Combinations of single-top-quark production cross-section measurements and |fLVVtb| determinations at s√=7 and 8 TeV with the ATLAS and CMS experiments

Abstract

his paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at s√=7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb−1 at s√=7 TeV, and 12.2 to 20.3 fb−1 at s√=8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5±5.7 pb and 87.7±5.8 pb at s√=7 and 8 TeV respectively. The combined tW cross-sections are 16.3±4.1 pb and 23.1±3.6 pb at s√=7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9±1.4 pb at s√=8 TeV. The square of the magnitude of the CKM matrix element Vtb multiplied by a form factor fLVis determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |Vtd|,|Vts|≪|Vtb|. All the |fLVVtb|2 determinations, extracted from individual ratios at s√=7 and 8 TeV, are combined, resulting in |fLVVtb|=1.02±0.04 (meas.) ±0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions