PreprintCC BY 4.0HAL
Observation of single top-quark production in the s-channel in proton--proton collisions at √s=13 TeV with the ATLAS detector
Abstract
The first single-experiment observation of single top-quark production in the s-channel is presented. Measurements of this process are essential to fully characterize the electroweak interactions of the top quark and probe for new physics, however its highly suppressed cross-section has so far caused it to evade direct detection at the Large Hadron Collider. The analysis uses proton--proton collision data collected at a center-of-mass energy of √s=13 TeV with the ATLAS detector, corresponding to an integrated luminosity of $140$ fb−1. The selected events contain exactly one electron or muon, missing transverse momentum, and exactly two b-quark-initiated jets. A Graph Neural Network is utilized to separate the signal from the top-quark pair, W+jets, and t-channel single top-quark backgrounds. A likelihood fit to the network output yields an observed (expected) signal significance of $5.1$ ($5.2$) standard deviations. The measured cross-section of σtb̅+t̅b = 10.8 ± 1.5 (stat.) ± 1.6 (syst.) pb is consistent with the Standard Model prediction.
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BibTeX
@misc{aad2026observation,
title = {{Observation of single top-quark production in the $s$-channel in proton--proton collisions at $\sqrts=13$ TeV with the ATLAS detector}},
author = {Georges Aad and Erlend Aakvaag and Braden Keim Abbott and Sara Abdelhameed and Kira Abeling and Nils Julius Abicht and Haider Abidi and Mohammed Aboelela and Asmaa Aboulhorma and Halina Abramowicz and Bobby Samir Acharya and Anke Ackermann and Jona Ackerschott and Claire Adam Bourdarios and Leszek Adamczyk and Sagar Addepalli and Jahred Adelman and Habeeb Adenle and Aytul Adiguzel and Tim Adye and Tony Affolder and Yoav Afik and Merve Nazlim Agaras and Anamika Aggarwal and Catalin Agheorghiesei and Ammara Ahmad and Faig Ahmadov and Sonakshi Ahuja and Xiaocong Ai and Giulio Aielli and Arya Aikot and Malak Ait Tamlihat and Torsten Akesson and Daiya Akiyama and Sina Aktas and Gian Luigi Alberghi and Justin Albert and Una Helena Alberti and Pietro Albicocco and Sara Alderweireldt and Zackary Lee Alegria and Martin Aleksa and Igor Alexandrov and Calin Alexa and Theodoros Alexopoulos and Fabrizio Alfonsi and Malte Algren and Muhammad Alhroob and Babar Ali and Hanadi Ali and Shahzad Ali and Samuel William Alibocus and Malik Aliev and Gianluca Alimonti and Corentin Allaire and Benedict Allbrooke and Derrick Allen and Jonny Allen and Camron Stephen Alley and Earl Russel Tang Almazan},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11465},
eprint = {2610.11465},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05829970v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observation of single top-quark production in the s-channel in proton--proton collisions at √s=13 TeV with the ATLAS detector
AU - Georges Aad
AU - Erlend Aakvaag
AU - Braden Keim Abbott
AU - Sara Abdelhameed
AU - Kira Abeling
AU - Nils Julius Abicht
AU - Haider Abidi
AU - Mohammed Aboelela
AU - Asmaa Aboulhorma
AU - Halina Abramowicz
AU - Bobby Samir Acharya
AU - Anke Ackermann
AU - Jona Ackerschott
AU - Claire Adam Bourdarios
AU - Leszek Adamczyk
AU - Sagar Addepalli
AU - Jahred Adelman
AU - Habeeb Adenle
AU - Aytul Adiguzel
AU - Tim Adye
AU - Tony Affolder
AU - Yoav Afik
AU - Merve Nazlim Agaras
AU - Anamika Aggarwal
AU - Catalin Agheorghiesei
AU - Ammara Ahmad
AU - Faig Ahmadov
AU - Sonakshi Ahuja
AU - Xiaocong Ai
AU - Giulio Aielli
AU - Arya Aikot
AU - Malak Ait Tamlihat
AU - Torsten Akesson
AU - Daiya Akiyama
AU - Sina Aktas
AU - Gian Luigi Alberghi
AU - Justin Albert
AU - Una Helena Alberti
AU - Pietro Albicocco
AU - Sara Alderweireldt
AU - Zackary Lee Alegria
AU - Martin Aleksa
AU - Igor Alexandrov
AU - Calin Alexa
AU - Theodoros Alexopoulos
AU - Fabrizio Alfonsi
AU - Malte Algren
AU - Muhammad Alhroob
AU - Babar Ali
AU - Hanadi Ali
AU - Shahzad Ali
AU - Samuel William Alibocus
AU - Malik Aliev
AU - Gianluca Alimonti
AU - Corentin Allaire
AU - Benedict Allbrooke
AU - Derrick Allen
AU - Jonny Allen
AU - Camron Stephen Alley
AU - Earl Russel Tang Almazan
PY - 2026
DA - 2026/10/08
PB - HAL
DO - 10.48550/arxiv.2610.11465
UR - https://hal.science/hal-05829970v1
AB - The first single-experiment observation of single top-quark production in the s-channel is presented. Measurements of this process are essential to fully characterize the electroweak interactions of the top quark and probe for new physics, however its highly suppressed cross-section has so far caused it to evade direct detection at the Large Hadron Collider. The analysis uses proton--proton collision data collected at a center-of-mass energy of √s=13 TeV with the ATLAS detector, corresponding to an integrated luminosity of $140$ fb^−1. The selected events contain exactly one electron or muon, missing transverse momentum, and exactly two b-quark-initiated jets. A Graph Neural Network is utilized to separate the signal from the top-quark pair, W+jets, and t-channel single top-quark backgrounds. A likelihood fit to the network output yields an observed (expected) signal significance of $5.1$ ($5.2$) standard deviations. The measured cross-section of σ_tb̅+t̅b = 10.8 ± 1.5 (stat.) ± 1.6 (syst.) pb is consistent with the Standard Model prediction.
ER -