Flavor-changing neutral Higgs boson couplings and top-quark-charm-quark production at the Next Linear Collider

Abstract

We explore the possibility of detecting flavor-changing neutral Higgs boson couplings at the Next Linear Collider (NLC) through e(+)e(-)->nu(e)<(nu)over bar>(e)t (c) over bar. In the framework of a general two-Higgs-doublet model, we perform a complete calculation and find that sigma(e(+)e(-)-->nu(e) nu(e)t (c) over bar nu(e)<(nu)over bar>(e) (t) over bar c) could reach similar to 9 fb for root s=2 TeV. This amounts to an annual production of 500 t (c) over bar plus (t) over bar c pairs at the NLC with an integrated luminosity of 50 fb(-1). The dependence of the tc-production rate on the neutral scalar mixing angle is mild except when sin(2) alpha-->0 or 1. The nu nu W+W- background should be manageable after b tagging, while vvt (t) over bar background should not be a problem when the signal event rate is still interesting. The process, together with e(+)e(-)-->nu(e)<(nu(e))over bar>W+W-,nu(e)<(nu(e))over bar>ZZ studies, offer the chance of measuring the t-c-Higgs-bsson coupling.