May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

Dielectron production in pp collisions at sqrt(s)=13 TeV measured in a dedicated low magnetic-field setting with ALICE

May 15, 2018, 5:00 PM
2h 40m
First floor and third floor (Palazzo del Casinò)

First floor and third floor

Palazzo del Casinò

Poster Electromagnetic and weak probes Poster Session


Jerome Jung (Johann-Wolfgang-Goethe Univ. (DE))


Low-mass dielectrons are an important probe for the hot and dense medium which is created in ultra-relativistic heavy-ion collisions. Since leptons do not interact strongly and are produced throughout the whole collision process, they carry information from all collision stages with negligible final-state interaction.

The ALICE detector is well-suited to perform this measurement due to its excellent tracking and particle identification capabilities at low momenta. However, Dalitz decays and photon conversions lead to a high combinatorial background with a signal-to-background ratio of 1:10 to 1:1000 in Pb-Pb collisions, depending on the invariant mass. Therefore, the minimization of the background is a key aspect of this analysis.
The reconstruction efficiency of low-$p_{\rm{T}}$ electrons can be increased by reducing the magnetic field of the ALICE central barrel solenoid from 0.5 T to 0.2 T. This allows a better rejection of the electron background and simultaneously gives the opportunity to increase the accessible phase space of the dielectron measurement. Such a configuration is planned in ALICE for part of the Pb-Pb campaigns in LHC Run 3 and 4 from 2021 on.

This poster will present the status of the dielectron measurement in pp collisions at $\sqrt{s}$ = 13 TeV from pilot runs taken with B=0.2 T in the ALICE central barrel. It will be shown how the analysis was adapted to the reduced-field configuration. The results will be compared to 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 will be compared to the expected yield from known hadronic sources.

Centralised submission by Collaboration Presenter name already specified
Content type Experiment
Collaboration ALICE

Primary author

Jerome Jung (Johann-Wolfgang-Goethe Univ. (DE))

Presentation materials