A search for the same-sign W-pair DPS events in the di-muon final state is done using data from proton-proton collisions at center-of-mass energy of 8 TeV in a single signal region corresponding to an integrated luminosity of 19.7 fb$^{-1}$ collected by CMS detector. Different observables, expected to be sensitive to WW events from DPS production, have been used in a BDT approach to enhance the sensitivity respect to the single parton scattering production mechanism. Although no direct measurements of DPS yield are allowed with current statistics, we set an exclusion limit on DPS signal strength. BDT response shape gives the limit estimation, excluding at 95% CLs a signal strength $r >$ 1.897 (28 DPS events), with an expected exclusion of $r >$ 2.01 (30 DPS events), which means an upper limit on $\sigma ^{\text{DPS}}_{\mathrm{WW }} <$ 1.12 pb at 95% of confidence level. Considering the two scattering to be independent and no correlation between interacting partons, one can put in relation the limit on $\sigma ^{\text{DPS}}_{\mathrm{WW }}$ with the $\sigma_{\text{eff}}$. Considering the cross section for the production of a W boson that decays leptonically $\sigma_{\mathrm{ W\to \ell \nu}} =$ 37 509 pb and the corresponding branching ratio $ \mathrm{BR}( \mathrm{ W \to \ell \nu } ) =$ 0.326, the lower limit on the $\sigma_{\text{eff}}$ can be written as:
$\sigma_{\text{eff}} >
\left( \sigma_{ \mathrm{ W \to \ell \nu } } \right)^2 \ / \ 2\, \left( \mathrm{BR}^2_{ \mathrm{ W\to \ell \nu} } \right) \, \sigma ^{\text{DPS}}_{\mathrm{WW}} =$ 5.91 mb.
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