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String 21 Flashers and AMANDA. Michelangelo D’Agostino UC Berkeley London Collaboration Meeting. Thanks. Dave Hardtke: for doing the first work on this Kurt: for being the ice guru John Pretz: for writing his wonderful, bugless merging module for the rest of us to use. IceTray. Outline.
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String 21 Flashers and AMANDA Michelangelo D’Agostino UC Berkeley London Collaboration Meeting
Thanks • Dave Hardtke: for doing the first work on this • Kurt: for being the ice guru • John Pretz: for writing his wonderful, bugless merging module for the rest of us to use IceTray
Outline • Are the String 21 flashers bright enough to be seen by AMANDA? • What do these events look like? • Can such flasher events be used for any calibration or ice property measurements?
closest AMANDA strings The Verdict: • Yes! • up to 60% of flashes trigger AMANDA • Roughly 40 to 50% of the AMANDA events were string- triggered
What do the events look like? DOM 23 flashing
What do the events look like? DOM 23 flashing
Stuck String What do the events look like? 16 10 9
What do the events look like? DOM 23 z position
DOM 32 DOM 12 DOM 23 Up and Down String 21
Analysis Details • in July, flasher runs were taken for all DOM’s on string 21 • 10 Hz, full brightness, all 12 LED’s • run monolith offline, requiring a simple multiplicity of 10 string 21 hits in a 5000 ns window
Analysis Details • use John’s Icetray merging module to look for AMANDA triggers with -20 s < t < -5 s of a String 21 trigger • filter out muons (about 1/4 of events): require that the flashing DOM be present in the event and that ATWD channel 3 has a digitized current pulse
what’s going on here? DOM 16 Up and Down String 21 Ryan’s dustlogger data for String 21 DOM 23
Ice Properties: Fluence Analysis • from Poissonian statistics, the average number of received photons in the diffusive regime is given by <N>=-log[P(0)], where P(0) is the probability that the receiver is not hit • 1/λ, where λ is the propagation length, is given by the slope of log[<N>d] vs. d, where d is distance from the light source
Ice Properties DOM 16 flashing 3 closest strings restrict z to +-5 m of the flashing DOM to probe a narrower ice layer corresponds to a λ of 45.3 m +-11.8 m photons all the way to ~400 m
maximum from previous graph dip from previous graph Ice Properties
Ice Properties • we have a biased sample though, since AMANDA had to be triggered to see the OM hits; the data is L1 filtered as well • P(0) is an overestimate <N> is an underestimate that varies with distance • thus, these are upper limits on the propagation lengths • flasher variability is more likely the culprit for the suspicious dip (cf. Chris Wendt’s talk); longer width runs are needed to tell
Conclusions • the flashers are pretty damn bright • ice properties have been measured over a greater horizontal distance and give reasonable agreement • since flashers should be seen in ~9 IceCube strings, such a method will be much more useful in the future for measuring local ice properties, especially with a unified trigger system
Conclusions • flasher coincidences might also be useful in AMANDA simulation—a simulation capable of reproducing the depth variation in this simple flasher system would surely have a better handle on systematics (COGz?)