The differential branching fraction of the rare decay Λ b 0  → Λμ + μ − is measured as a function of q 2, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment. Evidence of signal is observed in the q 2 region below the square of the J/ψ mass. Integrating over 15 < q 2 < 20 GeV2 /c 4 the differential branching fraction is measured as dB(Λ0b→Λμ+μ−)/dq2=(1.18+0.09−0.08±0.03±0.27)×10−7(GeV2/c4)−1, where the uncertainties are statistical, systematic and due to the normalisation mode, Λ b 0  → J/ψΛ, respectively. In the q 2 intervals where the signal is observed, angular distributions are studied and the forward-backward symmetries in the dimuon (A FB ℓ ) and hadron (A FB h ) systems are measured for the first time. In the range 15 < q 2 < 20 GeV2 /c 4 they are found to be AℓFB=−0.05±0.09(stat)±0.03(syst)andAhFB=−0.29±0.07(stat)±0.03(syst).

Differential branching fraction and angular analysis of Λ b 0  → Λμ + μ − decays

SATRIANO, Celestina;
2015-01-01

Abstract

The differential branching fraction of the rare decay Λ b 0  → Λμ + μ − is measured as a function of q 2, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment. Evidence of signal is observed in the q 2 region below the square of the J/ψ mass. Integrating over 15 < q 2 < 20 GeV2 /c 4 the differential branching fraction is measured as dB(Λ0b→Λμ+μ−)/dq2=(1.18+0.09−0.08±0.03±0.27)×10−7(GeV2/c4)−1, where the uncertainties are statistical, systematic and due to the normalisation mode, Λ b 0  → J/ψΛ, respectively. In the q 2 intervals where the signal is observed, angular distributions are studied and the forward-backward symmetries in the dimuon (A FB ℓ ) and hadron (A FB h ) systems are measured for the first time. In the range 15 < q 2 < 20 GeV2 /c 4 they are found to be AℓFB=−0.05±0.09(stat)±0.03(syst)andAhFB=−0.29±0.07(stat)±0.03(syst).
2015
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11563/114704
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