Rajeev KumarDua, Titiksha2019-04-222019-04-222019http://krishikosh.egranth.ac.in/handle/1/5810100817The research is based on study of the rare radiative decay B^0→J/ψγ, using data collected (corresponding to 772×〖10〗^6 BB ̅ pairs) by the Belle detector at Υ(4S) resonance at asymmetric e^+ e^- collider at KEK, Japan during its long run. In this annihilation decay, there is potential sign of New Physics from the possibility of (V+A) charged current admixture to the standard (V−A) current. Branching ratio measurement will help test the validity of various QCD models. A large Monte Carlo sample is generated to determine the signal reconstruction efficiency, which is obtained as 33.9±0.19%. The energy difference, ΔE=E_B^*-E_beam^*, the beam-constrained mass M_bc=√(E_beam^(*2)-p_B^(*2) ) and helicity (cos⁡θ) of J/ψ are used for signal extraction, where E_beam^* is the run dependent beam energy, E_B^* and p_B^* are the reconstructed energy and momentum, respectively of the B meson candidates in the center-of-mass frame. The peaking background in the signal region is dominated by B^0→J/ψ π^0 (π^0→ γγ), B^0→J/ψη (η→ γγ) mainly and also B^0→J/ψ K_L (K_L→3π^0 or 6γ) and B^0→J/ψ K_S and other combinatorial backgrounds. To suppress these backgrounds, we vetoed these photons that when combine with another photon of energy E_γ> 60 MeV and form a π^0 (η) candidate. Whereas, B→J/ψK_S and B→J/ψK_L are not peaking in ΔE but are peaking in M_bc signal region. The peaking backgrounds B→J/ψη and B→J/ψπ^0 correspond to 103.56±3.29 events.ennullThesis