  The cross section for the production of single top quarks in the t channel is
measured in proton-proton collisions at 13 TeV with the CMS detector at the
LHC. The analyzed data correspond to an integrated luminosity of 2.2 inverse
femtobarns. The event selection requires one muon and two jets where one of the
jets is identified as originating from a bottom quark. Several kinematic
variables are then combined into a multivariate discriminator to distinguish
signal from background events. A fit to the distribution of the discriminating
variable yields a total cross section of 238 +/- 13 (stat) +/- 29 (syst) pb and
a ratio of top quark and top antiquark production of R[t-ch.] = 1.81 +/- 0.18
(stat) +/- 0.15 (syst). From the total cross section the absolute value of the
CKM matrix element V[tb] is calculated to be 1.05 +/- 0.07 (exp) +/- 0.02
(theo). All results are in agreement with the standard model predictions.
