Faculty and Student Publications
Document Type
Article
Publication Date
3-1-2021
Abstract
We present measurements of the branching fractions for the decays B → Kμ+μ− and B → Ke+e−, and their ratio (RK), using a data sample of 711 fb−1 that contains 772 × 106BB¯ events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The ratio RK is measured in five bins of dilepton invariant-mass-squared (q2): q2 ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV2/c4, along with the whole q2 region. The RK value for q2 ∈ (1.0, 6.0) GeV2/c4 is 1.03−0.24+0.28 ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for RK are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q2 ∈ (1.0, 6.0) GeV2/c4 bin in the mode with muon final states. The measured differential branching fractions, dℬ /dq2, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ±e∓ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10−8 for B+ → K+μ±e∓, and B0 → K0μ±e∓ modes. [Figure not available: see fulltext.]
Relational Format
journal article
Recommended Citation
The BELLE collaboration, Choudhury, S., Sandilya, S., Trabelsi, K., Giri, A., Aihara, H., Al Said, S., Asner, D. M., Atmacan, H., Aulchenko, V., Aushev, T., Ayad, R., Babu, V., Bahinipati, S., Behera, P., Beleño, C., Belous, K., Bennett, J., Bernlochner, F., … Zhukova, V. (2021). Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays. Journal of High Energy Physics, 2021(3), 105. https://doi.org/10.1007/JHEP03(2021)105
DOI
10.1007/JHEP03(2021)105
Accessibility Status
Searchable text