First measurement of the top quark mass in pp collisions at $\sqrt{s

We present a measurement of the top quark mass $m_{top}$ in the dilepton decay channel $t\bar{t}\rightarrow(l^{+}\nu_l b)~(l^{-}\bar{\nu}_l \bar{b})$ in pp collisions at $\sqrt{s}=7$~TeV. The data sample of the measurement corresponds to an integrated luminosity of 36~pb$^{-1}$ collected with the CMS detector at the LHC. Events are selected by requiring two leptons, at least two jets, and missing transverse energy. The mass is reconstructed from the kinematic characteristics of the events with two numerical methods, a full kinematic analysis and an analytical matrix weighting technique. For each method, a set of templates are constructed from simulated samples and a likelihood fit is performed to derive the mass. The combination of the results yields a measurement of $m_{top}=175.5\pm4.6(stat)\pm4.6(syst)~\text{GeV}\!/\!c^2$.