A sample of $ L dt = 3.67 pb{-1} of minimum bias events observed using the ATLAS detector at the Large Hadron Collider at $\s=7 TeV is analyzed for Missing Transverse Energy (MET) response in the presence of in-time pile-up. We find that the MET resolution ($\sigma_\text{X,Y}$) is consistent with a simple model of the detector response for minimum bias events, scaling with respect to the sum of the scalar energy ($\sum E_\text{T}$) as $\sigma_\text{X,Y}=A\sqrt{\sum E_\text{T} }$. This behavior is observed in the presence of in-time pile-up and does not vary with global calibration schemes. We find a bias in the mean ($\mu_\text{X,Y}$) of the MET that is linear with respect to $\sum E_\text{T}$, leading to an asymmetry in the $\phi_\text{X,Y}$ distribution of the MET. We propose an explanation for this problem in terms of a misalignment of the nominal center of the ATLAS detector with respect to its real center. We contrast the data with a Monte Carlo sample produced using PYTHIA. We find that the resolution, bias and asymmetry are all approximately reproduced in simulation. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3437 |
| Date | 03 August 2011 |
| Creators | Wang, Kuhan |
| Contributors | Keeler, Richard K. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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