Limits on top FCNC decay t$\rightarrow$cH and t$\rightarrow$c$γ$ from CLIC at 380 GeV
Aleksander Filip Zarnecki, Naomi van der Kolk
备注：
9 pages, 6 figures. Talk presented at the International Workshop on Future Linear Colliders (LCWS2017), Strasbourg, France, 23-27 October 2017. C17-10-23.2. Presented on behalf of the CLICdp Collaboration
FCNC top decays are very strongly suppressed in the Standard Model and the observation of any such decay would be a direct signature of physics beyond SM. Many "new physics" scenarios predict contributions to FCNC processes and the largest enhancement in many models is for t$\rightarrow$cH decay. Enhancements for the decay channel t$\rightarrow$c$γ$ are more modest, but the decay still has a clearly identifiable kinematic signature. Prospects for measuring these decays at CLIC running at 380 GeV were studied with full detector simulation, taking the luminosity distribution, beam polarization and beam induced background into account. Top pair production events with t$\rightarrow$cH decays can be identified based on the kinematic constraints and flavour tagging information. The analysis was divided into three steps: classification of top pair candidate events, event quality determination and kinematic reconstruction based on signal or background hypotheses, and final separation of signal from background. To obtain optimal results, selection criteria based on the dedicated Boosted Decision Trees (BDT) were used at each step. The expected limit on BR(t$\rightarrow$cH)$\times$BR(H$\rightarrow b\bar{b}$) from a combined analysis of hadronic and semi-leptonic top pair samples, as well as the limit on BR(t$\rightarrow$c$γ$) from hadronic top pair decays are presented.
In the Standard Model (SM), flavour changing neutral current (FCNC) top decays, possible at loop level only, are very strongly suppressed. Observation of any such decay would be a direct signature of physics beyond the SM. Large enhancements are possible in many "new physics" scenarios and the largest enhancement is in most cases expected for the $t\rightarrow cH$ decay. A full study for CLIC was based on the WHIZARD simulation of FCNC top decays within the 2HDM(III) model. Beam polarization and beam-induced background were taken into account. Top pair production events with the FCNC decay $t\…
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Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of $τ$-leptons in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
Lepton Flavor Violating Higgs decays at the Compact Linear Collider
CERN（欧洲核子研究中心）；Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；Millenium Institute for Subatomic Physics at the High Energy Frontier - SAPHIR（高能前沿亚原子物理千年研究所 - SAPHIR）
The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies: 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the s…
