A measurement of the top quark mass (Mt) in the dileptonic t¯t decay channel is performed using data
from proton-proton collisions at a center-of-mass energy of 8 TeV. The data was recorded by the CMS
experiment at the LHC and corresponds to an integrated luminosity of 19.7 0.5 fb−1. Events are selected
with two oppositely charged leptons (l ¼ e, μ) and two jets identified as originating from b quarks. The
analysis is based on three kinematic observables whose distributions are sensitive to the value of Mt.
An invariant mass observable, Mbl, and a “stransverse mass” observable, MT2, are employed in a
simultaneous fit to determine the value of Mt and an overall jet energy scale factor (JSF). A complementary
approach is used to construct an invariant mass observable, Mblν, that is combined with MT2 to measure
Mt. The shapes of the observables, along with their evolutions in Mt and JSF, are modeled by a
nonparametric Gaussian process regression technique. The sensitivity of the observables to the value of Mt
is investigated using a Fisher information density method. The top quark mass is measured to be
172.22 0.18ðstatÞ þ0.89 −0.93 ðsystÞ GeV.