cern.ch

First observation of the decay $\Lambda_b^0 \to \eta_c(1S) p K^-$

[to restricted-access page]

Information

Tools

Abstract

The decay $\Lambda_b^0 \to \eta_c(1S) p K^-$ is observed for the first time using a data sample of proton-proton collisions, corresponding to an integrated luminosity of 5.5 $fb^{-1}$, collected with the LHCb experiment at a center-of-mass energy of 13 TeV. The branching fraction of the decay is measured, using the $\Lambda_b^0 \to J/\psi p K^-$ decay as a normalization mode, to be $\mathcal{B}(\Lambda_b^0 \to \eta_c(1S) p K^-)=(1.06\pm0.16\pm0.06^{+0.22}_{-0.19})\times10^{-4}$, where the quoted uncertainties are statistical, systematic and due to external inputs, respectively. A study of the $\eta_c(1S) p$ mass spectrum is performed to search for the $P_c(4312)^+$ pentaquark state. No evidence is observed and an upper limit of \begin{equation*} \frac{\mathcal{B}(\Lambda_b^0 \to P_c(4312)^+ K^-)\times \mathcal{B}(P_c(4312)^+ \to \eta_c(1S) p)}{\mathcal{B}(\Lambda_b^0 \to \eta_c(1S) p K^-)} < 0.24 \end{equation*} is obtained at the 95 confidence level.

Figures and captions

Distributions of (a) $m( p \overline p p K ^- )$ and (b) $m( p \overline p )$ of the selected candidates. The data are shown as black circles, while the blue solid line shows the fit result. Individual components are given in the legend.

Fig1a.pdf [23 KiB]
HiDef png [359 KiB]
Thumbnail [272 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [22 KiB]
HiDef png [325 KiB]
Thumbnail [250 KiB]
*.C file
Fig1b.pdf

The invariant-mass spectra of (a) the $\eta _ c $ $ p $ system of the $\Lambda ^0_ b \rightarrow \eta _ c p K ^- $ decays and (b) the $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ $ p $ system of the $\Lambda ^0_ b \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} p K ^- $ decays. The black points represent the background-subtracted data and the red points correspond to the expectation from a simulation generated according to a uniform phase-space model. The blue solid line in (a) shows the fit projection of the $\eta _ c $ $ p $ mass spectrum including the contribution from a $P_c(4312)^+$ resonance in the mass range $[4000, 4400]\text{ Me V /}c^2 $.

Fig2a.pdf [20 KiB]
HiDef png [354 KiB]
Thumbnail [291 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [18 KiB]
HiDef png [302 KiB]
Thumbnail [267 KiB]
*.C file
Fig2b.pdf

Animated gif made out of all figures.

PAPER-2020-012.gif
Thumbnail
thumbnail_PAPER-2020-012.gif

Tables and captions

Summary of the uncertainties on the branching fraction ratio $\mathcal{B} (\Lambda ^0_ b \rightarrow \eta _ c p K ^- )/\mathcal{B} (\Lambda ^0_ b \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} p K ^- )$. The total systematic uncertainty is obtained by summing the individual contributions in quadrature.

Table_1.pdf [70 KiB]
HiDef png [75 KiB]
Thumbnail [33 KiB]
tex code
Table_1.pdf

Supplementary Material [file]

Supplementary material full pdf

Supple[..].pdf [451 KiB]
Supplementary.pdf

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2020-012. The files are: Supplementary.pdf : An overview of the extra figures supplementary.tex : Source latex file for Supplementary.pdf *.pdf, *.png, *.eps : The figures in variuous formats *.C : cpp files to create the figures.

Fig1a-S.pdf [16 KiB]
HiDef png [209 KiB]
Thumbnail [220 KiB]
*C file
Fig1a-S.pdf
Fig1b-S.pdf [15 KiB]
HiDef png [185 KiB]
Thumbnail [196 KiB]
*C file
Fig1b-S.pdf
Fig2-S.pdf [23 KiB]
HiDef png [387 KiB]
Thumbnail [298 KiB]
*C file
Fig2-S.pdf
Fig3a-S.pdf [23 KiB]
HiDef png [364 KiB]
Thumbnail [280 KiB]
*C file
Fig3a-S.pdf
Fig3b-S.pdf [22 KiB]
HiDef png [282 KiB]
Thumbnail [198 KiB]
*C file
Fig3b-S.pdf
Fig4-S.pdf [23 KiB]
HiDef png [348 KiB]
Thumbnail [282 KiB]
*C file
Fig4-S.pdf
Fig5-S.pdf [21 KiB]
HiDef png [220 KiB]
Thumbnail [202 KiB]
*C file
Fig5-S.pdf
Fig6-S.pdf [27 KiB]
HiDef png [164 KiB]
Thumbnail [132 KiB]
*C file
Fig6-S.pdf

Created on 05 March 2021.