  A measurement of the top quark mass is reported in events containing a single
top quark produced via the electroweak t channel. The analysis is performed
using data from proton-proton collisions collected with the CMS detector at the
LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated
luminosity of 19.7 inverse femtobarns. Top quark candidates are reconstructed
from their decay to a W boson and a b quark, with the W boson decaying
leptonically to a muon and a neutrino. The final state signature and kinematic
properties of single top quark events in the t channel are used to enhance the
purity of the sample, suppressing the contribution from top quark pair
production. A fit to the invariant mass distribution of reconstructed top quark
candidates yields a value of the top quark mass of 172.95 +/- 0.77 (stat)
+0.97/-0.93 (syst) GeV. This result is in agreement with the current world
average, and represents the first measurement of the top quark mass in event
topologies not dominated by top quark pair production, therefore contributing
to future averages with partially uncorrelated systematic uncertainties and a
largely uncorrelated statistical uncertainty.
