Evidence for top quark production in nucleus-nucleus collisions
Collaboration
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Abstract:
Evidence for the production of top quarks in heavy ion collisions is reported in a data sample of lead-lead collisions recorded in 2018 by the CMS experiment at a nucleon-nucleon center-of-mass energy of TeV, corresponding to an integrated luminosity of . Top quark pair () production is measured in events with two opposite-sign high- isolated leptons (). We test the sensitivity to the signal process by requiring or not the additional presence of b-tagged jets, and hence the feasilibilty to identify top quark decay products irrespective of interacting with the medium (bottom quarks) or not (leptonically decaying W bosons). To that end, the inclusive cross section () is derived from likelihood fits to a multivariate discriminator, which includes different leptonic kinematic variables, with and without the b-tagged jet multiplicity information. The observed (expected) significance of the signal against the background-only hypothesis is 4.0 (6.0) and 3.8 (4.8) standard deviations, respectively, for the fits with and without the b-jet multiplicity input. After event reconstruction and background subtraction, the extracted cross sections are and , respectively, which are consistent with each other and lower than, but still compatible with, the expectations from scaled proton-proton data as well as from perturbative quantum chromodynamics predictions. This measurement constitutes the first step towards using the top quark as a novel tool for probing strongly interacting matter.Note:
- Preliminary results
- Monte-Carlo
- top: pair production
- top: production
- top: decay
- jet: multiplicity
- matter: interaction
- jet: bottom
- heavy ion: scattering
- nucleus nucleus: scattering
- quantum chromodynamics
References(69)
Figures(13)
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- [16]
- [17]
- [18]
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