# Four-top quark physics at the LHC

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## Abstract

**:**

## 1. Introduction

## 2. Current Status of Four-Top Quark Measurements

#### 2.1. Searches for $t\overline{t}t\overline{t}$ Production in Same-Charge Dilepton and Multi-Lepton Final States

#### 2.1.1. Event Selection and Backgrounds

#### 2.1.2. Signal Extraction and Results

#### 2.2. Searches for $t\overline{t}t\overline{t}$ Production in Single-Lepton and Opposite-Charge Dilepton Final States

#### 2.2.1. Event Selection and Backgrounds

#### 2.2.2. Signal Extraction and Results

#### 2.3. Search for $t\overline{t}t\overline{t}$ Production in the All-Hadronic Final State

#### 2.3.1. Event Selection and Backgrounds

#### 2.3.2. Signal Extraction and Results

#### 2.3.3. CMS Run 2 Combination

## 3. Interpretations

#### 3.1. Yukawa Coupling

#### 3.2. EFTs

#### 3.3. BSM Sensitivity

## 4. Future of Four-Top Quark Measurements

#### Opportunities

## 5. Conclusions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Selected Feynman graphs representing the main production modes of $t\overline{t}t\overline{t}$ production.

**Figure 3.**Observed and expected event yields as a function of ${log}_{10}(\mathrm{S}/\mathrm{B})$ where S and B are the post-fit signal and background yields in the single-lepton and opposite-charge dilepton ATLAS analysis [27] (

**left**). Post-fit and observed distribution of the event-level BDT in three separate signal-enriched regions in the $e\mu $ final state, from the single-lepton and opposite-charge dilepton CMS analysis on the 2016 data (

**right**) [28].

**Table 1.**Observed intervals at 95% CL for the coupling parameters of the four independent EFT operators contributing to $t\overline{t}t\overline{t}$ production. Intervals are reported for both the independent and marginalized scenarios [28].

Coupling Parameter | Marginalized ${\mathit{C}}_{\mathit{k}}/{\mathsf{\Lambda}}^{2}$ (TeV${}^{-2}$) | Independent (TeV${}^{-2}$) |
---|---|---|

${C}_{{\mathcal{O}}_{tt}^{1}}$ | [−2.2, 2.1] | [−2.1, 2.0] |

${C}_{{\mathcal{O}}_{QQ}^{1}}$ | [−2.2, 2.0] | [−2.2, 2.0] |

${C}_{{\mathcal{O}}_{Qt}^{1}}$ | [−3.7, 3.5] | [−3.5, 3.5] |

${C}_{{\mathcal{O}}_{Qt}^{8}}$ | [−8.0, 6.8] | [−7.9, 6.6] |

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**MDPI and ACS Style**

Blekman, F.; Déliot, F.; Dutta, V.; Usai, E.
Four-top quark physics at the LHC. *Universe* **2022**, *8*, 638.
https://doi.org/10.3390/universe8120638

**AMA Style**

Blekman F, Déliot F, Dutta V, Usai E.
Four-top quark physics at the LHC. *Universe*. 2022; 8(12):638.
https://doi.org/10.3390/universe8120638

**Chicago/Turabian Style**

Blekman, Freya, Fréderic Déliot, Valentina Dutta, and Emanuele Usai.
2022. "Four-top quark physics at the LHC" *Universe* 8, no. 12: 638.
https://doi.org/10.3390/universe8120638