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Dimensionless experiments test the invariance of plasma physics to changes in the dimensional plasma parameters, when the canonical dimensionless parameters, such as P*, V*, ?, q, ... are conserved. In particular, isotope identity experiments exploit the change in hydrogen isotope ion mass A = mi/mp to obtain plasmas with identical dimensionless profiles in the same tokamak. With this technique, NBI-heated L-mode and type I ELMy H-mode plasmas at moderate beta have been obtained in JET with the Be/W ITER-like wall in H and D, with similar profiles of the dimensionless plasma parameters Pi*, V*, ?th, q, as well as similar Zeff, Ti/Te and Mach-number profiles. In the core confinement region of these plasmas the dominant instabilities are ITG modes both in H and in D. The dimensionless thermal energy confinement time ?i ?E,th is identical in the L-mode isotope identity pair, indicating lack of isotope mass dependence of the dimensionless ?E,th., and the invariance principle is satisfied in the core confinement region. In the type I ELMy H-mode pair, similarity in H and D is found for both core and pedestal regions for the ELMaveraged profiles, but not for the pre-ELM profiles. ?i ?E,th is not identical in the H-mode pair and yields an isotope mass dependence ?i ?E,th ~ A0.51, consistent with the favourable isotope mass scaling of the dimensional TE,th observed in JET-ILW. Predictive flux driven simulations of core plasma transport with JETTO-TGLF (L-mode pair) and TRANSP-TGLF (H-mode pair) are in agreement with experiment for both isotopes: the stiff core heat transport, typical of JET-ILW NBI L-modes and NBI H-modes at moderate beta values, overcomes the local gyro-Bohm scaling of gradient-driven TGLF, explaining the lack of isotope mass dependence in the core confinement region of the L-mode plasmas and the increase of confinement with isotope mass in the H-mode plasmas, which originates in the pedestal region. The effect of ExB shearing from sheared toroidal rotation on the predicted core heat and particle transport channels is found to be negligible in the low beta and low momentum input L-mode plasmas, while it becomes apparent in the H-mode identity pair at moderate beta.