Measurement of differential t -channel single top (anti)quark production cross-sections at 13 TeV with the ATLAS detector

Ali, Hanadi and Alsolami, Zainab and Barton, A.E. and Borissov, G. and Bouhova-Thacker, E.V. and Fernandez Barbadillo, B. and Ferrando, James and Fox, H. and Hagan, Alina and Jones, R.W.L. and Kartvelishvili, V. and Love, P.A. and Marshall, Emma J. and McElhinney, Luke and Meng, L. and Sampson, Elliot and Smizanska, M. and Wharton, A.M. (2026) Measurement of differential t -channel single top (anti)quark production cross-sections at 13 TeV with the ATLAS detector. Journal of High Energy Physics, 2026 (5): 174. ISSN 1029-8479

Abstract

The production of single top quarks and top antiquarks via the t-channel exchange of a virtual W boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The full Run 2 data sample recorded with the ATLAS detector in the years 2015–2018 is used, corresponding to an integrated luminosity of 140 fb−1. The absolute and normalised production cross-sections are measured differentially as a function of the transverse momentum and absolute rapidity of the top quark and top antiquark. In addition, the ratio of top quark to top antiquark production cross-sections is measured. The measured distributions are compared with next-to-leading-order quantum chromodynamics predictions obtained with different combinations of matrix-element generators, parton-shower programs and proton parton distribution functions, as well as to next-to-next-to-leading-order calculations. Overall, good agreement is observed between the measurements and the theoretical predictions. For most measured distributions, the sensitivity to differences between the predictions is limited by the systematic uncertainties in the measurement. The measured differential distributions are also interpreted in an effective field theory approach to constrain the Wilson-Coefficient CQq3, 1 associated with a four-quark operator. The interpretation accounts for the effect of the selection efficiency, which is altered significantly by non-zero contributions from CQq3, 1.