CERN Accelerating science

Article
Title	Low-mass dielectron measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC
Author(s)	Sekihata, Daiki (Tokyo U., CNS)
Collaboration	ALICE Collaboration
Publication	2021
Number of pages	5
In:	PoS HardProbes2020 (2021) 047
In:	10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions : Hard Probes 2020 (HP2020), Austin, Texas, United States, 31 May - 5 June 2020, pp.047
DOI	10.22323/1.387.0047
Subject category	Nuclear Physics - Experiment ; Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ALICE
Abstract	The production of low-mass dielectrons is one of the most promising tools to understand the properties of the quark--gluon plasma (QGP) created in ultra-relativistic heavy-ion collisions. In this contribution, heavy-flavor ($\rm c\bar{c}$ and $\rm b\bar{b}$) production in pp and p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and the soft-dielectron excess in pp collisions at $\sqrt{s}$ = 13 TeV are presented. Dielectron production in p--Pb collisions plays an important role to investigate initial-state effects due to the presence of the cold nuclear matter in the collision. Heavy-flavor production cross sections have been extracted from the intermediate mass region by fitting to the dielectron invariant mass ($m_{\rm ee}$) and pair transverse momentum ($p_{\rm T,ee}$) in pp and p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, and the nuclear modification factor $R_{\rm pPb}$ as a function of $m_{\rm ee}$ is firstly extracted at the LHC energy. Results in pp collisions at $\sqrt{s}$ = 13 TeV with the reduced solenoid magnetic field at 0.2 T, allowing us to test very soft dielectron production, are also presented. An excess in the yields is observed at very low $p_{\rm T,ee}$ and the observed excess is described by neither hadronic bremsstrahlung nor thermal radiation.
Copyright/License	publication: © 2021-2025 The author(s) (License: CC-BY-NC-ND-4.0)

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