Measurement of the $t$-channel single top quark cross section in proton-proton collisions at $\sqrt{s}$ = 5.02 TeV

TL;DR

This paper reports the first measurement of the $t$-channel single top quark production cross section at 5.02 TeV proton-proton collisions, confirming consistency with standard model predictions and providing new insights into top quark production at this energy.

Contribution

It provides the first CMS measurement of the $t$-channel single top quark cross section at 5.02 TeV, including separate measurements for top and antitop production.

Findings

Measured combined cross section: 25.4 pb with uncertainties.

Individual cross sections: 17.6 pb for top, 6.6 pb for antitop.

Ratio of top to antitop cross sections: 2.7.

Abstract

The single top quark $t$-channel production cross section is measured in proton-proton collisions at the CERN LHC at $\sqrt{s}$ = 5.02 TeV, using data recorded with the CMS detector in 2017, corresponding to an integrated luminosity of 302 pb$^{-1}$, and resulting in the first CMS measurement of the process at that energy. Events with one electron or muon and two or more jets, among which at least one is identified as originating from a b quark fragmentation, are analyzed. The combined cross section of single top quark (tq) and single top antiquark ($\mathrm{\bar{t}q}$) production is $\sigma_{\mathrm{tq+\bar{t}q}}$ = 25.4$^{+3.6}_{-3.5}$ (stat) $^{+4.2}_{-3.9}$ (syst) $\pm$ 0.5 (lumi) pb. The individual cross sections are measured to be $\sigma_{\mathrm{tq}}$ = 17.6$^{+2.8}_{-2.7}$ (stat) $^{+2.6}_{-2.4}$ (syst) $\pm$ 0.3 (lumi) pb and $\sigma_{\mathrm{\bar{t}q}}$ = 6.6$^{+2.4}_{-1.6}$ (stat) $^{+2.1}_{-2.5}$ (syst) $\pm$ 0.1 (lumi) pb. Their ratio is measured to be $\mathcal{R}_{\mathrm{t-ch}}$ = 2.7$^{+1.5}_{-0.8}$ (stat) $^{+1.3}_{-0.3}$(syst). The absolute value of the Cabibbo$-$Kobayashi$-$Maskawa matrix element is found to be $\lvert f_{\mathrm{LV}}V_\mathrm{tb}\rvert$ = 0.92 $\pm$ 0.09 (exp) $\pm$ 0.01 (thy). The measurements are in good agreement with the standard model predictions at next-to-next-to-leading order accuracy in quantum chromodynamics.