Background: Observation of asymmetric fission of ${}^{180}\mathrm{Hg}$ has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region.

Background: The nature of asymmetric fission of preactinides is not yet understood in detail, despite intense experimental and theoretical studies carried out at present.

The NA62 experiment at CERN has the capability to collect data in a beam-dump mode, where 400 GeV protons are dumped on an absorber. In this configuration, New Physics particles, including dark photons, dark scalars, and axion-like particles, may be produced in the absorber and decay in the instrumented volume beginning approximately 80 m downstream of the dump. A search for these particles decaying in flight to hadronic final states is reported, based on an analysis of a sample of $$1.4 \times 10^{17}$$ 1.4 × 10 17 protons on dump collected in 2021. No evidence of a New Physics signal is observed, excluding new regions of parameter spaces of multiple models.

A bstract: Results from the study of the rare decays $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ K + → π + ν ν ¯ , K ⁺ → π ⁺ μ ⁺ μ ⁻ and K ⁺ → π ⁺ γγ at the NA62 experiment at CERN are interpreted in terms of improved limits for $$ \mathcal{B}\left({K}^{+}\to {\pi}^{+}X\right) $$ B K + → π + X and coupling parameters of hidden-sector models, where X is a mediator. World-leading limits are achieved for dark photon, dark scalar and axion-like particle models.

Background: Shell effects have been found to influence both the compound nuclear fission (CNF) and quasifission processes. Besides quasifission processes, which fission modes remain active at excitation energy ($E^{*}$) as high as 56 MeV should be investigated.

Background: The stability of the transfermium nucleus against fission is mainly determined by the shell correction depending on its angular momentum and excitation energy.