Associated non-prompt $J/\psi + \mu$ and $J/\psi + J/\psi$ production at LHC as a test for TMD gluon density

We consider the associated production of $J/\psi $ mesons and muons originating from the b-flavored hadron decays and non-prompt double $J/\psi $ production at the LHC using the $k_T$ -factorization approach. To describe the inclusive b-hadron decays into the different charmonium states we apply fragmentation approach and adopt fragmentation functions based on the non-relativistic QCD factorization. The transverse momentum dependent (TMD) gluon densities in a proton are determined using the Catani-Ciafaloni-Fiorani-Marchesini equation and Kimber-Martin-Ryskin prescription. We investigate the effects coming from parton showers, estimate the double parton scattering contribution and compare our predictions with the first experimental data taken by the ATLAS and LHCb Collaborations at $\sqrt{s} = 8\ \hbox {TeV}$ . These data can serve as an additional test for TMD gluon density function in a proton