The rare decay $B_c \rightarrow D_s^* \mu^+ \mu^-$ in a family   non-nuiversal model
  Using the form factors calculated in the three-point QCD sum rules approach, we calculate the new physics contributions to the physical observables of $B_c \to D_s^* \mu^+\mu^-$ decay in the family non-universal $Z^{\prime}$ model. Under the consideration of three cases of the new physics parameters, we find that: (a) the $Z^{\prime}$ boson can provide large contributions to the differential decay rates; (b) the FBA could be increased by about 47%, 38%, and 110% at most in S1, S2, and ELV, respectively. In addition, the zero crossing could be shifted in all the cases; (c) when $\hat{s}>0.08$, the value of $P_L$ could be changed from -1 in the SM to -0.5 in S1, and -0.6 in S2, 0 in ELV, respectively; (d) The new physics corrections to $P_T$ would decrease the SM prediction about 25% for the cases of S1 and S2, 100% for the case of ELV. 
Lu Lin-xia, Zhang Guo-fang, Wang Shuai-wei, Zhang Zhi-qing
hep-ph