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Observation of $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ decays

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Abstract

The multihadron decays $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ are observed in data corresponding to an integrated luminosity of 3fb$^{-1}$, collected in proton-proton collisions at centre-of-mass energies of 7 and 8TeV by the LHCb detector. Using the decay $\Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^-$ as a normalisation channel, the ratio of branching fractions is measured to be $$ \frac { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^+ p \pi^-\pi^- ) } { {\mathcal{B}} ( \Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^- ) } \times \frac { {\mathcal{B}} ( D^+ \rightarrow K^-\pi^+\pi^+) } { {\mathcal{B}} ( \Lambda_c^+ \rightarrow p K^-\pi^+ ) } = ( 5.35 \pm 0.21 \pm 0.16 ) \% , $$ where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ decays is found to be $$ \frac{ {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^- )} { {\mathcal{B}} ( \Lambda_b^0\rightarrow D^{+} p \pi^-\pi^- )} \times ( {\mathcal{B}}( D^{*+} \rightarrow \pi^0 ) + {\mathcal{B}}( D^{*+} \rightarrow \gamma )) = ( 61.3 \pm 4.3 \pm 4.0 ) \% . $$

Figures and captions

Mass distribution for selected $\Lambda ^0_ b \rightarrow D ^+ p \pi ^- \pi ^- $ candidates. The projection of an unbinned likelihood fit, described in the text, is superimposed.

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Mass distribution for selected $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $ candidates. The projection of an unbinned likelihood fit, described in the text, is superimposed.

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Background-subtracted $ p K ^- \pi ^+_{1,2}$ mass spectra from the $\Lambda ^0_ b \rightarrow D ^+ p \pi ^- \pi ^- $ channel with $ D ^+ \rightarrow K ^- \pi ^+_1\pi ^+_2 $ decays.

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Backgrounddash-subtracted (left) $\pi ^+ \pi ^- \pi ^- $ mass distribution from $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $ decays and (right) $ p K ^- \pi ^+_2$ mass distribution from $\Lambda ^0_ b \rightarrow \left( \Lambda ^+_ c \rightarrow p K ^- \pi ^+_1 \right)\pi ^+_2\pi ^- \pi ^- $ decays. The results of the fits described in text are overlaid.

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Background-subtracted $ D ^+ p $, $ D ^+ \pi ^- \pi ^- $, $ p \pi ^- \pi ^- $, $\pi ^- \pi ^- $, and maximum and minimum $ p \pi ^- $ mass spectra for $\Lambda ^0_ b \rightarrow D ^+ p \pi ^- \pi ^- $ decays. Expectations from phasedash-space (phsp.) and corrected (corr.) simulation are overlaid.

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Background-subtracted maximum and minimum $ D ^+ p \pi ^- $, and maximum and minimum $ D ^+ \pi ^- $ mass spectra for $\Lambda ^0_ b \rightarrow D ^+ p \pi ^- \pi ^- $ decays. Expectations from phasedash-space (phsp.) and corrected (corr.) simulation are overlaid.

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Background-subtracted $ D ^+ p $, $ D ^+ \pi ^- \pi ^- $, $ p \pi ^- \pi ^- $, $\pi ^- \pi ^- $, and maximum and minimum $ p \pi ^- $ mass spectra for $\Lambda ^0_ b \rightarrow D ^{*+} p \pi ^- \pi ^- $ decays. Expectations from phasedash-space (phsp.) and corrected (corr.) simulation are overlaid.

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Background-subtracted maximum and minimum $ D ^+ p \pi ^- $, and maximum and minimum $ D ^+ \pi ^- $ mass spectra for $\Lambda ^0_ b \rightarrow D ^{*+} p \pi ^- \pi ^- $ decays. Expectations from phasedash-space (phsp.) and corrected (corr.) simulation are overlaid.

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Background-subtracted maximum and minimum $\Lambda ^+_ c \pi ^+ \pi ^- $, and maximum and minimum $\pi ^+ \pi ^- $ mass spectra for the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $ decays. Expectations from uncorrected and corrected (corr.) simulation are overlaid.

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Background-subtracted $\pi ^- \pi ^- $, $\Lambda ^+_ c \pi ^+ $, $\Lambda ^+_ c \pi ^- \pi ^- $, $\Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $, and maximum and minimum $\Lambda ^+_ c \pi ^- $ mass spectra for the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $ decays. Expectations from uncorrected and corrected (corr.) simulation are overlaid.

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Animated gif made out of all figures.

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Tables and captions

Yields, \(N^{\mathrm{fit}}\), for the \( $\Lambda ^0_ b \rightarrow D ^+ p \pi ^- \pi ^- $ \), \( $\Lambda ^0_ b \rightarrow D ^{*+} p \pi ^- \pi ^- $ \) and \( $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^+ \pi ^- \pi ^- $ \) decays evaluated from fits to the \( $ D ^+$ $ p $ $\pi ^-$ $\pi ^-$ \) and \( $\Lambda ^+_ c $ $\pi ^+$ $\pi ^-$ $\pi ^-$ \) mass spectra. The yields with all corrections described in the text, \(N^{\mathrm{cor}}\), are also given. The uncertainties are statistical only.

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Relative systematic uncertainties for the ratios $\mathcal{R}_{ D ^+ }$ and $\mathcal{R}_{ D ^{*+} }$. The total uncertainty is obtained by summing all terms in quadrature.

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Created on 28 March 2024.