Background: State-of-the-art multi-reference energy density functional calculations require the computation of norm overlaps between different Bogoliubov quasiparticle many-body states. It is only recently that the efficient and unambiguous calculation of such norm kernels has become available under the form of Pfaffians [L. M. Robledo, Phys. Rev. C 79, 021302 (2009)]. Recently developed particle-number-restored Bogoliubov coupled-cluster (PNR-BCC) and particle-number-restored Bogoliubov many-body perturbation (PNR-BMBPT) ab initio theories [T. Duguet and A. Signoracci, J. Phys. G 44, 015103 (2017)] make use of generalized norm kernels incorporating explicit many-body correlations. In PNR-BCC and PNR-BMBPT, the Bogoliubov states involved in the norm kernels differ specifically via a global gauge rotation.

Purpose: The goal of this work is threefold. We wish (i) to propose and implement an alternative to the Pfaffian method to compute unambiguously the norm overlap between arbitrary Bogoliubov quasiparticle states, (ii) to extend the first point to explicitly correlated norm kernels, and (iii) to scrutinize the analytical content of the correlated norm kernels employed in PNR-BMBPT. Point (i) constitutes the purpose of the present paper while points (ii) and (iii) are addressed in a forthcoming paper.

Methods: We generalize the method used in another work [T. Duguet and A. Signoracci, J. Phys. G 44, 015103 (2017)] in such a way that it is applicable to kernels involving arbitrary pairs of Bogoliubov states. The formalism is presently explicated in detail in the case of the uncorrelated overlap between arbitrary Bogoliubov states. The power of the method is numerically illustrated and benchmarked against known results on the basis of toy models of increasing complexity.

Results: The norm overlap between arbitrary Bogoliubov product states is obtained under a closed-form expression allowing its computation without any phase ambiguity. The formula is physically intuitive, accurate, and versatile. It equally applies to norm overlaps between Bogoliubov states of even or odd number parity. Numerical applications illustrate these features and provide a transparent representation of the content of the norm overlaps.

Conclusions: The complex norm overlap between arbitrary Bogoliubov states is computed, without any phase ambiguity, via elementary linear algebra operations. The method can be used in any configuration mixing of orthogonal and non-orthogonal product states. Furthermore, the closed-form expression extends naturally to correlated overlaps at play in PNR-BCC and PNR-BMBPT. As such, the straight overlap between Bogoliubov states is the zero-order reduction of more involved norm kernels to be studied in a forthcoming paper.

The occurrence of octupolar shapes in the Ba isotopic chain was recently established experimentally up to $N=90$. To further extend the systematics, the evolution of shapes in the most neutron-rich members of the $Z=56$ isotopic chain accessible at present, ${}^{148,150}\mathrm{Ba}$, has been studied via $\beta$ decay at the ISOLDE Decay Station. This paper reports on the first measurement of the positive- and negative-parity low-spin excited states of ${}^{150}\mathrm{Ba}$ and presents an extension of the $\beta$-decay scheme of ${}^{148}\mathrm{Cs}$. Employing the fast timing technique, half-lives for the $2_1^{+}$ level in both nuclei have been determined, resulting in $T_{1/2}=1.51\left(1\right)$ ns for ${}^{148}\mathrm{Ba}$ and $T_{1/2}=3.4\left(2\right)$ ns for ${}^{150}\mathrm{Ba}$. The systematics of low-spin states, together with the experimental determination of the $B(E2:2^{+}\to 0^{+})$ transition probabilities, indicate an increasing collectivity in ${}^{148\text{–}150}\mathrm{Ba}$, towards prolate deformed shapes. The experimental data are compared to symmetry conserving configuration mixing (SCCM) calculations, confirming an evolution of increasingly quadrupole deformed shapes with a definite octupolar character.

The ground-state rotational band of the neutron-deficient californium ($Z=98$) isotope ${}^{244}\mathrm{Cf}$ was identified for the first time and measured up to a tentative spin and parity of $I^{\pi }={20}^{+}$. The observation of the rotational band indicates that the nucleus is deformed. The kinematic and dynamic moments of inertia were deduced from the measured $\gamma$-ray transition energies. The behavior of the dynamic moment of inertia revealed an up-bend due to a possible alignment of coupled nucleons in high-$j$ orbitals starting at a rotational frequency of about $\hslash \omega =0.20\mathrm{MeV}$. The results were compared with the systematic behavior of the even-even $N=146$ isotones as well as with available theoretical calculations that have been performed for nuclei in the region.

Background: In coupled-channels models the poles of the scattering $S$ matrix are located on different Riemann sheets. Physical observables are affected mainly by poles closest to the physical region but sometimes shadow poles have considerable effect too.

Purpose: The purpose of this paper is to show that in coupled-channels problems all poles of the $S$ matrix can be located by an expansion in terms of a properly constructed complex-energy basis.

Method: The Berggren basis is used for expanding the coupled-channels solutions.

Results: The locations of the poles of the $S$ matrix for the Cox potential, constructed for coupled-channels problems, were numerically calculated and compared with the exact ones. In a nuclear physics application the $J^{\pi }=3/2^{+}$ resonant poles of ${}^5\mathrm{He}$ were calculated in a phenomenological two-channel model. The properties of both the normal and shadow resonances agree with previous findings.

Conclusions: We have shown that, with an appropriately chosen Berggren basis, all poles of the $S$ matrix including the shadow poles can be determined. We have found that the shadow pole of ${}^5\mathrm{He}$ migrates between Riemann sheets if the coupling strength is varied.

A problem of analytical continuation of scattering data to the negative-energy region to obtain information about bound states is discussed within an exactly solvable potential model. This work is continuation of the previous one by the same authors [L. D. Blokhintsev et al., Phys. Rev. C 95, 044618 (2017)]. The goal of this paper is to determine the most effective way of analytic continuation for different systems. The $d+\alpha$ and $\alpha +{}^{12}\mathrm{C}$ systems are considered and, for comparison, an effective-range function approach and a recently suggested $\mathrm{\Delta }$ method [O. L. Ramírez Suárez and J.-M. Sparenberg, Phys. Rev. C 96, 034601 (2017).] are applied. We conclude that the $\mathrm{\Delta }$ method is more effective for heavier systems with large values of the Coulomb parameter, whereas for light systems with small values of the Coulomb parameter the effective-range function method might be preferable.

We study derivatives of the shift and penetration factors of collision theory with respect to energy, angular momentum, and charge. Definitive results for the signs of these derivatives are found for the repulsive Coulomb case. In particular, we find that the derivative of the shift factor with respect to energy is positive for the repulsive Coulomb case, a long anticipated but heretofore unproven result. These results are closely connected to the properties of the sum of squares of the regular and irregular Coulomb functions; we also present investigations of this quantity.

In peripheral heavy-ion collisions at ultrarelativistic energies, usually only parts of the colliding nuclei effectively interact with each other. In the overlapping zone, a fireball or quark-gluon plasma is produced. The excitation energy of the heavy remnant can range from a few tens to several hundreds of MeV, depending on the impact parameter. The decay of these excited spectators is investigated in this work for the first time within a dynamical approach based on the multidimensional stochastic Langevin equation. The potential of this exploratory work to understand the connection between electromagnetic fields generated by the heavy spectators and measured pion distributions is discussed.

Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of ${}^{203}\mathrm{At}(N=118)$ significantly. We have observed an isomeric $[\tau =14.1(3\left)\mu \mathrm{s}\right]$ state with a spin and parity of $29/2^{+}$. The isomeric state is suggested to originate from the $\pi \left(h_{9/2}\right)\otimes |{}^{202}\mathrm{Po};{11}^{-}\rangle$ coupling, and it is depopulated through 286 keV $E2$ and 366 keV $E3$ transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism.

We study phenomenologically inclusive spectra of the ${}^6\mathrm{Li}({\pi }^{-},K^{+})$ reaction at 1.2 GeV/$c$ within a distorted-wave impulse approximation with the optimal Fermi-averaging ${\pi }^{-}p\to K^{+}{\mathrm{\Sigma }}^{-}t$ matrix. We attempt to clarify the property of a $\mathrm{\Sigma }$-nucleus potential for ${\mathrm{\Sigma }}^{-}\text{−}{}^5\mathrm{He}$ by comparing the calculated spectra with the data of the J-PARC E10 experiment. The result shows that the repulsive and absorptive components of the ${\mathrm{\Sigma }}^{-}\text{−}{}^5\mathrm{He}$ potential provide the ability to explain the data of the continuum spectra in $\mathrm{\Sigma }$ and $\mathrm{\Lambda }$ regions; the strengths of $V_{\mathrm{\Sigma }}=+30\pm 10$ MeV and $W_{\mathrm{\Sigma }}=-26\pm 2$ MeV are favored within the Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of the size and potential range for ${\mathrm{\Sigma }}^{-}\text{−}{}^5\mathrm{He}$ in the neutron excess of $(N-Z)/(N+Z)=$ 0.2 are also discussed.

Isotope shift relative to ${}^{209}\mathrm{Bi}$ and hyperfine splitting for ${}^{211,213}\mathrm{Bi}$ have been measured by in-source laser spectroscopy at the 306.77-nm atomic transition. The pronounced shell effect both in radii and magnetic moments in Bi isotopes at $N=126$ has been observed. The isotopic trend of magnetic moment for $9/2^{-}$ ground states of even-$N$ Bi isotopes has been qualitatively explained by the change in the first-order core-polarization correction. The possible influence of the octupole degree of freedom on the magnetic moment behavior at $N>126$ has been discussed.

The level structures of ${}^{212}\mathrm{Ra}$ and ${}^{213}\mathrm{Ra}$ have been established via time-correlated $\gamma$-ray spectroscopy following the ${}^{204}\mathrm{Pb}$(${}^{12}\mathrm{C},4n$)${}^{212}\mathrm{Ra}$ and ${}^{204}\mathrm{Pb}$(${}^{13}\mathrm{C},4n$)${}^{213}\mathrm{Ra}$ reactions. In ${}^{212}\mathrm{Ra}$, levels up to $\sim 6.2\mathrm{MeV}$ were identified and firm spin-parity assignments were achieved to a $J^{\pi }={19}^{+}$ isomer with a mean life of 31(3) ns. For ${}^{213}\mathrm{Ra}$ the corresponding values were $\sim 4.5\mathrm{MeV}$ in excitation energy and $J^{\pi }=33/2^{+}$. Two isomeric states with $J^{\pi }=23/2^{+}, \tau =27\left(3\right)$ ns and $J^{\pi }=33/2^{+}, \tau =50\left(3\right)$ ns were discovered in ${}^{213}\mathrm{Ra}$. The experimental data were compared with semiempirical shell-model calculations, which allowed dominant configurations to be assigned to most of the observed levels.

Electron capture decays of ${}^{243}\mathrm{Bk}$ and ${}^{244}\mathrm{Bk}$ have been studied by measuring the $\gamma$-ray spectra of mass-separated sources and level structures of ${}^{243}\mathrm{Cm}$ and ${}^{244}\mathrm{Cm}$ have been deduced. In ${}^{243}\mathrm{Cm}$, the electron capture population to the ground state, $1/2^{+}\left[631\right]$, and $1/2^{+}\left[620\right]$ Nilsson states have been observed. The octupole $K^{\pi }=2^{-}$ band was identified in ${}^{244}\mathrm{Cm}$ at 933.6 keV. In addition, spins and parities were deduced for several other states and two-quasiparticle configurations have been tentatively assigned to them.

We argue that the large suppression of the $\psi \left(2S\right)$ inclusive cross section relative to the $J/\psi$ inclusive cross section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the color glass condensate (CGC) effective field theory and employ an improved color evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of $J/\psi$ and $\psi \left(2S\right)$ data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff $\mathrm{\Lambda }$, representing the average momentum kick from soft color exchanges, in the ICEM. Such soft exchanges have no perceptible effect on $J/\psi$ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semihard rescattering at short distances, causes a significant additional suppression of $\psi \left(2S\right)$ yields relative to that of the $J/\psi$. A good fit of all RHIC and LHC $J/\psi$ and $\psi \left(2S\right)$ data, for transverse momenta $P_{\perp }\le 5$ GeV in p+p and p+A collisions, is obtained for $\mathrm{\Lambda }\sim 10$ MeV.

In this work a study of the fractional momentum loss ($S_{\mathrm{loss}}$) as a function of the characteristic path length ($L$) and the Bjorken energy density times the equilibration time (${\epsilon }_{\mathrm{Bj}}{\tau }_0$) for heavy-ion collisions at different $\sqrt{s_{NN}}$ is presented. The study has been conducted using inclusive charged particles from intermediate to large transverse momentum ($5<p_T<20$ GeV/$c$). Within uncertainties and for all the transverse momentum values which were explored, the fractional momentum loss is found to increase linearly with ${\left({\epsilon }_{\mathrm{Bj}}{\tau }_0\right)}^{3/8}L$. For identified hadrons, albeit a smaller slope of $S_{\mathrm{loss}}$ vs. ${\left({\epsilon }_{\mathrm{Bj}}{\tau }_0\right)}^{3/8}L$ is observed for (anti)protons at ${p_T}^{}=5\mathrm{GeV}/c,S_{\mathrm{loss}}$ is also found to grow linearly with $L$. The behavior of data could provide important information aimed at understanding the parton energy loss mechanism in heavy-ion collisions and some insight into the expected effect for small systems.

Partial-wave amplitudes of meson photoproduction reactions are an important source of information in baryon spectroscopy. We investigate a new approach in single-energy partial-wave analyses of these reactions. Instead of using a constraint to theoretical models in order to achieve solutions which are continuous in energy, we enforce the analyticity of the amplitudes at fixed values of the Mandelstam variable $t$. We present an iterative procedure with successive fixed-$t$ amplitude analyses which constrain the single-energy partial-wave analyses and apply this method to the $\gamma p\to \eta p$ reaction. We use pseudodata, generated by the EtaMAID model, to test the method and to analyze ambiguities. Finally, we present an analytically constrained partial-wave analysis using experimental data for four polarization observables recently measured at MAMI and GRAAL in the energy range from threshold to $\sqrt{s}=1.85$ GeV.

We report the measurement of the $\gamma p\to K^{+}\mathrm{\Lambda }$ and $\gamma p\to K^{+}{\mathrm{\Sigma }}^0$ reactions at SPring-8. The differential cross sections and photon-beam asymmetries are measured at forward $K^{+}$ production angles using linearly polarized tagged-photon beams in the range of $E_{\gamma }=1.5–3.0$ GeV. With increasing photon energy, the cross sections for both $\gamma p\to K^{+}\mathrm{\Lambda }$ and $\gamma p\to K^{+}{\mathrm{\Sigma }}^0$ reactions decrease slowly. Distinct narrow structures in the production cross section have not been found at $E_{\gamma }=1.5–3.0$ GeV. The forward peaking in the angular distributions of cross sections, a characteristic feature of $t$-channel exchange, is observed for the production of $\mathrm{\Lambda }$ in the whole observed energy range. A lack of similar feature for ${\mathrm{\Sigma }}^0$ production reflects a less dominant role of $t$-channel contribution in this channel. The photon-beam asymmetries remain positive for both reactions, suggesting the dominance of $K^{*}$ exchange in the $t$ channel. These asymmetries increase gradually with the photon energy, and have a maximum value of +0.6 for both reactions. Comparison with theoretical predictions based on the Regge trajectory in the $t$ channel and the contributions of nucleon resonances indicates the major role of $t$-channel contributions as well as non-negligible effects of nucleon resonances in accounting for the reaction mechanism of hyperon photoproduction in this photon energy regime.

We present new results from investigations of the ${}^{240}\mathrm{Pu}+{}^{48}\mathrm{Ca}$ reaction at a projectile energy of 250 MeV. Three new decay chains of ${}^{285}\mathrm{Fl}$ were detected with decay properties mostly consistent with those measured in earlier studies. An additional chain was observed where the nuclei may decay through energy levels different from those of the other six chains registered so far. The cross section of the ${}^{240}\mathrm{Pu}$(${}^{48}\mathrm{Ca},3n$)${}^{285}\mathrm{Fl}$ reaction was measured to be $0.{58}_{-0.33}^{+0.60}\mathrm{pb}$, which is a factor of about 4–5 lower than that measured in the previous experiment at 245 MeV beam energy [V. K. Utyonkov et al., Phys. Rev. C 92, 034609 (2015).], consistent with expectations. The origin of an additional chain consisting of a recoil, $\alpha$ particle, and fission event is analyzed. The assignment of 25 short-lived SF events observed in this experiment is also discussed.

Lifetime measurements of $\beta$-decaying highly charged ions have been performed in the experimental storage ring (CSRe) by applying the isochronous Schottky mass spectrometry. The fully ionized ${}^{49}\mathrm{Cr}$ and ${}^{53}\mathrm{Fe}$ ions were produced in projectile fragmentation of ${}^{58}\mathrm{Ni}$ primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled ${}^{49}\mathrm{Cr}^{24+}$ and ${}^{53}\mathrm{Fe}^{26+}$ ions. The extracted half-lives $T_{1/2}\left({}^{49}\mathrm{Cr}^{24+}\right)=44.0\left(27\right)$ min and $T_{1/2}\left({}^{53}\mathrm{Fe}^{26+}\right)=8.47\left(19\right)$ min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities.

An attempt to unfold the respective influence of the fusion and fission stages on typical fission observables, and namely the neutron prescission multiplicity, is proposed. A four-dimensional dynamical stochastic Langevin model is used to calculate the decay by fission of excited compound nuclei produced in a wide set of heavy-ion collisions. The comparison of the results from such a calculation and experimental data is discussed, guided by predictions of the dynamical deterministic HICOL code for the compound-nucleus formation time. While the dependence of the latter on the entrance-channel properties can straigthforwardly explain some observations, a complex interplay between the various parameters of the reaction is found to occur in other cases. A multidimensional analysis of the respective role of these parameters, including entrance-channel asymmetry, bombarding energy, compound-nucleus fissility, angular momentum, and excitation energy, is proposed. It is shown that, depending on the size of the system, apparent inconsistencies may be deduced when projecting onto specific ordering parameters. The work suggests the possibility of delicate compensation effects in governing the measured fission observables, thereby highlighting the necessity of a multidimensional discussion.

Ordinary muon capture (OMC) on enriched ${}^{100}\mathrm{Mo}$ isotopes was studied for the first time to investigate neutrino nuclear responses for neutrinoless double-$\beta$ decays and supernova neutrino nuclear interactions. Muon capture on ${}^{100}\mathrm{Mo}$ proceeds mainly as ${}^{100}\mathrm{Mo}(\mu ,xn){}^{100-x}\mathrm{Nb}$ with $x$ being the number of neutrons emitted from negative muon capture. The Nb isotope mass distribution was obtained by measuring delayed $\gamma$ rays from radioactive ${}^{100-x}\mathrm{Nb}$. By using the neutron emission model after the muon capture, the neutrino response (the strength distribution) for OMC was derived. The OMC strength distribution shows a giant resonance (GR) at the peak energy around 11–14 MeV, suggesting the concentration of the OMC strength at the muon GR region.