The superheavy element with atomic number $Z=117$ was produced as an evaporation residue in the ${}^{48}\mathrm{Ca}+{}^{249}\mathrm{Bk}$ fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their $\alpha$-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-$\mu \mathrm{s}$ and a few days. Two decay chains comprising seven $\alpha$ decays and a spontaneous fission each were identified and are assigned to the isotope ${}^{294}117$ and its decay products. A hitherto unknown $\alpha$-decay branch in ${}^{270}\mathrm{Db}$ ($Z=105$) was observed, which populated the new isotope ${}^{266}\mathrm{Lr}$ ($Z=103$). The identification of the long-lived ($T_{1/2}={1.0}_{-0.4}^{+1.9}\mathrm{h}$) $\alpha$-emitter ${}^{270}\mathrm{Db}$ marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an “island of stability.”

The fusion-evaporation reaction Pu244(Ca48,3-4n)114288,289 was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of 114288,289. At a compound nucleus excitation energy of E*=39.8\char21{}43.9\,\,MeV, the 4n evaporation channel cross section was 9.8-3.1+3.9\,\,pb. At E*=36.1\char21{}39.5\,\,MeV, that of the 3n evaporation channel was 8.0-4.5+7.4\,\,pb. In one of the 3n evaporation channel decay chains, a previously unobserved $\alpha${}~branch in Ds281 was observed (probability to be of random origin from background: 0.1%). This $\alpha${}~decay populated the new nucleus Hs277, which decayed by spontaneous fission after a lifetime of 4.5~ms.

Neutrinos, and in particular their tiny but non-vanishing masses, can be considered one of the doors towards physics beyond the Standard Model. Precision measurements of the kinematics of weak...

Experiments with the new recoil separator, Transactinide Separator and Chemistry Apparatus (TASCA), at the GSI were performed by using beams of ${}^{48}\mathrm{Ca}$ to irradiate targets of ${}^{206-208}\mathrm{Pb}$, which led to the production of ${}^{252-254}\mathrm{No}$ isotopes. These studies allowed for evaluation of the performance of TASCA when coupled to a new detector and electronics system. By following these studies, the isotopes of element 114 (${}^{288-291}$114) were produced in irradiations of ${}^{244}\mathrm{Pu}$ targets with ${}^{48}\mathrm{Ca}$ beams at compound nucleus excitation energies around 41.7 and 37.5 MeV, demonstrating TASCA's ability to perform experiments with picobarn-level cross sections. A total of 15 decay chains were observed and were assigned to the decay of ${}^{288-291}$114. A new α-decay branch in ${}^{281}\mathrm{Ds}$ was observed, leading to the new nucleus ${}^{277}\mathrm{Hs}$.