Murnane, D.White, M.Williams, A.G.2019-06-162019-06-162019The Journal of High Energy Physics, 2019; 2019(4):076-1-076-261126-67081029-8479http://hdl.handle.net/2440/119501We perform a detailed study of the fine-tuning of the two-site, 4D, Next-to-Minimal Composite Higgs Model (NMCHM), based on the global symmetry breaking pattern SO(6) → SO(5). Using our previously-defined fine-tuning measure that correctly combines the effect of multiple sources of fine-tuning, we quantify the fine-tuning that is expected to result from future collider measurements of the Standard Model-like Higgs branching ratios, in addition to null searches for the new resonances in the model. We also perform a detailed comparison with the Minimal Composite Higgs Model, finding that there is in general little difference between the fine-tuning expected in the two scenarios, even after measurements at a high-luminosity, 1 TeV linear collider. Finally, we briefly consider the relationship between fine-tuning and the ability of the extra scalar in the NMCHM model to act as a dark matter candidate, finding that the realisation of a Z₂ symmetry that stabilises the scalar is amongst the most natural solutions in the parameter space, regardless of future collider measurements.enOpen Access, © The Authors. Article funded by SCOAP³.Beyond standard model; technicolor and composite models; effective field theories; global symmetriesJournal article003011338910.1007/JHEP04(2019)0760004647343000092-s2.0-85064249677469184White, M. [0000-0001-5474-4580]Williams, A.G. [0000-0002-1472-1592]