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Observation of the decay $B_s^0\to\bar{D}^0\phi$

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Abstract

First observation of the decay Bs -> D0bar phi is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb^-1, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The significance of the signal is 6.2 standard deviations. The branching fraction is measured relative to that of the decay Bs -> D0bar K*0bar to be 0.069 +/- 0.013 (stat) +/- 0.007 (syst). The first measurement of the ratio of branching fractions for the decays Bs -> D0bar K*0bar and Bd->D0bar K*0 is found to be 7.8 +/- 0.7 (stat) +/- 0.3 (syst) +/- 0.6 (f_s/f_d), where the last uncertainty is due to the ratio of the Bs and Bd fragmentation fractions.

Figures and captions

Feynman diagrams for the following decays: (a) $ B ^0_ s \rightarrow \overline{ D }{} ^0 \phi$ ; (b) $ B ^0_ s \rightarrow D ^0 \phi $; (c) $ B ^0 \rightarrow \overline{ D }{} ^0 K ^{*0} $ ; and (d) $ B ^0_ s \rightarrow \overline{ D }{} ^0 \overline{ K }{} ^{*0} $ . The $ B ^0_ s \rightarrow \overline{ D }{} ^0 \phi$ and $ B ^0_ s \rightarrow D ^0 \phi $ decay amplitudes interfere when $\overline{ D }{} ^0 $ and $ D ^0 $ decay to the same final state.

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Invariant mass distributions for (a) $ B ^0_ s \rightarrow \overline{ D }{} ^0 \phi$ , and (b) $ B ^0 \rightarrow \overline{ D }{} ^0 K ^{*0} $ or $ B ^0_ s \rightarrow \overline{ D }{} ^0 \overline{ K }{} ^{*0} $ decays. Data points are shown in black, the total fitted PDF as solid black line, and the components as detailed in the legends.

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Distribution of the cosine of the helicity angle of the $\phi$ candidates.

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Background-subtracted distributions of the reconstructed (left) $\phi$ mass from the $ B ^0_ s \rightarrow \overline{ D }{} ^0 \phi$ decay and (right) $\overline{ K }{} ^{*0} $ mass from the $ B ^0_ s \rightarrow \overline{ D }{} ^0 \overline{ K }{} ^{*0} $ decay. The dashed red line represents the S-wave component, the solid blue line the total fit result.

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Animated gif made out of all figures.

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Tables and captions

Uncorrected signal yields and the peaking (charmless, S-wave) background yields.

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Absolute systematic uncertainties of the measured ratio of branching fractions. The total is obtained as sum in quadrature of the different contributions.

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Created on 02 May 2024.