TY - JOUR

T1 - 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

AU - ATLAS Collaboration

AU - Newman, Paul

AU - Allport, Philip

AU - Aperio Bella, Ludovica

AU - Baca, Matthew

AU - Bracinik, Juraj

AU - Charlton, David

AU - Chisholm, Andrew

AU - Daniells, Andrew

AU - Gach, Grzegorz

AU - Hawkes, Christopher

AU - Head, Simon

AU - Hillier, Stephen

AU - Levy, Mark

AU - Mudd, Richard

AU - Slater, Mark

AU - Murillo Quijada, Javier

AU - Nikolopoulos, Konstantinos

AU - Owen, Rhys

AU - Thomas, Jurgen

AU - Thompson, Paul

AU - Watson, Miriam

AU - Wilson, John

AU - Watson, Alan

N1 - 26 pages plus author list + cover pages (42 pages total), 8 figures, 2 tables, submitted to JHEP, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2013-12

PY - 2015/10/13

Y1 - 2015/10/13

N2 - 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.

AB - 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.

KW - hep-ex

U2 - 10.1007/JHEP04(2016)023

DO - 10.1007/JHEP04(2016)023

M3 - Article

SN - 1126-6708

JO - JHEP

JF - JHEP

ER -