Polarization and spin correlations of top quarks at a future e+ e- linear collider
We discuss the polarization and spin correlations of top quarks produced above threshold at a future linear collider, including QCD radiative corrections.
hep-ph↗
arXiv subjects
M. Flesch
Publications and source records attributed to M. Flesch.
Effects of Higgs sector CP violation in top-quark pair production at the LHC
A striking manifestation of CP violation in the electroweak symmetry breaking sector would be the existence of neutral Higgs boson(s) with undefined CP parity. We analyse signatures of such a boson, with a mass of about 300 GeV or larger, produced in high energy proton-proton collisions at LHC energies in its top-quark antitop-quark decay channel. The large irreducible $t\bar t$ background is taken into account. We propose, both for the dilepton and the lepton + jets decay channels of $t\bar t$, several correlations and asymmetries with which (Higgs sector) CP violation can be traced. We show that for judiciously chosen cuts on the $t\bar t$ invariant mass these CP observables yield, for an LHC integrated luminosity of 100 $\rm{fb}^{-1}$, statistically significant signals for a range of Higgs boson masses and Yukawa couplings.
hep-ph↗
The spin density matrix of top quark pairs produced in electron-positron annihilation including QCD radiative corrections
We calculate the spin density matrix of top quark pairs for the reaction $e^+e^-\to t\bar{t}X$ to order $α_s$. As an application we show next-to-leading order results for a variety of spin observables for the $t\bar{t}$ system. These include the top quark and antiquark polarizations and $t\bar{t}$ spin-spin correlations as a function of the center-of-mass energy and of the top quark scattering angle for arbitrary longitudinal polarization of the electron/positron beam.
hep-ph↗
Signatures of Higgs Bosons in the Top Quark Decay Channel at Hadron Colliders
We analyze some signatures of neutral Higgs bosons, produced in high energy proton (anti)proton collisions, which decay primarily to top quarks. This channel is clouded by a large irreducible $t\bar t$ background. We investigate the $t\bar t$ invariant-mass distribution in the lepton+jets decay mode of $t\bar t$ and a $t\bar t$ spin-spin correlation in the dilepton decay mode. At the LHC such Higgs bosons can be detected in the $t\bar t$ invariant-mass spectrum, and the spin-spin correlation studied by us is also sensitive to a Higgs boson if this particle has a sizeable pseudoscalar component.
hep-ph↗
QCD Corrections to Decay Distributions of Neutral Higgs Bosons with (In)definite CP Parity
We compute the order $α_s$ QCD corrections to the density matrix for the decay of a neutral Higgs boson $ϕ$ with (in)definite CP parity into a quark antiquark pair, respectively the QED corrections for the decay into a pair of charged leptons. We classify and calculate single spin asymmetries and spin-spin correlations which are generated by the scalar and pseudoscalar Yukawa couplings. These spin effects can be traced in $ϕ\to τ^-τ^+$ and, for heavy Higgs bosons, in $ϕ\to t\bar{t}$. We also calculate resulting correlations among the final states and estimate, for the respective decay modes, the number of events needed to measure the Yukawa couplings with these correlations at the 3 sigma level.
hep-ph↗