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While the background for this signature is expected to be low, there are a number of caveats in detecting mesoscopic quirk pairs in the ATLAS detector in addition to theoretical uncertainties in quirk pair dynamics. In particularFirst, a quirk pair must be produced in association with a photon or jet or the tightly bound pair will be lost down the beampipe undetected. So, we must require a recoiling jet in the event, which also provides a missing energy trigger since the quirk pair will not generally be reconstructed by the trigger. Second, the quirks move slowly enough that the hits they make in the detector can be out-of-time with respect to particles traveling at the speed of light, a problem that is obviously less severe in the inner layers of the detector. So, the reconstruction technique focuses on the elements of the inner detector: the pixels, SCT and TRT tracking detectors. Meanwhile, the most critical inner layers of the detector, the ATLAS pixels, have limited dynamic range for large dE/dx, so hits from very slow moving quirks can simply be lost.
In order to fully understand and overcome these challenges In both cases, a full Geant4 simulation of quirks will be required to assess the signal sensitivity as a function of quirk masses and confinement scales and to develop signal-free samples of data that are needed to model the expected background for the searchbackgrounds.
Status
Because understanding the nature of the signal is critical defining both the search strategy and the required background samples, the top priority has been the development of a robust simulation of quirk dynamics that is as complete as possible. Towards this end, we have developed a standalone Monte Carlo simulation of quirk dynamics to better understand define the ATLAS-specific signature for and sensitivity to mesoscopic quirks. Initial results of this work indicate that we will double to mass reach of a previous search at the Tevatron with 1 fb-1 of collected data. However, a full Geant-based simulation is required to develop specific cuts for signal selection and allow the development of an unbiased background sample.
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