cern.ch

First measurement of the differential branching fraction and $C P$ asymmetry of the $B^\pm\to\pi^\pm\mu^+\mu^-$ decay

[to restricted-access page]

Information

Tools

Abstract

The differential branching fraction with respect to the dimuon invariant mass squared, and the $C P$ asymmetry of the $B^\pm\to\pi^\pm\mu^+\mu^-$ decay are measured for the first time. The CKM matrix elements $|V_{td}|$ and $|V_{ts}|$, and the ratio $|V_{td}/V_{ts}|$ are determined. The analysis is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The total branching fraction and $C P$ asymmetry of $B^\pm\to\pi^\pm\mu^+\mu^-$ decays are measured to be \begin{eqnarray} \mathcal{B}(B^\pm\to\pi^\pm\mu^+\mu^-) &=& (1.83 \pm 0.24 \pm 0.05) \times 10^{-8} \mathrm{and} \nonumber\\ \mathcal{A}_{C P}(B^\pm\to\pi^\pm\mu^+\mu^-) &=& -0.11 \pm 0.12 \pm 0.01 , \nonumber \end{eqnarray} where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model.

Figures and captions

Feynman diagrams of the penguin and box loop contributions to the $ b \rightarrow d \ell^+ \ell^-$ process.

feynman.pdf [32 KiB]
HiDef png [25 KiB]
Thumbnail [13 KiB]
*.C file
feynman.pdf

The fit to the invariant mass distribution of (left) selected $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ candidates and (right) selected $ B ^+ \rightarrow K ^+ \mu ^+\mu ^- $ candidates, with the total model and separate components as described in the legend.

pimumu[..].pdf [20 KiB]
HiDef png [329 KiB]
Thumbnail [264 KiB]
*.C file
pimumu_fitresult0_col.pdf
kmumu_[..].pdf [25 KiB]
HiDef png [255 KiB]
Thumbnail [199 KiB]
*.C file
kmumu_fitresult0_col.pdf

The fit to the invariant mass distribution of (left) selected $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ candidates and (right) selected $ B ^- \rightarrow \pi ^- \mu ^+\mu ^- $ candidates, with the total model and separate components as described in the legend.

piplus[..].pdf [20 KiB]
HiDef png [330 KiB]
Thumbnail [268 KiB]
*.C file
piplus_fit_32_bins_col.pdf
piminu[..].pdf [20 KiB]
HiDef png [318 KiB]
Thumbnail [261 KiB]
*.C file
piminus_fit_32_bins_col.pdf

The differential branching fraction of $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ in bins of dilepton invariant mass squared, $ q^2$ , compared to SM predictions taken from Refs. [1] (APR13), [6] (HKR15) and from lattice QCD calculations [7] (FNAL/MILC15).

pimumu[..].pdf [20 KiB]
HiDef png [445 KiB]
Thumbnail [229 KiB]
*.C file
pimumu_branching_fraction_col.pdf

The $ q^2$ spectrum of $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ candidates in the region 0.1 -- 1.0 $ {\mathrm{ Ge V^2 /}c^4}$ in a $\pm 50$ $\mathrm{ Me V}$ window around the nominal $ B ^+$ mass, showing a peaking structure at 0.6 $ {\mathrm{ Ge V^2 /}c^4}$ that is in the region of the $\rho ^0$ and $\omega$ masses squared.

rho.pdf [14 KiB]
HiDef png [81 KiB]
Thumbnail [44 KiB]
*.C file
rho.pdf

Animated gif made out of all figures.

 PAPER-2015-035.gif
Thumbnail
thumbnail_PAPER-2015-035.gif

Tables and captions

The yields of $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ decays in bins of dilepton invariant mass squared, with statistical uncertainties.

Table_1.pdf [52 KiB]
HiDef png [137 KiB]
Thumbnail [68 KiB]
tex code 		Table_1.pdf

The measured total yield from the simultaneous fit to the charge separated data, and the inferred yields of $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ and $ B ^- \rightarrow \pi ^- \mu ^+\mu ^- $ decays.

Table_2.pdf [41 KiB]
HiDef png [19 KiB]
Thumbnail [10 KiB]
tex code 		Table_2.pdf

The results for the differential branching fraction for $ B ^+ \rightarrow \pi ^+ \mu ^+\mu ^- $ in bins of $ q^2$ . The first uncertainties are statistical and the second are systematic.

Table_3.pdf [60 KiB]
HiDef png [100 KiB]
Thumbnail [52 KiB]
tex code 		Table_3.pdf

Created on 27 April 2024.