Top Quark at the New Physics Frontier

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "High Energy Nuclear and Particle Physics".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 17659

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Special Issue Editors

Department of Physics, National Taiwan University, Taipei, Taiwan
Interests: high-energy physics; top quark; standard model; Higgs boson; physics generators and modelling; calorimetry; high energy astrophysics; computational physics

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Guest Editor
CERN, PH-UCM Bat 40 3-A32 E24410, CH 1211 Geneva 23, Switzerland
Interests: high-energy physics; standard model; new physics; heavy ions; data analysis techniques; calorimetry

Special Issue Information

Dear Colleagues,

The hunt for top quarks began back in the 1970s after the proposal of the six-quark model by Kobayashi and Maskawa, and it was discovered in 1995 at the Fermilab Tevatron. It has been experimentally established by five different experiments in different production modes and a variety of collision energies.

At the CERN Large Hadron Collider (LHC), top quark–antiquark pairs are routinely produced at a rate of about 6 per minute, enabling experiments to make detailed measurements of the properties of top quarks. The analysis of the data collected by the first two LHC runs has revealed, so far, good agreement with the standard model (SM) predictions. The attained percentage-level precision in several measurements has been possible thanks to the excellent performance of the Tevatron and LHC accelerators and experiments. Accurate and precise theory calculations and Monte Carlo simulations also play a crucial role in the results obtained so far. In some cases, these accurate measurements are pushing the boundaries of physics and technology. 

The top quark is the most massive elementary particle identified to date: not only does it have a privileged Yukawa coupling to the Higgs boson, but also its mass is significantly higher than that of the Higgs boson. Owing to its large mass, the top quark decays before hadronization, making the study of “bare” quark properties possible in experimental settings. Therefore, top quark physics simultaneously pushes the frontier of quantum chromo-dynamics, electroweak, and flavor physics. Of particular relevance is the fact that, taken together, the top quark and the Higgs boson modify the tree level SM processes through radiative corrections. Such corrections are potentially sensitive to new physics contributions from energy scales larger than that which the current accelerators can achieve.

The aim of this Special Issue of Universe is to provide a comprehensive review of the current status and prospects of top quark physics at the LHC and possible future colliders. We especially welcome articles that emphasize where the present understanding is incomplete, and suggest new directions for research in this area.

Best regards,

Dr. Efe Yazgan
Dr. Pedro Ferreira da Silva
Guest Editors

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Keywords

  • Particles and Fields (12.00.00)
  • Top quark (14.65.Ha)
  • Quantum Chromodynamics (12.38.−t)
  • Electroweak interactions (12.15.−y)
  • Quark and lepton masses and mixing (12.15.Ff)
  • Models beyond the standard model (12.60.−i)
  • Experimental methods and instrumentation for elementary-particle and nuclear physics (29.00.00)
  • Data analysis (07.05.Kf)

Published Papers (13 papers)

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Editorial

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5 pages, 192 KiB  
Editorial
Top Quark at the New Physics Frontier
by Efe Yazgan and Pedro Silva
Universe 2024, 10(3), 124; https://doi.org/10.3390/universe10030124 - 5 Mar 2024
Viewed by 814
Abstract
This Special Issue of Universe is devoted to the most massive fundamental elementary particle known, the top quark [...] Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)

Research

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31 pages, 3206 KiB  
Article
Recent Cross-Section Measurements of Top-Quark Pair Production in Association with Gauge Bosons
by Joshuha Thomas-Wilsker
Universe 2023, 9(1), 39; https://doi.org/10.3390/universe9010039 - 6 Jan 2023
Viewed by 1266
Abstract
This article reviews recent cross-section measurements of tt¯ production in association with a photon, W or Z boson at the Large Hadron Collider (LHC). All measurements reviewed use proton–proton (pp) datasets collected by the ATLAS and CMS experiments between 2016 and [...] Read more.
This article reviews recent cross-section measurements of tt¯ production in association with a photon, W or Z boson at the Large Hadron Collider (LHC). All measurements reviewed use proton–proton (pp) datasets collected by the ATLAS and CMS experiments between 2016 and 2018 from collisions at a centre-of-mass energy of 13 TeV during the LHC Run 2. Differential and inclusive cross-section measurements are discussed along with the constraints on the effective field theory operators accessible through each process. Finally, we discuss the potential for measurements of these processes at future colliders. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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7 pages, 538 KiB  
Communication
Prospects for Probing Axionlike Particles at a Future Hadron Collider through Top Quark Production
by Yasaman Hosseini and Mojtaba Mohammadi Najafabadi
Universe 2022, 8(6), 301; https://doi.org/10.3390/universe8060301 - 26 May 2022
Cited by 2 | Viewed by 1536
Abstract
Axionlike particles (ALPs) emerge from spontaneously broken global symmetries in high energy extensions of the Standard Model (SM). This causes ALPs to be among the objectives of future experiments that intend to search for new physics beyond the SM. We discuss the reach [...] Read more.
Axionlike particles (ALPs) emerge from spontaneously broken global symmetries in high energy extensions of the Standard Model (SM). This causes ALPs to be among the objectives of future experiments that intend to search for new physics beyond the SM. We discuss the reach of future pp collider FCC-hh in probing the ALP model parameters through top quark pair production associated with ALP (tt¯+ALP) in a model-independent approach. The search is performed in the semi-leptonic decay mode of tt¯ and the analysis is performed using a parametric simulation of the detector response for a projected integrated luminosity of 30ab1. It is shown that tt¯+ALP production at the FCC-hh is a promising channel with significant sensitivity to probe the ALP coupling with gluons. The ALP coupling with gluons obtained from HL-LHC and other experiments is presented for comparison. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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Review

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18 pages, 1481 KiB  
Review
Properties of the Top Quark
by Andreas Jung
Universe 2024, 10(3), 106; https://doi.org/10.3390/universe10030106 - 26 Feb 2024
Viewed by 885
Abstract
Recent measurements of the properties of the top quark at the CERN Large Hadron Collider are discussed. The results were measured for single and top quark pair production in their final states, including jets with either one or two leptons or only in [...] Read more.
Recent measurements of the properties of the top quark at the CERN Large Hadron Collider are discussed. The results were measured for single and top quark pair production in their final states, including jets with either one or two leptons or only in hadronic final states. Top quark properties include angular correlations, top quark spin correlations, mass, and width. When looking towards the future, top quark properties open new and even interdisciplinary avenues for probing quantum information science. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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14 pages, 886 KiB  
Review
Diffractive and Photon-Induced Production of Top Quark
by Michael Pitt
Universe 2023, 9(11), 483; https://doi.org/10.3390/universe9110483 - 16 Nov 2023
Viewed by 1105
Abstract
The top quark plays a central role in particle physics, as many experiments at the Large Hadron Collider scrutinize its properties within the Standard Model. Although most of the measurements of the top quarks today concentrate on production modes initiated by quarks or [...] Read more.
The top quark plays a central role in particle physics, as many experiments at the Large Hadron Collider scrutinize its properties within the Standard Model. Although most of the measurements of the top quarks today concentrate on production modes initiated by quarks or gluons, this review will highlight the lesser-explored modes initiated by pomerons or photons. It aims to provide an in-depth look into both the phenomenological studies and the existing experimental measurements, emphasizing the necessity of exploring the diffractive and photon-induced production of top quarks to enhance the accuracy of top-quark measurements. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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37 pages, 2670 KiB  
Review
Single-Top Quark Physics at the LHC: From Precision Measurements to Rare Processes and Top Quark Properties
by Jérémy Andrea and Nicolas Chanon
Universe 2023, 9(10), 439; https://doi.org/10.3390/universe9100439 - 30 Sep 2023
Viewed by 1227
Abstract
Since the initial measurements of single-top quark production at the Tevatron in 2009, tremendous progress has been made at the LHC. While LHC Run 1 marked the beginning of a precision era for the single-top quark measurements in some of the main production [...] Read more.
Since the initial measurements of single-top quark production at the Tevatron in 2009, tremendous progress has been made at the LHC. While LHC Run 1 marked the beginning of a precision era for the single-top quark measurements in some of the main production mechanisms, LHC Run 2 witnessed the emergence and exploration of new processes associating top quark production with a neutral boson. In this paper, we review the measurements of the three main production mechanisms (t-channel, s-channel, and tW production), and of the associated production with a photon, a Z boson, or a Higgs boson. Differential cross-sections are measured for several of these processes and compared with theoretical predictions. The top quark properties that can be measured in single-top quark processes are scrutinized, such as Wtb couplings and top quark couplings with neutral bosons, and the polarizations of both the W boson and top quark. The effective field theory framework is emerging as a standard for interpreting property measurements. Perspectives for LHC Run 3 and the HL-LHC are discussed in the conclusions. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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0 pages, 1113 KiB  
Review
Measurements of the Cross-Section for the \({{\rm t}{\bar{\rm t}}}\) Heavy-Flavor Production at the LHC
by Jorgen D’Hondt and Tae Jeong Kim
Universe 2023, 9(5), 242; https://doi.org/10.3390/universe9050242 - 21 May 2023
Viewed by 1134
Abstract
At the LHC, the process of a Higgs boson decaying into bottom or charm quarks produced in association with a pair of top quarks, tt¯H, allows for an empirical exploration of the heavy-flavor quark Yukawa couplings to the Higgs [...] Read more.
At the LHC, the process of a Higgs boson decaying into bottom or charm quarks produced in association with a pair of top quarks, tt¯H, allows for an empirical exploration of the heavy-flavor quark Yukawa couplings to the Higgs boson. Accordingly, the cross-sections for the tt¯ + heavy-flavor production without the appearance of the Higgs boson have been measured at the LHC in various phase spaces using data samples collected in pp collisions at s = 7, 8 and 13 TeV with the ATLAS and CMS experiments. Flavor ratios of cross-sections of tt¯ + heavy-flavors to tt¯ + additional jets processes are also measured. In this paper, the measured cross-sections and ratios are reviewed and the prospects with more data are presented. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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10 pages, 506 KiB  
Review
Tests of Charge–Parity Symmetry and Lepton Flavor Conservation in the Top Quark Sector
by Kai-Feng Chen and Reza Goldouzian
Universe 2023, 9(2), 62; https://doi.org/10.3390/universe9020062 - 20 Jan 2023
Viewed by 782
Abstract
The Standard Model (SM) of particle physics is the most general renormalizable theory which is built on a few general principles and fundamental symmetries with the given particle content. However, multiple symmetries are not built into the model and are simply consequences of [...] Read more.
The Standard Model (SM) of particle physics is the most general renormalizable theory which is built on a few general principles and fundamental symmetries with the given particle content. However, multiple symmetries are not built into the model and are simply consequences of renormalizabilty, gauge invariance, and particle content of the theory. It is crucial to test the validity of these types of symmetries and related conservation laws experimentally. The CERN LHC provides the highest sensitivity for testing the SM symmetries at high energy scales involving heavy particles such as the top quark. In this article, we are going to review the recent experimental searches of charge–parity and charged-lepton flavor violation in the top quark sector. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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30 pages, 3503 KiB  
Review
Dark Matter Searches with Top Quarks
by J. Katharina Behr and Alexander Grohsjean
Universe 2023, 9(1), 16; https://doi.org/10.3390/universe9010016 - 27 Dec 2022
Cited by 3 | Viewed by 1469
Abstract
Collider signatures with top quarks provide sensitive probes of dark matter (DM) production at the Large Hadron Collider (LHC). In this article, we review the results of DM searches in final states with top quarks conducted by the ATLAS and CMS Collaborations at [...] Read more.
Collider signatures with top quarks provide sensitive probes of dark matter (DM) production at the Large Hadron Collider (LHC). In this article, we review the results of DM searches in final states with top quarks conducted by the ATLAS and CMS Collaborations at the LHC, including the most recent results on the full LHC Run 2 dataset. We highlight the complementarity of DM searches in final states with top quarks with searches in other final states in the framework of various simplified models of DM. A reinterpretation of a DM search with top quarks in the context of an effective field theory description of scalar dark energy is also discussed. Finally, we give an outlook on the potential of DM searches with top quarks in LHC Run 3, at the high-luminosity LHC, and possible future colliders. In this context, we highlight new benchmark models that could be probed by existing and future searches as well as those that predict still-uncovered signatures of anomalous top-quark production and decays at the LHC. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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15 pages, 514 KiB  
Review
Four-top quark physics at the LHC
by Freya Blekman, Fréderic Déliot, Valentina Dutta and Emanuele Usai
Universe 2022, 8(12), 638; https://doi.org/10.3390/universe8120638 - 30 Nov 2022
Cited by 9 | Viewed by 1243
Abstract
The production of four top quarks presents a rare process in the Standard Model that provides unique opportunities and sensitivity to Standard Model observables including potential enhancement of many popular new physics extensions. This article summarises the latest experimental measurements of the four-top [...] Read more.
The production of four top quarks presents a rare process in the Standard Model that provides unique opportunities and sensitivity to Standard Model observables including potential enhancement of many popular new physics extensions. This article summarises the latest experimental measurements of the four-top quark production cross section at the LHC. An overview is provided detailing interpretations of the experimental results regarding the top quark Yukawa coupling in addition to the limits on physics beyond the Standard Model. Further, prospects for future measurements and opportunities offered by this challenging final state are given herein. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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42 pages, 2650 KiB  
Review
Top Quark Asymmetries
by Thorsten Chwalek and Frédéric Déliot
Universe 2022, 8(12), 622; https://doi.org/10.3390/universe8120622 - 25 Nov 2022
Cited by 1 | Viewed by 890
Abstract
The production of top quark pairs (tt¯) via the quark-antiquark initial state is not symmetric under the exchange of top quark and antiquark. Calculations of this next-to-leading order effect predict asymmetries of about one to a few percent, depending [...] Read more.
The production of top quark pairs (tt¯) via the quark-antiquark initial state is not symmetric under the exchange of top quark and antiquark. Calculations of this next-to-leading order effect predict asymmetries of about one to a few percent, depending on the centre-of-mass energy and the selected phase space. Experimentally, this charge asymmetry of tt¯ production manifests itself in differences in angular distributions between top quarks and antiquarks. Sensitive observables are the rapidities of the produced top quarks and antiquarks as well as their energies. In dileptonic tt¯ events, the asymmetry of the tt¯ system is reflected in a similar asymmetry in the system of the produced lepton pair, with the crucial advantage of a simpler reconstruction procedure. In this article we review the measurements of this effect in different final states and using different observables by the ATLAS and CMS Collaborations in LHC collisions at three different centre-of-mass energies. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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17 pages, 723 KiB  
Review
Flavour-Changing Neutral Scalar Interactions of the Top Quark
by Nuno Filipe Castro and Kirill Skovpen
Universe 2022, 8(11), 609; https://doi.org/10.3390/universe8110609 - 21 Nov 2022
Cited by 6 | Viewed by 1670
Abstract
A study of the top-quark interactions via flavour-changing neutral current (FCNC) processes provides an intriguing connection between the heaviest elementary particle of the standard model (SM) of particle physics and the new scalar bosons that are predicted in several notable SM extensions. The [...] Read more.
A study of the top-quark interactions via flavour-changing neutral current (FCNC) processes provides an intriguing connection between the heaviest elementary particle of the standard model (SM) of particle physics and the new scalar bosons that are predicted in several notable SM extensions. The production cross sections of the processes with top-scalar FCNC interactions can be significantly enhanced to the observable level at the CERN Large Hadron Collider. The present review summarises the latest experimental results on the study of the top-quark interactions with the Higgs boson via an FCNC and describes several promising directions to look for new scalar particles. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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Other

11 pages, 318 KiB  
Essay
On Extra Top Yukawa Couplings of a Second Higgs Doublet
by George Wei-Shu Hou
Universe 2022, 8(9), 475; https://doi.org/10.3390/universe8090475 - 9 Sep 2022
Cited by 1 | Viewed by 1120
Abstract
A very likely New Physics in plain sight, but that the community does not see, is a second Higgs doublet that has a second set of Yukawa couplings. The extra tt and tc couplings can each drive baryogenesis, with O(1) Higgs quartic couplings [...] Read more.
A very likely New Physics in plain sight, but that the community does not see, is a second Higgs doublet that has a second set of Yukawa couplings. The extra tt and tc couplings can each drive baryogenesis, with O(1) Higgs quartic couplings providing a first order electroweak phase transition. A natural cancellation mechanism can tame electron EDM, if extra ee, tt couplings “know” the known fermion mass and mixing hierarchies. Colliding c with g produces tH/A, bH+ via extra tc coupling, and together with extra tt coupling give ttc(bar), ttt(bar), and btb(bar) signatures at the LHC. Extra tu coupling can also be probed, but more definitive would be the B to μν and τν decay rate ratio. Myriad extra Yukawa couplings can make an impact on flavor physics and CP violation, including on muon g-2. The opening to the prelude of a new physics Higgs and flavor era may unfold before us. Full article
(This article belongs to the Special Issue Top Quark at the New Physics Frontier)
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