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Studies of beauty baryon decays to $D^0 ph^-$ and $\Lambda_c^+ h^-$ final states

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Abstract

Decays of beauty baryons to the $D^0 p h^-$ and $\Lambda_c^+ h^-$ final states (where $h$ indicates a pion or a kaon) are studied using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector. The Cabibbo-suppressed decays $\Lambda_b^0\to D^0 p K^-$ and $\Lambda_b^0\to \Lambda_c^+ K^-$ are observed and their branching fractions are measured with respect to the decays $\Lambda_b^0\to D^0 p \pi^-$ and $\Lambda_b^0\to \Lambda_c^+ \pi^-$. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon $\Xi_b^0$ to the $D^0 p K^-$ final state, and a measurement of the $\Xi_b^0$ mass is performed. Evidence of the $\Xi_b^0\to \Lambda_c^+ K^-$ decay is also reported.

Figures and captions

Distributions of invariant mass for (a) $\Lambda ^+_ c \pi ^- $ and (b) $ D ^0 p \pi ^- $ candidates passing the loose selection (points with error bars) and results of the fit (solid line). The signal and background contributions are shown.

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Distributions of invariant mass for (a) $ D ^0 p \pi ^- $ and (b) $ D ^0 p K ^- $ candidates passing the tight selection (points with error bars) and results of the fit (solid line). The signal and background contributions are shown.

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Distributions of invariant mass for (a) $\Lambda ^+_ c \pi ^- $ and (b) $\Lambda ^+_ c K ^- $ candidates passing the tight selection (points with error bars) and results of the fit (solid line). The signal and background contributions are shown. The same distributions are magnified in (c) and (d) to better distinguish background components and $\Xi _{ b }^0 \rightarrow \Lambda ^+_ c K ^- $ signal.

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Dalitz plot of $\Lambda ^0_ b \rightarrow D ^0 p \pi ^- $ candidates in (a) the full phase space region, and magnified regions of (b) low $M^2( D ^0 p )$ and (c) low $M^2( p \pi ^- )$.

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Background-subtracted distributions of (a,b) $M( p \pi ^- )$ and (c,d) $M( D ^0 p )$ invariant masses in $\Lambda ^0_ b \rightarrow D ^0 p \pi ^- $ decays, where (b) and (d) are versions of (a) and (c), respectively, showing the lower invariant mass parts of the distributions. The distributions are not corrected for efficiency.

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(a) $\Lambda ^0_ b \rightarrow D ^0 p K ^- $ Dalitz plot and background-subtracted distributions of (b) $M( p K ^- )$ and (c) $M( D ^0 p )$ invariant masses. The distributions are not corrected for efficiency.

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Animated gif made out of all figures.

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Tables and captions

Results of the fit to the invariant mass distribution of $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \pi ^- $ and $\Lambda ^0_ b \rightarrow D ^0 p \pi ^- $ candidates passing the loose selection. The uncertainties are statistical only.

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Results of the fit to the invariant mass distributions of $\Lambda ^0_ b \rightarrow \Lambda ^+_ c h^-$ and $\Lambda ^0_ b \rightarrow D ^0 p h^-$ candidates passing the tight selection. The uncertainties are statistical only.

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Efficiency correction factors used to calculate the ratios of branching fractions.

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Measured ratios of branching fractions, with their statistical and systematic uncertainties in units of $10^{-2}$.

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Systematic uncertainties in the measurement of the mass difference $m_{\Xi _{ b }^0 }-m_{\Lambda ^0_ b }$.

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Supplementary Material [file]

dppics.{C,eps,pdf,png} - Distribution of "wrong-flavour" D0bar p pi invariant mass used to constrain background, and result of its fit. dpkcs.{C,eps,pdf,png} - Distribution of "wrong-flavour" D0bar p K invariant mass used to constrain background, and result of its fit.

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Created on 10 August 2020.