Precise test of lepton flavour universality in W-boson decays into muons and electrons in pp collisions at √s = 13 TeV with the ATLAS detector
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Date
2024
Authors
Aad, G.
Aakvaag, E.
Abbott, B.
Abdelhameed, S.
Abeling, K.
Abicht, N.J.
Abidi, S.H.
Aboelela, M.
Aboulhorma, A.
Abramowicz, H.
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European Physical Journal C, 2024; 84(10):993-1-993-33
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ATLAS Collaboration
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Abstract
The ratio of branching ratios of the W boson to muons and electrons, R μ/e W = B(W → μν)/B(W → eν), has been measured using 140 fb−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 crosssection in the ee, eμ and μμ dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio R μμ/ee Z for the Z boson measured in inclusive Z → ee and Z → μμ events. By using the precise value of R μμ/ee Z determined from e+e− colliders, the ratio R μ/e W is determined to be R μ/e W = 0.9995 ± 0.0022 (stat) ± 0.0036 (syst) ± 0.0014 (ext). The three uncertainties correspond to data statistics, experimental systematics and the external measurement of R μμ/ee Z , 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.
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© CERN for the benefit of the ATLAS Collaboration 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecomm ons.org/licenses/by/4.0/. Funded by SCOAP3.