cern.ch

Observation of the $\Lambda_b^0\to\Lambda\phi$ decay

[to restricted-access page]

Information

Tools

Abstract

The $\Lambda_b^0\to\Lambda\phi$ decay is observed using data corresponding to an integrated luminosity of 3.0fb$^{-1}$ recorded by the LHCb experiment. The decay proceeds at leading order via a $b\to s\bar{s}s$ loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of $5.9$ standard deviations. The value of the branching fraction is measured to be $(5.18\pm1.04\pm0.35 ^{+0.67}_{-0.62})\times10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero.

Figures and captions

Feynman diagram contributing to the $\Lambda ^0_ b \rightarrow \Lambda \phi$ decay.

Fig1.pdf [216 KiB]
HiDef png [97 KiB]
Thumbnail [57 KiB]
*.C file
Fig1.pdf

Fit projections to the $ { p \pi ^- K ^+ K ^- } $ invariant mass in the (a) long and (b) downstream datasets, the $ { K ^+ K ^- } $ invariant mass in the (c) long and (d) downstream datasets, and the $ { p \pi ^- } $ invariant mass in the (e) long and (f) downstream datasets. The total fit projection is given by the blue solid line. The blue and green dotted lines represent the $\phi$ + $\Lambda $ and pure combinatorial fit components, respectively. The red and magenta dashed lines represent the $\Lambda ^0_ b \rightarrow \Lambda \phi $ signal and the $\Lambda ^0_ b \rightarrow \Lambda K ^+ K ^- $ non-resonant components, respectively. Black points represent the data. Data uncertainties are Poisson 68% confidence intervals.

Fig2a.pdf [21 KiB]
HiDef png [310 KiB]
Thumbnail [244 KiB]
*.C file
Fig2a.pdf
Fig2c.pdf [20 KiB]
HiDef png [289 KiB]
Thumbnail [237 KiB]
*.C file
Fig2c.pdf
Fig2e.pdf [20 KiB]
HiDef png [297 KiB]
Thumbnail [233 KiB]
*.C file
Fig2e.pdf
Fig2b.pdf [22 KiB]
HiDef png [321 KiB]
Thumbnail [265 KiB]
*.C file
Fig2b.pdf
Fig2d.pdf [23 KiB]
HiDef png [344 KiB]
Thumbnail [279 KiB]
*.C file
Fig2d.pdf
Fig2f.pdf [22 KiB]
HiDef png [301 KiB]
Thumbnail [247 KiB]
*.C file
Fig2f.pdf

Fit projections to the $ {\pi ^+ \pi ^- K ^+ K ^- } $ invariant mass in the (a) long and (b) downstream datasets, the $ { K ^+ K ^- } $ invariant mass in the (c) long and (d) downstream datasets, and the { $ {\pi ^+ \pi ^- } $ } invariant mass in the (e) long and (f) downstream datasets. The total fit projection is given by the blue solid line. The green and blue dotted lines represent the combinatorial and $ K ^0_{\mathrm{ \scriptscriptstyle S}}$ + random $ K ^+$ $ K ^-$ fit components, respectively. The red and magenta dashed lines represent the $ B ^0 \rightarrow K ^0_{\mathrm{ \scriptscriptstyle S}} \phi $ signal and the $ B ^0 \rightarrow K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ K ^- $ non-resonant components, respectively. Black points represent the data. Data uncertainties are Poisson 68% confidence intervals.

Fig3a.pdf [23 KiB]
HiDef png [317 KiB]
Thumbnail [265 KiB]
*.C file
Fig3a.pdf
Fig3c.pdf [22 KiB]
HiDef png [318 KiB]
Thumbnail [259 KiB]
*.C file
Fig3c.pdf
Fig3e.pdf [22 KiB]
HiDef png [330 KiB]
Thumbnail [265 KiB]
*.C file
Fig3e.pdf
Fig3b.pdf [23 KiB]
HiDef png [345 KiB]
Thumbnail [279 KiB]
*.C file
Fig3b.pdf
Fig3d.pdf [23 KiB]
HiDef png [355 KiB]
Thumbnail [297 KiB]
*.C file
Fig3d.pdf
Fig3f.pdf [23 KiB]
HiDef png [369 KiB]
Thumbnail [300 KiB]
*.C file
Fig3f.pdf

Decay angles for the $\Lambda ^0_ b \rightarrow \Lambda \phi$ decay, where the angles are defined in the text.

Fig4.pdf [417 KiB]
HiDef png [157 KiB]
Thumbnail [74 KiB]
*.C file
Fig4.pdf

Distributions of the angular observables: (a) $\sin\Phi_{n_\Lambda }$, (b) $\cos\Phi_{n_\Lambda }$, (c) $\sin\Phi_{n_\phi}$, (d) $\cos\Phi_{n_\phi}$ from weighted $\Lambda ^0_ b \rightarrow \Lambda \phi$ data.

Fig5a.pdf [15 KiB]
HiDef png [89 KiB]
Thumbnail [48 KiB]
*.C file
Fig5a.pdf
Fig5b.pdf [15 KiB]
HiDef png [97 KiB]
Thumbnail [51 KiB]
*.C file
Fig5b.pdf
Fig5c.pdf [15 KiB]
HiDef png [102 KiB]
Thumbnail [57 KiB]
*.C file
Fig5c.pdf
Fig5d.pdf [15 KiB]
HiDef png [100 KiB]
Thumbnail [55 KiB]
*.C file
Fig5d.pdf

Animated gif made out of all figures.

PAPER-2016-002.gif
Thumbnail
thumbnail_PAPER-2016-002.gif

Tables and captions

Systematic uncertainty contributions to the branching fraction ratio.

Table_1.pdf [19 KiB]
HiDef png [100 KiB]
Thumbnail [43 KiB]
tex code
Table_1.pdf

Asymmetries measured from $\Lambda ^0_ b \rightarrow \Lambda \phi$ data events.

Table_2.pdf [42 KiB]
HiDef png [77 KiB]
Thumbnail [33 KiB]
tex code
Table_2.pdf

Systematic uncertainty contributions to the triple-product asymmetries.

Table_3.pdf [37 KiB]
HiDef png [66 KiB]
Thumbnail [29 KiB]
tex code
Table_3.pdf

Created on 08 August 2020.