$$\chi _{c1}$$ χ c 1 and $$\chi _{c2}$$ χ c 2 polarization as a probe of color octet channel

We analyze joint LHC data on the production of $$\chi _{c1}$$ and $$\chi _{c2}$$ mesons together with the polarization data obtained very recently by the CMS Collaboration at $$\sqrt{s} = 8$$  TeV. Our consideration is based on the $$k_T$$ -factorization approach and nonrelativistic QCD formalism for the formation of bound states. The observed polar anisotropy of $$\chi _{c1}$$ and $$\chi _{c2}$$ decays can be described as a combined effect of the color-singlet and color-octet contributions. We extract the corresponding long-distance matrix elements from the fits. Our fits point to unequal color singlet wave functions for $$\chi _{c1}$$ and $$\chi _{c2}$$ states.