We report on temporal and spectral study of a flat spectrum radio quasar, PKS B1222+216, in flare state to get insight into acceleration and emission mechanisms inside the jet. This is one of the brightest and highly active blazar in the MeV-GeV regime. Long term multi-waveband light curves of this object showed a flaring activity in 2014 with two distinct flares. Work presented here includes the study of flux-index variation, flare fitting, hardness ratio and spectral modelling of both X-ray and $gamma-$ray data. The flux-index correlation we have found in MeV-GeV regime indicates a softer when brighter feature. Modelling of $gamma-$ray light curves suggests that low energy particles initiate both the flares followed by the injection of high energy particles. The short rise time indicates the presence of Fermi first order acceleration. Multi-waveband spectral energy distributions (SEDs) generated for flares are fitted with a single-zone leptonic model. This SED modelling shows the inverse Compton scattering of photon field reprocessed from Broad Line Region (BLR) primarily accounts for GeV emission. We have also report a shift in break-energy in the soft X-ray regime during the flaring activity which is the consequence of a rapid change in injection spectra.
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