# Observation of the decays $\Lambda^0_b \to \chi_{c1}pK^-$ and $\Lambda^0_b \to \chi_{c2}pK^-$

LHCb Collaboration; Bernet, R; Müller, K; Serra, N; Steinkamp, O; Straumann, U; Vollhardt, A; et al (2017). Observation of the decays $\Lambda^0_b \to \chi_{c1}pK^-$ and $\Lambda^0_b \to \chi_{c2}pK^-$. Physical Review Letters, 119(6):062001.

## Abstract

The first observation of the decays $\Lambda^0_b \to \chi_{c1}pK^-$ and $\Lambda^0_b \to \chi_{c2}pK^-$ is reported using a data sample corresponding to an integrated luminosity of 3.0  fb$^{−1}$, collected by the LHCb experiment in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured:
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c1}pK^-)}{\mathscr{B}(\Lambda^0_b \to J/\psi pK^-)} = 0.242 \pm 0.014 \pm 0.013 \pm 0.009$,
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c2}pK^-)}{\mathscr{B}(\Lambda^0_b \to J/\psi pK^-)} = 0.248 \pm 0.020 \pm 0.014 \pm 0.009$,
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c2}pK^-)}{\mathscr{B}(\Lambda^0_b \to \chi_{c1}pK^-)} = 1.02 \pm 0.10 \pm 0.02 \pm 0.05$,
where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the $\chi_{c1} \to J/\psi\gamma$ and $\chi_{c2} \to J/\psi\gamma$ decays. Using both decay modes, the mass of the $\Lambda^0_b$ baryon is also measured to be $m_{\Lambda^0_b} = 5619.44 \pm 0.28 \pm 0.26 MeV/c^2$, where the first and second uncertainties are statistical and systematic, respectively.

## Abstract

The first observation of the decays $\Lambda^0_b \to \chi_{c1}pK^-$ and $\Lambda^0_b \to \chi_{c2}pK^-$ is reported using a data sample corresponding to an integrated luminosity of 3.0  fb$^{−1}$, collected by the LHCb experiment in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured:
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c1}pK^-)}{\mathscr{B}(\Lambda^0_b \to J/\psi pK^-)} = 0.242 \pm 0.014 \pm 0.013 \pm 0.009$,
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c2}pK^-)}{\mathscr{B}(\Lambda^0_b \to J/\psi pK^-)} = 0.248 \pm 0.020 \pm 0.014 \pm 0.009$,
$\frac{\mathscr{B}(\Lambda^0_b \to \chi_{c2}pK^-)}{\mathscr{B}(\Lambda^0_b \to \chi_{c1}pK^-)} = 1.02 \pm 0.10 \pm 0.02 \pm 0.05$,
where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the $\chi_{c1} \to J/\psi\gamma$ and $\chi_{c2} \to J/\psi\gamma$ decays. Using both decay modes, the mass of the $\Lambda^0_b$ baryon is also measured to be $m_{\Lambda^0_b} = 5619.44 \pm 0.28 \pm 0.26 MeV/c^2$, where the first and second uncertainties are statistical and systematic, respectively.

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