Search for CP violation in charmless three-body decays of strange-beauty baryons

Studies of charmless three-body decays of the Ξb ̅ and ꭥb baryons to ph-h’- final states, where h(‘) denotes a kaon or pion, are presented. The first part of the analysis is based on a sample of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies √s = 7 & 8TeV, corresponding to an integrated luminosity of 3 fb-1. In this analysis, the decay Ξb ̅→ pK-K- is observed with a significance of 8:7 standard deviations, and evidence at the level of 3:4 standard deviations is found for the Ξb ̅→pK-π- decay. The results are reported, relative to the B-→K+K-K- normalisation channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Ξb ̅→pK-π- and Ξb ̅→pK-K- relative to of Ξb ̅→pK-K- decays are also measured. In the second part of the analysis, an amplitude analysis of Ξb ̅→pK-K- decays is presented. This analysis is based on a data sample corresponding to integrated luminosities of 1 fb-1, 2 fb-1, 0:3 fb-1 and 1:7 fb-1 collected by LHCb during 2011 (√s = 7TeV), 2012 (√s = 8TeV), 2015 (√s = 13TeV) and 2016 (√s = 13TeV) respectively. Sensitivity to the CP violation parameters in Ξb ̅→ pK-K- decays is also presented. An updated search for the previously unobserved charmless decay ꭥb ̅→ pK- K- is also conducted

Measurements of prompt charm production cross-sections in pp collisions at s=5 TeV

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5 TeV. The data sample corresponds to an integrated luminosity of 8.60 ± 0.33 pb−1 collected by the LHCb experiment. The production cross-sections of D0, D+, Ds+, and D∗+ mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y. They cover the rapidity range 2.0 < y < 4.5 and transverse momentum ranges 0 < pT< 10 GeV/c for D0 and D+ and 1 < pT< 10 GeV/c for Ds+ and D∗+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < pT< 8 GeV/c are determined to be σpp→D0X=1004±3±54μb,σpp→D+X=402±2±30μb,σpp→Ds+X=170±4±16μb,σpp→D∗+X=421±5±36μb, where the uncertainties are statistical and systematic, respectively

Measurement of the properties of the Ξb∗ 0 baryon

We perform a search for near-threshold Ξb0 resonances decaying to Ξb−π+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. We observe one resonant state, with the following properties: mΞb∗0−mΞb−−mπ+=15.727±0.068stat±0.023systMeV/c2ΓΞb∗0=0.90±0.16stat±0.08systMeV.This confirms the previous observation by the CMS collaboration. The state is consistent with the JP = 3/2+ Ξb∗ 0 resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio σpp→Ξb∗0XℬΞb∗0→Ξb−π+σpp→Ξb−X=0.28±0.03stat.±0.01syst.

Observation of Λb0 → ψ(2S)pK− and Λb0 → J/ψπ+π−pK− decays and a measurement of the Λb0 baryon mass

The decays Λb0 → ψ(2S)pK− and Λb0 → J/ψπ+π−pK− are observed in a data sample corresponding to an integrated luminosity of 3 fb−1, collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The ψ(2S) mesons are reconstructed through the decay modes ψ(2S) → μ+μ− and ψ(2S) → J/ψπ+π−.The branching fractions relative to that of Λb0 → J/ψpK− are measured to be ℬΛb0→ψ2SpK−ℬΛb0→J/ψpK−=20.70±0.76±0.46±0.37×10−2, where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of J/ψ and ψ(2S) branching fractions. The mass of the Λb0 baryon is measured to be MΛb0=5619.65±0.17±0.17MeV/c2, where the uncertainties are statistical and systematic

Measurement of the B± production cross-section in pp collisions at s=7 and 13 TeV

The production of B± mesons is studied in pp collisions at centre-of-mass energies of 7 and 13 TeV, using B± → J/ψ K± decays and data samples corresponding to 1.0 fb−1 and 0.3 fb−1, respectively. The production cross-sections summed over both charges and integrated over the transverse momentum range 0 < pT < 40 GeV/c and the rapidity range 2.0 < y < 4.5 are measured to be σpp→B±X,s=7TeV=43.0±0.2±2.5±1.7μb, σpp→B±X,s=13TeV=86.6±0.5±5.4±3.4μb, where the first uncertainties are statistical, the second are systematic, and the third are due to the limited knowledge of the B± → J/ψ K± branching fraction. The ratio of the cross-section at 13 TeV to that at 7 TeV is determined to be 2.02 ± 0.02 (stat) ± 0.12 (syst). Differential cross-sections are also reported as functions of pT and y. All results are in agreement with theoretical calculations based on the state-of-art fixed next-to-leading order quantum chromodynamics

Measurement of the CP violation parameter A_{Γ} in D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} decays

Asymmetries in the time-dependent rates of D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3  fb^{-1}. The asymmetries in effective decay widths between D^{0} and D[over ¯]^{0} decays, sensitive to indirect CP violation, are measured to be A_{Γ}(K^{+}K^{-})=(-0.30±0.32±0.10)×10^{-3} and A_{Γ}(π^{+}π^{-})=(0.46±0.58±0.12)×10^{-3}, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two