New Standard Model constraints on the scales and dimension of spacetime

Using known estimates for the kaon-antikaon transitions, the mean lifetime of the muon and the mean lifetime of the tau, we place new and stronger constraints on the scales of the multi-fractional theories with weighted and q-derivatives. These scenarios reproduce a quantum-gravity regime where fields live on a continuous spacetime with a scale-dependent Hausdorff dimension. In the case with weighted derivatives, constraints from the muon lifetime are various orders of magnitude stronger than those from the tau lifetime and the kaon-antikaon transitions. The characteristic energy scale of the theory cannot be greater than E-*> 3 x 10(2) TeV, and is tightened to E-*> 9 x 10(8) TeV for the typical value = 1/2 of the fractional exponents in the spacetime measure. We also find an upper bound d(H)< 2.9 on the spacetime Hausdorff dimension in the ultraviolet. In the case with q-derivatives, the strongest bound comes from the tau lifetime, but it is about 10 orders of magnitude weaker than for the theory with weighted derivatives.