Search for $$D^{*}(2007)^{0} \rightarrow \mu ^{+} \mu ^{-}$$ D ∗ ( 2007 ) 0 → μ + μ - in $$B^{-}\rightarrow \pi ^{-} \mu ^{+} \mu ^{-}$$ B - → π - μ + μ - decays

Abstract

Abstract The very rare

$${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$

D

∗

( 2007 )

0

→

μ +

μ -

decay is searched for by analysing

$${{{B} ^-}} \!\rightarrow {{\pi } ^-} {\mu ^+\mu ^-} $$

B

-

→

π

-

μ +

μ -

decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9

$$\text {\,fb} ^{-1}$$

\,fb

- 1

. The signal signature corresponds to simultaneous peaks in the

$${\mu ^+\mu ^-} $$

μ +

μ -

and

$${{\pi } ^-} {\mu ^+\mu ^-} $$

π

-

μ +

μ -

invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at

$$\mathcal{B}({{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} ) < 2.6\times 10^{-8}$$

B

(

D

∗

( 2007 )

0

→

μ +

μ -

)

< 2.6 ×

10

- 8

at

$$90\%$$

90 %

confidence level. This is the first limit on the branching fraction of

$${{D} ^*} (2007)^0\!\rightarrow {\mu ^+\mu ^-} $$

D

∗

( 2007 )

0

→

μ +

μ -

decays and the most stringent limit on

$${{D} ^*} (2007)^0$$

D

∗

( 2007 )

0

decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.