Search for the Standard Model Higgs boson in the two photon decay channel with the ATLAS detector at the LHC
A search for the Standard Model Higgs boson in the two photon decay channel is reported, using 1.08 fb−11.08 fb[superscript −1] of proton–proton collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS detector. No significant excess is observed in the investigated mass range of 110–150 GeV. Upper limits on the cross-section times branching ratio of between 2.0 and 5.8 times the Standard Model prediction are derived for this mass range.
Search for long-lived neutral particles produced in pp collisions at s=13 TeV decaying into displaced hadronic jets in the ATLAS inner detector and muon spectrometer
A search is presented for pair production of long-lived neutral particles using 33 fb − 1 of √ s = 13 TeV proton–proton collision data, collected during 2016 by the ATLAS detector at the LHC. This search focuses on a topology in which one long-lived particle decays in the ATLAS inner detector and the other decays in the muon spectrometer. Special techniques are employed to reconstruct the displaced tracks and vertices in the inner detector and in the muon spectrometer. One event is observed that passes the full event selection, which is consistent with the estimated background. Limits are placed on scalar boson propagators with masses from 125 GeV to 1000 GeV decaying into pairs of …
Study of heavy-flavor quarks produced in association with top-quark pairs at s=7 TeV using the ATLAS detector
Using a sample of dilepton top-quark pair ((tt) over bar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, the sum of (tt) over bar + b + X and (tt) over bar + c + X, collectively referred to as (tt) over bar + HF. The data set used corresponds to an integrated luminosity of 4.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF (b or c) quarks in the (tt) over bar sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b quarks from the (tt) over bar decays a…
Measurement of soft-drop jet observables in pp collisions with the ATLAS detector at s=13 TeV
Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from 32.9 fb-1 of pp collisions collected with the ATLAS detector at s=13 TeV. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant αS. Other observables, such as the momentum sharing between the two subjets, are nearly independent of αS. These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tra…
Measurement of theZZproduction cross section inpp¯collisions ats=1.96 TeV
The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2 fb⁻¹ of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7 +2.2 −2.0 (stat.) +0.9 −0.7 (syst.) +1.0 −0.7 (lumi.) pb. The results agree with standard model predictions.