Observation of the B0 s → χc1(3872)π +π – decay

Abstract

Abstract

The first observation of the

B s 0

$$ {B}_s^0 $$ → (χc1(3872) → J/ψπ+π−)π+π− decay is reported using proton-proton collision data, corresponding to integrated luminosities of 1, 2 and 6 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ratio of branching fractions relative to the

B s 0

$$ {B}_s^0 $$ → (ψ(2S) → J/ψπ+π−)π+π− decay is measured to be

B

B s 0

→

χ

c 1

3872

π +

π −

× B

χ

c 1

3872

→ J / ψ

π +

π −

B

B s 0

→ ψ

2 S

π +

π −

× B

ψ

2 S

→ J / ψ

π +

π −

=

6.8 ± 1.1 ± 0.2

×

10

− 2

,

$$ \frac{\mathcal{B}\left({B}_s^0\to {\chi}_{c1}(3872){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left({\chi}_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}_s^0\to \psi (2S){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left(\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}=\left(6.8\pm 1.1\pm 0.2\right)\times {10}^{-2}, $$

where the first uncertainty is statistical and the second systematic. The mass spectrum of the π+π− system recoiling against the χc1(3872) meson exhibits a large contribution from

B s 0

$$ {B}_s^0 $$ → χc1(3872) (f0(980) → π+π−) decays.