Observation of $\Lambda_b^0 \to \Lambda_c^+ \bar{D}^{()0} K^-$ and $\Lambda_b^0 \to \Lambda_c^+ D_s^{-}$ decays

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LHCb-PAPER-2023-034
CERN-EP-2023-244
arXiv:2311.14088 [PDF]

(Submitted on 23 Nov 2023)
EPJC
Inspire 2725948

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Abstract

The decays $\Lambda_b^0 \to \Lambda_c^+\bar{D}^{(*)0}K^-$ and $\Lambda_b^0 \to \Lambda_c^+ D_s^{*-}$ are observed for the first time, in proton-proton collision data at $\sqrt{s}=13$TeV corresponding to an integrated luminosity of 5.4 fb${}^{-1}$ collected with the LHCb detector. Their ratios of branching fractions with respect to the $\Lambda_b^0 \to\Lambda_c^+\mathrm{D}_s^-$ mode are measured to be \begin{align*} \begin{split} \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+\bar{D}^0 K^-)}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 0.1908 {}_{-0.0034}^{+0.0036} {}_{-0.0018}^{+0.0016} \pm 0.0038 \\ \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+\bar{D}^{*0} K^-)}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 0.589 {}_{-0.017}^{+0.018} {}_{-0.018}^{+0.017} \pm 0.012 \\ \frac{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^{*-})}{\mathcal{B}(\Lambda_b^0 \to \Lambda_c^+ D_s^-)} & = 1.668 \pm 0.022 {}_{-0.055}^{+0.061}\ , \end{split} \end{align*} where the first uncertainties are statistical, the second systematic, and the third, for the $\Lambda_b^0 \to \Lambda_c^+ \bar{D}^{(*)0} K^-$ decays, are due to the uncertainties on the branching fractions of the $D_s^- \to K^- K^+ \pi^-$ and $\bar{D}^0 \to K^+\pi^-$ decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in $\Lambda_b^0 \to \Lambda_c^+ \bar{D}^{(*)0}K^-$ decay channels.

Figures and captions

Dominant Feynman diagrams for (left, middle) the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c \overline{ D } {}^{()0} K ^- $ decays and (right) the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c D ^{()-}_ s $ decays.		[Failure to get the plot]
Invariant-mass distributions of (top) $\Lambda ^+_ c D ^-_ s $ and (bottom) $\Lambda ^+_ c \overline{ D } {}^0 K ^- $ candidates with the results of the baseline fit overlaid.		[Failure to get the plot]

Tables and captions

Explicitly rejected physics backgrounds. Some background contributions are present only in the $\Lambda ^+_ c \overline{ D } {}^0 K ^- $ or $\Lambda ^+_ c D ^-_ s $ systems, while others in both. A particle, $M_\mathrm{misID}$, that decays through a real particle $a$, which is reconstructed as a particle with different mass hypothesis $b$, is denoted as $ M_\mathrm{misID} \rightarrow \{a \leftarrow b\}X $, where $X$ corresponds to the rest of the decay. As there are two $ K ^- $ mesons in the final state, the subscripts "$\Lambda ^+_ c $" and "com" (for companion) or "$ D ^-_ s $" denote the assignment in the $\Lambda ^+_ c \overline{ D } {}^0 K ^- $ or $\Lambda ^+_ c D ^-_ s $ reconstruction chain. Cases where the proton is misidentified as a pion or kaon and combined into a $ D ^0 $ candidate, are marked with the $ D ^0 $ subscript.	Table_1.pdf [91 KiB] HiDef png [42 KiB] Thumbnail [20 KiB] tex code
Systematic uncertainties relative to the branching fraction ratio measurements. The relative statistical uncertainty is shown as a reference. Values are given in percent.		[Error creating the table]

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [392 KiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2023-034. The files are: supplementary.pdf : An overview of the extra figures .pdf, .png, *.eps : The figures in variuous formats	Fig1a-S.pdf [80 KiB] HiDef png [193 KiB] Thumbnail [150 KiB] *C file
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