Speaker
Stefania De Curtis
(Universita e INFN, Firenze (IT))
Description
Future e+e- colliders have a great potential for the Higgs and the Top-quark physics, not only as a test of the SM but also for New Physics (NP) indication.
Theoretical arguments supporting the importance of sub-percent Higgs coupling precision measurements continue to grow, especially to find hints for non-SM Higgs: how can we decide if it is the elementary SM Higgs or a composite state from a strong dynamics? The attractive idea is that new interactions at the TeV scale bind the Higgs constituents and are responsible for EWSB. This is compatible with a Higgs light and weakly coupled if the Higgs is a pseudo-Goldstone Boson. Compositeness of the Higgs can bring compositeness of the Top quark and the prediction of new particles. If nothing is seen, or, better, if the LHC will give some evidence, future e+e- machines will have a great potential in testing indirectly the salient features of composite Higgs models (CHMs). Realistic scenarios can be built and analyzed with the full spectrum: the 4DCHM (De Curtis,Redi,Tesi,JHEP1204,042(2012)) embeds the main characteristics of CHMs with a partially composite Top quark, new spin-1 and spin-1/2 resonances. We use this general parameterization to test the power of the FCC-ee to exclude the CHMs or to fully characterize their properties. In particular the observables from Top pair production offer a unique possibility to determine the left- and right-handed couplings of the Top quark to the photon and the Z. The sensitivity could be pushed down to less than 1% (HL-LHC cannot be competitive). The precise determination of these couplings is crucial to distinguish among various NP scenarios but, the very important outcome of the analysis, is that the FCC-ee will be sensible to finite mass effects from new particle exchanges. In fact the unequalled precision in extracting the Top form factors allows to find imprints of the interference effects of new Z’, and to make quantitative estimations of their mass and couplings.
Author
Stefania De Curtis
(Universita e INFN, Firenze (IT))
Co-authors
Patrick Janot
(CERN)
Stefano Moretti
(STFC - Rutherford Appleton Lab. (GB))
