Abstract

An overview of a measurement of time-dependent CP asymmetry parameters in Bs0→J/ψ(μ+μ−)ϕ(K+K−) decays using 80.5 fb−1 of integrated luminosity collected with the ATLAS detector from 13 TeV pp collisions at the LHC is presented. A manifestation of the CP violation is an interference between direct and mixing-mediated Bs0 decays, producing a common final state. In the Standard Model, it is characterized by a phase shift ϕs related to the CKM matrix. In the case of Bs0→J/ψϕ, this shift is predicted to be small, ϕs=−0.0363−0.0015+0.0016 rad. New physics can enhance ϕs whilst satisfying all existing constraints. Results presented in this talk are compatible with those obtained from 19.2 fb−1 of 7 TeV and 8 TeV data as well as with the Standard Model predictions and other LHC measurements.

Highlights

  • The B0s → J/ψφ decay channel is expected to be sensitive to new physics contributions in the CP violation

  • The analysis presented here introduces a measurement of parameters describing the CP violation in the B0s → J/ψφ decay using 80.5 fb−1 of LHC pp 13 TeV data collected by the ATLAS detector during 2015 2017 [2]

  • The ATLAS experiment [4] is a multipurpose particle detector at the LHC. It consists of three main parts: the Inner Detector (ID) immersed in a 2 T axial magnetic field, electromagnetic and hadronic calorimeters, and a Muon Spectrometer (MS), all located within the magnetic field produced by three large superconducting air-core toroid systems

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Summary

Introduction

The B0s → J/ψφ decay channel is expected to be sensitive to new physics contributions in the CP violation. In this channel, CP violation occurs due to interference between direct decays and decays occurring through B0s −B0s mixing. Many New Physics (NP) models allow a larger value of φs whilst satisfying all existing constraints, including the precisely measured value of ∆Ms. The analysis presented here introduces a measurement of parameters describing the CP violation in the B0s → J/ψφ decay using 80.5 fb−1 of LHC pp 13 TeV data collected by the ATLAS detector during 2015 2017 [2]. The results are combined with those obtained from the analysis of 19.2 fb−1 of data collected at 7 TeV and 8 TeV [3]

The ATLAS detector
Flavour tagging
13 TeV and Run 1 combined
Maximum likelihood fit
Results
Summary
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