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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 $\mathcal{R}(J/\mathrm{ψ})$ , defined as $\mathcal{R}(J/\mathrm{ψ})≡\mathcal{B}(B_c^{+}→J/\mathrm{ψ}{\mathrm{Ï„}}^{+}{\mathrm{ν}}_{\mathrm{Ï„}})/\mathcal{B}(B_c^{+}→J/\mathrm{ψ}{\mathrm{μ}}^{+}{\mathrm{ν}}_{\mathrm{μ}})$ , 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 $\mathcal{R}(J/\mathrm{ψ})=0.51Â\pm 0.12(\mathrm{stat})Â\pm 0.08(\mathrm{syst})$ , which is within 1.8 standard deviations of the predictions from the standard model assuming lepton flavor universality.

Abstract:

Abstract Testbeam results from a 300 μm-thick 3D silicon sensor bump-bonded to a Timepix4 ASIC, are presented. The hit detection efficiency, spatial resolution, and timing performance of the 3D sensor are studied for several track angles, bias voltages and charge thresholds. The time measurements are corrected for Timepix4 clock-frequency variations and timewalk, while for the spatial studies, nonlinear charge-sharing corrections are determined. At perpendicular incidence, the time resolution of the 3D detector is equal to 245 ps with a 97 % hit detection efficiency. An optimal angle of 8 ∘ with respect to the beam direction of the 3D detector was found, in which the time resolution improves by 6 % compared to normal incidence, while the hit detection efficiency reaches above 99 % and the spatial resolution is approximately 7 μm. Intrapixel studies show that a time resolution of 153 ps at the most probable value of the signal charge can be achieved for hits between the electrodes at normal incidence, while the timing performance of these best-performing regions deteriorate upon sensor rotation. The timing properties at different depths of the 3D sensor have been investigated with tracks at grazing-angle incidence, revealing a dependence of the time resolution along the sensor depth.

Abstract:

A precision measurement of the muon charge asymmetry from $W$ -boson decays in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ is presented. The analysis utilizes data corresponding to an integrated luminosity of $5.1{\mathrm{fb}}^{−1}$ , recorded by the LHCb detector during 2016, 2017, and 2018. The asymmetry is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. This result represents the most precise determination of the muon charge asymmetry in the forward region to date, exhibiting excellent agreement with next-to-next-to-leading-order predictions in perturbative quantum chromodynamics. The measured asymmetries are corrected for experimental efficiencies, resolution, and final-state photon radiation.