Measurement of transverse momentum flow relative to the dijet system in PbPb and pp collisions at sqrt(sNN) = 2.76 TeV

An analysis of the momentum flow in PbPb and pp collisions containing high momentum jets is performed in order to understand the energy loss of partons traveling in a hot and dense medium. The analysis uses data sets for PbPb and pp collisions with integrated luminosities of 150$\mu\rm{b}^{-1}$ and 5.3$\rm{pb}^{-1}$, respectively, collected in 2011 and 2013 at collision energies of $\sqrt{s_{\rm{NN}}} = 2.76$ TeV. For both systems, dijet events were selected containing a leading jet with transverse momentum $p_{\rm T,1}>120$ GeV/c and a subleading jet with $p_{\rm T,2}>50$ GeV/c, reconstructed with the anti-$k_T$ algorithm with distance parameter $R=0.3$. For PbPb collisions, there is an increase in the fraction of dijet events with large momentum asymmetry between the leading and subleading jets compared to what is seen in pp collisions. The radiation balancing this asymmetry is characterized in terms of the multiplicity, angular and momentum spectra of charged particles with $p_{\mathrm{T}}>0.5$ GeV/c. The measurement is done as a function of PbPb collision centrality, dijet asymmetry and dijet momentum difference.