298 research outputs found

    Observation of an Excited Bc+ State

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    Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

    Observation of the Λb0 → χc1 (3872) pK− decay

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    Measurement of CP -violating and mixing-induced observables in Bs0→ϕγ decays

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    A time-dependent analysis of the B 0 s → ϕ γ decay rate is performed to determine the C P -violating observables S ϕ γ and C ϕ γ and the mixing-induced observable A Δ ϕ γ . The measurement is based on a sample of p p collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3     fb − 1 at center-of-mass energies of 7 and 8 TeV. The measured values are S ϕ γ = 0.43 ± 0.30 ± 0.11 , C ϕ γ = 0.11 ± 0.29 ± 0.11 , and A Δ ϕ γ = − 0.67 + 0.37 − 0.41 ± 0.17 , where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative B 0 s decays. The results are consistent with the standard model predictions

    Observation of CP Violation in Charm Decays

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    A search for charge-parity (CP) violation in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb(-1) collected at a center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D* (2010)(+) -> D-0 pi(+) decays or from the charge of the muon in (B) over bar -> D-0 mu(-)(nu) over bar X-mu decays. The difference between the CP asymmetries in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays is measured to be Delta A(CP) = [-18.2 +/- 3.2(stat) +/- 0.9(syst)] x 10(-4) for pi-tagged and Delta A(CP) = [-9 +/- 8(stat) +/- 5(syst)] x 10(-4) for mu-tagged D-0 mesons. Combining these with previous LHCb results leads to Delta A(CP) = (-15.4 +/- 2.9) x 10(-4), where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons

    Observation of an Excited Bc⁺ state

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    Using p p collision data corresponding to an integrated luminosity of 8.5     fb − 1 recorded by the LHCb experiment at center-of-mass energies of √ s = 7 , 8, and 13 TeV, the observation of an excited B + c state in the B + c π + π − invariant-mass spectrum is reported. The observed peak has a mass of 6841.2 ± 0.6 ( stat ) ± 0.1 ( syst ) ± 0.8 ( B + c )     MeV / c 2 , where the last uncertainty is due to the limited knowledge of the B + c mass. It is consistent with expectations of the B ∗ c ( 2 3 S 1 ) + state reconstructed without the low-energy photon from the B ∗ c ( 1 3 S 1 ) + → B + c γ decay following B ∗ c ( 2 3 S 1 ) + → B ∗ c ( 1 3 S 1 ) + π + π − . A second state is seen with a global (local) statistical significance of 2.2 σ ( 3.2 σ ) and a mass of 6872.1 ± 1.3 ( stat ) ± 0.1 ( syst ) ± 0.8 ( B + c )     MeV / c 2 , and is consistent with the B c ( 2 1 S 0 ) + state. These mass measurements are the most precise to date

    Precision measurement of the Ξcc++Ξcc++ {\varXi}_{cc}^{++} mass

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    A measurement of the Ξ++cc mass is performed using data collected by the LHCb experiment between 2016 and 2018 in pp collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.6 fb−1. The Ξ++cc candidates are reconstructed via the decay modes Ξ++cc→Λ+cK−π+π+ and Ξ++cc→Ξ+cπ+. The result, 3621.55 ± 0.23 (stat) ± 0.30 (syst) MeV/c2, is the most precise measurement of the Ξ++cc mass to date

    Study of the psi(2)(3823) and chi(c1)(3872) states in B+->(J/psi pi(+)pi(-))K(+)decays

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    The decays B+J/ψπ+πK+B^+\rightarrow J/\psi \pi^+ \pi^- K^+ are studied using a data set corresponding to an integrated luminosity of 9fb1^{-1} collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ2(3823)\psi_2(3823), χc1(3872)\chi_{c1}(3872) and ψ(2S)\psi(2S) states are reported. The decay of B+ψ2(3872)K+B^+\rightarrow \psi_2(3872)K^+ with ψ2(3823)Jψπ+π\psi_2(3823)\rightarrow J\psi\pi^+\pi^- is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ2(3823)\psi_2(3823), χc1(3872)\chi_{c1}(3872) and ψ(2S)\psi(2S) states are measured to be mχc1(3872)mψ2(3823)=47.50±0.53±0.13MeV/c2,mψ2(3823)mψ(2S)=137.98±0.53±0.14MeV/c2,mχc1(3872)mψ(2S)=185.49±0.06±0.03MeV/c2, \begin{array}{rcl} m_{\chi_{c1(3872)}} - m_{\psi_2(3823)} &= & 47.50 \pm 0.53 \pm 0.13\,\mathrm{MeV/}c^2\,, \\ m_{\psi_2(3823)} - m_{\psi(2S)} &= & 137.98 \pm 0.53 \pm 0.14\,\mathrm{MeV/}c^2\,, \\ m_{\chi_{c1}(3872)} - m_{\psi(2S)} &= & 185.49 \pm 0.06 \pm 0.03\,\mathrm{MeV/}c^2\,, \end{array} resulting in the most precise determination of the χc1(3782)\chi_{c1}(3782) mass. The width of the ψ2(3823)\psi_2(3823) state is found to be below 5.2MeV at 90\% confidence level. The Breit-Wigner width of the χc1(3872)\chi_{c1}(3872) state is measured to be Γχc1(3872)BW=0.960.18+0.19±0.21MeV, \Gamma^{\mathrm{BW}}_{\chi_{c1}(3872)} = 0.96^{+0.19}_{-0.18}\pm0.21 \mathrm{MeV}, which is inconsistent with zero by 5.5 standard deviations.Comment: 26 pages, 3 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-009.html (LHCb public pages

    Erratum to: Measurement of ϒ production in pp collisions at s√ = 13 TeV

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    Observation of a narrow pentaquark state, P-c(4312)(+), and of the two-peak structure of the P-c(4450)(+)

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    A narrow pentaquark state, P-c(4312)(+), decaying to J/psi p, is discovered with a statistical significance of 7.3 sigma in a data sample of Lambda(0)(b) -&gt; J/psi pK(-) decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P-c(4450)(+) pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P-c(4440)(+) and P-c(4457)(+), where the statistical significance of this two-peak interpretation is 5.4 sigma. The proximity of the Sigma(+)(c)(D) over bar (0) and Sigma(+)(c)(D) over bar (*0) thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states
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