The authors as part of the HWW team of the ATLAS experiment at the LHC have studied events with two opposite-sign muons and two electrons in the search for the Standard Model Higgs boson
H
and a ...heavy resonance
R
in the channel of decay into two
W
-bosons. The analysis was carried out using the complete statistics of proton–proton collision events for 2015–2018 exposure for the c.m.s. energy of protons
= 13 TeV. The application of a deep neural network made it possible to significantly improve our earlier results for separation of the
H
-boson signal in the vector-boson-fusion production mechanism. Various theoretical models were used to calculate the new expected upper limits for the production of
R
resonance with a spin 0, 1, or 2 in addition to those obtained earlier in a toy NWA model for a heavy Higgs boson.
To investigate the Higgs boson properties in the
h
→
WW*
→
е
νμν decay channel, events with an electron, muon, and two hadron jets in the final state recorded with the ATLAS experiment at the LHC are ...analyzed by the authors as members of the ATLAS Higgs Working Group. The complete statistics of proton–proton collisions at
=
13 TeV recorded during 2015–2018 exposition is analyzed. Compared to our previous analysis, the statistics was quadrupled, the event-reconstruction procedures and the samples of simulated signal and background events were updated, and special attention was now paid to the events recorded during high-luminosity operation of the LHC. The Monte Carlo simulation is found to satisfactorily describe the measured hadron jet spectra in the signal region in the first stages of initial selection. It is shown that even during high-luminosity operation of the LHC hadron jets emitted at small polar angles are efficiently detected. The kinematic distributions in the control regions of major backgrounds are reasonably reproduced by the MC simulation.
Events with final-state electron and muon pairs produced in
pp
collisions at
= 13 TeV are analyzed toward detecting
H
→
WW
→
decays of a hypothetical heavy Higgs boson. The analysis relies on the ...total sample of proton–proton collisions recorded in 2015–2018 by the ATLAS experiment at the LHC, which corresponds to an integrated luminosity of 139 fb
−1
. Through a simulation, selections of signal events are formulated and the control kinematic region for the dominant Drell–Yan background is selected. Expected upper limits on production cross sections of a heavy Higgs boson are estimated under various model assumptions. These upper limits prove to be but slightly inferior to those that can be imposed in the
H
→
WW
→
decay channel by analyzing events with final-state μ
e
pairs.
The control region of
Z
-bosons produced in
pp
collisions at 13 TeV with the ATLAS detector at LHC is studied. This investigation, carried out by the authors as members of the HWW working group, is ...aimed at checking the algorithms applied for reconstructing the
H → WW → ℓvℓv
decays of a hypothetical heavy Higgs boson (HHB) sought by the LHC experiments. The analysis relies on the complete sample of proton-proton collisions recorded by ATLAS in 2015–2016 and pays special attention to variations of hadron-jet kinematic characteristics with the collider luminosity. A dedicated software package within the HWW information medium is developed and implemented for plotting kinematic distributions for correlated jets as functions of the number of collisions per beam crossing and of the number of primary vertices per event. On the whole, mean values of kinematic characteristics are found to follow linear dependences on the luminosity which are adequately reproduced by the simulation. Since the hadron-jet selection criteria are similar for the hypothetical HHB and for the Standard Model Higgs boson (SM H) already discovered at the LHC, the reported analysis is also relevant for experimental studies of the SM H properties. In this paper, we also report on initial results of the new search for the HHB at 13 TeV based on ameliorated event reconstruction algorithms and updated software. No significant differences between the results of the new and previous analyses are revealed.
A signal kinematical region is analyzed by the Higgs Boson Working Group (HWW) within the framework of a study of the Standard Model Higgs boson properties in the
H → WW* → evεv
decay channel in the ...ATLAS experiment on the Large Hadron Collider (LHC). The analysis is based on the full statistics of proton-proton collision data during exposures in 2015–2016 at the center-of-mass energy of 13 TeV. As compared to our previous analysis, the reconstruction software is updated and the simulation accuracy of backgrounds is improved. Events taken at low and high LHC luminosity are studied separately. In addition, the kinematics at the later stages of event selection is investigated in detail and systematic uncertainties are fully estimated. It is shown that the Monte Carlo modeling satisfactorily describes the experimental data at different selection stages. Kinematic distributions for hadron jets are studied also in the Z-boson control region, where the acquired data reach the order of ten million events. As compared to the previous investigation, the modeling accuracy of
Z
and background processes is noticeably improved, and events at low and high LHC luminosities are studied separately. Furthermore, all systematic uncertainties related to jets are estimated as well. As a whole, good agreement between experimental results and Monte Carlo simulation data is observed. No problems that would be caused by high luminosity are observed.
The authors as part of the HWW team of the ATLAS experiment at the LHC have studied events with two opposite-sign muons and two electrons in the search for the Standard Model Higgs boson H and a ...heavy resonance R in the channel of decay into two W-bosons. The analysis was carried out using the complete statistics of proton-proton collision events for 2015-2018 exposure for the c.m.s. energy of protons Formula omitted = 13 TeV. The application of a deep neural network made it possible to significantly improve our earlier results for separation of the H-boson signal in the vector-boson-fusion production mechanism. Various theoretical models were used to calculate the new expected upper limits for the production of R resonance with a spin 0, 1, or 2 in addition to those obtained earlier in a toy NWA model for a heavy Higgs boson.
Events with final-state electron and muon pairs produced in pp collisions at Formula omitted = 13 TeV are analyzed toward detecting H right arrow WW right arrow Formula omitted decays of a ...hypothetical heavy Higgs boson. The analysis relies on the total sample of proton-proton collisions recorded in 2015-2018 by the ATLAS experiment at the LHC, which corresponds to an integrated luminosity of 139 fb.sup.-1. Through a simulation, selections of signal events are formulated and the control kinematic region for the dominant Drell-Yan background is selected. Expected upper limits on production cross sections of a heavy Higgs boson are estimated under various model assumptions. These upper limits prove to be but slightly inferior to those that can be imposed in the H right arrow WW right arrow Formula omitted decay channel by analyzing events with final-state mue pairs.
The authors, members of the ATLAS Higgs boson working group (HWW), studied events with two leptons in the h/H right arrow WW.sup.(*.sup.) right arrow ðνðν decay in pp collisions at 13 TeV using the ...ATLAS detector at the LHC. The complete data sample recorded during 2015-2018 exposures, which corresponds to an integrated luminosity of 139 fb.sup.-1, was used in the analysis. Attention was focused on the properties of forward going hadron jets. Such jets accompany Higgs boson production through vector boson fusion. Two jet reconstruction algorithms, EMTopo and PFlow, are compared. The second algorithm is chosen for further analyses as more reliable at high LHC luminosity. Jet kinematics is studied separately for the exposures at various differential luminosities. The first results of the analysis of control regions of the main sources of background to the production of the heavy Higgs boson based on complete 13 TeV statistics are presented.
