Measurement of double$~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$productions with the CMS detector

We present the new measurement of the cross section for the simultaneous production of two $~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$ mesons in proton-proton collisions at 7 TeV with the CMS detector. The two$~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$mesons are fully reconstructed in the $\mu^+\mu^-$ decay and the signal yield is extracted with an extended maximum likelihood fit. The differential cross section is measured in bins of the double$~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$invariant mass, the absolute difference in rapidity of the two$~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$mesons, and the transverse momentum of the double$~\mathrm{J}\hspace{-.08em}/\hspace{-.14em}\psi~$system.