# Search for anomalous couplings in the $Wtb$ vertex from the measurement of double differential angular decay rates of single top quarks produced in the $t$-channel with the ATLAS detector

Abstract : The electroweak production and subsequent decay of single top quarks is determined by the properties of the $Wtb$ vertex. This vertex can be described by the complex parameters of an effective Lagrangian. An analysis of angular distributions of the decay products of single top quarks produced in the $t$-channel constrains these parameters simultaneously. The analysis described in this paper uses 4.6 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}$ = 7 TeV collected with the ATLAS detector at the LHC.Two parameters are measured simultaneously in this analysis. The fraction $f_1$ of decays containing transversely polarised $W$ bosons is measured to be $0.37 \pm 0.07$ (stat.$\oplus$syst.). The phase $\delta_{-}$ between amplitudes for transversely and longitudinally polarised $W$ bosons recoiling against left-handed $b$-quarks is measured to be $-0.14\pi \pm 0.036\pi$ (stat.$\oplus$syst.).The correlation in the measurement of these parameters is $0.15$. These values result in two-dimensional limits at the 95% confidence level on the ratio of the complex coupling parameters $g_\mathrm{R}$ and $V_\mathrm{L}$, yielding Re [$g_\mathrm{R}/V_\mathrm{L}$] $\in [-0.36,0.10]$ and Im [$g_\mathrm{R}/V_\mathrm{L}$] $\in [-0.17,0.23]$ with a correlation of 0.11. The results are in good agreement with the predictions of the Standard Model.
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Article dans une revue
Journal of High Energy Physics, Springer Verlag (Germany), 2016, 04, pp.023. 〈10.1007/JHEP04(2016)023〉
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http://hal.in2p3.fr/in2p3-01215348
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Soumis le : mercredi 14 octobre 2015 - 07:50:28
Dernière modification le : mardi 24 juillet 2018 - 15:46:14

### Citation

G. Aad, S. Albrand, J. Collot, S. Crépé-Renaudin, P.A. Delsart, et al.. Search for anomalous couplings in the $Wtb$ vertex from the measurement of double differential angular decay rates of single top quarks produced in the $t$-channel with the ATLAS detector. Journal of High Energy Physics, Springer Verlag (Germany), 2016, 04, pp.023. 〈10.1007/JHEP04(2016)023〉. 〈in2p3-01215348〉

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