Kumar, Devender2024-05-152024-05-152024ROLL NO.176121010https://gyan.iitg.ac.in/handle/123456789/2611Supervisor: Bhuyan, BipulWe report the first search for the decay B0s → J/ψπ0 using 121.4 fb−1 of data collected at Υ(5S) resonance state by the Belle detector at the KEKB asymmetric energy e+e− collider located at the High Energy Accelerator Research Organisation, Japan. We observe no signal and report an upper limit on the branching fraction, B(B0 s → J/ψπ0) of 1.21 × 10−5 at 90% confidence level. This result is the most stringent, improving the previous bound by two orders of magnitude.enThesis