Séminaires, soutenances

Séminaire de 2eme année de thèse: The photon polarization in b->s gamma penguins from B_s ->phi gamma at LHCb

par M. Mostafa HOBALLAH (LPC-Clermont)

Europe/Paris
Amphi Recherche (Dept.Phys.)

Amphi Recherche

Dept.Phys.

Description
The Flavor Changing Neutral Currents are forbidden at the tree level in the Standard Model (SM). At the leading order , the radiative b->s gamma transition proceeds through one-loop electromagnetic penguins. In several New Physics (NP) scenarii, new heavy particles contribute virtually to the loop and can introduce sizable deviation to the predicted dynamics of the transition. The radiative decay of b-hadrons is considered as one of the most powerful probe for the indirect search of NP effects in the flavor sector. The LHCb experiment is a well-suited laboratory for the precise study of these rare radiative decays. Branching ratios, asymmetries are accessible with an unprecedented precision in several radiative decays of B0, Bs mesons and b-baryons. One of the main physics goal of the LHCb experiment is the accurate measurement of the photon polarization in the b->s \gamma transitions. The SM predicts the emitted photons to be mostly left-handed, the right-handed polarization being strongly suppressed. Several experimental strategies have been proposed for the measurement of the photon polarization. I will focus my presentation on the measurement of the time-dependent decay rate of the Bs->phiGamma transition that can be directly connected to the rate of the right-handed photon polarization. From an experimental point of view, the reconstruction of radiative B decays relies on the good performance of the calorimetric system. Performant reconstruction and identification of photons is required. I will describe the analysis tools that have been developed for the identification of the photon and its separation from energetic neutral pions.