cern.ch

Measurement of the ratio of branching fractions of the decays $\Lambda_b^0 \!\to \psi(2S) \Lambda$ and $\Lambda_b^0 \!\to J\!/\!\psi \Lambda$

[to restricted-access page]

Information

Tools

Contact

Abstract

Using $pp$ collisions corresponding to 3$\,\text{fb}^{-1}$ integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8$\,\text{TeV}$, the ratio of branching fractions \begin{align*} \mathcal{B}(\Lambda^0_b\!\to\psi(2S) \Lambda )/\mathcal{B}(\Lambda^0_b\!\to J/\psi \Lambda)= 0.513 \pm 0.023\, (\text{stat}) \pm 0.016 \, (\text{syst}) \pm 0.011\, (\mathcal{B}) \end{align*} is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.

Figures and captions

Interpolated efficiency function for long-track candidates for (a) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (b) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ and for downstream-track candidates for (c) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (d) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ candidates. The distribution of the candidates on data is shown with black dots (each dot refers to one candidate). Statistical fluctuations of the simulated sample are contributing to the efficiency function at the phase-space boundaries, where data candidates are not affected.

Fig1a.pdf [59 KiB]
HiDef png [980 KiB]
Thumbnail [177 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [107 KiB]
HiDef png [1 MiB]
Thumbnail [189 KiB]
*.C file
Fig1b.pdf
Fig1c.pdf [77 KiB]
HiDef png [1 MiB]
Thumbnail [181 KiB]
*.C file
Fig1c.pdf
Fig1d.pdf [268 KiB]
HiDef png [1 MiB]
Thumbnail [194 KiB]
*.C file
Fig1d.pdf

Fits to the (unweighted) invariant-mass distributions of long-track candidates for (a) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (b) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ and for downstream-track candidates for (c) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (d) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ candidates. The signal (blue, dashed), the combinatorial background (green, dotted), the $ B ^0 \!\rightarrow \psi K ^0_{\mathrm{ \scriptscriptstyle S}} $ background (cyan, long-dash-dotted) and the $\Xi ^-_ b \!\rightarrow \psi \Xi ^- $ background (violet, dash-triple-dotted) are indicated.

Fig2a.pdf [20 KiB]
HiDef png [211 KiB]
Thumbnail [69 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [21 KiB]
HiDef png [203 KiB]
Thumbnail [65 KiB]
*.C file
Fig2b.pdf
Fig2c.pdf [34 KiB]
HiDef png [265 KiB]
Thumbnail [85 KiB]
*.C file
Fig2c.pdf
Fig2d.pdf [36 KiB]
HiDef png [252 KiB]
Thumbnail [75 KiB]
*.C file
Fig2d.pdf

Fits to the weighted invariant-mass distributions of long-track candidates for (a) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (b) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ and for downstream-track candidates for (c) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and (d) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ candidates. The signal (blue, dashed), the combinatorial background (green, dotted), the $ B ^0 \!\rightarrow \psi K ^0_{\mathrm{ \scriptscriptstyle S}} $ background (cyan, long-dash-dotted) and the $\Xi ^-_ b \!\rightarrow \psi \Xi ^- $ background (violet, dash-triple-dotted) are indicated.

Fig3a.pdf [21 KiB]
HiDef png [220 KiB]
Thumbnail [73 KiB]
*.C file
Fig3a.pdf
Fig3b.pdf [21 KiB]
HiDef png [216 KiB]
Thumbnail [68 KiB]
*.C file
Fig3b.pdf
Fig3c.pdf [36 KiB]
HiDef png [263 KiB]
Thumbnail [83 KiB]
*.C file
Fig3c.pdf
Fig3d.pdf [37 KiB]
HiDef png [259 KiB]
Thumbnail [77 KiB]
*.C file
Fig3d.pdf

Animated gif made out of all figures.

PAPER-2017-041.gif
Thumbnail
thumbnail_PAPER-2017-041.gif

Tables and captions

Yields from the invariant-mass fits in the range 5350 to 5750 $ {\mathrm{\,Me V\!/}c^2}$ of (top) $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ decays and (bottom) $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ decays for each component.

Table_1.pdf [60 KiB]
HiDef png [60 KiB]
Thumbnail [9 KiB]
tex code
Table_1.pdf

Efficiency-corrected yields of $\Lambda ^0_ b \!\rightarrow \psi {(2S)} \Lambda $ and $\Lambda ^0_ b \!\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \Lambda $ signal decays from the fit to the weighted invariant mass for both track types.

Table_2.pdf [65 KiB]
HiDef png [55 KiB]
Thumbnail [8 KiB]
tex code
Table_2.pdf

Relative systematic uncertainties on the ratio of branching fractions.

Table_3.pdf [31 KiB]
HiDef png [167 KiB]
Thumbnail [24 KiB]
tex code
Table_3.pdf

Created on 20 April 2019.Citation count from INSPIRE on 25 April 2019.