Measurement of lepton differential distributions and the top quark mass in $$t\bar{t}$$ t t ¯

Abstract

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic tt events produced in 20.2 fb −1 of √ s = 8 TeV pp collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge eμ pair and one or two btagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of m pole t = 173.2 ± 0.9 ± 0.8 ± 1.2 GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical

Coherent showers in decays of colored resonances

“…The leading order predictions show large shape differences with respect to data, while the NLO matched predictions are consistent with both data and each other. The level of variation is consistent with that seen in the original analysis [66]. FIG.…”

“…FIG. 12: Differential cross section with respect to the transverse momentum of the lepton pair, a, and the azimuthal angle between the lepton pair, b, as measured by ATLAS [66] in dileptonic tt production at √ s = 8…”

Multi-lepton signatures of additional scalar bosons beyond the Standard Model at the LHC

“…It is relevant to note that the discrepancy in the di-lepton invariant mass reported in Ref. [30] appears to be correlated with the di-lepton azimuthal angle difference reported in Ref [35] in the context of the tt spin correlation analysis with the same dataset. This indicates that the apparent discrepancy between the data and the MC in the di-lepton azimuthal The event yields reflect the number of BSM events to fit the data in excess of the SM prediction, first using the previously calculated value of β 2 g and then at the best fit point for the measurement in question.…”

“…Distributions of the ATLAS data and SM background comparing to the BSM signal for the di-lepton invariant mass. In (a) events are required to have two opposite-charge leptons (e, µ) with at least one b-tagged jet [30]. In (b) events are required to have two opposite-charge leptons with different-flavour (eµ) and (c) with same-flavour (ee/µ µ), where both analyses require zero jets [31].…”

Top quark pair production near threshold: single/double distributions and mass determination

“…Following the above discussions, it is clear that to extract the top quark mass, one needs to use observables that are strongly dependent on m t , and in the same time can be experimentally measured and theoretically calculated with high precisions. An often used observable is the tt pair invariant-mass distribution and related multi-differential cross sections in the top quark pair production process [15,16]. It can be easily anticipated that the kinematic region most sensitive to m t is where the pair invariant mass M tt is near JHEP06(2020)158 the 2m t threshold.…”