Measurement of CP violation in B0→ D+D− and Bs0→Ds+Ds− decays

Abstract

Abstract A time-dependent, flavour-tagged measurement of CP violation is performed with B 0 → D + D

− and

$$ {B}_s^0 $$

B s 0

→

$$ {D}_s^{+}{D}_s^{-} $$

D s +

D s −

decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb −1. In B 0 → D + D

− decays the CP-violation parameters are measured to be

$$ {\displaystyle \begin{array}{c}{S}_{D^{+}{D}^{-}}=-0.552\pm 0.100\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right),\\ {}{C}_{D^{+}{D}^{-}}=0.128\pm 0.103\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right).\end{array}} $$

S

D +

D −

= − 0.552 ± 0.100

stat

± 0.010

syst

,

C

D +

D −

= 0.128 ± 0.103

stat

± 0.010

syst

.

In

$$ {B}_s^0 $$

B s 0

→

$$ {D}_s^{+}{D}_s^{-} $$

D s +

D s −

decays the CP-violating parameter formulation in terms of ϕ

s and |λ| results in

$$ {\displaystyle \begin{array}{c}{\phi}_s=-0.086\pm 0.106\left(\textrm{stat}\right)\pm 0.028\left(\textrm{syst}\right)\textrm{rad},\\ {}\mid {\lambda}_{D_s^{+}{D}_s^{-}}\mid =1.145\pm 0.126\left(\textrm{stat}\right)\pm 0.031\left(\textrm{syst}\right).\end{array}} $$

ϕ s

= − 0.086 ± 0.106

stat

± 0.028

syst

rad ,

∣

λ

D s +

D s −

∣ = 1.145 ± 0.126

stat

± 0.031

syst

.

These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B 0 → D + D

− decays with a significance exceeding six standard deviations.