Nuclear effects in Drell-Yan pair production in high-energy<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mi>A</mml:mi></mml:math>collisions

The Drell-Yan (DY) process of dilepton pair production off nuclei is not affected by final state interactions, energy loss, or absorption. A detailed phenomenological study of this process is thus convenient for investigation of the onset of initial-state effects in proton-nucleus ($pA$) collisions. In this paper, we present a comprehensive analysis of the DY process in $pA$ interactions at RHIC and LHC energies in the color dipole framework. We analyze several effects affecting the nuclear suppression, ${R}_{pA}&lt;1$, of dilepton pairs, such as the saturation effects, restrictions imposed by energy conservation (the initial-state effective energy loss), and the gluon shadowing, as a function of the rapidity, the invariant mass of the dileptons, and their transverse momenta ${p}_{T}$. In this analysis, we take into account not only the ${\ensuremath{\gamma}}^{*}$ but also the ${Z}^{0}$ contribution to the production cross section, thus extending the predictions to large dilepton invariant masses. Besides the nuclear attenuation of produced dileptons at large energies and forward rapidities emerging due to the onset of shadowing effects, we predict a strong suppression at large ${p}_{T}$, dilepton invariant masses, and Feynman variable ${x}_{F}$ caused by the initial-state interaction effects in kinematic regions where no shadowing is expected. The manifestations of nuclear effects are also investigated in terms of the correlation function in the azimuthal angle between the dilepton pair and a forward pion $\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}$ for different energies, dilepton rapidities, and invariant dilepton masses. We predict that the characteristic double-peak structure of the correlation function around $\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}\ensuremath{\simeq}\ensuremath{\pi}$ arises for very forward pions and large-mass dilepton pairs.

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