Speaker
Description
We investigate the prospects of discovering the top quark decay into
a charm quark and a Higgs boson ($t \to c h^0$) in top quark pair
production at the CERN Large Hadron Collider (LHC).
A general two Higgs doublet model is adopted to study flavor changing
neutral Higgs (FCNH) interactions.
We apply parton level analysis as well as Monte Carlo simulations
with PYTHIA8 and Delphes to study a flavor changing top decay
$t \to c h^0$, followed by the Higgs decaying into $\tau \bar{\tau}$,
and another top quark decaying hadronically to a bottom quark ($b$) and
two light jets.
To study a Higgs signal with low physics background,
we consider only the leptonic decays
of tau leptons, $\tau^+\tau^- \to e^\pm\mu^\mp +\slashed{E}_T$,
where $\slashed{E}_T$ represents missing transverse energy from neutrinos.
We employ collinear approximation for highly boosted tau decays to
reconstruct Higgs mass and top mass with high precision as well as
to remove physics background effectively.
In addition, the energy distribution of charm quark helps us to set
acceptance cuts to remove more background and improve the statistical
significance.
We study the discovery potential for the FCNH top decay
at the LHC with collider energy $\sqrt{s} = 13$ and 14 TeV as well as
a future hadron collider with $\sqrt{s} = 27$ TeV.
Our analysis suggests that a high energy LHC at $\sqrt{s} = 27$ TeV
will be able to discover this FCNH signal with an integrated
luminosity $L = 3$ ab$^{-1}$ for a branching fraction
${\cal B}(t \to ch^0) \agt 1.4 \times 10^{-4}$
that corresponds to a FCNH coupling $|\lambda_{tch}| \agt 0.023$.
This FCNH couplings is significantly below the current ATLAS combined limit
$|\lambda_{tch}| \agt 0.064$.
