Critical basis dependence in bounding R-parity breaking couplings from neutral meson mixing

Assuming one nonzero product of two $\lambda'$-type couplings and working in two different bases for the left-handed quark superfields, the neutral meson mixings are used to bound these products. We emphasize the strong basis dependence of the bounds: in one basis many products contribute to neutral meson mixings at tree level, while in the other these products except one contribute at 1-loop level only and the GIM mechanism takes place. Correspondingly, these bounds differ between bases by orders of magnitudes.