# Measurement of $CP$ Violation in $B^0 \to D^+D^−$ Decays

LHCb Collaboration; Bernet, R; Müller, K; Steinkamp, O; Straumann, U; Vollhardt, A; et al (2016). Measurement of $CP$ Violation in $B^0 \to D^+D^−$ Decays. Physical Review Letters, 117(26):261801.

## Abstract

The $CP$ violation observables $S$ and $C$ in the decay channel $B^0 \to D^+D^−$ are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The observable $S$ describes $CP$ violation in the interference between mixing and the decay amplitude, and $C$ parametrizes direct $CP$ violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis:
\begin{align*} S = -0.54 \, ^{+0.17}_{-0.16} \, \text{(stat)} \pm 0.05 \,\text{(syst)}\,,\newline C = \phantom{-}0.26 \, ^{+0.18}_{-0.17} \, \text{(stat)} \pm 0.02 \,\text{(syst)}\,. \end{align*}
These values provide evidence for $CP$ violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order Standard Model corrections is constrained to a small value of
\begin{align*}\Delta\phi = -0.16\,^{+0.19}_{-0.21}\,\text{rad}\,.\end{align*}

## Abstract

The $CP$ violation observables $S$ and $C$ in the decay channel $B^0 \to D^+D^−$ are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The observable $S$ describes $CP$ violation in the interference between mixing and the decay amplitude, and $C$ parametrizes direct $CP$ violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis:
\begin{align*} S = -0.54 \, ^{+0.17}_{-0.16} \, \text{(stat)} \pm 0.05 \,\text{(syst)}\,,\newline C = \phantom{-}0.26 \, ^{+0.18}_{-0.17} \, \text{(stat)} \pm 0.02 \,\text{(syst)}\,. \end{align*}
These values provide evidence for $CP$ violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order Standard Model corrections is constrained to a small value of
\begin{align*}\Delta\phi = -0.16\,^{+0.19}_{-0.21}\,\text{rad}\,.\end{align*}

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics English 2016 17 Jan 2017 08:51 17 Jan 2017 08:51 American Physical Society 0031-9007 Publisher DOI. An embargo period may apply. https://doi.org/10.1103/PhysRevLett.117.261801

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