Measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays D⁺ → K⁺π⁰, D⁺ → K⁺η and D⁺ → K⁺η′

Using 20.3 fb⁻¹ of e⁺e⁻ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we present the measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays D⁺ → K⁺π⁰, D⁺ → K⁺η and D⁺ → K⁺η′ with the double-tag method, with significantly improved precision compared to the previous measurements. The statistical significance of each signal decay exceeds 10σ. The branching fractions are determined to be ℬ(D⁺ → K⁺π⁰) = (1.45 ± 0.06 ± 0.08) × 10−4, ℬ(D+ → K+η) = (1.17 ± 0.10 ± 0.03) × 10−4 and ℬ(D+ → K+η′) = (1.88 ± 0.15 ± 0.11) × 10−4, where the first uncertainties are statistical and the second systematic. The branching fractions of D⁺ → K⁺η and D⁺ → K⁺η′ are consistent with the world average values. The reported branching fraction of D⁺ → K⁺π⁰ deviates with the world average value by 3σ.