Search for the lepton-flavour-violating decays $B^{0}_{s}\to\tau^{\pm}\mu^{\mp}$ and $B^{0}\to\tau^{\pm}\mu^{\mp}$

Information

LHCb-PAPER-2019-016
CERN-EP-2019-076
arXiv:1905.06614 [PDF]

(Submitted on 16 May 2019)
Phys. Rev. Lett. 123 (2019) 211801
Inspire 1735300

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Abstract

A search for $B^{0}_{s}\to\tau^{\pm}\mu^{\mp}$ and $B^{0}\to\tau^{\pm}\mu^{\mp}$ decays is performed using data corresponding to an integrated luminosity of 3 fb$^{-1}$ of proton-proton collisions, recorded with the LHCb detector in 2011 and 2012. For this search, the $\tau$ lepton is reconstructed in the $\tau^{-}\to\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$ channel. No significant signal is observed. Assuming no contribution from $B^{0}\to\tau^{\pm}\mu^{\mp}$ decays, an upper limit is set on the $B^{0}_{s}\to\tau^{\pm}\mu^{\mp}$ branching fraction of $\mathcal{B}\left( B^{0}_{s}\to\tau^{\pm}\mu^{\mp}\right) < 4.2\times 10^{-5}$ at $95\%$ confidence level. If instead no contribution from $B^{0}_{s}\to\tau^{\pm}\mu^{\mp}$ decays is assumed, a limit of $\mathcal{B}\left( B^{0}\to\tau^{\pm}\mu^{\mp}\right) < 1.4\times 10^{-5}$ is obtained at $95\%$ confidence level. These are the first limit on $\mathcal{B}\left( B^{0}_{s}\to\tau^{\pm}\mu^{\mp}\right)$ and the world's best limit on $\mathcal{B}\left( B^{0}\to\tau^{\pm}\mu^{\mp}\right)$.

Figures and captions

Normalized distributions of the reconstructed invariant mass for $ B ^0_ s $ and $ B ^0$ in simulated event samples and for same-sign candidates in data, after applying the initial event selection (see the text).	Fig1.pdf [16 KiB] HiDef png [344 KiB] Thumbnail [240 KiB] *.C file
Final BDT output binned distributions for data and simulated signal samples. The markers are displaced horizontally to improve visibility.	Fig2.pdf [15 KiB] HiDef png [238 KiB] Thumbnail [218 KiB] *.C file
Distributions of the reconstructed $ B $ invariant-mass in data in the four final BDT bins with the projections of the fit for the $ B ^0_ s $ signal-only hypothesis overlaid. The lower-part of each figure shows the normalised residuals.	Fig3a.pdf [19 KiB] HiDef png [193 KiB] Thumbnail [183 KiB] *.C file
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The expected and observed p-values derived with the CLs method as a function of the $ B ^0_ s \rightarrow \tau ^\pm \mu ^\mp $ branching fraction.	Fig4.pdf [16 KiB] HiDef png [195 KiB] Thumbnail [154 KiB] *.C file
The expected and observed p-values derived with the CLs method as a function of the $ B ^0 \rightarrow \tau ^\pm \mu ^\mp $ branching fraction.	Fig5.pdf [16 KiB] HiDef png [199 KiB] Thumbnail [157 KiB] *.C file
Animated gif made out of all figures.	PAPER-2019-016.gif Thumbnail

Tables and captions

Expected and observed $90\%$ and $95\%$ CL limits on the $ B ^0_{( s )} \rightarrow \tau ^\pm \mu ^\mp $ branching fraction.

Table_1.pdf [68 KiB]
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tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [324 KiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2019-016. The files are: Fig.pdf, Fig.png, Fig.eps : The figures in various formats supplementary.pdf : An overview of the extra figures .tex : The latex source file to produce 'supplementary.pdf' (main is supplementary.tex)	Fig10.pdf [20 KiB] HiDef png [264 KiB] Thumbnail [247 KiB] *C file
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