Search for CP violation in Λb0→pK− and Λb0→pπ− decays

A search for CP violation in Λb0→pK− and Λb0→pπ− decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0fb−1. The CP -violating asymmetries are measured to be ACPpK−=−0.020±0.013±0.019 and ACPpπ−=−0.035±0.017±0.020, and their difference ACPpK−−ACPpπ−=0.014±0.022±0.010, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date

Observation of Two New Excited Ξb0 States Decaying to Λb0 K-π+

Two narrow resonant states are observed in the Λb0K-π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Λb0K-π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Ξb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0]<2.20(2.56) and Γ[Ξb(6333)0]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances

Measurement of CPCP asymmetry in Bs0→Ds∓K±B_s^0 \to D_s^{\mp} K^{\pm} decays

We report the measurements of the $CP$-violating parameters in $B_s^0 \to D_s^{\mp} K^{\pm}$ decays observed in $pp$ collisions, using a data set corresponding to an integrated luminosity of $3.0\,\text{fb}^{-1}$ recorded with the LHCb detector. We measure $C_f = 0.73 \pm 0.14 \pm 0.05$, $A^{\Delta \Gamma}_f = 0.39 \pm 0.28 \pm 0.15$, $A^{\Delta \Gamma}_{\overline{f}} = 0.31 \pm 0.28 \pm 0.15$, $S_f = -0.52 \pm 0.20 \pm 0.07$, $S_{\overline{f}} = -0.49 \pm 0.20 \pm 0.07$, where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the $B_s^0$ mixing phase, $-2\beta_s$, to obtain a measurement of the CKM angle $\gamma$ from $B_s^0 \to D_s^{\mp} K^{\pm}$ decays, yielding \gamma = (128\,_{-22}^{+17})^\circ modulo $180^\circ$, where the uncertainty contains both statistical and systematic contributions. This corresponds to $3.8\,\sigma$ evidence for $CP$ violation in the interference between decay and decay after mixing.We report the measurements of the CP -violating parameters in B$_{s}^{0}$  → D$_{s}^{∓}$ K$^{±}$ decays observed in pp collisions, using a data set corresponding to an integrated luminosity of 3.0 fb$^{−1}$ recorded with the LHCb detector. We measure C$_{f}$ = 0.73 ± 0.14 ± 0.05, A$_{f}^{ΔΓ}$  = 0.39 ± 0.28 ± 0.15, ${A}_{\overline{f}}^{\varDelta \varGamma }=0.31\pm 0.28\pm 0.15$ , S$_{f}$ = −0.52 ± 0.20 ± 0.07, ${S}_{\overline{f}}=-0.49\pm 0.20\pm 0.07$ , where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the B$_{s}^{0}$ mixing phase, −2β$_{s}$ , to obtain a measurement of the CKM angle γ from B$_{s}^{0}$  → D$_{s}^{∓}$ K$^{±}$ decays, yielding γ = (128$_{− 22}^{+ 17}$ )° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This corresponds to 3.8 σ evidence for CP violation in the interference between decay and decay after mixing

Measurement of the electron reconstruction efficiency at LHCb

The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fb−1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+→ J/ψ(e+e−)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%

Measurement of the CKM angle γ using B± → DK± with D → K S 0 π+π−, K S 0 K+K− decays

A binned Dalitz plot analysis of B ± → DK ± decays, with D→K0Sπ+π− and D→K0SK+K−, is performed to measure the CP-violating observables x ± and y ±, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle γ. The analysis exploits a sample of proton-proton collision data corresponding to 3.0 fb−1 collected by the LHCb experiment. Measurements from CLEO-c of the variation of the strong-interaction phase of the D decay over the Dalitz plot are used as inputs. The values of the parameters are found to be x + = (−7.7 ± 2.4 ± 1.0 ± 0.4) × 10− 2, x − = (2.5 ± 2.5 ± 1.0 ± 0.5) × 10− 2, y + = (−2.2 ± 2.5 ± 0.4 ± 1.0) × 10− 2 and y − = (7.5 ± 2.9 ± 0.5 ± 1.4) × 10− 2. The first, second, and third uncertainties are the statistical, the experimental systematic, and that associated with the precision of the strong-phase parameters. These are the most precise measurements of these observables and correspond to γ = (62 − 14 + 15) ° , with a second solution at γ → γ + 180°, and r B  = 0.080 − 0.021 + 0.019, where r B is the ratio between the suppressed and favoured B decay amplitudes

Erratum to: Study of gamma production in pPb collisions at root sNN = 8:16 TeV

The production of Υ(nS) mesons (n = 1, 2, 3) in pPb and Pbp collisions at a centre-of-mass energy per nucleon pair √ sNN = 8.16 TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb−1 . The Υ(nS) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the Υ(1S) and Υ(2S) states, their forward-to-backward ratios and nuclear modification factors. The measurements are performed as a function of the transverse momentum pT and rapidity in the nucleon-nucleon centre-of-mass frame y ∗ of the Υ(nS) states, in the kinematic range pT < 25 GeV/c and 1.5 < y∗ < 4.0 (−5.0 < y∗ < −2.5) for pPb (Pbp) collisions. In addition, production cross-sections for Υ(3S) are measured integrated over phase space and the production ratios between all three Υ(nS) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models

Prompt Lambda(+)(c) baryons and D-0 meson production cross-section and nuclear modification in pPb collisions at root S-NN=5.02 TeV with the LHCb detector

A(c)(+) baryons and D-0 mesons are studied in pPb collisions at root S-NN = 5.02 TeV. The nuclear modification factor and forward-backward cross-section asymmetry are measured in order to study the cold nuclear matter effects. The prompt A(c)(+) production cross-section is compared to that of the prompt D-0 mesons, providing insights into the hadronisation mechanism of charmed hadrons

Search for lepton-flavour-violating decays of Higgs-like bosons

A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb −1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2

Observation of the doubly Cabibbo-suppressed decay Ξ c + → pϕ

The doubly Cabibbo-suppressed decay Ξ c+ → pϕ with ϕ → K + K − is observed for the first time, with a statistical significance of more than fifteen standard deviations. The data sample used in this analysis corresponds to an integrated luminosity of 2 fb −1 recorded with the LHCb detector in pp collisions at a centre-of-mass energy of 8 TeV. The ratio of branching fractions between the decay Ξ c+ → pϕ and the singly Cabibbo-suppressed decay Ξ c+ → pK − π + is measured to beℬ(Ξc+→pϕ)ℬ(Ξc+→pK−π+)=(19.8±0.7±0.9±0.2)×10−3, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the ϕ → K + K − branching fraction.[Figure not available: see fulltext.