Precise test of lepton flavour universality in $W$-boson decays into muons and electrons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866909331965870080 |
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| author | ATLAS Collaboration |
| author_facet | ATLAS Collaboration |
| contents | The ratio of branching ratios of the $W$ boson to muons and electrons, $R^{μ/e}_W=B(W\rightarrow μν)/B(W\rightarrow eν)$, has been measured using 140 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the $t\bar{t}$ 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 $R^{μμ/ee}_Z$ for the $Z$ boson measured in inclusive $Z\rightarrow ee$ and $Z\rightarrowμμ$ 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 $R^{μ/e}_W = 0.9995 \pm 0.0022 \pm 0.0036 \pm 0.0014$. 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2403_02133 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Precise test of lepton flavour universality in $W$-boson decays into muons and electrons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector ATLAS Collaboration High Energy Physics - Experiment The ratio of branching ratios of the $W$ boson to muons and electrons, $R^{μ/e}_W=B(W\rightarrow μν)/B(W\rightarrow eν)$, has been measured using 140 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the $t\bar{t}$ 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 $R^{μμ/ee}_Z$ for the $Z$ boson measured in inclusive $Z\rightarrow ee$ and $Z\rightarrowμμ$ 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 $R^{μ/e}_W = 0.9995 \pm 0.0022 \pm 0.0036 \pm 0.0014$. 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. |
| title | Precise test of lepton flavour universality in $W$-boson decays into muons and electrons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector |
| topic | High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2403.02133 |