Precise test of lepton flavour universality in W-boson decays into muons and electrons in pp collisions at s=13TeV with the ATLAS detector

Summary, in English

The ratio of branching ratios of the W boson to muons and electrons, RWμ/e=B(W→μν)/B(W→eν), has been measured using 140fb-1 of pp collision data at s=13 TeV collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the tt¯ production cross-section in the ee, eμ and μμ dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio RZμμ/ee for the Z boson measured in inclusive Z→ee and Z→μμ events. By using the precise value of RZμμ/ee determined from e+e- colliders, the ratio RWμ/e is determined to be (Formula presented.) The three uncertainties correspond to data statistics, experimental systematics and the external measurement of RZμμ/ee, giving a total uncertainty of 0.0045, and confirming the Standard Model assumption of lepton flavour universality in W-boson decays at the 0.5% level. © The Author(s) 2024.

• Author: G. Aad; T.P.A. Åkesson; K.S.V. Astrand; C. Doglioni; P.A. Ekman; V. Hedberg; H. Herde; B. Konya; E. Lytken; R. Poettgen; N.D. Simpson; O. Smirnova; E.J. Wallin; L. Zwalinski
• Department/s: Particle and nuclear physics; eSSENCE: The e-Science Collaboration
• Publishing year: 2024
• Language: English
• Publication/Series: European Physical Journal C
• Volume: 84
• Issue: 10
• Links: http://dx.doi.org/10.1140/epjc/s10052-024-13070-4
• Document type: Journal article
• Publisher: Springer Nature
• Topic: Subatomic Physics
• Keywords: Colliding beam accelerators; Linear accelerators; Positive ions; ATLAS detectors; Branching ratio; Dileptons; Final state; Lepton-flavor; Measurements of; Production cross section; Square-root; Systematic uncertainties; W bosons; Bosons
• Status: Published
• ISBN/ISSN/Other: ISSN: 1434-6044