1,160 research outputs found

    Observation of the B0→ ̄D*0K+π− and B0s→ ̄D*0K−π+ decays

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    The first observations of B0→D ̄∗(2007)0K+π- and Bs0→D ̄∗(2007)0K-π+ decays are presented, and their branching fractions relative to that of the B0→D ̄∗(2007)0π+π- decay are reported. These modes can potentially be used to investigate the spectroscopy of charm and charm-strange resonances and to determine the angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle. It is also important to understand them as a source of potential background in determinations of γ from B+→DK+ and B0→DK+π- decays. The analysis is based on a sample corresponding to an integrated luminosity of 5.4 fb-1 of proton-proton collision data at 13 TeV center-of-mass energy recorded with the LHCb detector. The D ̄∗(2007)0 mesons are fully reconstructed in the D ̄0π0 and D ̄0γ channels with the D ̄0→K+π- decay. A novel weighting method is used to subtract background while simultaneously applying an event-by-event efficiency correction to account for resonant structures in the decays

    Amplitude analysis of the B+ →d+D-K+ decay

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    Results are reported from an amplitude analysis of the B+→D+D-K+ decay. The analysis is carried out using LHCb proton-proton collision data taken at s=7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb-1. In order to obtain a good description of the data, it is found to be necessary to include new spin-0 and spin-1 resonances in the D-K+ channel with masses around 2.9 GeV/c2, and a new spin-0 charmonium resonance in proximity to the spin-2 χc2(3930) state

    Test of lepton flavor universality using B0 →D∗-τ+ντ decays with hadronic τ channels

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    The branching fraction B(B0→D∗-τ+ντ) is measured relative to that of the normalization mode B0→D∗-π+π-π+ using hadronic τ+→π+π-π+(π0)ν ̄τ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1. The measured ratio is B(B0→D∗-τ+ντ)/B(B0→D∗-π+π-π+)=1.70±0.10-0.10+0.11, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0→D∗-π+π-π+ and B0→D∗-μ+νμ modes, the lepton universality test R(D∗-)B(B0→D∗-τ+ντ)/B(B0→D∗-μ+νμ) is calculated, R(D∗-)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements

    Amplitude analysis of the B+ →d+D-K+ decay

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    Results are reported from an amplitude analysis of the B+ -> D+D-K+ decay. The analysis is carried out using LHCb proton-proton collision data taken at root s = 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb(-1). In order to obtain a good description of the data, it is found to be necessary to include new spin-0 and spin-1 resonances in the D-K+ channel with masses around 2.9 GeV/c(2), and a new spin-0 charmonium resonance in proximity to the spin-2 chi(c2)(3930) state

    First observation of Λb0→Σc(*)++D(*)−K− decays

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    The four decays, Λ0 b → ΣðÞþþ c DðÞ−K−, are observed for the first time using proton-proton collision data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb−1. By considering the Λ0 b → Λþ c D¯ 0K− decay as reference channel, the following branching fraction ratios are measured to be BðΛ0 b→Σþþ c D−K−Þ BðΛ0 b→Λþ c D¯ 0K−Þ = 0.282 0.016 0.016 0.005, BðΛ0 b→Σþþ c D−K−Þ BðΛ0 b→Σþþ c D−K−Þ = 0.460 0.052 0.028, BðΛ0 b→Σþþ c D−K−Þ BðΛ0 b→Σþþ c D−K−Þ = 2.261 0.202 0.129 0.046, BðΛ0 b→Σþþ c D−K−Þ BðΛ0 b→Σþþ c D−K−Þ = 0.896 0.137 0.066 0.018, where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more datasets to become available following the LHCb upgrade

    Measurement of the D* longitudinal polarization in B0 →d*−τ+ντ decays

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    The longitudinal polarization fraction of the D* meson is measured in B0→D*-τ+ντ decays, where the τ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb-1. The D* polarization fraction FLD* is measured in two q2 regions, below and above 7 GeV2/c4, where q2 is defined as the squared invariant mass of the τντ system. The FLD∗ values are measured to be 0.52±0.07±0.04 and 0.34±0.08±0.02 for the lower and higher q2 regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q2 range is FLD∗=0.41±0.06±0.03. These results are compatible with the Standard Model predictions

    First observation of the decay B-0 -> D-0(D)over-bar(0)K(+)pi(-)

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    The first observation of the decay B0→D0D ̄0K+π- is reported using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb-1 collected by the LHCb experiment in 2011, 2012 and 2016. The measurement is performed in the full kinematically allowed range of the decay outside of the D∗- region. The ratio of the branching fraction relative to that of the control channel B0→D∗-D0K+ is measured to be R=(14.2±1.1±1.0)%, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of B0→D0D ̄0K+π- decays is thus determined to be B(B0→D0D ̄0K+π-)=(3.50±0.27±0.26±0.30)×10-4, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays

    Measurement of the DD^* longitudinal polarization in B0Dτ+ντB^0 \to D^{* -}\tau^+\nu_{\tau} decays  

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    The longitudinal polarization fraction of the DD^* meson is measured in B0Dτ+ντB^0 \to D^{* -}\tau^+\nu_{\tau} decays, where the τ\tau lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb1^{-1}. The DD^* polarization fraction FLDF_L^{D^*} is measured in two q2q^2 regions, below and above 7 GeV2^2/c4^4, where q2q^2 is defined as the squared invariant mass of the τντ\tau\nu_{\tau} system. The FLDF_L^{D^*} values are measured to be 0.51±0.07±0.030.51 \pm 0.07 \pm 0.03 and 0.35±0.08±0.020.35 \pm 0.08 \pm 0.02 for the lower and higher q2q^2 regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q2q^2 range is: FLD=0.43±0.06±0.03.F_L^{D^*} = 0.43 \pm 0.06 \pm 0.03. These results are compatible with the Standard Model predictions.The longitudinal polarization fraction of the D* meson is measured in B0→D*-τ+ντ decays, where the τ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5  fb-1. The D* polarization fraction FLD* is measured in two q2 regions, below and above 7  GeV2/c4, where q2 is defined as the squared invariant mass of the τντ system. The FLD* values are measured to be 0.52±0.07±0.04 and 0.34±0.08±0.02 for the lower and higher q2 regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q2 range is FLD*=0.41±0.06±0.03. These results are compatible with the Standard Model predictions.The longitudinal polarization fraction of the DD^{*} meson is measured in B0Dτ+ντB^0\to D^{*-}\tau^{+}\nu_{\tau} decays, where the τ\tau lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb1^{-1}. The DD^{*} polarization fraction FLDF_{L}^{D^{*}} is measured in two q2q^{2} regions, below and above 7 GeV2/c4^{2}/c^{4}, where q2q^{2} is defined as the squared invariant mass of the τντ\tau\nu_{\tau} system. The FLDF_{L}^{D^{*}} values are measured to be 0.52±0.07±0.040.52 \pm 0.07 \pm 0.04 and 0.34±0.08±0.020.34 \pm 0.08 \pm 0.02 for the lower and higher q2q^{2} regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole q2q^{2} range is: FLD=0.41±0.06±0.03.F_{L}^{D^{*}} = 0.41 \pm 0.06 \pm 0.03. These results are compatible with the Standard Model predictions

    Angular analysis of B0 → D∗−D∗+s with D∗+s → D+sγ decays

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    The first full angular analysis of the B0 → D∗−D∗+ s decay is performed using 6 fb−1 of pp collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The D∗+ s → D+ s γ and D∗− → D 0 π − vector meson decays are used with the subsequent D+ s → K+K−π + and D 0 → K+π − decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be fL = 0.578±0.010±0.011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [B(B0 → D∗−D∗+ s ) × B(D∗+ s → D+ s γ)]/B(B0 → D∗−D+ s ) is measured to be 2.045 ± 0.022 ± 0.071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed Bs → D∗−D+ s decay is made with a significance of seven standard deviations. The branching fraction ratio B(Bs → D∗−D+ s )/B(B0 → D∗−D+ s ) is measured to be 0.049 ± 0.006 ± 0.003 ± 0.002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions

    Amplitude analysis of the B+ →d+D-K+ decay

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    Results are reported from an amplitude analysis of the B+→D+D-K+ decay. The analysis is carried out using LHCb proton-proton collision data taken at s=7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb-1. In order to obtain a good description of the data, it is found to be necessary to include new spin-0 and spin-1 resonances in the D-K+ channel with masses around 2.9 GeV/c2, and a new spin-0 charmonium resonance in proximity to the spin-2 χc2(3930) state
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