Dielectron production in proton-proton and proton-lead collisions at √s_NN =5.02 TeV

The first measurements of dielectron production at midrapidity (|η_e|<0.8) in proton-proton and proton-lead collisions at √s_NN=5.02TeV at the LHC are presented. The dielectron cross section is measured with the ALICE detector as a function of the invariant mass m_ee and the pair transverse momentum p_T,ee in the ranges m_ee<3.5 GeV/c² and p_T,ee<8 GeV/c, in both collision systems. In proton-proton collisions, the charm and beauty cross sections are determined at midrapidity from a fit to the data with two different event generators. This complements the existing dielectron measurements performed at √s=7 and 13 TeV. The slope of the √s dependence of the three measurements is described by FONLL calculations. The dielectron cross section measured in proton-lead collisions is in agreement, within the current precision, with the expected dielectron production without any nuclear matter effects for e⁺e^- pairs from open heavy-flavor hadron decays. For the first time at LHC energies, the dielectron production in proton-lead and proton-proton collisions are directly compared at the same √s_NN via the dielectron nuclear modification factor R_pPb. The measurements are compared to model calculations including cold nuclear matter effects, or additional sources of dielectrons from thermal radiation.