A concept to search for a neutron electric dipole moment (nEDM) is presented, which employs a pulsed neutron beam instead of the established use of storable ultracold neutrons (UCN). The technique takes advantage of the high peak flux and the time structure of a next-generation pulsed spallation source like the planned European Spallation Source. It is demonstrated that the sensitivity for a nEDM can be improved by several orders of magnitude compared to the best beam experiments performed in the 1970s and can compete with the sensitivity of UCN experiments.

The decay of ${}^{84}$Ga has been reinvestigated at the PARRNe online mass separator of the electron-driven installation ALTO at IPN Orsay. The nominal primary electron beam of 10 $\mu$A (50 MeV) on a ${}^{238}$UC${}_x$ target in combination with resonant laser ionization were used for the first time at ALTO. Improved level schemes of the neutron-rich ${}^{83,84}$Ge ($Z=32$) isotopes were obtained. The experimental results are compared with the state-of-the-art shell model calculations and discussed in terms of collectivity development in the natural valence space outside the ${}^{78}$Ni core.

Nuclear shell model predictions for the proton spectroscopic factor of the $1^{+}$, $E_x=5.68$ MeV level in ${}^{26}$Si are about 50 times smaller than the value suggested by the measured ($\alpha$,${}^3$He) cross section for the $E_x=5.69$ MeV mirror level in ${}^{26}$Mg, assuming purely single-particle transfer. Given that the 5.69 MeV level has been very weakly, if at all, populated in previous studies of the simpler ${}^{25}$Mg($d,p$) reaction, it is unclear if the ($\alpha$,${}^3$He) result is a true single-particle spectroscopic factor. If we assume the ($\alpha$,${}^3$He) result, the thermonuclear rate of the ${}^{25}$Al($p$,$\gamma$)${}^{26}$Si reaction would increase by factors of $\approx 6–50$ over stellar temperatures of $T\approx 0.05–0.2$ GK. We examine the implications of this enhanced rate for model predictions of nucleosynthesis in classical nova explosions.

The isoscalar (IS) and isovector (IV) quadrupole responses of nuclei are systematically investigated using the time-dependent Skyrme energy density functional including pairing in the BCS approximation. Using two different Skyrme functionals, Sly4 and SkM*, respectively 263 and 324 nuclei have been found to be spherical along the nuclear charts. The time-dependent evolution of these nuclei has been systematically investigated, giving access to their quadrupole responses. It is shown that the mean energy of the collective high-energy state globally reproduces the experimental IS and IV collective energy but fails to reproduce their lifetimes. It is found that the mean collective energy depends rather significantly on the functional used in the mean-field channel. Pairing by competing with parity effects can slightly affect the collective response around magic numbers and induces a reduction of the collective energy compared to the average trend. Low-lying states, that can only be considered if pairing is included, are investigated. While the approach provides a fair estimate of the low-lying state energy, it strongly underestimates the transition rate $B\left(E2\right)$. Finally, the possibility to access the density dependence of the symmetry energy through parallel measurements of both the IS and IV giant quadrupole resonances is discussed.

Background: The self-conjugate nuclei of the $A\sim 70$ mass region display rapid shape evolution over isotopic or isotonic chains. Shape coexistence has been observed in Se and Kr isotopes reflecting the existence of deformed subshell gaps corresponding to different shell configurations. As and Ge isotopes are located halfway between such deformed nuclei and the $Z=28$ shell closure.

Purpose: The present work aims at clarifying the low-lying spectroscopy of ${}^{66}$Ge and ${}^{67}$As, and providing a better insight into the evolution of collectivity in light even-even Ge and even-odd As isotopes.

Methods: We investigate the low-lying levels and collectivity of the neutron deficient ${}^{67}$As and ${}^{66}$Ge through intermediate-energy Coulomb excitation, inelastic scattering, and proton knockout measurements. The experiment was performed using a cocktail beam of ${}^{68}$Se, ${}^{67}$As, and ${}^{66}$Ge nuclei at an energy of 70–80 MeV/nucleon. Spectroscopic properties of the low-lying states are compared to those calculated via shell model with the JUN45 interaction and beyond-mean-field calculations with the five-dimensional collective Hamiltonian method implemented using the Gogny D1S interaction. The structure evolution of the lower-mass Ge and As isotopes is discussed.

Results: Reduced electric quadrupole transition probabilities $B\left(E2\right)$ have been extracted from the Coulomb-excitation cross sections measured in ${}^{66}$Ge and ${}^{67}$As. The value obtained for the $B(E2;0_1^{+}\to 2_1^{+})$ in ${}^{66}$Ge is in agreement with a recent measurement, ruling out the existence of a minimum at $N=34$ in the $B\left(E2\right)$ systematics as previously observed. New transitions have been found in ${}^{67}$As and were assigned to the decay of low-lying negative-parity states.

The ${}^{257}$Rf isotope has been populated via the ${}^{208}$Pb(${}^{50}$Ti, $n$) fusion-evaporation reaction and delayed $\gamma$-ray and electron decay spectroscopy has been performed. The existence of a high-$K$ isomeric state in ${}^{257}$Rf has been confirmed. The isomeric state decays into a rotational band based on the 11/2${}^{-}$[725] excitation, which was observed up to spin of (23/2${}^{-}$). Three multipolarity-$E1$ $\gamma$ transitions depopulating the isomeric state have been observed, which fixes the spin for that state to (21/2${}^{+}$). This assignment agrees with theoretical predictions calculated with the microscopic-macroscopic approach, which suggest the isomeric state to be formed by coupling an unpaired $11/2^{-}$[725] quasineutron to the $(1/2^{-}$[521]$\otimes 9/2^{+}$[624])${}_{5^{-}}$ two-quasiproton state. The same two-quasiproton excitation is possible for the lowest isomer in ${}^{256}$Rf.

The dynamical effects of initial orientation and deformation (with and without ${\beta }_4$ deformation) of projectile and target on the ${}^{238}$U+${}^{238}$U reaction have been investigated by using the improved quantum molecular dynamics model. The deformation of colliding nuclei at touching configuration is distributed with a wide width, especially for the nose-nose orientation case. The influence of different orientations and deformations on the average lifetime of the transient composite system and the production probability of superheavy fragments (SHF) with $Z>110$ at incident energies 7–12 $A$ MeV is studied. The average lifetime of the composite system as a function of incident energy peaks at about 9–10 $A$ MeV for the side-side orientation and 11–12 $A$ MeV for the nose-nose orientation, respectively. The inclusion of ${\beta }_4$ deformation in prolate uranium seems to enhance the production probability of SHF in the side-side case as the more stable structure of initial uranium effectively reduces the excitation energy of the composite system. It is suggested that the optimal initial condition for production of SHF in ${}^{238}$U+${}^{238}$U could be the side-side orientation and prolate deformation with a small ${\beta }_4$ deformation (the ground state of uranium). Considering that the symmetry axis of the initial nuclei is oriented in an arbitrary direction with an equal probability, the lifetime of composite system and the SHF production probability are also studied with randomly selected orientation direction of initial nuclei.

The relationship between the backward elastic scattering probabilities and the reaction cross sections is derived. This is a very simple and useful method to extract reaction cross sections for heavy-ion systems. We compare the results of our method with those that use the traditional full elastic scattering angular distributions for several systems at energies near and above the Coulomb barrier. From the calculated reaction and capture cross sections that use the present method, we derive the cross sections of other mechanisms for weak nearly spherical systems.

We study the dynamics of energy loss and flow of heavy quarks produced in ultrarelativistic heavy-ion collisions within the framework of a Langevin equation coupled to a ($2+1$)-dimensional viscous hydrodynamic model that simulates the spacetime evolution of the produced hot and dense QCD matter. The classical Langevin approach is improved such that, apart from quasielastic scatterings, radiative energy loss is incorporated by treating gluon radiation as an additional force term. The hadronization of emitted heavy quarks is simulated via a hybrid fragmentation plus recombination model. Our calculation shows significant contribution from gluon radiation to heavy quark energy loss at high energies, and we find the recombination mechanism is important for heavy flavor meson production at intermediate energies. We present numerical results for the nuclear modification and elliptic flow of $D$ mesons, which are consistent with measurements at both the CERN Large Hadron Collider (LHC) and the BNL Relativistic Heavy-Ion Collider (RHIC); predictions for $B$ mesons are also provided.

The experimental data obtained from the reaction of ${}^6$Li projectiles at 2$A$ GeV on a fixed graphite target were analyzed to study the invariant mass distributions of $d+{\pi }^{-}$ and $t+{\pi }^{-}$. Indications of a signal in the $d+{\pi }^{-}$ and $t+{\pi }^{-}$ invariant mass distributions were observed with significances of 5.3 $\sigma$ and 5.0 $\sigma$, respectively, when including the production target, and 3.7 $\sigma$ and 5.2 $\sigma$, respectively, when excluding the target. The estimated mean values of the invariant mass for $d+{\pi }^{-}$ and $t+{\pi }^{-}$ signal were 2059.3 $\pm$ 1.3 $\pm$ 1.7 MeV/c${}^2$ and 2993.7 $\pm$ 1.3 $\pm$ 0.6 MeV/c${}^2$ respectively. The lifetime estimation of the possible bound states yielding to $d+{\pi }^{-}$ and $t+{\pi }^{-}$ final states were deduced to be as ${181}_{-24}^{+30}\pm 25$ ps and ${190}_{-35}^{+47}\pm 36$ ps, respectively. Those final states may be interpreted as the two-body and three-body decay modes of a neutral bound state of two neutrons and a $\Lambda$ hyperon, ${}_{\Lambda }^{3}n$.

We discuss two-photon exchange (TPE) in elastic electron scattering off the trinucleon systems, ${}^3$He and ${}^3$H. The calculations are done in the semirelativistic approximation with the trinucleon wave functions obtained with the Paris and CD-Bonn nucleon-nucleon potentials. An applicability area of the model is wide enough and includes the main part of kinematical domain where experimental data exist. All three TPE amplitudes (generalized form factors) for electron ${}^3$He elastic scattering are calculated. We find that the TPE amplitudes are a few times more significant in the scattering of electrons off ${}^3$He then in the electron-proton scattering.

While jet quenching in ultrarelativistic heavy-ion collisions is firmly established as a phenomenon resulting from the interplay between hard perturbative and soft fluid-dynamical Quantum Chromodynamics (or equivalently the interaction between hard probes and bulk QCD matter), less is known with certainty about the reaction of bulk matter to the passage of a jet. On general grounds, a jet interacting while passing through a medium represents a source of energy and momentum for the bulk matter fluid. If the precise form of such a source term is known, the reaction of the medium can be computed using fluid dynamics. Recent advances in the understanding of hard probes due to the wealth of data from the Relativistic Heavy Ion Collider and the Large Hadron Collider allow us to constrain the source term better by determining the energy flow away from hard modes. The aim of this work is to discuss what can be learned from such constraints in the context of the in-medium shower evolution code YaJEM-DE and to illustrate the role of fluctuations in the energy deposition.

Event-by-event fluctuations in the initial conditions for a hydrodynamical description of heavy ion collisions are characterized. We propose a Bessel-Fourier decomposition with respect to the azimuthal angle, the radius in the transverse plane, and rapidity. This allows for a complete characterization of fluctuations in all hydrodynamical fields including energy density, pressure, fluid velocity, shear stress, and bulk viscous pressure. It has the advantage that fluctuations can be ordered with respect to their wavelength and that they can be propagated mode by mode within the hydrodynamical formalism. Event ensembles can then be characterized in terms of a functional probability distribution. For the event ensemble of a Monte Carlo Glauber model, we provide evidence that the latter is close to Gaussian form, thus allowing for a particularly simple characterization of the event distribution.

In heavy-ion (A-A) collisions, the correlations among the particles produced across a wide range in rapidity probe the early stages of the reaction. The analyses of forward-backward multiplicity correlations in these collisions are complicated by several effects, which are absent or minimized in hadron-hadron collisions. This includes effects, such as the centrality selection in the A-A collisions, that interfere with the measurement of the dynamical correlations. A method that takes into account the fluctuations in centrality selection has been utilized to determine the forward-backward correlation strength $b_{\mathrm{corr}}$ in A-A collisions. This method has been validated by using the hijing event generator in the case of Au-Au collisions at $\sqrt{s_{NN}}=200$ GeV and Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. It is shown that the effect of impact parameter fluctuations is to be considered properly in order to obtain meaningful results.

Based on our previous studies, we predict the nuclear-matter effects on $J/\psi$ production in proton-nucleus collisions for the recent Large Hadron Collider $p$Pb runs at $\sqrt{s_{NN}}=5$ TeV. We have analyzed the effects of the modification of the gluon parton distribution functions in the nucleus, using an exact kinematics for a $2\to 2$ process, namely, $g+g\to J/\psi +g$ as expected from leading-order perturbative QCD. This allows us to constrain the transverse-momentum while computing the nuclear modification factor for different rapidities, unlike with the usual simplified kinematics. Owing to the absence of measurement in $pp$ collisions at the same $\sqrt{s_{NN}}$ and owing to the expected significant uncertainties in yield interpolations which would hinder definite interpretations of the nuclear modification factor $R_{p\mathrm{Pb}}$, we have derived forward-to-backward and central-to-peripheral yield ratios in which the unknown proton-proton yield cancels. These have been computed without and with a transverse-momentum cut, e.g., to comply with the ATLAS and CMS constraints in the central-rapidity region.

The excited states of the odd-odd ${}^{154}$Ho nucleus have been studied by using in-beam $\gamma$-ray spectroscopy with the ${}^{141}$Pr (${}^{16}$O, 3$n$) ${}^{154}$Ho reaction at $E_{\mathrm{lab}}=75$ MeV. The beam was provided by the 12UD Pelletron accelerator at the University of Tsukuba. In this work, the complicated decay pattern of low energy transitions just above the $T_{1/2}=3.10$ min isomer have been established. In addition, a number of new states and $\gamma$-ray transitions, especially those associated with energetically favored band termination, have been observed for the first time in ${}^{154}$Ho. A negative collective band and its signature partner built on the 11${}^{-}$ level are interpreted as being based on the $\pi$$h$${}_{11/2}\otimes \nu$$i$${}_{13/2}$ configuration. A positive band built on the 10${}^{+}$ level is based on the $\pi$$h$${}_{11/2}\otimes \nu$$h$${}_{9/2}$ configuration while another positive band built on the 9${}^{+}$ level is being associated with the $\pi$$h$${}_{11/2}\otimes \nu$$f$${}_{7/2}$ configuration. An energetically favored level $J^{\pi }={19}^{-}$ can be interpreted as being attributed to the $\pi$$h$${}_{11/2}\otimes \nu$$i$${}_{13/2}$ configuration coupled to the 8${}^{+}$ state in neighboring core ${}^{152}$Dy, namely, a four-quasiparticle alignment based on the [$\pi$$h$${}_{11/2}\nu$$i$${}_{13/2}$]${}_{{11}^{-}}\otimes$[$\nu$($h$${}_{9/2}$$f$${}_{7/2}$)]${}_{8^{-}}$ configuration. Another energetically favored state at $J^{\pi }={27}^{-}$ is assigned the six-quasiparticle [$\pi$($h$${}_{11/2}{)}^3$]${}_{27/2^{-}}\otimes$[$\nu$($f$${}_{7/2}$$h$${}_{9/2}$$i$${}_{13/2}$)]${}_{27/2^{-}}$ configuration.

The ${}^{135}$La nucleus has been studied using the fusion-evaporation reaction ${}^{124}$Sn(${}^{17}$N,$6n$) induced by the ${}^{17}$N radioactive beam. The level scheme has been constructed from the $\gamma -\gamma$ coincidence measurement with an array of 12 HPGe detectors, and the lifetimes of two previously known isomeric states has been deduced. The transitions and their intensities observed in the current work as well as the level scheme derived from them is in agreement with the results of a recently published work. However, our interpretation of the results differs significantly in terms of spin and parity assignments, thus solving various contradictions concerning the configurations of some of the bands discussed in the aforementioned work.

We study vector meson photoproduction from the deuteron at high momentum transfer, accompanied by the breakup of the deuteron into a proton and neutron. The large $-t$ involved allows one of the nucleons to be identified as struck, and the other as a spectator to the $\gamma N\to VN$ subprocess. Corrections to the plane wave impulse approximation involve final-state interactions (FSIs) between the struck nucleon or the vector meson, either of which is energetic, with the slow spectator nucleon. In this regime, the eikonal approximation is valid, and so is employed to calculate the cross section for the reaction. Due to the high-energy nature of the FSIs, the maxima of the rescatterings are located at nearly transverse directions of the fast hadrons. This results in two peaks in the angular distribution of the spectator nucleon, each corresponding to either the $V$-$N$ or the $p$-$n$ rescattering. The $V$-$N$ peak provides a means of probing the $V$-$N$ interaction. This is checked for near-threshold $\varphi$ and $J/\Psi$ photoproduction reactions, which demonstrate that the $V$-$N$ peak can be used to extract the largely unknown amplitudes of $\varphi$-$N$ and $J/\Psi$-$N$ interactions. Two additional phenomena are observed when extending the calculation of $J/\Psi$ photoproduction to the subthreshold and high-energy domains. In the first case we observe overall suppression of FSI effects due to a restricted phase space for subthreshold production in the rescattering amplitude. In the second, we observe cancellation of the $V$-$N$ rescattering amplitudes for vector mesons produced off of different nucleons in the deuteron.

We investigate the nuclear and the Coulomb contributions to the breakup cross sections of ${}^6$Li in collisions with targets in different mass ranges. Comparing cross sections for different targets at collision energies corresponding to the same $E/V_{\mathrm{B}}$, we obtain interesting scaling laws. First, we derive an approximate linear expression for the nuclear breakup cross section as a function of $A_{\mathrm{T}}^{1/3}$. We then confirm the validity of this expression performing continuum-discretized coupled-channels (CDCC) calculations. Scaling laws for the Coulomb breakup cross section are also investigated. In this case, our CDCC calculations indicate that this cross section has a linear dependence on the atomic number of the target. This behavior is explained by qualitative arguments. Our findings, which are consistent with previously obtained results for higher energies, are important when planning for experiments involving exotic weakly bound nuclei.

Background: Within the last decade, below the giant dipole resonance the existence of a concentration of additional electric dipole strength has been established. This accumulation of low-lying $E1$ strength is commonly referred to as pygmy dipole resonance (PDR).

Purpose: The photoresponse of ${}^{60}$Ni has been investigated experimentally and theoretically to test the evolution of the PDR in a nucleus with only a small neutron excess. Furthermore, the isoscalar and isovector $M1$ resonances were investigated.

Method: Spin-1 states were excited by exploiting the $(\gamma ,{\gamma }^{\prime })$ nuclear resonance fluorescence technique with unpolarized continuous bremsstrahlung as well as with fully linearly polarized, quasimonochromatic, Compton-backscattered laser photons in the entrance channel of the reaction.

Results: Up to 10 MeV a detailed picture of $J=1$ levels was obtained. For the preponderant number of the individual levels spin and parity were firmly assigned. Furthermore, branching ratios, transition widths, and reduced $B\left(E1\right)$ or $B\left(M1\right)$ excitation probability were calculated from the measured scattering cross sections. A comparison with theoretical results obtained within the quasiparticle phonon model allows an insight into the microscopic structure of the observed states.

Conclusions: Below 10 MeV the directly observed $E1$ strength $[\sum B(E1)\uparrow =(153.8\pm 9.5)$ $e^2$(fm)${}^2]$ exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value increases to 0.8% of the sum rule $[\sum B(E1)\uparrow =(250.9\pm 31.1)$ $e^2$(fm)${}^2]$ when indirectly observed branches to lower-lying levels are considered. Two accumulations of $M1$ excited spin-1 states near 8 and 9 MeV excitation energy are identified as isoscalar and isovector $M1$ resonances dominated by proton and neutron $f_{7/2}\to f_{5/2}$ spin-flip excitations. The $B\left(M1\right)\uparrow$ strength of these structures accumulates to 3.94(27)${\mu }_N^2$.