Observation of $${{\varXi } ^0_{b}} \rightarrow {{\varXi } ^+_{c}} {{D} ^-_{s}} $$ Ξ b 0 → Ξ c + D s - and $${{\varXi } ^-_{b}} \rightarrow {{\varXi } ^0_{c}} {{D} ^-_{s}} $$ Ξ b - → Ξ c 0 D s - decays

Abstract

Abstract The

$$\Xi _b^0 \rightarrow \Xi _c^+ D_s^-$$

Ξ b 0

→

Ξ c +

D s -

and

$$\Xi _b^- \rightarrow \Xi _c^0 D_s^-$$

Ξ b -

→

Ξ c 0

D s -

decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of

$$\sqrt{s}=13\,\,\textrm{TeV}$$

s

= 13

TeV

, corresponding to an integrated luminosity of

$$5.1\,\,\textrm{fb}^{-1}$$

5.1

fb

- 1

. The branching fractions times the production cross-sections of

$$\Xi _b$$

Ξ b

baryons relative to that of

$$\Lambda _b^0$$

Λ b 0

baryon are measured to be

$$\begin{aligned} \mathcal {R}\left( \frac{\Xi _b^0}{\Lambda _b^0}\right)&\equiv \frac{\sigma \left( \Xi _b^0\right) }{\sigma \left( \Lambda _b^0\right) } \times \frac{\mathcal {B}\left( \Xi _b^0 \rightarrow \Xi _c^+ D_s^-\right) }{\mathcal {B}\left( \Lambda _b^0 \rightarrow \Lambda _c^0 D_s^-\right) }\\&=(15.8\pm 1.1\pm 0.6\pm 7.7)\%,\\ \mathcal {R}\left( \frac{\Xi _b^-}{\Lambda _b^0}\right)&\equiv \frac{\sigma \left( \Xi _b^-\right) }{\sigma \left( \Lambda _b^0\right) } \times \frac{\mathcal {B}\left( \Xi _b^- \rightarrow \Xi _c^0 D_s^-\right) }{\mathcal {B}\left( \Lambda _b^0 \rightarrow \Lambda _c^0 D_s^-\right) } \\&=(16.9\pm 1.3\pm 0.9\pm 4.3)\%, \end{aligned}$$

R

Ξ b 0

Λ b 0

≡

σ

Ξ b 0

σ

Λ b 0

×

B

Ξ b 0

→

Ξ c +

D s -

B

Λ b 0

→

Λ c 0

D s -

= ( 15.8 ± 1.1 ± 0.6 ± 7.7 ) % ,

R

Ξ b -

Λ b 0

≡

σ

Ξ b -

σ

Λ b 0

×

B

Ξ b -

→

Ξ c 0

D s -

B

Λ b 0

→

Λ c 0

D s -

= ( 16.9 ± 1.3 ± 0.9 ± 4.3 ) % ,

where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the decay branching fractions of relevant charmed baryons. The masses of

$$\Xi _b^0$$

Ξ b 0

and

$$\Xi _b^-$$

Ξ b -

baryons are measured to be

$$m_{\Xi _b^0}=5791.12\pm 0.60\pm 0.45\pm 0.24\,\,\textrm{MeV}/c^2$$

m

Ξ b 0

= 5791.12 ± 0.60 ± 0.45 ± 0.24

MeV /

c 2

and

$$m_{\Xi _b^-}=5797.02\pm 0.63\pm 0.49\pm 0.29\,\,\textrm{MeV}/c^2$$

m

Ξ b -

= 5797.02 ± 0.63 ± 0.49 ± 0.29

MeV /

c 2

, where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively.