Abstract

The four decays, $\Lambda_{b}^{0} \rightarrow \Sigma_c^{(*)++} D^{(*)-} K^{-}$, are observed for the first time using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of $13 \rm{TeV}$, corresponding to an integrated luminosity of $6 \rm{fb}^{-1}$. By considering the $\Lambda_b^0 \rightarrow \Lambda_c^{+} \overline{D}^0 K^{-}$ decay as reference channel, the following branching fraction ratios are measured to be, $$\frac{\cal{B} (\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{++} \rm{D}^{-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Lambda_c^{+} \rm \overline{D}^0 {K}^{-})} = {0.282}\pm{0.016}\pm{0.016}\pm{0.005}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{*++} \rm {D}^{-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm {D}^{-} {K}^{-})} = {0.460}\pm{0.052}\pm{0.028}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{++} \rm {D}^{*-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm {D}^{-} {K}^{-})} = {2.261}\pm{0.202}\pm{0.129}\pm{0.046}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{*++} \rm D^{*-} K^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm D^{-} K^{-})} = {0.896}\pm{0.137}\pm{0.066}\pm{0.018},$$ where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more data set to become available following the LHCb upgrade.

Figures and captions

Feynman diagrams for (left) color-suppressed and (right) color-favored tree processes of the $\Lambda ^0_ b $ baryon decaying into $\Sigma_{c}^{(*)} \overline{ D } {}^{(*)} K ^- $ or $\Lambda ^+_ c \overline{ D } {}^{(*)0} K ^- $.	Fig_1.pdf [62 KiB] HiDef png [29 KiB] Thumbnail [14 KiB] *.C file tex code
Two-dimensional invariant mass fits of the $\Lambda ^0_ b \rightarrow \Sigma_c^{(*)++} D ^- K ^- $ decay, projected onto (top left) $m_{\Lambda ^+_ c \pi ^+ }$ and (top right) $m_{\Lambda ^+_ c D ^- K ^- \pi ^+ }$. A similar fit to $\Lambda ^0_ b \rightarrow \Sigma_c^{(*)++} D ^{*-} K ^- $ decay is projected onto (bottom left) $m_{\Lambda ^+_ c \pi ^+ }$ and (bottom right) $m_{\Lambda ^+_ c D ^{*-} K ^- \pi ^+ }$. The two signal contributions with resonant $\Sigma ^{++}_ c $ and $\Sigma ^{*++}_ c $ are drawn as a single component (red dashed line). Similarly, the two resonant $\Sigma_c^{(*)++}$ backgrounds without $\Lambda ^0_ b $ peaks are drawn together (cyan fill).	Sigmac_M.pdf [35 KiB] HiDef png [305 KiB] Thumbnail [240 KiB] *.C file
	Lb_PVF[..].pdf [25 KiB] HiDef png [230 KiB] Thumbnail [175 KiB] *.C file
	Lb_PVF[..].pdf [22 KiB] HiDef png [223 KiB] Thumbnail [166 KiB] *.C file
Animated gif made out of all figures.	PAPER-2023-044.gif Thumbnail

Tables and captions

Summary of systematic uncertainties. The correlation between those due to the limited statistics of simulated samples and other sources is considered. Systematics uncertainties due to the modeling of track reconstruction and trigger efficiencies are assumed to cancel out in the ratios between signal modes.

Table_1.pdf [95 KiB] HiDef png [74 KiB] Thumbnail [27 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [226 KiB]
	Fig1a_S.pdf [26 KiB] HiDef png [157 KiB] Thumbnail [90 KiB] *C file
	Fig1b_S.pdf [19 KiB] HiDef png [118 KiB] Thumbnail [66 KiB] *C file
	Fig2a_S.pdf [16 KiB] HiDef png [176 KiB] Thumbnail [148 KiB] *C file
	Fig2b_S.pdf [16 KiB] HiDef png [166 KiB] Thumbnail [141 KiB] *C file

Created on 17 May 2024.