# Measurement of the top quark mass in the dileptonic t t-bar decay channel using the mass observables M[bl], M[T2], and M[blnu] in pp collisions at sqrt(s) = 8 TeV

## TL;DR

This paper presents a precise measurement of the top quark mass in dileptonic decay channels using innovative kinematic observables and Gaussian process modeling, based on 8 TeV proton-proton collision data from the CMS experiment.

## Contribution

The study introduces a combined analysis of multiple mass observables with Gaussian process regression to improve top quark mass measurement accuracy.

## Key findings

- Measured top quark mass as 172.22 GeV with high precision.
- Utilized novel kinematic observables M[bl], M[T2], and M[blnu].
- Achieved detailed modeling of observable shapes and sensitivities.

## Abstract

A measurement of the top quark mass (M[t]) in the dileptonic t t-bar 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 corresponding to an integrated luminosity of 19.7 +/- 0.5 inverse femtobarns. Events are selected with two oppositely charged leptons (l = e, mu) 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[bl], 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[blnu], 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.