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.

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

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Cited by in corpus (23)

• Matching of gauge invariant dimension 6 operators for $b\to s$ and $b\to c$ transitions
• Constraining the top-Higgs sector of the Standard Model Effective Field Theory
• Right-handed charged currents in the era of the Large Hadron Collider
• Is there room for CP violation in the top-Higgs sector?
• Measurement of the W boson helicity fractions in the decays of top quark pairs to lepton + jets final states produced in pp collisions at sqrt(s) = 8 TeV
• Measurement of the $W$ boson polarisation in $t\bar{t}$ events from $pp$ collisions at $\sqrt{s}$ = 8 TeV in the lepton+jets channel with ATLAS
• Single top-quark production at the Tevatron and the LHC
• Top-Quark Physics: Status and Prospects
• Probing the $Wtb$ vertex structure in $t$-channel single-top-quark production and decay in $pp$ collisions at $\sqrt{\mathrm{s}}=8$ TeV with the ATLAS detector
• New limits on anomalous contributions to the $Wtb$ vertex
• Probing anomalous $Wtb$ couplings at the LHC in single top quark production through $t$-channel
• Top-quark physics at the Large Hadron Collider
• Analysis of the $Wtb$ vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the $t$-channel at $\sqrt{s}$ = 8 TeV with the ATLAS detector
• Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• $tbW$ Anomalous Couplings in the Two Higgs Doublet Model
• Measurement of $\tau$ polarisation in $Z/{\gamma }^{\ast }\to \tau \tau$ decays in proton-proton collisions at $\sqrt{s}=8$ TeV with the ATLAS detector
• MINLO t-channel single-top plus jet
• Minimal Dilaton Model and the Diphoton Excess
• Single Top Quark Production with and without a Higgs Boson
• $T$-odd correlations in polarized top quark decays in the sequential decay $t(\uparrow )\to X_b+W^{+}(\to {\ell }^{+}+{\nu }_{\ell })$ and in the quasi three-body decay $t(\uparrow )\to X_b+{\ell }^{+}+{\nu }_{\ell }$
• Single-top quark physics at the LHC: from precision measurements to rare processes and top quark properties
• A Global Analysis of the Standard Model Effective Field Theory in the Production and Decay Channels of a Single Top Quark
• Modeling of processes with anomalous interactions by means of auxiliary fields