A Study Of Missing Transverse Energy In Minimum Bias Events With In Time Pile Up At The Large Hadron Collider Using The Atlas Detector And Center Of Mass Energy

A Study of Missing Transverse Energy in Minimum Bias Events with In-time Pile-up at The Large Hadron Collider Using The ATLAS Detector and Center of Mass Energy

A Study of Missing Transverse Energy in Minimum Bias Events with In-time Pile-up at the Large Hadron Collider Using the ATLAS Detector and S

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 (ox, 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.

Search for Diphoton Events with Missing Transverse Energy with the ATLAS Detector at the LHC