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Séminaires
CPPM PhD days 3 : Atlas
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Europe/Paris
Amphithéâtre (CPPM)
Amphithéâtre
CPPM
Description
13:30 - 15:00 PhD Student présentation
Estimation of fake lepton background in the two same-sign lepton ttH final states with the ATLAS experiment at LHC
Hadef Asma
The search for ttH production benefits with the dataset of 2015-2016 @ √s=13 TeV from a ten times increased statistics than in the first run, which will allow to measure directly for the first time the top-Higgs Yukawa coupling and indirectly search for New Physics. In the multilepton ttH, the
generic signature of two leptons (electron or muon) of same- sign electric charge is almost SM
background free. Fake leptons are the main detector background though. Its estimation is performed using data-driven method using pT parametrization that relies on real and fake lepton efficiencies measurements. First public results using 2015+2016 data @ √s=13 TeV were issued last summer and show consistency with the Standard Model expectation. Further studies are ongoing to reduce the contribution of fake leptons and its corresponding uncertainties.
earch for the production of WWW using 8 TeV data collected by the ATLAS detector and study the anomalous quartic gauge couplings(aQGCs)
Zhang Ruiqi
The main backgrounds are from fake leptons and eletron charge mis-identification which are estimated with data-driven techniques. No significant deviation from the SM is observed. Limits on aQGCs are set. Paper now is under 3rd circulation in ATLAS. Search for Doubly Charged Higgs: a triplet is introduced to allow mass for neutrinos and results in 5 Higgs bosons and two of them are doubly charged. The search focuses on pair production mode in which case there are two doubly charged Higgs bosons, I am working on the channel where two W bosons from one Higgs decay leptonically and other two W bosons from another Higgs decay hadronically. Main backgrounds in this channel is fake lepton background from ttbar/Vjets which is estimated
with fake factor method and electrons charge mis-identified background which is estimated with the wrongly reconstructed same-sign events of a Z->ee sample. The signal is obtained from a fit performed in a dedicated framework and taking into account statistical and systematic errors. Plan to have paper for the winter conference.
Electron reconstruction efficiency measurement, and study of the Higgs coupling to the top quark with two same sign leptons final state channels with the ATLAS detector at the LHC
De Vasconcelos Corga Kevin
In the hadronic environnement produced by proton-proton collisions at the LHC, leptons are often chosen as a baseline signature for many analyses looking for New Physics, or performing high precision measurements. Precise electron reconstruction efficiency measurements are crucial for all analyses involving electrons. Data driven results are obtained with the 2015 and 2016 data using the tag and probe method in the Z boson decay channel into an electron-positron pair, allowing to reach a sub-percent precision level.
The second part of this first year of PhD deals with the estimate of the instrumental background amount in the associated top quark pair - Higgs boson production with two same sign leptons in the final state.
Measurement of electron efficiency using W → eν decays. Study of the Higgs production in association with tt quarks
Dumitriu Ana Elena
As a part of my qualification task I am studying the electron efficiency measurements using the ATLAS detector in the Run 1 and Run 2 proton-proton collision data at centre of mass energy of 13 TeV by applying the Tag and Probe method in W→eν decay channel on Monte Carlo (MC) data and real data. The systematic studies includes the dependence of the efficiency on the signal and background templates, on the choice of the isolation variable, the η-ET binning, the trigger match and the topology of the W TP. Also, trigger emulation studies were performed and consequently a proposal for a new set of triggers with improved parameters was released for the new data and MC production.
As a part of my PhD thesis subject, I am studying the Higgs production in association with tt quarks, being involved in the ttH to multileptons group, responsible with the final state of 4 leptons (and 3 leptons). For the ICHEP and beyond, optimisation and fake estimate studies were performed.
Search for Chargino-Neutralino-> 1l+h(bb)+MET with Atlas at LHC Run 2
El Kosseifi Rima
The LHC 8 TeV Run 1 came out with a negative outcome for C1 N2 searches and exclusion limits of mC1,N2 > 250 GeV for a massless LSP were set. Taking advantage of the increase in the center-of-mass energy and the luminosity compared with run1, we’re searching for C1N2 → 1 l + h0(bb) + MET within ATLAS at LHC 13 TeV Run 2. In line with the b-jets in the final state, my ATLAS authorship project is on the b-jet identification. We studied the impact of several simulated scenarios for pixel dead modules, inspired from 2016 data quality flags, on overall b-tagging performance. In fact the pixel modules play a crucial role in tracks reconstruction and vertexing, hence it highly affect the b-jets identification and it is necessary to quantify the loss in performance for such scenarios.
On the phenomenology side, we’re developing a new version of the SuSy Spectrum calculator
“Suspect3” using the inverted bottom-up procedure from physical masses to constraint SUSY
parameters in the Higgs and stop sectors.
Data taking with the Liquid Argon Demonstrator for the Phase-I trigger readout electronics upgrade of the ATLAS experiment and studies on associated Higgs boson production with top quark pair
Wolff Robert
The first part of the presentation will cover the analysis done on the data taken during proton-proton collisions with the Liquid Argon demonstrator. The device was installed in July 2014 as a pre-prototype for the planned Phase I trigger upgrade. An increase in granularity of the calorimeter readout to the Level-1 trigger processors will provide the required improvements of the trigger for Run 3 of the ATLAS experiment at the Large Hadron Collider. The first signal electrons detected by the demonstrator were analysed, together with an performance study and further tuning.
The second part will describe the contributions to the analysis of associated Higgs boson production with top quark pair in the multileptonic final state, in particular the selection optimisations and the statistical combination of several multi-lepton channels.
Join the meeting by clicking this link: https://vidyoportal.cern.ch/flex.html?roomdirect.html&key=R8hWPzxNsly4
