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The microscopic structure of the low-energy electric dipole response, commonly denoted as pygmy dipole resonance (PDR), was studied for ^{120}Sn in a ^{119}Sn(d,pγ)^{120}Sn experiment. Unprecedented access to the single-particle structure of excited 1^{-} states below and around the neutron-separation threshold was obtained by comparing experimental data to predictions from a novel theoretical approach. The novel approach combines detailed structure input from energy-density functional plus quasiparticle-phonon model theory with reaction theory to obtain a consistent description of both the structure and reaction aspects of the process. The presented results show that the understanding of one-particle-one-hole structures of the 1^{-} states in the PDR region is crucial to reliably predict properties of the PDR and its contribution to nucleosynthesis processes.

The dipole response of the proton-magic nucleus $${}^{124}\hbox {Sn}$$ 124 Sn was previously investigated with electromagnetic and hadronic probes. Different responses were observed revealing the so-called isospin splitting of the Pygmy Dipole Resonance (PDR). Here we present the results of a new study of $${}^{124}\hbox {Sn}$$ 124 Sn using inelastic proton scattering at low energies to test an additional probe possibly exciting states of the PDR. The response to the new probe as well as the $$\gamma $$ γ -decay behavior of excited states were studied. The $${}^{124}\hbox {Sn}$$ 124 Sn (p,p’$$\gamma $$ γ ) experiment was performed at $$E_p = {15}\,\,\hbox {MeV}$$ E p = 15 MeV using the combined spectroscopy setup SONIC@HORUS at the Tandem accelerator of the University of Cologne. Proton-$$\gamma $$ γ coincidences were recorded, enabling a state-to-state analysis due to the excellent energy resolution for both particles and $$\gamma $$ γ rays. $$ J=1 $$ J = 1 states in the PDR region were populated in the present inelastic proton scattering experiment. Many $$\gamma $$ γ -decay branching ratios could be determined.

The dipole strength of the $N=28$ closed-shell nuclide $^{54}\mathrm{Fe}$ was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of kinetic energies of 7.5 and 13.9 MeV at the $\ensuremath{\gamma}\mathrm{ELBE}$ facility as well as using quasimonoenergetic and linearly polarized photon beams of 26 different energies within the range from 5.5 to 11.4 MeV at the $\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$ facility. About 100 $J=1$ states were newly identified, out of them 19 with ${1}^{+}$ and 30 with ${1}^{\ensuremath{-}}$ assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical $\ensuremath{\gamma}$-ray cascades. As a result, the photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental $M1$ strengths from resolved ${1}^{+}$ states are compared with results of large-scale shell-model calculations.

Background: The term Pygmy Dipole Resonance (PDR) denotes an accumulation of electric dipole excitations below and around the neutron separation threshold. It may be important, e.g., for the nucleosynthesis of heavy nuclei or the symmetry energy in the Equation of State (EoS). For a deeper understanding of the PDR, systematic studies are essential.Purpose: The tin isotopic chain is a well-suited candidate to investigate the systematics of the PDR, and the ($\ensuremath{\gamma},{\ensuremath{\gamma}}^{\ensuremath{'}}$) reactions on $^{112,116,120,124}\mathrm{Sn}$ have already been measured in experiments using bremsstrahlung. It was claimed that the extracted electric dipole transition strengths of these isotopes increase with increasing neutron-to-proton ratio with the exception of $^{120}\mathrm{Sn}$. Furthermore, previous results from elastic photon scattering experiments on $^{120}\mathrm{Sn}$ are in disagreement with corresponding $(p,{p}^{\ensuremath{'}})$ Coulomb excitation data. To examine this discrepancy an additional high-sensitivity bremsstrahlung experiment on $^{120}\mathrm{Sn}$ was performed.Method: The Nuclear Resonance Fluorescence (NRF) method is used, which is based on the scattering of real photons. The bremsstrahlung experiment presented in this work was performed with a maximum energy of ${E}_{\ensuremath{\gamma},\mathrm{max}}=9.5\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$ at the $\ensuremath{\gamma}\mathrm{ELBE}$ facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Besides a state-to-state analysis, the quasicontinuum was investigated as well.Results: Above ${E}_{x}=4$ MeV 228 dipole transitions were clearly identified; 163 were observed for the first time. Assuming that all identified dipole transitions have electric dipole character the summed electric dipole strength equals $\ensuremath{\sum}B(E1)\ensuremath{\uparrow}=369(49)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{4pt}{0ex}}{e}^{2}{\text{fm}}^{2}$ [which amounts to 0.58(8)% of the Thomas-Reiche-Kuhn sum rule] for transitions from 4 MeV to ${S}_{n}=9.1$ MeV. This is an enhancement of a factor 2.3 compared to the previously published $^{120}\mathrm{Sn}(\ensuremath{\gamma},{\ensuremath{\gamma}}^{\ensuremath{'}})$ results. This increase can be explained by the contribution of many weak, previously not included transitions in the state-to-state analysis. The photoabsorption cross sections deduced from the quasicontinuum analysis exceed those of the $(p,{p}^{\ensuremath{'}})$ experiment in average by about $50%$ between 5.9 and 8.7 MeV.Conclusion: The newly extracted summed $B(E1)$ value of the state-to-state analysis is larger than those of $^{112,116}\mathrm{Sn}$ and smaller than that of $^{124}\mathrm{Sn}$. The difference between the electric dipole transition strengths deduced from isolated peaks of the present ($\ensuremath{\gamma},{\ensuremath{\gamma}}^{\ensuremath{'}}$) data and those from the inelastic proton scattering experiment above 6.3 MeV is still striking. The analysis of the photoabsorption cross section including the quasicontinuum of levels overcomes this problem and the results are in the order of magnitude of the $(p,{p}^{\ensuremath{'}})$ data and continue the $(\ensuremath{\gamma},n)$ cross sections at the neutron separation threshold.

Background: Reaction rates of radiative capture reactions can play a crucial role in the nucleosynthesis of heavy nuclei in explosive stellar environments. These reaction rates depend strongly on $\ensuremath{\gamma}$-ray decay widths in the reaction products, which are, for nonresonant capture reactions at high excitation energies, derived from the $\ensuremath{\gamma}$-ray strength function and the nuclear level density. Recently, the ratio method was applied to primary $\ensuremath{\gamma}$ rays observed from ($d,p$) reactions and nuclear resonance fluorescence measurements to extract the dipole strength in atomic nuclei and to test the generalized Brink-Axel hypothesis.Purpose: The purpose of this work is to apply the ratio method to primary $\ensuremath{\gamma}$-ray intensities of the $^{63,65}\mathrm{Cu}(p,\ensuremath{\gamma})$ reactions to extract $\ensuremath{\gamma}$-ray strength information on the nuclei $^{64,66}\mathrm{Zn}$. The impact of spin distribution, total $\ensuremath{\gamma}$-ray decay widths, level densities, and width fluctuations on the application of the ratio method will be discussed. Additionally, by comparing the relative $\ensuremath{\gamma}$-ray strength at different excitation energies, conclusions on the validity of the generalized Brink-Axel hypothesis can be made.Method: The radiative proton capture reaction measurements have been performed at the HORUS $\ensuremath{\gamma}$-ray spectrometer of the University of Cologne at one excitation energy for each reaction. Primary $\ensuremath{\gamma}$-ray intensities have been determined by normalizing secondary $\ensuremath{\gamma}$-ray transitions in two-step cascades using their absolute branching ratio. The ratio method was applied to the measured primary $\ensuremath{\gamma}$-ray intensities as well as to previous measurements by Erlandsson $et$ $al.$ at different excitation energies.Results: The relative strength function curve for $^{64}\mathrm{Zn}$ from our measurement shows no significant deviation from the previous measurement at a different excitation energy. The same is true for $^{66}\mathrm{Zn}$ where both measurements were at almost the same excitation energy. Absolute $\ensuremath{\gamma}$-strength function values have been obtained by normalizing the relative curves to quasiparticle random phase approximation calculations because of the absence of experimental data in the respective energy region.Conclusion: The generalized Brink-Axel hypothesis, i.e., the independence of the strength function on the excitation energy, seems to hold in the studied energy region and nuclei. The method to obtain primary $\ensuremath{\gamma}$-ray intensities from two-step cascade spectra was shown to be a valuable and sensitive tool although its uncertainties are connected to the knowledge of the low-energy level scheme of the investigated nucleus. The scaling in the ratio method should be taken with care, because the relative strength is not a simple sum of ${f}_{E1}$ and ${f}_{M1}$ but a somewhat complex linear combination dependent on the excitation energy of the nucleus.

The European physical journal / A 56(4), 105 (2020). doi:10.1140/epja/s10050-020-00118-8, Published by Springer, Heidelberg

27TH INTERNATIONAL NUCLEAR PHYSICS CONFERENCE (INPC2019), Glasgow, Scotland, 29 Jul 2019 - 2 Aug 2019; Journal of physics / Conference series 1643, 012148 (2020). doi:10.1088/1742-6596/1643/1/012148, Published by IOP Publ., Bristol

Background: The low-lying electric dipole strength provides insights into the parameters of the nuclear equation of state via its connection with the pygmy dipole resonance and nuclear neutron skin thickness.Purpose: The aim was to complement the systematic of the pygmy dipole resonance and first study its behavior across the $N=28$ neutron shell closure.Methods: Photon-scattering cross sections of states of $^{50,54}\mathrm{Cr}$ were measured up to an excitation energy of 9.7 MeV via the nuclear resonance fluorescence method using $\ensuremath{\gamma}$-ray beams from bremsstrahlung and Compton backscattering.Results: Transitions strengths, spin and parity quantum number, and average branching ratios for 55 excited states, 44 of which were observed for the first time, were determined. The comparison between the total observed strengths of the isotopes $^{50,52,54}\mathrm{Cr}$ shows a significant increase above the shell closure.Conclusions: The evolution of the pygmy dipole resonance is heavily influenced by the shell structure.

This paper illustrates the principle of the Doppler-shift attenuation method (DSAM) using particle-γ coincidences, a method for determining lifetimes of excited nuclear levels in the range of few femtoseconds up to one picosecond. The coincident detection holds several advantages towards conventional DSAM experiments, such as the elimination of background and feeding transitions. Using the experimental data on 94Zr, the concept of the (p,p’γ) DSAM analysis is presented. Additional experimental results are highlighted.

Background: In the $A\ensuremath{\approx}50$ mass region $M1$ spin-flip transitions are prominent around 9 MeV. An accumulation of ${1}^{\ensuremath{-}}$ states between 5 and 8 MeV generating additional $E1$ strength, also denoted as pygmy dipole resonance, has been established in many nuclei with neutron excess within the last decade.Purpose: The $\ensuremath{\gamma}$-decay behavior of $J=1$ states has been investigated in an NRF experiment. $M1$ excitations have been compared to shell model calculations.Methods: $J=1$ states were excited by quasi-monoenergetic, linearly polarized $\ensuremath{\gamma}$-ray beams generated by laser-Compton backscattering at the $\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$ facility, Durham, NC, USA. Depopulating $\ensuremath{\gamma}$ rays were detected with the multidetector array ${\ensuremath{\gamma}}^{3}$.Results: For eleven beam-energy settings the $\ensuremath{\gamma}$-decay behavior of dipole states was analyzed by a state-to-state analysis and average $\ensuremath{\gamma}$-decay branching ratios have been investigated. 34 parity quantum numbers were assigned to $J=1$ states.Conclusions: Six ${1}^{\ensuremath{-}}$ states and two ${1}^{+}$ states have been investigated in NRF experiments for the first time. The $M1$ strength distribution is in good agreement with shell-model calculations.

The low-lying $M1$-strength of the open-shell nucleus $^{50}$Cr has been studied with the method of nuclear resonance fluorescence up to 9.7 MeV, using bremsstrahlung at the superconducting Darmstadt linear electron accelerator S-DALINAC and Compton backscattered photons at the High Intensity $\gamma$-ray Source (HI$\gamma$S) facility between 6 and 9.7 MeV of the initial photon energy. Fifteen $1^{+}$ states have been observed between 3.6 and 9.7 MeV. Following our analysis, the lowest $1^{+}$ state at 3.6 MeV can be considered as an isovector orbital mode with some spin admixture. The obtained results generally match the estimations and trends typical for the scissors-like mode. Detailed calculations within the Skyrme Quasiparticle Random-Phase-Approximation method and the Large-Scale Shell Model justify our conclusions. The calculated distributions of the orbital current for the lowest $1^{+}$-state suggest the schematic view of Lipparini and Stringari (isovector rotation-like oscillations inside the rigid surface) rather than the scissors-like picture of Lo Iudice and Palumbo. The spin M1 resonance is shown to be mainly generated by spin-flip transitions between the orbitals of the $fp$-shell.

12TH INTERNATIONAL SPRING SEMINAR ON NUCLEAR PHYSICS: CURRENT PROBLEMS AND PROSPECTS FOR NUCLEAR STRUCTURE, Napoli, Italy, 15 May 2017 - 19 May 2017; Journal of physics / Conference Series 966, 012035 (2018). doi:10.1088/1742-6596/966/1/012035, Published by IOP Publ., Bristol

Last year, the new silicon-detector array SONIC with up to 8 silicon-detector positions was in- stalled inside the existing γ-ray spectrometer HORUS consisting of 14 HPGe detectors. The combined setup SONIC@HORUS allows for a coincident detection of γ-rays and light charged particles in the exit channel of inelastic scattering and transfer reactions. As a first physics case, the Pygmy Dipole Resonance (PDR) in 92 Mo has been investigated in a (p,p'γ) experiment at E p = 10.5 MeV. Since a specific excitation energy can be chosen offline in the coincidence data, the sensitivity to weak decay branchings of PDR states is increased. Additionally, a second reaction mechanism for the excitation of PDR states has been tested with the new setup. In a 119 Sn(d,pγ) transfer reaction at Ed = 8.5 MeV, PDR states in 120 Sn could be excited. Since this one-neutron transfer reaction is sensitive to the neutron single-particle structure, it could reveal new information on the microscopic structure of the PDR.

A virtual hospital is realized as an interactive information system based on a 3D- model of a real hospital. In preparation for a future stay, a patient can visit the location, where later a therapy may take place, and get a first impression or look at the data in his electronic patient record, as described in [1]. To be able to experience an almost realistic impression of the real healthcare process, it is also necessary to offer the patient the possibility to see and interact with doctors, nurses, administration personnel and also other patients in the virtual hospital. The authors present a system of virtual actors that can be used to fill the wards and stations with virtual life. One special purpose for employing virtual actors is the simulation of diagnostic or therapeutic treatment. For example, to present an orthopaedic diagnosis, a virtual doctor can take the leg of a virtual patient and make a reflex test with a rubber hammer.

This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002.

Composite fragments of 2 < Z < 10 have been measured in the Plastic Ball Spectrometer in 200 MeV/nucleon Au + Au and Au + Fe collisions. Strong azimuthal alignment of the fragments reveal the collective behaviour of the reaction.

More than 65 million individuals worldwide are estimated to have Long COVID (LC), a complex multisystemic condition, wherein patients of all ages report fatigue, post-exertional malaise, and other symptoms resembling myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS). With no current treatments or reliable diagnostic markers, there is an urgent need to define the molecular underpinnings of these conditions. By studying bioenergetic characteristics of peripheral blood lymphocytes in over 16 healthy controls, 15 ME/CFS, and 15 LC, we find both ME/CFS and LC donors exhibit signs of elevated oxidative stress, relative to healthy controls, especially in the memory subset. Using a combination of flow cytometry, bulk RNA-seq analysis, mass spectrometry, and systems chemistry analysis, we also observed aberrations in ROS clearance pathways including elevated glutathione levels, decreases in mitochondrial superoxide dismutase levels, and glutathione peroxidase 4 mediated lipid oxidative damage. Critically, these changes in redox pathways show striking sex-specific trends. While females diagnosed with ME/CFS exhibit higher total ROS and mitochondrial calcium levels, males with an ME/CFS diagnosis have normal ROS levels, but larger changes in lipid oxidative damage. Further analyses show that higher ROS levels correlates with hyperproliferation of T cells in females, consistent with the known role of elevated ROS levels in the initiation of proliferation. This hyperproliferation of T cells can be attenuated by metformin, suggesting this FDA-approved drug as a possible treatment, as also suggested by a recent clinical study of LC patients. Thus, we report that both ME/CFS and LC are mechanistically related and could be diagnosed with quantitative blood cell measurements. We also suggest that effective, patient tailored drugs might be discovered using standard lymphocyte stimulation assays.

Previous reports show that Ly49 + CD8 + T cells can suppress autoimmunity in mouse models of autoimmune diseases. Here we find a markedly increased frequency of CD8 + T cells expressing inhibitory Killer cell Immunoglobulin like Receptors (KIR), the human equivalent of the Ly49 family, in the blood and inflamed tissues of various autoimmune diseases. Moreover, KIR + CD8 + T cells can efficiently eliminate pathogenic gliadin-specific CD4 + T cells from Celiac disease (CeD) patients' leukocytes in vitro . Furthermore, we observe elevated levels of KIR + CD8 + T cells, but not CD4 + regulatory T cells, in COVID-19 and influenza-infected patients, and this correlates with disease severity and vasculitis in COVID-19. Expanded KIR + CD8 + T cells from these different diseases display shared phenotypes and similar T cell receptor sequences. These results characterize a regulatory CD8 + T cell subset in humans, broadly active in both autoimmune and infectious diseases, which we hypothesize functions to control self-reactive or otherwise pathogenic T cells., One-Sentence Summary: Here we identified KIR + CD8 + T cells as a regulatory CD8 + T cell subset in humans that suppresses self-reactive or otherwise pathogenic CD4 + T cells.