Mini experimental review of low $x$ physics and hard diffraction at the LHC

Feasibility studies are presented on forward jet production at the LHC with the CMS detector, assuming an integrated luminosity of 1~pb$^{-1}$, together with studies of low-mass Drell Yan muon pair production with the LHCb detector. The potential sensitivity of the CMS and the LHCb experiments to the proton PDFs at low $x$ is discussed. The feasibility of observing hard diffraction at the LHC with the first 10-100 ~pb$^{-1}$ of data collected by the CMS detector is also summarized.