| dc.contributor.advisor | Quadt, Arnulf Prof. Dr. | |
| dc.contributor.author | Sabatini, Paolo | |
| dc.date.accessioned | 2020-07-28T12:08:43Z | |
| dc.date.available | 2020-07-28T12:08:43Z | |
| dc.date.issued | 2020-07-28 | |
| dc.identifier.uri | http://hdl.handle.net/21.11130/00-1735-0000-0005-1439-5 | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-8133 | |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject.ddc | 530 | de |
| dc.title | Search for the production of four top quarks in proton-proton collisions at $\sqrt{s}=13$ TeV in the single lepton and opposite-sign dilepton channels with the ATLAS detector at the Large Hadron Collider | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Quadt, Arnulf Prof. Dr. | |
| dc.date.examination | 2020-02-10 | |
| dc.subject.gok | Physik (PPN621336750) | de |
| dc.description.abstracteng | This thesis presents the search for the production of $t\bar{t}t\bar{t}$ from $pp$ collision at $\sqrt{s} = 13$ TeV. The analysed dataset has been collected by the ATLAS detector during the LHC Run 2, corresponding to an integrated luminosity of $139$ fb$^{-1}$. The analysis uses events containing either one lepton or two leptons with opposite-sign charges, at large jet and $b$-jet multiplicities. The output of a Boosted Decision Tree is used as a discriminating variable in a profile likelihood fit for the measurement of the $t\bar{t}t\bar{t}$ signal strength $\mu_{t\bar{t}t\bar{t}} = \sigma_{t\bar{t}t\bar{t}} / \sigma_{t\bar{t}t\bar{t}}^\text{SM} $. The estimation of the dominant $t\bar{t}$+jets background is given by the data-driven t$\overline{\text{t}}$TRF method. The measured signal strength in the single lepton and opposite-sign dilepton channel is $\mu_{t\bar{t}t\bar{t}}^\text{1L+OS2L} = 0.9^{+0.5}_{-0.5}~\text{(stat.)}^{+1.0}_{-0.9}~\text{(syst.)}= 0.9^{+1.1}_{-1.0}$, compatible with the Standard Model expectation and corresponding to a deviation of $0.9$ ($1.0$) standard deviations from the background-only hypothesis. This result is combined with a complementary measurement, using events with two leptons with same-sign charges or three leptons in the final state. The combination provides a measurement of the $t\bar{t}t\bar{t}$ cross-section of $24\pm6$ fb, compatible with the Standard Model prediction within $1.8$ standard deviations. The measured significance of the $t\bar{t}t\bar{t}$ process over the background of $4.4$ standard deviations, providing evidence of the $t\bar{t}t\bar{t}$ production process. | de |
| dc.contributor.coReferee | Lai, Stan Prof. Dr. | |
| dc.subject.eng | top quark | de |
| dc.subject.eng | four tops | de |
| dc.subject.eng | ATLAS | de |
| dc.subject.eng | CERN | de |
| dc.subject.eng | Statistical evidence | de |
| dc.subject.eng | Data analysis | de |
| dc.subject.eng | Pixel Detector | de |
| dc.subject.eng | $t\bar{t}t\bar{t}$ | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-21.11130/00-1735-0000-0005-1439-5-2 | |
| dc.affiliation.institute | Fakultät für Physik | de |
| dc.identifier.ppn | 1725821176 | |