Measurement of Lepton Mass Squared Moments in B → X_c ℓ ν_ℓ Decays with the Belle II Experiment

2022/05/12 by Belle II Collaboration
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2205.06372

Abstract

We present measurements of the first to fourth moments of the lepton mass squared q² of \mboxB → X_c ℓ ν_ℓ decays for ℓ = e, μ and with X_c a hadronic system containing a charm quark. These results use a sample of electron-positron collisions at the Υ(4S) resonance corresponding to 62.8 fb^-1 of integrated luminosity and collected by the Belle II experiment in 2019 and 2020. To identify the X_c system and reconstruct q², one of the B mesons from an Υ(4S) → B \kern 0.18em\kern -0.18em B decay is fully reconstructed in a hadronic decay mode using a multivariate B tagging algorithm. We report raw and central moments for q² > 1.5 GeV²/c⁴ up to q² > 8.5 GeV²/c⁴, probing up to 77% of the accessible \mboxB → X_c ℓ ν_ℓ phase space. This is the first measurement of moments in the experimentally challenging range of [ 1.5, 2.5 ] GeV²/c⁴.

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