Measurement of the t-channel single top quark cross section in proton-proton collisions at s=5. 02 TeV

A bstract The single top quark t -channel production cross section is measured in proton-proton collisions at the CERN LHC at s=5. 02 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 (tq t ¯ q) production is (tq+tq) =25. 5-₃. ₅^+3. 6 (stat) -₃. ₉^+4. 2 (syst) 0. 5 (lumi) σ tq + t ¯ q = 25. 5 − 3. 5 + 3. 6 stat − 3. 9 + 4. 2 syst ± 0. 5 lumi pb. The individual cross sections are measured to be (tq) =17. 7-₂. ₇^+2. 9 (stat) -₂. ₄^+2. 6 (syst) 0. 3 (lumi) σ tq = 17. 7 − 2. 7 + 2. 9 stat − 2. 4 + 2. 6 syst ± 0. 3 lumi pb and (tq) =6. 7-₁. ₆^+2. 4 (stat) -₂. ₅^+2. 1 (syst) 0. 1 (lumi) σ t ¯ q = 6. 7 − 1. 6 + 2. 4 stat − 2. 5 + 2. 1 syst ± 0. 1 lumi pb. Their ratio is measured to be Rₓ-₂₇=2. 7-₀. ₈^+1. 5 (stat) -₀. ₃^+1. 2 (syst) R t