Small x Physics with CMS

\indent We present the capabilities of the CMS experiment at the LHC to study small-x physics. The LHC is designed to provide p+p, p+A and A+A collisions at maximal $\sqrt{s_{NN}}$~=~14, 8.8 and 5.5 TeV respectively with peak luminosities of $10^{34}$, $10^{29}$ and $5\cdot10^{26}$ $cm^{-2}s^{-1}$. Such large energies and luminosities will allow detailed QCD studies at unexplored low-x values using different probes like jets, quarkonia, heavy quarks, etc. \\ \indent CMS is a general-purpose experiment designed for the exploration of the physics at the TeV energy scale. CMS is the largest acceptance detector at the LHC. This detector is a 22 m (length)$\times$15 m (diameter) apparatus featuring a 3.8 T solenoid surrounding central tracking detectors (silicon pixel and microstrip detectors) and electromagnetic ($\mid\eta\mid<$~3) and hadronic ($\mid\eta\mid<$~5) calorimeters. Muon detectors ($\mid\eta\mid<$~2.4) are embedded in the flux return iron yoke of magnet. CMS has unique detection capabilities in the forward region thanks to CASTOR (-6.6~$<\eta<$~-5.2) and the ZDC ($\mid\eta\mid>$~8.3) calorimeters. \\ \indent We present a selection of five observables which are sensitive to parton saturation effects and measurable in CMS in both p+p (forward jets, Mueller-Navelet dijets, energy flow) and Pb+Pb (charged hadron rapidity density, ultra-peripheral photoproduction of $\Upsilon$) collisions. Also first experimental results from 0.9, 2.36 and 7 TeV p+p collisions at LHC are presented.