Precision measurement of $CP$ violation in $B_s^0 \to J/\psi K^+K^-$ decays

Information

LHCb-PAPER-2014-059
CERN-PH-EP-2014-271
arXiv:1411.3104 [PDF]

(Submitted on 12 Nov 2014)
Phys. Rev. Lett. 114 (2015) 041801
Inspire 1327481

Tools

Abstract

The time-dependent $CP$ asymmetry in $B_s^0 \to J/\psi K^+K^-$ decays is measured using $pp$ collision data, corresponding to an integrated luminosity of $3.0$fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of $7$ and $8$TeV. In a sample of 96 000 $B_s^0 \to J/\psi K^+K^-$ decays, the $CP$-violating phase $\phi_s$ is measured, as well as the decay widths $\Gamma_{L}$ and $\Gamma_{H}$ of the light and heavy mass eigenstates of the $B_s^0-\bar{B}_s^0$ system. The values obtained are $\phi_s = -0.058 \pm 0.049 \pm 0.006$ rad, $\Gamma_s \equiv (\Gamma_{L}+\Gamma_{H})/2 = 0.6603 \pm 0.0027 \pm 0.0015$ps$^{-1}$, and$\Delta\Gamma_s \equiv \Gamma_{L} - \Gamma_{H} = 0.0805 \pm 0.0091 \pm 0.0032$ps$^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of those quantities to date. A combined analysis with $B_s^{0} \to J/\psi \pi^+\pi^-$ decays gives $\phi_s = -0.010 \pm 0.039 $rad. All measurements are in agreement with the Standard Model predictions. For the first time the phase $\phi_s$ is measured independently for each polarisation state of the $K^+K^- $ system and shows no evidence for polarisation dependence.

Figures and captions

(a) Background-subtracted invariant mass distributions of the $K^{+}K^{-}$ system in the selected $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K^{+}K^{-}$ candidates (black points). The vertical red lines denote the boundaries of the six bins used in the maximum likelihood fit. (b) Distribution of $m( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- )$ for the data sample (black points) and projection of the maximum likelihood fit (blue line). The $ B ^0_ s $ signal component is shown by the red dashed line and the combinatorial background by the green long-dashed line. Background from misidentified $ B ^0$ and $\Lambda ^0_ b $ decays is subtracted, as described in the text.	KKMass[..].pdf [19 KiB] HiDef png [147 KiB] Thumbnail [144 KiB] *.C file
	JpsiKK[..].pdf [23 KiB] HiDef png [193 KiB] Thumbnail [152 KiB] *.C file
Decay-time and helicity-angle distributions for $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- $ decays (data points) with the one-dimensional fit projections overlaid. 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 (dotted-dashed purple) contributions.	timeLog.pdf [24 KiB] HiDef png [232 KiB] Thumbnail [190 KiB] *.C file
	ctk.pdf [19 KiB] HiDef png [224 KiB] Thumbnail [190 KiB] *.C file
	ctl.pdf [19 KiB] HiDef png [222 KiB] Thumbnail [183 KiB] *.C file
	phi.pdf [20 KiB] HiDef png [213 KiB] Thumbnail [190 KiB] *.C file
Animated gif made out of all figures.	PAPER-2014-059.gif Thumbnail

Tables and captions

Values of the principal physics parameters determined from the polarisation-independent fit.	Table_1.pdf [53 KiB] HiDef png [60 KiB] Thumbnail [29 KiB] tex code
Values of the polarisation-dependent parameters $\phi_s^k$ and $\|\lambda^k\|$ determined from the polarisation-dependent fit.	Table_2.pdf [50 KiB] HiDef png [51 KiB] Thumbnail [25 KiB] tex code
Statistical and systematic uncertainties for the polarisation-independent result.	Table_3.pdf [56 KiB] HiDef png [126 KiB] Thumbnail [51 KiB] tex code
Statistical and systematic uncertainties for the polarisation-dependent result.	Table_4.pdf [53 KiB] HiDef png [68 KiB] Thumbnail [28 KiB] tex code
Statistical correlation matrix from the polarisation-independent fit.	Table_5.pdf [47 KiB] HiDef png [53 KiB] Thumbnail [25 KiB] tex code
Total statistical and systematic correlation matrix from the polarisation-independent fit.	Table_6.pdf [47 KiB] HiDef png [54 KiB] Thumbnail [25 KiB] tex code
Statistical correlation matrix for the $\phi_s^{k}$ and $\|\lambda^k\|$ parameters from the polarisation-dependent fit.	Table_7.pdf [46 KiB] HiDef png [54 KiB] Thumbnail [26 KiB] tex code
Total statistical and systematic correlation matrix for the $\phi_s^{k}$ and $\|\lambda^k\|$ parameters from the polarisation-dependent fit.	Table_8.pdf [46 KiB] HiDef png [54 KiB] Thumbnail [26 KiB] tex code
S-wave parameter estimates in each $m( K ^+ K ^- )$ bin from the polarisation-independent fit. Only statistical uncertainties are shown.	Table_9.pdf [43 KiB] HiDef png [211 KiB] Thumbnail [90 KiB] tex code

Supplementary Material [file]

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