Measurement of the top quark mass in the dileptonic tt¯ decay channel using the mass observables Mbℓ

Abstract

Measurement of the top quark mass in the dileptonic tt decay channel using the mass observables M b , M T2 , and M b ν in pp collisions at √ s = 8 TeVThe CMS Collaboration * AbstractA measurement of the top quark mass (M t ) in the dileptonic tt 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 ( = 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 M t . An invariant mass observable, M b , and a 'stransverse mass' observable, M T2 , are employed in a simultaneous fit to determine the value of M t and an overall jet energy scale factor (JSF). A complementary approach is used to construct an invariant mass observable, M b ν , that is combined with M T2 to measure M t . The shapes of the observables, along with their evolutions in M t and JSF, are modeled by a nonparametric Gaussian process regression technique. The sensitivity of the observables to the value of M t is investigated using a Fisher information density method. The top quark mass is measured to be 172.22 ± 0.18 (stat) +0.89 −0.93 (syst) GeV. Published in Physical Review D asWe select dileptonic tt events from a data set recorded at √ s = 8 TeV during 2012 corresponding to an integrated luminosity of 19.7 ± 0.5 fb −1 [17]. Events are required to pass one of several triggers that require at least two leptons, ee, eµ, or µµ, where the leading (higher-p T ) lepton

On the cutoff dependence of the quark mass parameter in angular ordered parton showers

“…In Ref. [31] the sensitivity of m MC t determinations from exclusive hadronic variables such as the B-meson energy E B [32], the B-lepton invariant mass m B [33] or the transverse mass variables m T 2 [34][35][36][37] to variations of the parameters of the MC hadronization models in PYTHIA 8 and Herwig 6 was studied. They found that for top mass determinations based on these distributions to be competitive with direct reconstruction methods these hadronization parameters would have to be constrained significantly more precisely than what is possible from usual multi-purpose tuning.…”

Resolving combinatorial ambiguities in dilepton tt¯ event topologies with constrained M2Debnath1, Kim2, Kim3 et al. 2017Phys. Rev. D242410View full textAdd to dashboardCite

“…• This event topology is realized in the SM production of tt events, providing a useful toy playground for testing new ideas for studying new physics [57][58][59][60].…”

A theoretical study of top-mass measurements at the LHC using NLO+PS generators of increasing accuracy

“…[35], the use of lowest Mellin moments of lepton kinematic distributions is discussed. In the leptonic channel, it is also possible to use distributions based on the "stransverse" mass variable [36], which generalizes the concept of transverse mass for a system with two identical decay branches [37,38].…”