial widths of the 8861- and 9650-keV states of ${}^{32}\mathrm{S}$ have been determined. In addition, the ${}^{31}\mathrm{P}(p,\alpha ){}^{28}\mathrm{Si}$ resonance strength of the 9650-keV state has been limited to $\omega \gamma <9.8$ meV, which is an improvement over direct measurements.

Conclusion: An enhanced decay scheme has been constructed. Most of the excited bound ${}^{32}\mathrm{S}$ states that would correspond to allowed and first-forbidden $\beta$-decay transitions have been observed, demonstrating the potential of $\beta$-decay experiments to approach complete spectroscopy measurements at the next generation of radioactive beam facilities. The observed positive-parity levels are well matched by $sd$ shell-model calculations.

We performed the first direct mass measurements of neutron-rich vanadium ${}^{52–55}\mathrm{V}$ isotopes passing the $N=32$ neutron shell closure with TRIUMF's Ion Trap for Atomic and Nuclear science. The new direct measurements confirm all previous indirect results. Through a reduced uncertainty of the mass of ${}^{55}\mathrm{V}$ we confirm the quenching of the $N=32$ neutron shell closure in vanadium. We discuss the evolution of the $N=32$ neutron shell closure between K and Cr and show similar signatures in the half-life surface when studied along the isotopic chains.

The beam energy dependence of net baryon number susceptibilities is studied in the framework of the hadron resonance gas model with the attractive and repulsive van der Waals interactions between baryons. The collision energy dependences for the skewness $S\sigma$ and kurtosis $\kappa {\sigma }^2$ deviate significantly from the Poisson baseline and demonstrate the existence of rich structures at moderate collision energies. This behavior may result from the critical end point of the nuclear liquid-gas first-order phase transition. In particular, $\kappa {\sigma }^2$ shows a nonmonotonic energy dependence, and, in contrast to the standard scenario for the QCD critical point, it does not decrease at low collision energies. It is also found that the measurable net proton fluctuations differ significantly from the net baryon fluctuations when interactions between baryons cannot be neglected. The results are compared with the experimental net proton number fluctuations measured by the STAR collaboration.

Background: Earlier measurements of fission lifetimes of the highly excited uraniumlike nuclei by K x-ray fluorescence and crystal blocking techniques obtained slow fission (fission time $\sim {10}^{-18}\mathrm{s}$) for most of the fission events and were shown to be incompatible with the very short fission time ($\sim {10}^{-20}\mathrm{s}$) obtained by the nuclear techniques and also with the very small (≤5%) percentage of such slow fission events predicted by simple statistical models. One weakness of the earlier fluorescence experiments is that the observed K x-ray peaks were very broad [full width at half maximum $\left(\mathrm{FWHM}\right)\approx 15\mathrm{keV}$] and the precise energies of the relevant K x-ray lines could not be determined from such measurements.

Purpose: The purpose is to look at the relevant K x-ray energy region in coincidence with the fission fragments with a high resolution (≈1 keV) spectrometer to obtain evidence of slow fission and determine its percentage.

Method: Highly excited plutonium nuclei were produced in the fusion of ${}^4\mathrm{He}+{}^{238}\mathrm{U}$ at $E{\left({}^4\mathrm{He}\right)}_{\mathrm{Lab}}=60\mathrm{MeV}$. The intrinsic width of plutonium K x-ray lines in coincidence with the fission fragments was determined as a direct measure (or lower limit) of the fission time of the slow ($\sim {10}^{-18}\mathrm{s}$) fission events. The minimum percentage of slow fission events has been determined from the K x-ray multiplicity per fission event and the probability of creation of K-orbital vacancies in plutonium.

Results: A narrow peak (FWHM ≈ 1 keV) observed in the coincidence photon spectrum at (102.8 ± 0.5) keV, just below the characteristic plutonium $K_{\alpha 1}$ line (103.7 keV) has been attributed to the plutonium $K_{\alpha 1}$ line on the basis of supporting evidence and calculations and we deduce that most of the fission events are slow (fission time $>{10}^{-18}\mathrm{s}$). No peak has been observed exactly at 103.7 keV.

Conclusions: The shift [(0.9 ± 0.5) keV] of plutonium K x-ray lines is plausible, if the fissioning plutonium nucleus spends most of its long fission time in a highly deformed dumbbell shape (beyond saddle) and the corresponding results are in agreement with those obtained earlier by the atomic techniques. Alternatively, if no significant shift of plutonium K x-ray lines can be expected, the absence of a peak at 103.7 keV contradicts earlier atomic technique claims of a significant percentage of slow fission events.

We develop a new dynamical model for high-energy heavy-ion collisions in the beam energy region of the highest net-baryon densities on the basis of nonequilibrium microscopic transport model jam and macroscopic ($3+1$)-dimensional hydrodynamics by utilizing a dynamical initialization method. In this model, dynamical fluidization of a system is controlled by the source terms of the hydrodynamic fields. In addition, time-dependent core-corona separation of hot regions is implemented. We show that our new model describes multiplicities and mean transverse mass in heavy-ion collisions within a beam-energy region of $3<\sqrt{s_{NN}}<30$ GeV. Good agreement of the beam-energy dependence of the $K^{+}/{\pi }^{+}$ ratio is obtained, which is explained by the fact that a part of the system is not thermalized in our core-corona approach.