GeV scale dark matter and B→ K+ missing energy phenomenology in the U(1)B-L model

We elucidate the recently observed discrepancy in the branching ratio of B⁺→ K⁺ +inv decay mode using a GeV scale scalar dark matter in an anomaly-free U(1)B-L gauge extension of the Standard Model. We constrain the new parameters by using consistency with the existing bounds on Dark matter relic density, direct detection, collider and BR(B→ K^*νν̄) measured at the Belle II experiment. We investigate couplings between the mediator and the SM fermions as well as the dark matter particle. We then estimate the branching ratios of b → s ν ν decay processes such as B→ (K⁺,K^*)νν̄, Bₛ→ (η,η')νν̄, Bₛ→ φνν̄ and Bc→ (Dₛ, Dₛ^*)νν̄ in a common parameter space, meeting the current experimental bounds of both sectors simultaneously.