Abstract: The $K^+ \rightarrow \pi^+ \nu \bar{\nu}$  decay is a golden mode for flavour physics. Its branching ratio is predicted with a high precision by the Standard Model to be less than $\mathcal{O}(10^{-10})$. This decay mode is highly sensitive to indirect effects of new physics up to the highest mass scales. The NA62 experiment at the CERN SPS is designed to study the $K^+ \rightarrow \pi^+ \nu \bar{\nu}$ decay, and provided the world’s most precise investigation of this decay using 2016-18 data. Building on this success, the first results from a significantly improved analysis of new data, taken in 2021-22 after beam-line and detector upgrades, are presented, as well as the combination with the 2016-18 results.

The MAgnetized Disk and Mirror Axion eXperiment (MADMAX) is a future experiment aiming to detect dark matter 
axions from the galactic halo by resonant conversion to photons in a strong magnetic field. It uses a novel 
concept based on a stack of dielectric disks, called booster, to enhance the potential signal from axion-photon 
conversion over a significant mass range. In its final version, MADMAX will scan the uncharted QCD axion mass range 
around 100 mu-eV, favoured by post-inflationary theories. Several small scale prototypes have been tested these 
last three years, allowing to validate the dielectric haloscope novel concept and perform competitive axion and 
dark photon dark matter searches. The seminar will give an overview of these results.
The next foreseen steps will also be discussed, as well as the french contributions to the MADMAX project.

ISOLDE (Isotope Separator On-Line DEvice) is a radioactive ion beam facility at CERN. ISOLDE provides radioactive ion beams with high intensity and excellent emittance, at a wide range of energies including post-accelerated beams. The beams from ISOLDE are used in a very rich and diverse scientific programme with a focus on the physics of exotic nuclei, but extending to atomic and molecular physics, solid-state physics, material science and medical isotopes. This seminar will provide an introduction to the facility and illustrate some of the physics highlights for non-experts.

Abstract: Our knowledge of $B$-meson decays to hadrons is limited, and about 40% of the total $B$ width is not known in terms of exclusive branching fractions. Therefore, the unmeasured decays are usually simulated with relevant assumptions and coarse approximations for the description of the dynamics, as in the PYTHIA fragmentation model. This limits the capability of understanding and controlling the backgrounds of many $B$-decay analyses. A large part of the Belle II experiment physics program relies on the so-called $B$-tagging, i.e. identifying the partner $B$ meson produced in association with the signal $B$ meson to infer the properties of the signal. The impact of our limited knowledge of hadronic $B$ decays on $B$-tagging and Belle II measurements in general are discussed in this seminar. The Belle II collaboration is doing a great effort to mitigate the problem, studying new high-purity hadronic $B$ decay channels. The unknown fraction of the total $B$ width is spread across multiple exclusive channels, therefore improvements are not expected from single results, but require the systematic exploration of a significant fraction of them. This effort is presented, with a particular attention to the recent $\overline B\to D^{(*)} K^- K^{(*)0}_{(S)}$ and $B^-\to D^0\rho(770)^-$ Belle II measurements.