First evidence for mixing-induced $CP$ violation in B${}_{\mathrm{s}}^0$ $\to$ J/$\psi \varphi$(1020) decays in pp collisions at $\sqrt{s}=$ 13 TeV

Abstract

A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27000 tagged B${}_{\mathrm{s}}^0$ $\to$ J/$\psi \varphi$(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 ${\mu }^{+}{\mu }^{-}$K${}^{+}$K${}^{-}$ final state, consistent with a $\varphi$(1020) $\to$ K${}^{+}$K${}^{-}$ decay, is used to measure parameters of the ${\mathrm{B}}_{\mathrm{s}}^0-{\overline{\mathrm{B}}}_{\mathrm{s}}^0$ system. The weak phase is measured to be ${\varphi }_{\mathrm{s}}$ = $-$73 $\pm$ 22 (stat) $\pm$ 10 (syst) mrad, which, combined with the $\sqrt{s}$ $=$ 8 TeV CMS result, gives ${\varphi }_{\mathrm{s}}$ = $-$75 $\pm$ 23 mrad. This value differs from zero by 3.2 standard deviations, providing the first evidence for mixing-induced $CP$ violation in B${}_{\mathrm{s}}^0$ $\to$ J/$\psi \varphi$(1020) decays. All measured physics parameters are found to agree with standard model predictions where available.

arXiv commentReplaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-23-004 (CMS Public Pages)

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