scholarly journals Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at $$ \sqrt{s} $$ = 13 TeV

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
◽  
N. Tonon ◽  
H. Aarup Petersen ◽  
M. Aldaya Martin ◽  
P. Asmuss ◽  
...  
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Top Quark ◽  
Z Boson ◽  
Top Quarks ◽  
Effective Field ◽  
Machine Learning Techniques ◽  
Final States ◽  
Associated Production ◽  
Five Dimension

Abstract A search for new top quark interactions is performed within the framework of an effective field theory using the associated production of either one or two top quarks with a Z boson in multilepton final states. The data sample corresponds to an integrated luminosity of 138 fb−1 of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV collected by the CMS experiment at the LHC. Five dimension-six operators modifying the electroweak interactions of the top quark are considered. Novel machine-learning techniques are used to enhance the sensitivity to effects arising from these operators. Distributions used for the signal extraction are parameterized in terms of Wilson coefficients describing the interaction strengths of the operators. All five Wilson coefficients are simultaneously fit to data and 95% confidence level intervals are computed. All results are consistent with the SM expectations.

scholarly journals Search for new physics in top quark production with additional leptons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV using effective field theory

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
T. Bergauer ◽  
...  
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Top Quark ◽  
Center Of Mass ◽  
Top Quarks ◽  
New Physics ◽  
Effective Field ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions

Abstract Events containing one or more top quarks produced with additional prompt leptons are used to search for new physics within the framework of an effective field theory (EFT). The data correspond to an integrated luminosity of 41.5 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, collected by the CMS experiment in 2017. The selected events are required to have either two leptons with the same charge or more than two leptons; jets, including identified bottom quark jets, are also required, and the selected events are divided into categories based on the multiplicities of these objects. Sixteen dimension-six operators that can affect processes involving top quarks produced with additional charged leptons are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A simultaneous fit of the 16 WCs to the data is performed and two standard deviation confidence intervals for the WCs are extracted; the standard model expectations for the WC values are within these intervals for all of the WCs probed.

scholarly journals Resummation of non-global logarithms in cross sections with massive particles

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Marcel Balsiger ◽  
Thomas Becher ◽  
Andrea Ferroglia
Keyword(s):  
Field Theory ◽  
Cross Section ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Top Quark ◽  
Parton Shower ◽  
Top Quarks ◽  
Effective Field ◽  
Group Evolution ◽  
Theory Framework

Abstract A factorization formalism for jet processes involving massive colored particles such as the top quark is developed, extending earlier results for the massless case. The factorization of soft emissions from the underlying hard process is implemented in an effective field theory framework, which forms the basis for the resummation of large logarithms. The renormalization group evolution giving rise to non-global logarithms is implemented into a parton shower code in the large-Nc limit. After a comparison of the massive and massless radiation patterns, the cross section for $$ t\overline{t} $$ t t ¯ production with a veto on additional central jet activity is computed, taking into account radiation both from the production and the decay of the top quarks. The resummation of the leading logarithms leads to an improved description of ATLAS measurements at $$ \sqrt{s} $$ s = 7 TeV.

scholarly journals A Monte Carlo global analysis of the Standard Model Effective Field Theory: the top quark sector

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Nathan P. Hartland ◽  
Fabio Maltoni ◽  
Emanuele R. Nocera ◽  
Juan Rojo ◽  
Emma Slade ◽  
...  
Keyword(s):  
Field Theory ◽  
Monte Carlo ◽  
Standard Model ◽  
Effective Field Theory ◽  
Top Quark ◽  
Global Analysis ◽  
Effective Field ◽  
Quark Sector ◽  
The Standard Model

scholarly journals Effective field theory for nonstandard top quark couplings

2011 ◽  
Vol 704 (3) ◽  
pp. 218-222 ◽  
Author(s):  
Nicolas Greiner ◽  
Scott Willenbrock ◽  
Cen Zhang
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Top Quark ◽  
Effective Field

scholarly journals Top-philic heavy resonances in four-top final states and their EFT interpretation

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Luc Darmé ◽  
Benjamin Fuks ◽  
Fabio Maltoni
Keyword(s):  
Top Quark ◽  
Top Quarks ◽  
New Physics ◽  
Effective Field ◽  
Effective Theory ◽  
Final States ◽  
Large Transverse Momentum ◽  
Simplified Models ◽  
Quark Pairs ◽  
Heavy Resonances

Abstract With an expected rate of about one event per 100,000 top-quark pairs, four top-quark final states very rarely arise at the LHC. Though scarce, they offer a unique window onto top-quark compositeness, self-interactions and more generically, onto any top-philic new physics. By employing simplified models featuring heavy resonances, we study the range of validity of effective theory interpretations of current four top-quark analyses at the LHC and establish their future reach at the HL-LHC. We find that for the class of models under consideration, the effective field theory interpretations are not applicable. We therefore present the most up-to-date limits obtained from public CMS analyses using simplified models. Finally, we put forward a novel recasting strategy for the experimental results based on the production of top quarks with large transverse momentum.

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