Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of the decay $ \Lambda_b^0\rightarrow
  \Lambda_c^+\tau^-\overline{\nu}_{\tau}$   The first observation of the semileptonic $b$-baryon decay $ \Lambda_b^0
\rightarrow \Lambda_c^+ \tau^-\overline{\nu}_{\tau}$, with a significance of
$6.1\,\sigma$, is reported using a data sample corresponding to 3 fb$^{-1}$ of
integrated luminosity, collected by the LHCb experiment at centre-of-mass
energies of 7 and 8 TeV at the LHC. The $\tau^-$ lepton is reconstructed in the
hadronic decay to three charged pions. The branching fraction
${\mathcal{B}}(\Lambda_b^0 \rightarrow \Lambda_c^+\tau^-\overline{\nu}_{\tau})
= (1.50 \pm 0.16\pm 0.25\pm 0.23)\%$ is obtained, where uncertainties are
statistical, systematic and from the external branching fraction of the
normalisation channel $\Lambda_b^0\rightarrow \Lambda_c^+\pi^-\pi^+\pi^-$. The
ratio of semileptonic branching fractions ${\mathcal{R}}( \Lambda_c^+)\equiv
{\mathcal{B}}( \Lambda_b^0 \rightarrow \Lambda_c^+
\tau^-\overline{\nu}_{\tau})/{\mathcal{B}}( \Lambda_b^0 \rightarrow \Lambda_c^+
\mu^-\overline{\nu}_{\mu})$ is derived to be $0.242 \pm 0.026 \pm 0.040\pm
0.059$, where the external branching fraction uncertainty from the channel
$\Lambda_b^0\rightarrow \Lambda_c^+\mu^-\overline{\nu}_{\mu}$ contributes to
the last term. This result is in agreement with the Standard Model prediction.

1
The categories of this paper are: cs
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th