The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set ...corresponding to an integrated luminosity of 0.5 nb − 1 . The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV / c , represent the first direct determination of the antiproton production cross section in p − He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set ...corresponding to an integrated luminosity of 0.5 nb − 1 . The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV / c , represent the first direct determination of the antiproton production cross section in p − He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
The decay-time-dependent CP asymmetry in B 0 s →J/ψ(→μ + μ − )K + K − decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb −1 , collected with the ...LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B 0 s signal decays with an invariant K + K − mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B 0 s −¯B 0 s system, ΔΓ s , and the difference of the average B 0 s and B 0 meson decay widths, Γ s −Γ d . The values obtained are ϕ s =−0.039±0.022±0.006 rad, ΔΓ s =0.0845±0.0044±0.0024 ps −1 , and Γ s −Γ d =−0.0056 +0.0013 −0.0015 ±0.0014 ps −1 , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕs is also measured independently for each polarization state of the K + K − system and shows no evidence for polarization dependence.
The doubly charmed baryon decay Ξ + + c c → Ξ + c π + is observed for the first time, with a statistical significance of 5.9 σ , confirming a recent observation of the baryon in the Λ + c K − π + π + ...final state. The data sample used corresponds to an integrated luminosity of 1.7 fb − 1 , collected by the LHCb experiment in p p collisions at a center-of-mass energy of 13 TeV. The Ξ + + c c mass is measured to be 3620.6 ± 1.5 ( stat ) ± 0.4 ( syst ) ± 0.3 ( Ξ + c ) MeV / c 2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be B ( Ξ + + c c → Ξ + c π + ) × B ( Ξ + c → p K − π + ) / B ( Ξ + + c c → Λ + c K − π + π + ) × B ( Λ + c → p K − π + ) = 0.035 ± 0.009 ( stat ) ± 0.003 ( syst )
The doubly charmed baryon decay Ξ + + c c → Ξ + c π + is observed for the first time, with a statistical significance of 5.9 σ , confirming a recent observation of the baryon in the Λ + c K − π + π + ...final state. The data sample used corresponds to an integrated luminosity of 1.7 fb − 1 , collected by the LHCb experiment in p p collisions at a center-of-mass energy of 13 TeV. The Ξ + + c c mass is measured to be 3620.6 ± 1.5 ( stat ) ± 0.4 ( syst ) ± 0.3 ( Ξ + c ) MeV / c 2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be B ( Ξ + + c c → Ξ + c π + ) × B ( Ξ + c → p K − π + ) / B ( Ξ + + c c → Λ + c K − π + π + ) × B ( Λ + c → p K − π + ) = 0.035 ± 0.009 ( stat ) ± 0.003 ( syst )
Measurement of the Ωc0 Baryon Lifetime Alfonso Albero, Alejandro; Calvo Gómez, Míriam; Camboni, Alessandro ...
Physical review letters,
08/2018
Journal Article
Recenzirano
Odprti dostop
We report a measurement of the lifetime of the Ω 0 c baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb − 1 ...collected by the LHCb experiment. The sample consists of about 1000 Ω − b → Ω 0 c μ − ¯ ν μ X signal decays, where the Ω 0 c baryon is detected in the p K − K − π + final state and X represents possible additional undetected particles in the decay. The Ω 0 c lifetime is measured to be τ Ω 0 c = 268 ± 24 ± 10 ± 2 fs , where the uncertainties are statistical, systematic, and from the uncertainty in the D + lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.
Measurement of the Ωc0 Baryon Lifetime Alfonso Albero, Alejandro; Calvo Gómez, Míriam; Camboni, Alessandro ...
Physical review letters,
08/2018
Journal Article
Recenzirano
Odprti dostop
We report a measurement of the lifetime of the Ω 0 c baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb − 1 ...collected by the LHCb experiment. The sample consists of about 1000 Ω − b → Ω 0 c μ − ¯ ν μ X signal decays, where the Ω 0 c baryon is detected in the p K − K − π + final state and X represents possible additional undetected particles in the decay. The Ω 0 c lifetime is measured to be τ Ω 0 c = 268 ± 24 ± 10 ± 2 fs , where the uncertainties are statistical, systematic, and from the uncertainty in the D + lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.
The first measurements of the forward-backward asymmetry of the dimuon pair ( A FB ), the triple-product asymmetry ( A 2 ϕ ), and the charge-parity-conjugation asymmetry ( A C P ), in D 0 → π + π − μ ...+ μ − and D 0 → K + K − μ + μ − 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 5 fb − 1 . The asymmetries are measured to be A FB ( D 0 → π + π − μ + μ − ) = ( 3.3 ± 3.7 ± 0.6 ) % , A 2 ϕ ( D 0 → π + π − μ + μ − ) = ( − 0.6 ± 3.7 ± 0.6 ) % , A C P ( D 0 → π + π − μ + μ − ) = ( 4.9 ± 3.8 ± 0.7 ) % , A FB ( D 0 → K + K − μ + μ − ) = ( 0 ± 11 ± 2 ) % , A 2 ϕ ( D 0 → K + K − μ + μ − ) = ( 9 ± 11 ± 1 ) % , A C P ( D 0 → K + K − μ + μ − ) = ( 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.
The first measurements of the forward-backward asymmetry of the dimuon pair ( A FB ), the triple-product asymmetry ( A 2 ϕ ), and the charge-parity-conjugation asymmetry ( A C P ), in D 0 → π + π − μ ...+ μ − and D 0 → K + K − μ + μ − 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 5 fb − 1 . The asymmetries are measured to be A FB ( D 0 → π + π − μ + μ − ) = ( 3.3 ± 3.7 ± 0.6 ) % , A 2 ϕ ( D 0 → π + π − μ + μ − ) = ( − 0.6 ± 3.7 ± 0.6 ) % , A C P ( D 0 → π + π − μ + μ − ) = ( 4.9 ± 3.8 ± 0.7 ) % , A FB ( D 0 → K + K − μ + μ − ) = ( 0 ± 11 ± 2 ) % , A 2 ϕ ( D 0 → K + K − μ + μ − ) = ( 9 ± 11 ± 1 ) % , A C P ( D 0 → K + K − μ + μ − ) = ( 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.
The first measurement of the lifetime of the doubly charmed baryon Ξ + + c c is presented, with the signal reconstructed in the final state Λ + c K − π + π + . The data sample used corresponds to an ...integrated luminosity of 1.7 fb − 1 , collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Ξ + + c c lifetime is measured to be 0.25 6 + 0.024 − 0.022 ( stat ) ± 0.014 ( syst ) ps .
