Abstract
A search is performed for the as yet unobserved baryonic $\Lambda_b \rightarrow \Lambda \eta^\prime$ and $\Lambda_b \rightarrow \Lambda \eta$ decays with 3$fb^{-1}$ of proton-proton collision data recorded by the LHCb experiment. The $B^0 \rightarrow K_S^0 \eta^\prime$ decay is used as a normalisation channel. No significant signal is observed for the $\Lambda_b \rightarrow \Lambda \eta^\prime$ decay. An upper limit is found on the branching fraction of $\mathcal{B}(\Lambda_b \rightarrow \Lambda \eta^\prime)<3.1\times10^{-6}$} at 90\% confidence level. Evidence is seen for the presence of the $\Lambda_b \rightarrow \Lambda \eta$ decay at the level of $3\sigma$ significance, with a branching fraction $\mathcal{B}(\Lambda_b \rightarrow \Lambda \eta)=(9.3^{+7.3}_{-5.3})\times10^{-6}$}.
Highlights
One consequence of the mixing is the difference in branching fractions for b-hadron decays to final states containing η and η mesons
This paper describes the search for the Λ0b → Λη and Λ0b → Λη decays and measurement of the relative branching fractions with respect to the B0 → K0η decay, using the 3 fb−1 of data in pp collisions collected in 2011 and 2012 by the LHCb experiment
A search is performed for the Λ0b → Λη and Λ0b → Λη decays in the full dataset recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3 fb−1
Summary
An unbinned extended maximum likelihood fit to the candidate b-hadron mass spectrum is performed on the data which pass the selection. The most likely backgrounds are: b-hadron decay modes to mesons with open charm and an η( ) meson, with a π0 meson which is not reconstructed; the nonresonant decays to K0S or Λ particles with two charged pions which are combined with a combinatorial photon, π0 or η meson to form an η( ) meson candidate; or, in the case of the η → π+π−γ decays, the nonresonant B0 → K0Sπ+π−γ or Λ0b → Λπ+π−γ decays. An unbinned extended maximum likelihood fit is performed using the same model as for the B0 decay, with an exponential function to describe the combinatorial background and a sum of two Gaussian functions to model the signal; all parameters are fixed to the values found from fits to the simulation, and only the numbers of signal and background events are allowed
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