Studies of dijet and photon-jet properties in pp, pPb and PbPb collisions with CMS

Studies of dijet and photon-jet properties in pPb collisions are of greatimportance to establish a QCD baseline for hadronic interactions with cold nuclearmatter. Dijet and photon-jet production have been measured in pPb collisions at anucleon-nucleon center-of-mass energy of 5.02 TeV. The transverse momentum balanceand azimuthal angle correlations are studied in both dijet and photon-jet channels,leading to the observation that there is no significant modification, which allowsthese systems to be used as tools to probe the nuclear modifications of the partondistribution functions (PDFs). In the dijet system, pseudorapidity distributionsare studied as a function of the transverse energy in the forward calorimeters($\mathrm{E}_\mathrm{T}^{HF}$). The mean value of the dijet pseudorapidity is foundto change monotonically with increasing $\mathrm{E}_\mathrm{T}^{HF}$, indicating acorrelation between the energy emitted at large pseudorapidity and the longitudinalmotion of the dijet frame. The pseudorapidity distribution of the dijet system iscompared with next-to-leading-order perturbative QCD predictions obtained from bothnucleon and nuclear PDFs, and the data more closely match the latter.In addition to the studies of initial state, the photon-jet measurements related toquenching in PbPb are updated to have a more precise pp reference based on the 2013 LHC run at 2.76 TeV.