Exploring the Top-Higgs FCNC Couplings at Polarized Linear Colliders with Top Spin Observables

Abstract

We study the nature of the flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the $t\bar{t}$ production at linear colliders. There are previous bounds on such tqH couplings at both, linear and hadronic colliders, with the assumption that it couples equally to the left and the right handed fermions. In this paper we examine the chirality of the tqH coupling and construct different observables which will be sensitive to it. The kinematics of the emitted q from t $\to$ qH in $t\bar{t}$ production is discussed and it was found that the polar angle distribution of q is sensitive to the chiral nature of tqH couplings. The observables in the context of top-antitop spin correlations, which are sensitive to new physics in the top decay are considered using different spin-quantization bases. It was found that in particular the off-diagonal basis can be useful to distinguish among the chiral tqH couplings. The sensitivity of the unpolarized ILC in probing the couplings at the 3$\sigma$ level at $\sqrt{s}$ = 500 GeV and L = 500 fb${}^{-1}$ is also studied, resulting in predicted BR(t $\to$ qH) < 1.19 $\times 10^{-3}$. This limit is further improved to BR(t $\to$ qH) < 8.84 $\times 10^{-4}$ with the inclusion of initial beam polarization of left handed electrons and right handed positrons.

arXiv comment32 pages, 24 figures, minor revisions, the version to be published in JHEP

References in corpus (24)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• FastJet user manual
• Asymptotic formulae for likelihood-based tests of new physics
• FeynRules 2.0 - A complete toolbox for tree-level phenomenology
• MadGraph 5 : Going Beyond
• Top quark pair production and decay at hadron colliders
• Flavour-Changing Decays of a 125 GeV Higgs-like Particle
• A new evaluation of the t->cH decay width in the standard model
• Maximizing Spin Correlations in Top Quark Pair Production at the Tevatron
• QCD-corrected spin analysing power of jets in decays of polarized top quarks
• Spin Correlations in Top-Quark Pair Production at $e^{+}{e}^{-}$ Colliders
• Probing top flavour-changing neutral scalar couplings at the CERN LHC
• Anomalous Top-Higgs Couplings and Top Polarisation in Single Top and Higgs Associated Production at the LHC
• Maximizing the spin correlation of top quark pairs produced at the LHC
• Discerning New Physics in Top-Antitop Production using Top Spin Observables at Hadron Colliders
• Disentangling Flavor Violation in the Top-Higgs Sector at the LHC
• Optimal-Observable Analysis of the Angular and Energy Distributions for Top-Quark Decay Products at Polarized Linear Colliders
• Constraints on top quark FCNC from electroweak precision measurements
• The spin density matrix of top quark pairs produced in electron-positron annihilation including QCD radiative corrections
• Constraining the flavor changing Higgs couplings to the top-quark at the LHC
• Enhancing $thj$ Production from Top-Higgs FCNC Couplings
• Single decay-lepton angular distributions in polarized e+e- --> t tbar and simple angular asymmetries as a measure of CP-violating top dipole couplings
• Search for t->ch at e+e- Linear Colliders

Cited by in corpus (3)

• Exploring the Anomalous Top-Higgs FCNC Couplings at the electron proton colliders
• Flavour-changing neutral scalar interactions of the top quark
• Probing anomalous top-Higgs couplings at the HL-LHC via $H\to W{W}^{\ast }$ decay channels