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Measurement of the CP-violating phase and decay-width difference in $B_s^0\to\psi(2S)\phi$ decays

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Abstract

A time-dependent angular analysis of $B_s^0\to\psi(2S)\phi$ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0\invfb collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the $B_s^0$ system are measured to be $\phi_s = 0.23^{+0.29}_{-0.28} \pm 0.02$ rad and $\Delta\Gamma_s = 0.066^{+0.041}_{-0.044} \pm 0.007$ ps$^{-1}$, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that $\phi_s$ and $\Delta\Gamma_s$ have been measured in a decay containing the $\psi(2S)$ resonance.

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Definition of helicity angles.

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Distribution of $m(\psi(2S) K ^+ K ^- )$ for the selected $ B ^0_ s \rightarrow \psi(2S)\phi$ candidates. The total fit model is shown by the solid blue line, which is composed of a sum of two Crystal Ball functions for the signal and an exponential function for the background (long-dashed green line).

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Distribution of $m(\psi(2S) K ^+ \pi^-)$ of the selected $ B ^0 \rightarrow \psi(2S)K^{*}(892)^{0}$ candidates. The total fit model is shown by the solid blue line, which is composed of a sum of two Crystal Ball functions for the signal and an exponential function for the background (long-dashed green line).

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Decay-time efficiency $\varepsilon_{\rm data}^{ B ^0_ s }(t)$ in arbitrary units.

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Decay-time and helicity-angle distributions for $ B ^0_ s \rightarrow \psi(2S)\phi$ decays (data points) with the one-dimensional projections of the fitted PDF. The solid blue line shows the total signal contribution, which is composed of $ C P$ -even (long-dashed red), $ C P$ -odd (short-dashed green) and $S$-wave (dash-dotted purple) contributions.

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$|A_0|^2$ as a function of the invariant mass squared of the dimuon system, $q^2$. Data points are taken from Ref. [38] ($ B ^0_ s \rightarrow \phi\mu^+\mu^-$, circles), Ref. [3] ($ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi$, diamond) and this paper (square).

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Animated gif made out of all figures.

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Tables and captions

Results of the maximum likelihood fit to the selected $ B ^0_ s \rightarrow \psi(2S)\phi$ candidates including all acceptance and resolution effects. The first uncertainty is statistical and the second is systematic, which will be discussed in Section 7.

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Correlation matrix of statistical uncertainties.

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Summary of statistical and systematic uncertainties. Fields containing a dash (--) correspond to systematic uncertainties that are negligible.

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Created on 27 April 2024.