LHCb

Abstract:

Using a dataset corresponding to an integrated luminosity of 9 fb−1 collected in proton-proton collisions between 2011 and 2018 by the LHCb experiment, evidence is found for the decay Bs0→ϕη′$$ {B}_s^0\to {\phi \eta}^{\prime } $$ with 3.5σ significance. The branching ratio relative to the Bs0→ϕϕ$$ {B}_s^0\to \phi \phi $$ decay is determined to be ℛ = (3.56 ± 0.79 ± 0.18 ± 0.06) × 10−2. This corresponds to a branching fraction, BBs0→ϕη′=0.66±0.15±0.03±0.02×10−6$$ \mathcal{B}\left({B}_s^0\to {\phi \eta}^{\prime}\right)=\left(0.66\pm 0.15\pm 0.03\pm 0.02\right)\times {10}^{-6} $$ where, in both cases, the first uncertainty is statistical, the second systematic, and the third due to external branching fractions.

Abstract:

A measurement of the ratio of semileptonic branching fractions $\mathcal{R}(J/\psi )$ , defined as $\mathcal{R}(J/\psi )\equiv \mathcal{B}(B_c^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau })/\mathcal{B}(B_c^{+}\to J/\psi {\mu }^{+}{\nu }_{\mu })$ , is reported using a sample of proton-proton collision data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ recorded by the LHCb experiment in 2016–2018 at a center-of-mass energy of 13 TeV. The measured value is found to be $\mathcal{R}(J/\psi )=0.51\pm 0.12(\mathrm{stat})\pm 0.08(\mathrm{syst})$ , which is within 1.8 standard deviations of the predictions from the standard model assuming lepton flavor universality.