Measurements of the cross section for producing b quarks in the reaction pp -> b (b) over barX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity. in the range 2 < ...eta < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered. range are 72.0 +/- 0.3 +/- 6.8 and 154.3 +/- 1.5 +/- 14.3 +/- mu b for 7 and 13 TeV. The ratio is 2.14 +/- 0.02 +/- 0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower eta than the model prediction.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay ¯ B 0 → K 0 S π + π − is studied using a p p collision data sample recorded with the LHCb detector, corresponding ...to an integrated luminosity of 3.0 fb − 1 . The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the ¯ B 0 → K 0 S π + π − decay branching fraction and C P asymmetries of the flavor-specific amplitudes are measured. The C P asymmetry between the conjugate ¯ B 0 → K ∗ ( 892 ) − π + and B 0 → K ∗ ( 892 ) + π − decay rates is determined to be − 0.308 ± 0.062.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay ¯ B 0 → K 0 S π + π − is studied using a p p collision data sample recorded with the LHCb detector, corresponding ...to an integrated luminosity of 3.0 fb − 1 . The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the ¯ B 0 → K 0 S π + π − decay branching fraction and C P asymmetries of the flavor-specific amplitudes are measured. The C P asymmetry between the conjugate ¯ B 0 → K ∗ ( 892 ) − π + and B 0 → K ∗ ( 892 ) + π − decay rates is determined to be − 0.308 ± 0.062.
Evidence for the Rare Decay Σ+ →pμ+μ Alfonso Albero, Alejandro; Badalov, Alexey; Calvo Gómez, Míriam ...
Physical review letters,
05/2018
Journal Article
Recenzirano
Odprti dostop
A search for the rare decay Σ + → p μ + μ − is performed using p p collision data recorded by the LHCb experiment at center-of-mass energies √ s = 7 and 8 TeV, corresponding to an integrated ...luminosity of 3 fb − 1 . An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured Σ + → p μ + μ − branching fraction is ( 2.2 + 1.8 − 1.3 ) × 10 − 8 , where statistical and systematic uncertainties are included, which is consistent with the standard model prediction.
Evidence for the Rare Decay Σ+ →pμ+μ Alfonso Albero, Alejandro; Badalov, Alexey; Calvo Gómez, Míriam ...
Physical review letters,
05/2018
Journal Article
Recenzirano
Odprti dostop
A search for the rare decay Σ + → p μ + μ − is performed using p p collision data recorded by the LHCb experiment at center-of-mass energies √ s = 7 and 8 TeV, corresponding to an integrated ...luminosity of 3 fb − 1 . An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured Σ + → p μ + μ − branching fraction is ( 2.2 + 1.8 − 1.3 ) × 10 − 8 , where statistical and systematic uncertainties are included, which is consistent with the standard model prediction.
The ratio of branching fractions R ( D * − ) ≡ B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − μ + ν μ ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at ...center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb − 1 . For the first time, R ( D * − ) is determined using the τ -lepton decays with three charged pions in the final state. The B 0 → D * − τ + ν τ yield is normalized to that of the B 0 → D * − π + π − π + mode, providing a measurement of B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − π + π − π + ) = 1.97 ± 0.13 ± 0.18 , where the first uncertainty is statistical and the second systematic. The value of B ( B 0 → D * − τ + ν τ ) = ( 1.42 ± 0.094 ± 0.129 ± 0.054 ) % is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B 0 → D * − μ + ν μ decay, a value of R ( D * − ) = 0.291 ± 0.019 ± 0.026 ± 0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B 0 → D * − μ + ν μ modes. This measurement is in agreement with the standard model prediction and with previous results.
The ratio of branching fractions R ( D * − ) ≡ B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − μ + ν μ ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at ...center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb − 1 . For the first time, R ( D * − ) is determined using the τ -lepton decays with three charged pions in the final state. The B 0 → D * − τ + ν τ yield is normalized to that of the B 0 → D * − π + π − π + mode, providing a measurement of B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − π + π − π + ) = 1.97 ± 0.13 ± 0.18 , where the first uncertainty is statistical and the second systematic. The value of B ( B 0 → D * − τ + ν τ ) = ( 1.42 ± 0.094 ± 0.129 ± 0.054 ) % is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B 0 → D * − μ + ν μ decay, a value of R ( D * − ) = 0.291 ± 0.019 ± 0.026 ± 0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B 0 → D * − μ + ν μ modes. This measurement is in agreement with the standard model prediction and with previous results.
A measurement is reported of the ratio of branching fractions R ( J / ψ ) = B ( B + c → J / ψ τ + ν τ ) / B ( B + c → J / ψ μ + ν μ ) , where the τ + lepton is identified in the decay mode τ + → μ + ...ν μ ¯ ν τ . This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb − 1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B + c → J / ψ τ + ν τ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R ( J / ψ ) = 0.71 ± 0.17 ( stat ) ± 0.18 ( syst ) . This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
A measurement is reported of the ratio of branching fractions R ( J / ψ ) = B ( B + c → J / ψ τ + ν τ ) / B ( B + c → J / ψ μ + ν μ ) , where the τ + lepton is identified in the decay mode τ + → μ + ...ν μ ¯ ν τ . This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb − 1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B + c → J / ψ τ + ν τ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R ( J / ψ ) = 0.71 ± 0.17 ( stat ) ± 0.18 ( syst ) . This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
The B 0 s π ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to ...3 fb − 1 of p p collision data at √ s = 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X ( 5568 ) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π ± final state. The same limits also apply to a possible exotic meson decaying through the chain B * 0 s π ± , B * 0 s → B 0 s γ where the photon is excluded from the reconstructed decays.
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