Study of B c + → χ c π + decays
Journal of High Energy Physics Springer 2024:2 (2024) 173
Abstract:
A study of Bc+→χcπ+ decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The decay Bc+→χc2π+ is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the Bc+→J/ψπ+ decay is measured to beBBc+→χc2π+BBc+→J/ψπ+=0.37±0.06±0.02±0.01, where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the χc2→ J/ψγ branching fraction. No significant Bc+→χc1π+ signal is observed and an upper limit for the relative branching fraction for the Bc+→χc1π+ and Bc+→χc2π+ decays of BBc+→χc1π+BBc+→χc2π+=<0.49 is set at the 90% confidence level.A model-independent measurement of the CKM angle γ in partially reconstructed B ± → D * h ± decays with D → K S 0 h + h − ( h = π, K )
Journal of High Energy Physics Springer 2024:2 (2024) 118
Abstract:
A measurement of CP-violating observables in B± → D*K± and B± → D*π± decays is made where the photon or neutral pion from the D*→ Dγ or D*→ Dπ0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D → KS0π+π− or D → KS0K+K−. The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb−1. The B± → D*K± and B± → D*π±CP-violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ = (92−17+21)°. The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.Measurement of the Z boson production cross-section in pp collisions at s = 5. 02 TeV
Journal of High Energy Physics Springer 2024:2 (2024) 70
Abstract:
The first measurement of the Z boson production cross-section at centre-of-mass energy s = 5.02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 ± 2 pb−1. The production cross-section is measured for final-state muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momentum pT> 20 GeV/c. The integrated cross-section is determined to beσZ→μ+μ−=39.6±0.7stat±0.6syst±0.8lumipb for the di-muon invariant mass in the range 60 < Mμμ< 120 GeV/c2. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant. Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at sNN = 5.02 TeV, the nuclear modification factor RpPb is measured for the first time at this energy. The measured values are 1.2−0.3+0.5 (stat) ± 0.1(syst) in the forward region (1.53A search for rare B → Dμ + μ − decays
Journal of High Energy Physics Springer 2024:2 (2024) 32
Abstract:
A search for rare B → Dμ+μ− decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. No significant signals are observed in the non-resonant μ+μ− modes, and upper limits of BB0→D¯0μ+μ−<5.1×10−8, BB+→Ds+μ+μ−<3.2×10−8, BBs0→D¯0μ+μ−<1.6×10−7 and fc/fu·BBc+→Ds+μ+μ−<9.6×10−8 are set at the 95 % confidence level, where fc and fu are the fragmentation fractions of a B meson with a c and u quark respectively in proton-proton collisions. Each result is either the first such measurement or an improvement by three orders of magnitude on an existing limit. Separate upper limits are calculated when the muon pair originates from a J/ψ → μ+μ− decay. The branching fraction of Bc+→Ds+J/ψ multiplied by the fragmentation-fraction ratio is measured to befcfu·BBc+→Ds+J/ψ=1.63±0.15±0.13×10−5, where the first uncertainty is statistical and the second systematic.Helium identification with LHCb
Journal of Instrumentation IOP Publishing 19:02 (2024) P02010-P02010