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.

Precise test of lepton flavour universality in $$\varvec{W}$$-boson decays into muons and electrons in $$\varvec{pp}$$ collisions at $$\varvec{\sqrt{s}}=13\,\text {T}\text {e}\hspace{-1.00006pt}\text {V} $$ with the ATLAS detector

Carrá, S.;Gaudio, G.;Introzzi, G.;Manco, G.;Negri, A.;Pareti, A.;Rebuzzi, D. M.;Romano, E.;
2024-01-01

Abstract

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.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/1552435
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