Dielectron Production in pp Collisions at √s = 13 TeV Measured in a Dedicated Low Magnetic-Field Setting with ALICE^†

The low-mass dielectron production in pp collisions at $\sqrt{s}$ = 13 TeV was measured by ALICE with a reduced field of the ALICE central barrel solenoid magnet. This increases the reconstruction efficiency of low- $p_{\mathrm{T}}$ electrons and allows a better electron background rejection while simultaneously giving the opportunity to access a similar phase space as covered by the AFS experiment at the Intersecting Storage Rings at CERN. There, an excess of dielectron pairs over the expectation from known dielectron sources was measured at low invariant mass and small pair transverse momenta in pp collisions at $\sqrt{s}$ = 63 GeV in 1987. It is shown how the ALICE dielectron analysis of the pp pilot runs at $\sqrt{s}$ = 13 TeV with B=0.2 T is adapted to the reduced-field configuration. Preliminary results are compared to the published reference data recorded with the nominal field, to illustrate the benefits of the low magnetic-field setting. Finally, the invariant-mass and pair-transverse-momentum distributions are compared to the AFS measurement to address a possible excess at low $m_{\mathrm{ee}}$ and $p_{\mathrm{T},\mathrm{ee}}$ .