Search for lepton number violating decays of D_s⁺ → h⁻h⁰e⁺e⁺

Based on 7.33 fb⁻¹ of e⁺e⁻ collision data collected by the BESIII detector operating at the BEPCII collider at center-of-mass energies from 4.128 to 4.226 GeV, a search for the Majorana neutrino ν_m is conducted in the lepton-number-violating decays of Ds+ → h⁻h⁰e⁺e⁺. Here, h⁻ represents a K⁻ or π⁻, and h⁰ represents a π⁰, KS0 or ϕ. No significant signal is observed, and the upper limits of their branching fractions at the 90% confidence level are determined to be B(Ds+ → ϕπ⁻e⁺e⁺) < 6.9 × 10⁻⁵, B(Ds+ → ϕK⁻e⁺e⁺) < 9.9 × 10⁻⁵, B(Ds+→KS0π⁻e⁺e⁺) < 1.3 × 10⁻⁵, B(Ds+ → KS0K⁻e⁺e⁺) < 2.9 × 10⁻⁵, B(Ds+ → π⁻π⁰e⁺e⁺) < 2.9 × 10⁻⁵ and B(Ds+ → K⁻π⁰e⁺e⁺) < 3.4 × 10⁻⁵. The Majorana neutrino is searched for with different mass assumptions within the range [0.20, 0.80] GeV/c² in the decay of Ds+ → ϕe⁺ν_m with ν_m → π⁻e⁺, and the upper limits of the branching fractions at the 90% confidence level are at the level of 10⁻⁵–10⁻², depending on the mass of the Majorana neutrino.