Dielectron and heavy-quark production in inelastic and high-multiplicity proton-proton collisions at root s=13 TeV

S. Acharya, F. Torals-Acosta, D. Adamova, J Adolfsson, MM. Aggarwal, G.A. Rinella, Maria Agnello, N. Agrawl, Z. Ahammed, S.U. Ahn, S. Aiola, A. Akindinov, M. Al-Turany, SN Alam, DSD Albuguerque, D. Aleksandrov, B Alessandro, R. Alfaro Molina, Y. Ali, A. AliciA. Alkin, J. Alme, T. Alt, L. Altenkamper, I. Altsybeev, MN Anaam, C. Andrei, Ian Bearden, Jens Jørgen Gaardhøje, Christian Alexander Bourjau, Marek Chojnacki, bsm989 bsm989, You Zhou, Børge Svane Nielsen, rtc312 rtc312, Vojtech Pacik, Katarina Gajdosova, Freja Thoresen, Vytautas Vislavicius, Alice Collaboration

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Abstract

The measurement of dielectron production is presented as a function of invariant mass and transverse momentum (pT) at midrapidity (|ye|<0.8) in proton–proton (pp) collisions at a centre-of-mass energy of s=13 TeV. The contributions from light-hadron decays are calculated from their measured cross sections in pp collisions at s=7 TeV or 13 TeV. The remaining continuum stems from correlated semileptonic decays of heavy-flavour hadrons. Fitting the data with templates from two different MC event generators, PYTHIA and POWHEG, the charm and beauty cross sections at midrapidity are extracted for the first time at this collision energy: dσcc¯/dy|y=0=974±138(stat.)±140(syst.)±214(BR)μb and dσbb¯/dy|y=0=79±14(stat.)±11(syst.)±5(BR)μb using PYTHIA simulations and dσcc¯/dy|y=0=1417±184(stat.)±204(syst.)±312(BR)μb and dσbb¯/dy|y=0=48±14(stat.)±7(syst.)±3(BR)μb for POWHEG. These values, whose uncertainties are fully correlated between the two generators, are consistent with extrapolations from lower energies. The different results obtained with POWHEG and PYTHIA imply different kinematic correlations of the heavy-quark pairs in these two generators. Furthermore, comparisons of dielectron spectra in inelastic events and in events collected with a trigger on high charged-particle multiplicities are presented in various pT intervals. The differences are consistent with the already measured scaling of light-hadron and open-charm production at high charged-particle multiplicity as a function of pT. Upper limits for the contribution of virtual direct photons are extracted at 90% confidence level and found to be in agreement with pQCD calculations.

Original languageEnglish
JournalPhysics Letters B
Volume788
Pages (from-to)505-518
Number of pages14
ISSN0370-2693
DOIs
Publication statusPublished - 10 Jan 2019

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