Measurement of Missing Transverse Energy With the CMS Detector at the LHC

The performance of the Compact Muon Solenoid detector for measuring missing transverse energy is evaluated using fully simulated pp collisions at a center-of-mass energy of 14 TeV at the Large Hadron Collider. For minimum bias events without pileup, a resolution of 6.1 GeV is computed, corresponding to a stochastic contribution of $0.63 \sqrt{\Sigma E_{\rm T}}~{\rm GeV}^{1/2}$, where $\Sigma E_{\rm T}$ is the summed transverse energy in all calorimeter towers. When the contribution of pileup is included, the resolution degrades according to the overall deposited $\Sigma E_{\rm T}$ with the same stochastic coefficient. For QCD dijet events with event pileup corresponding to a luminosity ${\cal L} = 2\times 10^{33}{\rm~cm}^{-2} {\rm s}^{-1}$, we compute $\sigma= [(3.8 {\rm ~GeV})^2+(0.97 {\rm ~GeV}^{1/2}\sqrt{\Sigma E_{\rm T}})^2+ (0.012\Sigma E_{\rm T})^2]^{1/2}$ resulting in a resolution of 45 GeV for jet events with reconstructed transverse momentum of 800 GeV/$c$. Monte Carlo samples of ${\rm t}{\rm \bar t}$ and W+jet events with high-momentum ($p_T> 20 {\rm ~GeV}/c$) lepton decays leading to true missing transverse energy were used to determine the azimuthal angle resolution to be 0.1 radians (0.2 radians) for a reconstructed missing transverse energy of 200 GeV (100 GeV).