Sebastian Ordoñez
jsordonezs@unal.edu.co
1st of July 2021
Final state: two leptons, \(E_{T}^{miss}\), two jets.
"The probability of a non-prompt lepton to be incorrectly associated with the primary vertex or a jet to fake the lepton signature is not well modelled in the Monte Carlo. " Shalu
In order to calculate the non-prompt background, four lepton categories are used.
On thruth-level:
On detector-level we have:
The reducible background is calculated by using:
\(F\)
Relation between the truth-level categories and the detector-level categories:
It follows that
We define the fake factor as the following ratio
For a complete application of the Matrix method in the signal region we have to evaluate the \(N^{\text{non-prompt}}\) estimate in auxiliary regions, the validation regions.
Signal region
\(F\) final application
\(F\) validation
\(F\) extraction
Validation
regions
Control region
\(m_{ll}\) distribution
\(E_{T}^{miss}\) distribution
The LowMjj validation region was already used with a non-prompt contribution of about 25%. It is necessary to build new validation regions with a higher contribution.
Non-prompt muons in the signal region originate almost exclusively from \(b\) quarks coming from \(t\bar{t}\) events.
A trilepton validation region for testing the modelling of non-prompt muons was built by requiring events to:
We need to guarantee that non-prompt muons have a \(p_{T}>27\) GeV in order to be able to apply the fake factor.
Preselection
Selection
Non-prompt electrons in the signal region originate primarily from light flavour jets of \(W+jets\) events. However, it is not possible to achieve that composition using a trilepton region.
That is why we look for a similar composition coming from \(Z+jets\) events.
Similarly, a trilepton electron validation region was bulit for testing the modelling of non-prompt electrons. We require the following cuts:
Preselection
Selection
Criteria considered when building these validation regions:
One of the main goals of these validation regions is to improve the first point, since the LowMjj region had a contribution of only about 25% non-prompt Ana events.
\(E_{T}^{miss}\) distribution for Non-Ana events
\(E_{T}^{miss}\) distribution for Ana events
\(E_{T}^{miss}\) distribution in the Low \(m_{jj}\) region
The contribution of non-prompt muons in the Trilepton muon region is almost 50%. It was achieved a higher contribution than that of the LowMjj region.
Signal Region:
All non-prompt Non-Ana muons
Trilepton muon
Region:
Trilepton muon
Region:
Only Non-prompt Ana muons
Signal Region:
\(m_{\mu\mu}\) distribution for Non-Ana events
\(m_{\mu\mu}\) distribution for Ana events
The contribution of non-prompt Ana electrons in the Trilepton electron region is about 31%. Once again, it was achieved a higher non-prompt contribution than that of the LowMjj region.
Signal Region:
All non-prompt Non-Ana electrons
Trilepton muon
Region:
Trilepton muon
Region:
Only Non-prompt Ana electrons
Signal Region:
This could be a problem!
MC-data-driven
In an ideal scenario it would be expected that:
\(p_{T}\) distribution for non-prompt muons
\(m_{lll}\) distribution
\(E_{T}^{miss}\) distribution
\(m_{jj}\) distribution
Leading jet \(p_{T }\) distribution
Subleading lepton \(p_{T }\) distribution
Leading lepton \(p_{T }\) distribution
Third lepton \(p_{T }\) distribution
Subleading jet \(p_{T }\) distribution
\(p_{T}\) distribution for the non-prompt electron
In this case, the number of MC-data-driven events is notably below the MC events according to truth-level information.
\(m_{\mu\mu}\) distribution
\(E_{T}^{miss}\) distribution
\(m_{jj}\) distribution
Leading jet \(p_{T }\) distribution
Leading lepton \(p_{T }\) distribution
Subleading lepton \(p_{T }\) distribution
Subleading jet \(p_{T}\) distribution
Third lepton \(p_{T }\) distribution
Data-driven
In an ideal scenario it would be expected that:
The result found in the MC closure is confirmed here. It is clear a not negligible overestimation of data by the sum of the data-driven estimated non-prompt bkg and the prompt contribution predicted by MC simulations.
\(m_{lll}\) distribution
\(E_{T}^{miss}\) distribution
Leading lepton \(p_{T}\)
Leading jet \(p_{T}\)
Subleading jet \(p_{T}\)
\(m_{jj}\) distribution
Subleading lepton \(p_{T}\)
Third lepton \(p_{T}\)
Electron \(p_{T}\) distribution
Once again the result seen in the MC closure is confirmed. It is clear a significant underestimation of the data. This underestimation is approximately a factor two in the non-prompt estimate.
\(m_{\mu\mu}\) distribution
\(E_{T}^{miss}\) distribution
\(m_{jj}\) distribution
Leading jet \(p_{T }\) distribution
Leading lepton \(p_{T }\) distribution
Subleading lepton \(p_{T }\) distribution
Third lepton \(p_{T }\) distribution
Subleading jet \(p_{T}\) distribution
Especial thanks to Max for being such a nice supervisor!