Abstract
The $\Lambda_b^0\to\Lambda\phi$ decay is observed using data corresponding to an integrated luminosity of 3.0fb$^{-1}$ recorded by the LHCb experiment. The decay proceeds at leading order via a $b\to s\bar{s}s$ loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of $5.9$ standard deviations. The value of the branching fraction is measured to be $(5.18\pm1.04\pm0.35\,^{+0.67}_{-0.62})\times10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero.
Highlights
In the Standard Model (SM), the flavour-changing neutral current decay Λb0 → Λφ proceeds via a b → sss loop process
Measurements of CP violation in the decay have been performed with the flavourspecific B0 → K ∗0φ channel [8]
Measurements with Λb0 baryons offer the possibility to look for CP violation in the decay, both by studying CP asymmetries and by means of T -odd observables
Summary
In the Standard Model (SM), the flavour-changing neutral current decay Λb0 → Λφ proceeds via a b → sss loop (penguin) process. This transition has been the subject of theoretical and experimental interest in. Proposed methods to study T -odd asymmetries of Λb0 baryons [12] exploit the polarisation structure of. An. LHCb measurement of the initial polarisation in Λb0 → J/ψΛ decays has yielded a value consistent with zero, though polarisation at the level of 10% is possible given statistical uncertainties [13]. The Λb0 → Λφ sample is used to perform measurements of the T -odd triple-product asymmetries, which do not require a control channel.
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