Extended investigation of the twelve-flavor $β$-function

Abstract: We report new results from high precision analysis of an important BSM gauge theory with twelve massless fermion flavors in the fundamental representation of the SU(3) color gauge group. The range of the renormalized gauge coupling is extended from our earlier work {Fodor:2016zil} to probe the existence of an infrared fixed point (IRFP) in the $\beta$-function reported at two different locations, originally in {Cheng:2014jba} and at a new location in {Hasenfratz:2016dou}. We find no evidence for the IRFP of the $\beta$-function in the extended range of the renormalized gauge coupling, in disagreement with {Cheng:2014jba,Hasenfratz:2016dou}. New arguments to guard the existence of the IRFP remain unconvincing {Hasenfratz:2017mdh}, including recent claims of an IRFP with ten massless fermion flavors {Chiu:2016uui,Chiu:2017kza} which we also rule out. Predictions of the recently completed 5-loop QCD $\beta$-function for general flavor number are discussed in this context.