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Accueil du site > Formation > Thèses - Stages de M2 & ingénieur

M2 - Study of time resolution and time acceptance of the LHCb detector to decays of B mesons into four tracks and photons for the search of new physics in Bs → J/psi Eta(‘) mesons.

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A physics observable sensitive to new physics is the mixing phase of the Bs-Bs meson system. Responsible for a small violation of CP symmetry in these mesons, it manifests itself through the interference of the mixing amplitude with the decay amplitude and is thus measured through different decay channels at collider experiments. The LHCb collaboration published measurements in Bs decays to J/ψ φ and J/ψ π π final states while CP violation in Bs → J/ψ η(‘) decays is yet unexplored. The extraction of the mixing phase from the LHCb data relies on an excellent control of the detector time acceptance which distorts the time-dependent probabilities of the decays. Furthermore, the fast oscillations between Bs and Bs meson can only be resolved with an excellent time resolution which should be carefully controlled as well. The goal of the master project is to study the time acceptance and time resolution of the LHCb detector to Bs → J/ψ η(‘) decays where the J/ψ meson further decays into two muons and the η(‘) mesons to two pions and photons. In practice, the candidate will use a control decay mode without photons (B0 → J/ψ K π) to provide with high statistical precision the relevant time performance. The candidate will also study the systematics uncertainty associated to the absence of photons in the control mode. The work should prepare for a time-dependent CP violation study and a measurement of the mixing phase in these decay modes, complementary to the existing constraints and could possibly leads to a PhD thesis on this topic.

Participation to the data-taking at CERN in 2023 could be foreseen.

o Level : Master 2 internship

o Date of the internship : spring 2023

o Supervisor : M. Chefdeville, J.-F. Marchand, S. T’jampens

o Phone : 04 50 09 16 34

o e-mail : chefdevi@lapp.in2p3.fr