Estimating ɛ^′/ɛ in the standard model independent of Im λ_t

The CP-violating parameter ɛ^′/ɛ is estimated in a novel way by including the explicit computation of ɛ in the ratio as opposed to the usual procedure of taking its value from experiment. This approach has the advantage of being independent of the determination of the CKM parameters Im λ_t and of showing more directly the dependence on the long-distance parameters. The matrix elements are taken from the chiral quark model approach, the parameters of which have been recently determined by an updated fit of the CP-conserving amplitudes entering the ΔI=1/2 rule. By sampling the ranges of the experimental inputs according to a normal distribution and those of the theoretical uncertainties according to a flat one, it is found that ɛ^′/ɛ=(2.5±0.9)×10^-3, in agreement with the current experimental data. A more conservative estimate 0.9×10^-3<ɛ^′/ɛ<5.8×10^-3 is found by considering the smallest and the largest values obtained by taking a flat distribution for all inputs.