• Energy Research

We present the first direct measurement of the top-quark mass using $\ttbar$ events decaying in the hadronic $��$ + jets decay channel. Using data corresponding to an integrated luminosity of 2.2 fb$^{-1}$ collected by the CDF II detector in $p\bar{p}$ collisions at $\sqrt{s}=1.96 ~TeV$ at the Fermilab Tevatron, we measure the $t\bar{t}$ cross section, $��_{t\bar{t}}$, and the top-quark mass, M$_{top}$. We extract M$_{top}$ from a likelihood based on per-event probabilities calculated with leading-order signal and background matrix elements. We measure $��_{t\bar{t}} = 8.8 \pm 3.3 ~(\mathrm{stat}) \pm 2.2 ~(\mathrm{syst}) ~\mathrm{pb}$ and M$_{top} = 172.7 \pm 9.3 ~(\mathrm{stat}) \pm 3.7 ~(\mathrm{syst}) ~GeV/c^2$. 7 pages and 2 figures, accepted for publication in Phys. Rev. Lett

A precision measurement of the top quark mass m_t is obtained using a sample of ttbar events from ppbar collisions at the Fermilab Tevatron with the CDF II detector. Selected events require an electron or muon, large missing transverse energy, and exactly four high-energy jets, at least one of which is tagged as coming from a b quark. A likelihood is calculated using a matrix element method with quasi-Monte Carlo integration taking into account finite detector resolution and jet mass effects. The event likelihood is a function of m_t and a parameter DJES to calibrate the jet energy scale /in situ/. Using a total of 1087 events, a value of m_t = 173.0 +/- 1.2 GeV/c^2 is measured. 7 pages, 3 figures. Edited in response to referee comments and resubmitted to Phys. Rev. Lett

Abstract The dynamics of isolated-photon plus two-jet production in pp collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset corresponding to an integrated luminosity of 36.1 fb−1. Cross sections are measured as functions of a variety of observables, including angular correlations and invariant masses of the objects in the final state, γ + jet + jet. Measurements are also performed in phase-space regions enriched in each of the two underlying physical mechanisms, namely direct and fragmentation processes. The measurements cover the range of photon (jet) transverse momenta from 150 GeV (100 GeV) to 2 TeV. The tree-level plus parton-shower predictions from Sherpa and Pythia as well as the next-to-leading-order QCD predictions from Sherpa are compared with the measurements. The next-to-leading-order QCD predictions describe the data adequately in shape and normalisation except for regions of phase space such as those with high values of the invariant mass or rapidity separation of the two jets, where the predictions overestimate the data.