Abstract

The first observation of the $B^0_s \to D^{*+}D^{*-}$ decay and the measurement of its branching ratio relative to the $B^0 \to D^{*+}D^{*-}$ decay are presented. The data sample used corresponds to an integrated luminosity of $9 \text{fb}^{-1}$ of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and $13 \text{TeV}$ between 2011 and 2018. The decay is observed with more than $10$ standard deviations and the time-integrated ratio of branching fractions is determined to be \begin{align*} \frac{\mathcal{B}(B^0_s \to D^{*+}D^{*-})}{\mathcal{B}(B^0 \to D^{*+}D^{*-})} = 0.269 \pm 0.032 \pm 0.011 \pm 0.008 , \end{align*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio $f_s/f_d$. The $B^0_s \to D^{*+}D^{*-}$ branching fraction is calculated to be \begin{align*} \mathcal{B}(B^0_s \to D^{*+}D^{*-}) = (2.15 \pm 0.26 \pm 0.09 \pm 0.06 \pm 0.16)\times 10^{-4} , \end{align*} where the fourth uncertainty is due to the $B^0 \to D^{*+}D^{*-}$branching fraction. These results are calculated using the average $B^0_s$ meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light $B^0_s$ eigenstate is considered.

Figures and captions

Dominant Feynman diagrams for $ B \rightarrow D D $ decays comprising (top left) tree, (top right) penguin, (bottom left) $ W $ -exchange and (bottom right) penguin-annihilation transitions. The $ B ^0_ s \rightarrow D ^{*+} D ^{*-} $ decay can only occur via the $ W $ -exchange or penguin-annihilation diagram.	Figure1a.pdf [35 KiB] HiDef png [26 KiB] Thumbnail [12 KiB] *.C file
	Figure1b.pdf [45 KiB] HiDef png [30 KiB] Thumbnail [15 KiB] *.C file
Distributions of the $ D ^{*+}$ $ D ^{*-}$ mass for (left) Run 1 and (right) Run 2 data samples, with the fit results overlaid. In addition to the full fit result (solid black), each of the individual components are shown: the $ B ^0 \rightarrow D ^{*+} D ^{*-} $ signal (dotted blue), the $ B ^0_ s \rightarrow D ^{*+} D ^{*-} $ signal (dash-dotted red) and the combinatorial background (dashed green).	Figure2a.pdf [24 KiB] HiDef png [266 KiB] Thumbnail [239 KiB] *.C file
	Figure2b.pdf [31 KiB] HiDef png [276 KiB] Thumbnail [250 KiB] *.C file
Animated gif made out of all figures.	PAPER-2022-023.gif Thumbnail

Tables and captions

Systematic uncertainties relative to the measured value of the ratio of branching fractions for Run 1, Run 2, and their combination, taking into account correlations.

Table_1.pdf [49 KiB] HiDef png [70 KiB] Thumbnail [31 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [196 KiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2022-023. The files are: supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps : The figures in variuous formats	Figure3a.pdf [32 KiB] HiDef png [293 KiB] Thumbnail [250 KiB] *C file
	Figure3b.pdf [31 KiB] HiDef png [171 KiB] Thumbnail [143 KiB] *C file

Created on 26 April 2024.