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Searches for rare $ {B}_s^0 $ and B$^{0}$ decays into four muons

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Abstract

Searches for rare $B_s^0$ and $B^0$ decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$. Direct decays and decays via light scalar and $J/\psi$ resonances are considered. No evidence for the six decays searched for is found and upper limits at the 95 confidence level on their branching fractions ranging between $1.8\times10^{-10}$ and $2.6\times10^{-9}$ are set.

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Feynman diagrams for nonresonant $ B ^0_ s , B ^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ decays.

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Feynman diagram for $ B ^0_ s , B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ decays.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right) \phi\left(\mu ^+\mu ^- \right)$ selection, with the fit model used to determine the control sample yield overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ selection in the most sensitive BDT interval, with the fit models used to determine the branching fractions of (left) $ B ^0_ s \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ and (right) $ B ^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ decays overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow a \left(\mu ^+\mu ^- \right) a \left(\mu ^+\mu ^- \right)$ selection, with the fit models used to determine the branching fractions of (left) $ B ^0_ s \rightarrow a \left(\mu ^+\mu ^- \right) a \left(\mu ^+\mu ^- \right)$ and (right) $ B ^0 \rightarrow a \left(\mu ^+\mu ^- \right) a \left(\mu ^+\mu ^- \right)$ decays overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ selection in the most sensitive BDT interval, with the fit models used to determine the branching fractions of (left) $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ and (right) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ decays overlaid.

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Confidence levels ($\mathrm{CL_s}$) obtained from the $\text{CL}_\text{s}$ method to set limits on the branching fractions of (top left) $ B ^0_ s \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ , (top right) $ B ^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ , (middle left) $ B ^0_ s \rightarrow a \left(\mu ^+\mu ^- \right) a \left(\mu ^+\mu ^- \right)$ , (middle right) $ B ^0 \rightarrow a \left(\mu ^+\mu ^- \right) a \left(\mu ^+\mu ^- \right)$ , (bottom left) $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ and (bottom right) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ decays.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ selection in (top left) the lowest BDT interval, (top right) the second lowest BDT interval and (bottom) the second highest BDT interval, with the fit models used to determine the branching fraction of $ B ^0_ s \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ selection in (top left) the lowest BDT interval, (top right) the second lowest BDT interval and (bottom) the second highest BDT interval, with the fit models used to determine the branching fraction of $ B ^0 \rightarrow \mu ^+\mu ^-\mu ^+\mu ^- $ overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ selection in (top left) the lowest BDT interval, (top right) the second lowest BDT interval and (bottom) the second highest BDT interval, with the fit models used to determine the branching fraction of $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ overlaid.

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Distribution of the $\mu ^+\mu ^- \mu ^+\mu ^- $ invariant mass of candidates passing the $ B _{( s )}^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ selection in (top left) the lowest BDT interval, (top right) the second lowest BDT interval and (bottom) the second highest BDT interval, with the fit models used to determine the branching fraction of $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi } \left(\mu ^+\mu ^- \right)\mu ^+\mu ^- $ overlaid.

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Created on 20 April 2024.