Dilepton azimuthal correlations in $t\bar{t}$ production

Abstract

The dilepton azimuthal correlation, namely the difference $\varphi$ between the azimuthal angles of the positive and negative charged lepton in the laboratory frame, provides a stringent test of the spin correlation in $t\bar{t}$ production at the Large Hadron Collider. We introduce a parameterisation of the differential cross section $d\sigma /d\varphi$ in terms of a Fourier series and show that the third-order expansion provides a sufficiently accurate approximation. This expansion can be considered as a `bridge' between theory and data, making it very simple to cast predictions in the Standard Model (SM) and beyond, and to report measurements, without the need to provide the numbers for the whole binned distribution. We show its application by giving predictions for the coefficients in the presence of (i) an anomalous top chromomagnetic dipole moment; (ii) an anomalous $tbW$ interaction. The methods presented greatly facilitate the study of this angular distribution, which is of special interest given the $3.2(3.7)\sigma$ deviation from the SM next-to-leading order prediction found by the ATLAS Collaboration in Run 2 data.

LaTeX 25 pages. v2: added an appendix extending the discussion about top chromomagnetic moments. v3: added a discussion of the ATLAS 13 TeV deviation. Version to appear in JHEP

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Cited by in corpus (8)

• Higher order corrections to spin correlations in top quark pair production at the LHC
• Breaking down the entire spectrum of spin correlations of a pair of particles involving fermions and gauge bosons
• Revisiting the top quark chromomagnetic dipole moment in the SM
• Constraining New Physics with Single Top production at LHC
• On two-body and three-body spin correlations in leptonic $t\bar{t}Z$ production and anomalous couplings at the LHC
• A template method to measure the $t\bar{t}$ polarisation
• Testing CP-violation in a Heavy Higgs Sector at CLIC
• Probing top quark anomalous moments in $W$ boson associated single top quark production at the LHC using polarization and spin correlation