12.07.2015 Views

Mohamad-Ziad Charif - Antares

Mohamad-Ziad Charif - Antares

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Chapter 4Monte-Carlo & DataIn this chapter the data acquisition is discussed followed by how each event isreconstructed. And then how the background is simulated.4.1 Data acquisitionThe acquisition of data[94] is divided into frames, each frame is 104 ms long.After the data are collected from the detector they are then sent to an offshorecomputing center (located in Toulon, France) where each frame is sent to a dedicatedprocessor to minimize the congestion. However, not all frames are sent butonly when the L0 hardware trigger has been triggered. L0 trigger in reality representsa threshold of 0.3 photo-electron (p.e) of a hit on the PMT, below this valuethe electrical noise of the PMT dominates the signal. If L0 is triggered then onthe offshore station a series of trigger algorithms (will be explained in 4.1.2) areapplied to the frame and if any eventis found then the frame is saved on a run file.The process continues until the size of this file reaches a size of 2 GB. Dependingon how many trigger algorithms are applied, a single run file can contain from 1hour and up to 3 hours of data.4.1.1 Optical backgroundWhile the depth of ANTARES ensures that no light coming from the Sun reachesthe detector the sea bed is not in total obscurity[95]. As previously mentionedthe decay of 40 K[96] can produce photons (eq 4.1 and 4.2) which can be detectedby ANTARES OMs. In the case of eq 4.1 the produced electron can be energeticenough to produce a Cherenkov effect in water. The average decay rate of 40 Kis stable over time and produce a constant rate of hit on the OMs of the order of65

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