Type: Article
Publication Date: 2019-12-01
Citations: 15
DOI: https://doi.org/10.1007/jhep12(2019)155
A bstract A measurement of the time-dependent CP-violating asymmetry in $$ {B}_s^0\to \phi \phi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:mi>ϕϕ</mml:mi> </mml:math> decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5 . 0 fb − 1 collected by the LHCb experiment at centre-of-mass energies $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 $$ {B}_s^0\to \phi \phi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>→</mml:mo> <mml:mi>ϕϕ</mml:mi> </mml:math> decays is obtained. The CP-violating phase $$ {\phi}_s^{s\overline{s}s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>ϕ</mml:mi> <mml:mi>s</mml:mi> <mml:mrow> <mml:mi>s</mml:mi> <mml:mover> <mml:mi>s</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>s</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> is measured to be − 0 . 073 ± 0 . 115(stat) ± 0 . 027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be |λ| = 0 . 99 ± 0 . 05(stat) ± 0 . 01(syst). In addition, T -odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in $$ \overline{b}\to \overline{s}s\overline{s}s $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>b</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mo>→</mml:mo> <mml:mover> <mml:mi>s</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>s</mml:mi> <mml:mover> <mml:mi>s</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>s</mml:mi> </mml:math> transitions. Finally, a limit on the branching fraction of the B 0 → ϕϕ decay is determined to be $$ \mathcal{B}\left({B}^0\to \phi \phi \right)<2.7\times {10}^{-8} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> <mml:mfenced> <mml:mrow> <mml:msup> <mml:mi>B</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>ϕϕ</mml:mi> </mml:mrow> </mml:mfenced> <mml:mo><</mml:mo> <mml:mn>2.7</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> </mml:math> at 90 % confidence level.