Strong tW scattering at the LHC

Abstract

Deviations of the top electroweak couplings from their Standard Model values imply that certain amplitudes for the scattering of third generation fermions and longitudinally polarized vector bosons or Higgses diverge quadratically with momenta. This high-energy growth is a genuine signal of models where the top quark is strongly coupled to the sector responsible for electroweak symmetry breaking. We propose to profit from the high energies accessible at the LHC to enhance the sensitivity to non-standard top-Z couplings, which are currently very weakly constrained. To demonstrate the effectiveness of the approach, we perform a detailed analysis of tW → tW scattering, which can be probed at the LHC via pp → ttW j. By recasting a CMS analysis at 8 TeV, we derive the strongest direct bounds to date on the Ztt couplings. We also design a dedicated search at 13 TeV that exploits the distinctive features of the ttW j signal. Finally, we present other scattering processes in the same class that could provide further tests of the top-Higgs sector.

The other effective fermion compositeness

“…Wilson coefficients of the standard four-fermion operators scale as g (6) * /m (6) * an intuition that we confirmed with dedicated analyses. Since E exp /m (6) * 1 in a sensible EFT, for g (8) * ∼ g (6) * bounds on goldstino-compositeness are always poorer than those on chiral-compositeness: by a factor of 4 for light quarks (tested at LHC) and by a factor of 20 for light leptons (tested at LEP-2).…”

“…strongly (as opposed to weakly) coupled dynamics, associated with the compositeness of SM particles, can produce sizable deviations in their interactions at high energy and become the principal target of these SM precision tests [1][2][3][4][5][6][7][8][9][10].…”

“…6 They provide a map from the spacetime to an element of the SUSY transformations, x → g(x), up to the identification g(x) ∼ g(x)h(x) where h(x) is an element of the unbroken symmetry group that includes 5 There is a priori a different starting point to this construction in which R-symmetry is gauged (necessarily together with supergravity) [34]. However, in such theories R-symmetry is broken at very high scales by the VEV of the superpotential, in order to cancel the cosmological constant; see however [35] for a possible caveat.…”

“…However, in such theories R-symmetry is broken at very high scales by the VEV of the superpotential, in order to cancel the cosmological constant; see however [35] for a possible caveat. 6 Different and yet equivalent parametrizations are often adopted for the Goldstini, like the one provided by the constrained superfield formalism, see e.g. [24,37] and references therein.…”

Large NLO corrections in t t ¯ W ± $$ t\overline{t}{W}^{\pm } $$ and

“…[33] that EW pp → ttW ± j production involves tW → tW scattering via the gq → ttW ± q channel. Even though ref.…”