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.

La construction du détecteur à pixels du nouveau trajectographe d'ATLAS, le ITK,  a commencé. Ce séminaire vous donnera un aperçu de 10 années de travail pour construire le plus gros trajectographe en Silicium jamais installé sur un accélérateur. Nous aborderons les difficultés et les défis à vaincre pour parvenir à concevoir et à fabriquer un tel objet. Un tour des activités qui auront lieu dans le laboratoire durant les deux prochaines années vous sera proposé, afin de vous expliquer ce que les équipes du CPPM vont réaliser.

The quest for PeVatrons, sources of galactic cosmic rays accelerated up to PeV energies, saw an exciting development in the last years, thanks to the many gamma-ray sources detected by ground array experiments at energy above 100 TeV. Among those sources, the supernova remnant SNR G106.3+2.7 (including the Boomerang PWN) is a promising PeVatron candidate for which the ultra-high energy emission can be explained with both hadronic and leptonic emission scenarios. It was detected with a very high significance detection above 100 TeV by LHAASO, making it a candidate for the emission of PeV protons.
Imaging Atmospheric Cherenkov Telescopes (IACTs) are ideal instruments to investigate the nature of the most energetic sources of the Universe in gamma-ray astronomy thanks to their optimal angular and energy resolution. The Cherenkov Telescope Array Observatory (CTAO) will be the leading instrument for observations between tens of GeV and hundreds of TeV thanks to an hybrid array of IACTs. It will allow for high resolution observation of the TeV sky in a complementary energy range with LHAASO. Using the LST-1, the Large-Sized Telescope prototype of the Cherenkov Telescope Array Observatory, together with the two neighbors IACTs of the MAGIC experiment, we are currently observing the SNR G106.3+2.7 at Large Zenith Angle (LZA), which allows us to explore the 1-50 TeV region of the energy spectrum.
I will give an overview of the CTAO and its first telescope, the LST-1. Then I will describe the status of the knowledge on galactic PeVatrons and present the work lead by CPPM on the observation of the SNR G106.3+2.7 with LST-1 and MAGIC.