$C\!P$-Violation in a General-Purpose Detector: $\sin{(2\beta)}$ with CMS

by Dr Valeriia Lukashenko (Universität Zürich)

Thursday 2 Jul 2026, 16:00 → 17:00 Europe/Berlin

CP-03-123 (TU Dortmund)

The Cabibbo–Kobayashi–Maskawa (CKM) angle $\beta$ is one of the most precisely determined parameters of the CKM unitarity triangle and provides one of the most stringent tests of the Standard Model flavour sector. The decay $B^0_d \to J/\psi K^0_S$ is the golden mode for measuring $\sin(2\beta)$. At the same time, the effective CP-violating phase extracted from this decay is sensitive to contributions from beyond the Standard Model physics. However, its interpretation is limited by higher order penguin contributions, which can shift the measured phase. These penguin contributions can be constrained using $SU(3)$ symmetric decays, such as $B^0_s \to J/\psi K^0_S$.

In this seminar, the first high-precision measurements of CP violation performed by CMS in the decays $B^0_d \to J/\psi K^0_S$ and its penguin-control counterpart $B^0_s \to J/\psi K^0_S$, using the Run 3 dataset, will be shown. While precision CP-violation measurements have traditionally been dominated by the dedicated flavour experiments such as LHCb, advances in data collection have enabled competitive studies with the CMS detector. These measurements demonstrate the growing potential of CMS in precision flavour physics.

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To participate virtually, please connect to this Zoom room.

Seminar_sin2beta.pdf