期刊
JOURNAL OF HIGH ENERGY PHYSICS
卷 -, 期 3, 页码 -出版社
SPRINGER
DOI: 10.1007/JHEP03(2020)154
关键词
NLO Computations; QCD Phenomenology
资金
- National Research, Development and Innovation Office in Hungary [K 125105]
- Institute for Theoretical Particle Physics and Cosmology of RWTH Aachen University
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme [772099]
- German Research Foundation (DFG) Individual Research Grant: Top-Quarks under the LHCs Magnifying Glass: From Process Modelling to Parameter Extraction
- DFG Collaborative Research Centre/Transregio project [CRC/TRR 257: P3H]
- Bundesministerium fur Bildung und Forschung (BMBF)
- STFC [ST/P001246/1] Funding Source: UKRI
We present a comparative study of various approaches for modelling of the e+ve mu-v over bar mu bb over bar gamma final state in tt over bar gamma production at the LHC. Working at the NLO in QCD we compare the fully realistic description of the top quark decay chain with the one provided by the narrow-width-approximation. The former approach comprises all double, single and non-resonant diagrams, interferences, and off-shell effects of the top quarks. The latter incorporates only double resonant contributions and restricts the unstable top quarks to on-shell states. We confirm that for the integrated cross sections the finite top quark width effects are small and of the order of O(Gamma t/mt). We show, however, that they are strongly enhanced for more exclusive observables. In addition, we investigate fractions of events where the photon is radiated either in the production or in the decay stage. We find that large fraction of isolated photons comes from radiative decays of top quarks. Based on our findings, selection criteria might be developed to reduce such contributions, that constitute a background for the measurement of the anomalous couplings in the t (t) over bar gamma vertex.
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