cern.ch

Search for the $\Lambda_b^0 \rightarrow \Lambda \eta^\prime$ and $\Lambda_b^0\rightarrow \Lambda \eta$ decays with the LHCb detector

[to restricted-access page]

Abstract

A search is performed for the as yet unobserved baryonic $\Lambda_b \rightarrow \Lambda \eta^\prime$ and $\Lambda_b \rightarrow \Lambda \eta$ decays with 3$fb^{-1}$ of proton-proton collision data recorded by the LHCb experiment. The $B^0 \rightarrow K_S^0 \eta^\prime$ decay is used as a normalisation channel. No significant signal is observed for the $\Lambda_b \rightarrow \Lambda \eta^\prime$ decay. An upper limit is found on the branching fraction of $\mathcal{B}(\Lambda_b \rightarrow \Lambda \eta^\prime)<3.1\times10^{-6}$} at 90% confidence level. Evidence is seen for the presence of the $\Lambda_b \rightarrow \Lambda \eta$ decay at the level of $3\sigma$ significance, with a branching fraction $\mathcal{B}(\Lambda_b \rightarrow \Lambda \eta)=(9.3^{+7.3}_{-5.3})\times10^{-6}$}.

Figures and captions

Feynman diagrams for the $\Lambda ^0_ b \!\rightarrow \Lambda \eta ^{(\prime)} $ decay. The non-spectator and anomalous diagrams are available only to the $\eta ^{\prime}$ through the gluonic contribution.

LbEtap[..].png [30 KiB]
HiDef png [57 KiB]
Thumbnail [11 KiB]
*.C file
LbEtapL_std.png
LbEtap[..].png [49 KiB]
HiDef png [87 KiB]
Thumbnail [16 KiB] *.C file
LbEtapL_non-spec.png
LbEtap[..].png [38 KiB]
HiDef png [64 KiB]
Thumbnail [12 KiB] *.C file
LbEtapL_anom.png

Mass distribution of the selected $ B ^0 \!\rightarrow K ^0_{\rm\scriptscriptstyle S} \eta ^{\prime} $ ( $\eta ^{\prime} \!\rightarrow \pi ^+ \pi ^- \gamma$ ) candidates in the 2011 and 2012 data, reconstructed in the L (left) and D (right) categories. The results of the fit, as described in the text, are overlaid.

Fig2a.pdf [19 KiB]
HiDef png [245 KiB]
Thumbnail [70 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [19 KiB]
HiDef png [236 KiB]
Thumbnail [68 KiB] *.C file
Fig2b.pdf

Mass distribution of the reconstructed $\eta ^{\prime}$ meson for selected $ B ^0 \!\rightarrow K ^0_{\rm\scriptscriptstyle S} \eta ^{\prime} $ ( $\eta ^{\prime} \!\rightarrow \pi ^+ \pi ^- \gamma$ ) candidates, in the L (left) and D (right) categories. The results of the fit, as described in the text, are overlaid.

Fig3a.pdf [18 KiB]
HiDef png [228 KiB]
Thumbnail [67 KiB]
*.C file
Fig3a.pdf
Fig3b.pdf [18 KiB]
HiDef png [240 KiB]
Thumbnail [69 KiB] *.C file
Fig3b.pdf

Mass distribution of the selected $\Lambda ^0_ b \!\rightarrow \Lambda \eta ^{\prime} $ ( $\eta ^{\prime} \!\rightarrow \pi ^+ \pi ^- \gamma$ ) candidates in the 2011 and 2012 data, reconstructed in the L (left) and D (right) categories. The results of the fit, as described in the text, are overlaid.

Fig4a.pdf [17 KiB]
HiDef png [189 KiB]
Thumbnail [61 KiB]
*.C file
Fig4a.pdf
Fig4b.pdf [18 KiB]
HiDef png [202 KiB]
Thumbnail [63 KiB] *.C file
Fig4b.pdf

Mass distribution of the selected $\Lambda ^0_ b \!\rightarrow \Lambda \eta ^{\prime} $ ( $\eta ^{\prime} \!\rightarrow \pi ^+ \pi ^- \eta $ ) candidates in the 2011 and 2012 data, reconstructed in the L (left) and D (right) categories. The results of the fit, as described in the text, are overlaid.

Fig5a.pdf [17 KiB]
HiDef png [188 KiB]
Thumbnail [58 KiB]
*.C file
Fig5a.pdf
Fig5b.pdf [16 KiB]
HiDef png [177 KiB]
Thumbnail [54 KiB] *.C file
Fig5b.pdf

Mass distribution of the selected $\Lambda ^0_ b \!\rightarrow \Lambda \eta $ ( $\eta \!\rightarrow \pi ^+ \pi ^- \pi ^0 $ ) candidates in the 2011 and 2012 data, reconstructed in the L (left) and D (right) categories. The results of the fit, as described in the text, are overlaid.

Fig6a.pdf [16 KiB]
HiDef png [175 KiB]
Thumbnail [54 KiB]
*.C file
Fig6a.pdf
Fig6b.pdf [17 KiB]
HiDef png [197 KiB]
Thumbnail [57 KiB] *.C file
Fig6b.pdf

Animated gif made out of all figures.

PAPER-2015-019.gif
Thumbnail
thumbnail_PAPER-2015-019.gif

Tables and captions

Components contributing to the scale factor $\alpha.$

Table_1.pdf [75 KiB]
HiDef png [56 KiB]
Thumbnail [9 KiB]
tex code
Table_1.pdf

Fractional systematic uncertainties, in percent, on the ratio of branching fractions.

Table_2.pdf [78 KiB]
HiDef png [80 KiB]
Thumbnail [13 KiB]
tex code
Table_2.pdf

Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.