We present a measurement of the $\Lambda_{b}$ polarization based on an angular analysis of the decay $\Lambda_b \rightarrow J/\psi \Lambda$, using data from pp collisions at $\sqrt{s}=7$ TeV and 8 TeV collected with the CMS detector. A transverse Λb polarization of 0.00 ±0.06(stat) ±0.02(syst). Our result for $\alpha_{1}$ , the asymmetry parameter, is compatible with predictions that lie in the range $10\%-20\%$, but it does not agree with the prediction of HQET of $77\%$ reported in the literature. The measured values for the helicity amplitudes are consistent with the values reported by LHCb and ATLAS. Accordingly, the $\Lambda_b$ decay has suppressed positive-helicity states for $\Lambda^0$ corresponding to a total negative longitudinal polarization for $\Lambda^0$.