63 research outputs found
Search for beautiful tetraquarks in the <i>Ï</i>(1<i>S</i>)ÎŒ<sup>+</sup>ÎŒ<sup>â</sup> invariant-mass spectrum
International audienceThe Ï(1S)ΌΌ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two quarks, . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2.0, 5.0], and the state has rapidity in the range [2.0, 4.5] and transverse momentum less than 15 GeV/c
Measurement of angular and CP asymmetries in D0âÏ+Ï-ÎŒ+ÎŒ- and D0âK+K-ÎŒ+ÎŒ- decays
The first measurements of the forward-backward asymmetry of the dimuon pair (A_{FB}), the triple-product asymmetry (A_{2Ï}), and the charge-parity-conjugation asymmetry (A_{CP}), in D0âÏ+Ï-ÎŒ+ÎŒ- and D0âK+K-ÎŒ+ÎŒ- decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5ââfb^{-1}. The asymmetries are measured to be A_{FB}(D^{0}âÏ^{+}Ï^{-}ÎŒ^{+}ÎŒ^{-})=(3.3±3.7±0.6)%, A_{2Ï}(D^{0}âÏ^{+}Ï^{-}ÎŒ^{+}ÎŒ^{-})=(-0.6±3.7±0.6)%, A_{CP}(D^{0}âÏ^{+}Ï^{-}ÎŒ^{+}ÎŒ^{-})=(4.9±3.8±0.7)%, A_{FB}(D^{0}âK^{+}K^{-}ÎŒ^{+}ÎŒ^{-})=(0±11±2)%, A_{2Ï}(D^{0}âK^{+}K^{-}ÎŒ^{+}ÎŒ^{-})=(9±11±1)%, A_{CP}(D^{0}âK^{+}K^{-}ÎŒ^{+}ÎŒ^{-})=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions
Evidence for an ηc(1S) Ïâ Resonance in B0 â ηc(1S) K+ Ïâ Decays
A Dalitz plot analysis of B0 â ηc(1S) K+ Ïâ decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of âs =7, 8 and 13 TeV, corresponding to a total integrated luminosity of 4.7 fb^â1. A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S) Ïâ resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096 ± 20{â22}{+18} MeV and 152 ± 58{â35}{+60} MeV, respectively. The spin-parity assignments JP = 0+ and JP = 1â are both consistent with the data. In addition, the first measurement of the B0 â ηc(1S) K+ Ïâ branching fraction is performed and gives B(B0 â ηc(1S) K+ Ïâ) = (5.73 ± 0.24 ± 0.13 ± 0.66) Ă 10^â4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions
Evidence for an ηc(1S)Ï- resonance in B0âηc(1S)K+Ï- decays
A Dalitz plot analysis of B0âηc(1S)K+Ï- decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of s=7,8 and 13TeV , corresponding to a total integrated luminosity of 4.7fb-1 . A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)Ï- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096±20-22+18MeV and 152±58-35+60MeV , respectively. The spin-parity assignments JP=0+ and JP=1- are both consistent with the data. In addition, the first measurement of the B0âηc(1S)K+Ï- branching fraction is performed and gives B(B0âηc(1S)K+Ï-)=(5.73±0.24±0.13±0.66)Ă10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions
Measurement of the time-integrated <i>CP</i> asymmetry in <i>D</i><sup>0</sup>âââ<i>K <sub>S</sub></i> <sup>0</sup> <i>K <sub>S </sub></i><sup>0</sup> decays
A measurement of the time-integrated asymmetry in decays is reported. The data correspond to an integrated luminosity of
about fb collected in 2015-2016 by the LHCb collaboration in
collisions at a centre-of-mass energy of TeV. The candidate is
required to originate from a decay, allowing
the determination of the flavour of the meson using the pion charge. The
decay, which has a well measured asymmetry,
is used as a calibration channel. The asymmetry for is measured to be \begin{equation*} \mathcal{A}^{CP}(D^0\rightarrow
K^0_S K^0_S) = (4.3\pm 3.4\pm 1.0)\%, \end{equation*} where the first
uncertainty is statistical and the second is systematic. This result is
combined with the previous LHCb measurement at lower centre-of-mass energies to
obtain \begin{equation*} \mathcal{A}^{CP}(D^0\rightarrow K^0_S K^0_S) = (2.3\pm
2.8\pm 0.9)\%. \end{equation*}Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-012.htm
Measurement of the CKM angle Îł using<i> B</i><sup>±</sup> â <i>DK</i><sup>±</sup> with DâââK <sub>S</sub> <sup>0</sup> Ï<sup>+</sup>Ï<sup>â</sup>,âK <sub>S</sub> <sup>0</sup> K<sup>+</sup>K<sup>â</sup> decays
A binned Dalitz plot analysis of decays, with and , is used to perform a
measurement of the CP-violating observables and , which are
sensitive to the Cabibbo-Kobayashi-Maskawa angle . The analysis is
performed without assuming any decay model, through the use of information
on the strong-phase variation over the Dalitz plot from the CLEO collaboration.
Using a sample of proton-proton collision data collected with the LHCb
experiment in 2015 and 2016, and corresponding to an integrated luminosity of
2.0, the values of the CP violation parameters are found to
be , , , and . The first
uncertainty is statistical, the second is systematic, and the third is due to
the uncertainty on the strong-phase measurements. These values are used to
obtain \gamma = \left(87\,^{+11}_{-12}\right)^\circ, , and , where is the ratio
between the suppressed and favoured -decay amplitudes and is the
corresponding strong-interaction phase difference. This measurement is combined
with the result obtained using 2011 and 2012 data collected with the \lhcb
experiment, to give \gamma = \left(80\,^{+10}_{\,-9}\right)^\circ, , and .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-017.html.
Version 2 includes minor changes made during journal revie
Observation of the decay Î <sub>b</sub> <sup>0</sup> âââÏ(2S)pÏ<sup>â</sup>
International audienceThe Cabibbo-suppressed decay Î âââÏ(2S)pÏ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The Ï(2S) mesons are reconstructed in the ΌΌ final state. The branching fraction with respect to that of the Î âââÏ(2S)pK decay mode is measured to b
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Search for lepton-flavour-violating decays of Higgs-like bosons
Abstract: A search is presented for a Higgs-like boson with mass in the range 45 to 195GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8TeV, collected by the LHCb experiment, corresponding to an integrated luminosity of 2fb-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 22pb for a boson mass of 45GeV/c2 to 4pb for a mass of 195GeV/c2
First measurement of the -violating phase in decays
A flavour-tagged decay-time-dependent amplitude analysis of B âââ(KÏ)(KÏ) decays is presented in the KÏ mass range from 750 to 1600MeV/c. The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb. Several quasi-two-body decay modes are considered, corresponding to KÏ combinations with spin 0, 1 and 2, which are dominated by the K (800) and K (1430), the K(892) and the K (1430) resonances, respectively. The longitudinal polarisation fraction for the decay is measured as f = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase, , in transitions is performed, yielding a value of (syst) rad.A flavour-tagged decay-time-dependent amplitude analysis of decays is presented in the mass range from 750 to 1600 MeV. The analysis uses collision data collected with the LHCb detector at centre-of-mass energies of and TeV, corresponding to an integrated luminosity of fb. Several quasi-two-body decay modes are considered, corresponding to combinations with spin 0, 1 and 2, which are dominated by the and , the and the resonances, respectively. The longitudinal polarisation fraction for the decay is measured as , where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced -violating phase, , in transitions is performed, yielding a value of (stat) (syst) rad
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