A Monte Carlo simulation for Prompt Gamma Time Imaging in protontherapy

• Alicia Garnier

<b>Abstract: </b> We are developing a Geant4 Monte Carlo simulation of the TIARA detector dedicated to Prompt Gamma Time Imaging (PGTI) used for dose deposition monitoring in protontherapy. The Time-of-flight Imaging ArRAy (TIARA) is composed of a beam monitor and 30 PbF₂ Cerenkov radiator surrounding the phantom. Computed Tomography (CT) scans of the setup tested at the Mediterranean Institute for Protontherapy of the Centre Antoine Lacassagne (CAL) in Nice are used to precisely define the geometry of the simulated setup. The simulated proton beam reproduces the specifications that are used at CAL. The phantom used is a RANDO phantom head described using the materials it is made of, using the DICOM data from the phantom scans. The purpose is to compare the results obtained with the simulation to the experimental data. We describe the Monte Carlo implementation of the PGTI setup and preliminary results against experimental data.

Search for $B^0 \rightarrow K^{*0} \tau \ell$ lepton flavour violating decays at Belle II

• Clotilde LEMETTAIS

<b>Abstract: </b> Lepton Flavour Violation (LFV) being forbidden in the Standard Model, LFV searches represent a powerful probe for New Physics. Studying $B^0 \rightarrow K^{*0} \tau \ell$ decays, where $\ell$ is an electron or muon, is particularly interesting: it allows to explore both $b \rightarrow s\ell\ell'$ transitions and the third generation coupling with $\tau$ leptons which could be more sensitive to New Physics. The Belle II experiment is located at the SuperKEKB $e^+e^-$ collider at KEK, and collected a total of 365 fb$^{-1}$ of data at the $\Upsilon(4S)$ resonance ($10.58~\text{GeV}$) during its first data taking period, from 2019 to 2022. Designed to produce $B\bar{B}$ pairs in a clean environment and almost hermetic detector, the Belle II experiment provides a well-suited environment for the study of $B^0 \rightarrow K^{*0} \tau \ell$ decays, where the partner $B$ meson from the $B\bar{B}$ pair production is reconstructed hadronically. This analysis uses a cut-based selection coupled to machine learning techniques to reject the background. An upper limit on the $B^0 \rightarrow K^{*0} \tau \ell$ branching fraction is extracted from a fit to the recoil mass of the $\tau$ lepton.

(postponed)

• Simone Sartori