First Evidence for Mixing-Induced C P Violation in B s 0 → J / ψ ϕ ( 1020 ) Decays in p p Collisions at s = 13 TeV

2024/12/27 by A. Hayrapetyan, CMS Collaboration, A. Tumasyan +151 · 1 voice · 2 citations
Physics and Astronomy · #Branching fraction #CP violation #Elementary particle #High-Energy Particle Collisions Research #Neutrino Physics Research #Nuclear physics #Particle Detector Development and Performance #Particle decay #Particle physics #Particle physics theoretical and experimental studies #Physics #Physics beyond the Standard Model #Quantum Chromodynamics and Particle Interactions #hep-ex

paper · pdf · open access · doi:10.1103/ctqx-vxrj

published in Physical Review Letters 136(18), 181801 (American Physical Society)

openalex created_date 2025/01/01 · openalex publication_date 2026/01/30 · openalex updated_date 2026/08/04

Abstract

A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27 500 tagged B_s⁰→J/ψϕ(1020) decays from pp collisions at sqrt[s]=13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 96.5 fb^-1. A time- and flavor-dependent angular analysis of the μ⁺μ^-K⁺K^- final state, consistent with a ϕ(1020)→K⁺K^- decay, is used to measure parameters of the B_s⁰-B[over ¯]_s⁰ system. The weak phase is measured to be ϕ_s=-73±22(stat)±10(syst) mrad, which, combined with the sqrt[s]=8 TeV CMS result, gives ϕ_s=-75±23 mrad. This value differs from zero by 3.2 standard deviations, providing the first evidence for mixing-induced CP violation in B_s⁰→J/ψϕ(1020) decays. All measured physics parameters are found to agree with standard model predictions where available.

Citations

• CP-Violation in the Renormalizable Theory of Weak Interaction
• Predictions of selected flavor observables within the standard model
• Observation ofBs0−B¯s0Oscillations
• Measurement of theCP-violating phaseβsJ/ψϕinBs0→J/ψϕdecays with the CDF II detector
• Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
• Measurement of the CP-violating weak phase ϕs and the decay width difference ΔΓs using the Bs0→J/ψ<mml:mspace width="0.2em"/>ϕ(1020) decay channel in pp collisions at s=8 TeV
• Measurement of the CP -violating phaseϕsinB¯s0→J/ψπ+π−decays
• First study of the CP-violating phase and decay-width difference in Bs0→ψ(2S)ϕ decays
• Flavor tagged time-dependent angular analysis of theBs0→J/ψϕdecay and extraction ofΔΓsand the weak phaseϕsin ATLAS
• Measurement of the CP-violating phase φ _s in B_s⁰ → J/ψ φ decays in ATLAS at 13 TeV
• Development of the CMS detector for the CERN LHC Run 3
• Review of Particle Physics
• Determination of the Sign of the Decay Width Difference in theBs0System
• Remarks on Some Nonparametric Estimates of a Density Function
• On Estimation of a Probability Density Function and Mode
• Parton distributions from high-precision collider data

Discussions

• The study of CP violation, or the difference in behaviour between composite matter and antimatter particles, is a very active field of study of the LHC. #CMSPaper 1374 studies CP oscillation (check t [bsky, 16 points, 0 comments]

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• Bs Mixing, DeltaGamma_s and CP Violation