Abstract
Using the color dipole formalism we study production of Drell-Yan (DY) pairs in proton-nucleus interactions in the kinematic region corresponding to LHC experiments. Lepton pairs produced in a hard scattering are not accompanied with any final state interactions leading to either energy loss or absorption. Consequently, dileptons may serve as more efficient and cleaner probes for the onset of nuclear effects than nclusive hadron production. We perform a systematic analysis of these effects in production of Drell-Yan pairs in pPb interaction at the LHC. We present predictions for the nuclear suppression as a function of the dilepton transverse momentum, rapidity and invariant mass which can be verified by the LHC measurements. We found that a strong nuclear suppression can be interpreted as an effective energy loss proportional to the initial energy universally induced by multiple initial state interactions. In addition, we study a contribution of coherent effects associated with the gluon shadowing affecting the observables predominantly at small and medium-high transverse momenta. (Less)
Highlights
The Drell-Yan (DY) process provides an important test of the Standard Model as well as a comprehensive tool for studies of strong interaction dynamics in an extended kinematical range of energies and rapidities
In the case of pp collisions, we found a good agreement of the differential cross section as a function of the dilepton invariant mass M with the ATLAS and CMS data
We demonstrate that for production of DY pairs on nuclear targets, the long coherence length (LCL) limit can be safely employed in the LHC kinematic region
Summary
The Drell-Yan (DY) process provides an important test of the Standard Model as well as a comprehensive tool for studies of strong interaction dynamics in an extended kinematical range of energies and rapidities. We focus on dilepton pairs coming from decay of virtual γ∗/Z0 as a probe of nuclear effects in proton-lead (pPb) collisions at LHC In this case, the DY process represents a cleaner probe than typical hadron production since the dilepton pairs have no final state interactions leading to either energy loss or absorption in the hot medium. The second effect is the so-called effective energy loss due to the initial state interactions (ISI) The latter describes a suppression of the cross section at large dilepton pT which was indicated at midrapidity, y = 0, by the PHENIX data [2] on π0 production in central dAu collisions and on direct photon production in central AuAu collisions [3]. We present new results on dilepton-pion azimuthal correlation in proton-lead collisions, where the characteristic double peak structure sensitive to the saturation scale is predicted
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