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[en] Empirical correlations in isotopic differentials of charge radii have been combined with the differentials for data on the energy of the first excited 2+ state, on R4/2=E(4+1)/E(2+1), on the transition rate from the 2+1 to the ground state and the two neutron separation energies. These differential results exhibit remarkable consistency with each other although, individually, structure and/or mass observables reveal different patterns. In the past, there are number of valuable studies of isotope shifts comparable to different observables but not the direct correlations as will be presented here. We show that a single general pattern occurs for five different observables for each mass region. This helps one to follow the structural changes more easily by looking at one type of pattern. This study may be a guide for both experimental studies, future measurements in charge radii, masses, spectroscopic observables, and theoretical studies.
[en] The Kitaev-Heisenberg model is source of a topological quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. The material -RuCl is composed of weakly van der Waals bound honeycomb layers of edge sharing RuCl octahedra which has recently emerged as a prime candidate for realising such physics. We studied -RuCl by means of thermal transport measurements, a valuable tool to probe elementary excitations of systems with low dimensional spin structure. While the in-plane, longitudinal heat transport is governed by heat conduction of phonons that strongly scatter off the magnetic excitations present in the system, studying the thermal Hall effect (Rhighi-Leduc effect) opens up a new path towards detecting a direct contribution of unconventional magnetic excitations to entropy transport. We have observed a sizeable transversal heat conductivity , the agreement of which with the theoretical predictions for the pure Kitaev model being suggestive of heat transport by fractionalised quasiparticles in -RuCl.
[en] We study a fractional Josephson two-vortex molecule in a long Josephson 0-κ-2κ junction. The ground state is degenerate, corresponding to two configurations with topological charges (κ, κ-2π) and (κ-2π, κ) of fractional vortices. We propose to use such a system to study macroscopic quantum phenomena involving fractional vortices. Similar to the previous proposal based on a 0-π-0 junction, the two-vortex-molecule states can be mapped to a double well potential. However, by changing the value of κ during experiment we are able to tune the energy barrier separating the two classical ground states. We calculate characteristic properties (e.g. barrier height, eigenfrequency) and demonstrate that a controlled transition into the quantum regime is possible in such a system.
[en] Relativistic Coulomb excitations of odd-mass Po and Bi isotopes were performed during the PreSPEC-AGATA campaign at GSI to study the quadrupole collectivity in the direct vicinity of the heaviest stable doubly-magic nucleus "2"0"8Pb. The PreSPEC-AGATA campaign is the predecessor of the HISPEC (High-resolution In-flight Spectroscopy) experiment in the FAIR context. It was running 2012 and 2014 at GSI. Up to 23 AGATA crystals were used in this campaign, located behind the FRagment Separator. We present the status of the ongoing data analysis and discuss the challenges of data analysis for this type of experiments.
[en] Boosted decision trees are commonly used for classification in the field of particle physics. A similar technique, gradient boosted regression trees, can be applied to regression tasks. The resolution of missing transverse energy is an important quantity in particle physics and can be improved by using multivariate analysing techniques. In this talk the performance of gradient boosted regression trees will be compared with other methods to calculate this quantity.
[en] The main reason given nowadays for supporting nuclear plant construction around the world is that the plants do not produce CO2. The negative aspects are costs so high as to require subsidies, the possible connection with proliferation, and since the Fukushima accident, a renewed concern about nuclear safety. To make a dent on global climate, we would need many power reactors, perhaps a thousand worldwide, perhaps more. Such a scale-up is not likely in view of nuclear power's high cost. Fukushima demonstrated that LWRs are capable of large accidental releases of radioactivity, roughly comparable to that at Chernobyl. While effective evacuation can protect people, the evacuates may never be able to return. The half- life of cesium 137, the main contaminant, is about 30 years, and it may take several half-lives to make an area acceptable for rehabilitation. In Fukushima about 100,000 persons were evacuated from an area of about 1000 square kilometer. When it comes to proliferation, there are strong arguments over whether we can have nuclear power without nuclear weapons. The 1946 US Acheson-Lilienthal Report argued that gaining nuclear energy's benefits without proliferation required strict international control. Inspection alone couldn't afford any reasonable security against the diversion of such materials to the purposes of war. The authors view is that the connection between technologies for nuclear power and nuclear weapons is still so close that you can't get the benefits of power without increasing the risks of weapons spread. Up to now we have allowed our interest in nuclear power to trump our bomb worries. It is time to rethink the proliferation risk of a large increase in nuclear power capacity.
[en] We study charge-exchange transitions in stable and exotic nuclei. These reactions are of interest to study electron capture process during the collapse of massive stars. The charge exchange excitations are calculated by QRPA from a self-consisting HFB ground state. We use an extended QRPA ansatz which, besides pairing effects, also accounts for the coupling to the continuum and dissipative contributions. The spectral distributions and transition probabilities are extracted from the polarization propagator. The polarization propagator is calculated by solving directly the Dyson-equation. For studying the Ikeda sum rule the analysis of the continuum region is of importance. Results of different nuclei in the carbon and in the Fe-Ni region for natural and unnatural parity excitations are discussed.
[en] The Recoil-Distance Doppler-Shift (RDDS) technique is a well established method to measure lifetimes of excited nuclear states in the pico-second range. In standard RDDS experiments at non-relativistc beam-energies, the velocities of the emerging recoils are usually distributed narrowly around a mean velocity v = left angle v right angle v. Under these circumstances, the effect of the velocity distribution is neglectable and the assumption that all nuclei move with the average velocity is justified. In this poster we investigate the influence of broader velocity distributions on lifetimes determined using the standard lifetime analysis-method DDCM. This can be observed, e.g., in experiments with thick targets. In particular, it is shown that the effect of the velocity distribution on the deduced lifetime is minimised at the maximum amplitude of the derivative of the decay function.