# 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. fig1a.pdf [18 KiB] HiDef png [354 KiB] Thumbnail [263 KiB] *.C file fig1b.pdf [18 KiB] HiDef png [346 KiB] Thumbnail [273 KiB] *.C file 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. fig2a.pdf [17 KiB] HiDef png [362 KiB] Thumbnail [275 KiB] *.C file fig2b.pdf [20 KiB] HiDef png [454 KiB] Thumbnail [345 KiB] *.C file 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. fig3a.pdf [17 KiB] HiDef png [354 KiB] Thumbnail [261 KiB] *.C file fig3b.pdf [20 KiB] HiDef png [403 KiB] Thumbnail [306 KiB] *.C file fig3c.pdf [18 KiB] HiDef png [424 KiB] Thumbnail [318 KiB] *.C file fig3d.pdf [18 KiB] HiDef png [439 KiB] Thumbnail [337 KiB] *.C file 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 $M^2( p \pi ^- )$. fig4.pdf [197 KiB] HiDef png [256 KiB] Thumbnail [222 KiB] *.C file 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. fig5.pdf [24 KiB] HiDef png [321 KiB] Thumbnail [343 KiB] *.C file (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. fig6.pdf [27 KiB] HiDef png [145 KiB] Thumbnail [141 KiB] *.C file Animated gif made out of all figures. PAPER-2013-056.gif Thumbnail

## 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. Table_1.pdf [50 KiB] HiDef png [69 KiB] Thumbnail [29 KiB] tex code 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. Table_2.pdf [53 KiB] HiDef png [190 KiB] Thumbnail [82 KiB] tex code Efficiency correction factors used to calculate the ratios of branching fractions. Table_3.pdf [66 KiB] HiDef png [33 KiB] Thumbnail [16 KiB] tex code Measured ratios of branching fractions, with their statistical and systematic uncertainties in units of $10^{-2}$. Table_4.pdf [71 KiB] HiDef png [111 KiB] Thumbnail [49 KiB] tex code Systematic uncertainties in the measurement of the mass difference $m_{\Xi _{ b }^0 }-m_{\Lambda ^0_ b }$. Table_5.pdf [30 KiB] HiDef png [52 KiB] Thumbnail [25 KiB] tex code

## 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. dpkcs.pdf [10 KiB] HiDef png [308 KiB] Thumbnail [260 KiB] *C file dppics.pdf [9 KiB] HiDef png [233 KiB] Thumbnail [227 KiB] *C file

Created on 18 October 2019.