for photons and electrons it is almost momentum-independent. Muons normally deposit a little energy ( ∼ 1 GeV) in the calorimeter, which is almost independent of the muon mo- mentum. Neutrinos escape without interacting and lead to an imbalance in the measured p$_{T}$ in the event. The observed jet energy must be corrected for the calorimeter response and other detector effects. The two collaborations employ different techniques to determine these jet energy scale corrections. The CDF collaboration’s technique [37] depends on an accurate modeling of the calorimeter response to single particles and a knowledge of the p$_{T}$ spectrum of the particles in a jet, whereas the DØ technique is data-driven and utilizes the fact that in photon-jet events p$_{T,Jet}$ = p$_{T,γ}$ [38]. These techniques are used to calibrate the central region of the calorimeter where the tracking system is available to measure the charged particle momentum and also the calorimeter response is uniform. This approach was applied in the optimum calorimeter region for both collaborations. The calorimeter response was extended to other regions (0 . 1 < | η | , | η | > 0 . 7 for CDF and | η | > 0 . 5 for DØ), by using dijet balancing to scale the jet energy response in the other regions to the one in the optimum region. The energy from additional p ¯ p interactions in the same bunch crossing is subtracted, based on the number of reconstructed primary vertices in an event. For cone jets, this correction is determined from minimum bias events by summing the energy in towers in a cone of radius R placed randomly in the calorimeter. The procedure for k$_{T}$ jets is described in Section V B. a. Photon-Jet balancing: In this technique, the jet energy is determined by scaling the measured jet p$_{T}$ to the photon’s p$_{T}$ in photon-jet events. The photon energy is measured by the electromagnetic (EM) calorimeter which is linear and has very good energy resolution. In the approximation of 2 → 2 scattering, the jet transverse energy p$_{T}$ is equal to the photon p$_{T}$ . The real situation is a little more complicated due to presence of initial state radiation ISR, the energy not clustered in the jet, and contributions to the clustered jet from the multiple parton interactions. To be insensitive to these effects (especially ISR), DØ evaluates the missing p$_{T}$ ( E /$_{T}$ ) projection fraction along the photon direction using: The hadronic recoil correction factor, R$_{had}$ , is the scale factor to the entire recoil system. By requiring that the jet is back-to-back with the photon and, in the absence of any additional jet(s) in the event, R$_{had}$ is almost equal to the jet response. The derived response is expressed R$_{had}$ = 1 + ⃗ E /$_{T}$ · ⃗ p$_{T,γ}$ p 2 T,γ (5) 13