String 21 Flashers and AMANDA

1. String 21 Flashers and AMANDA Michelangelo D’Agostino UC Berkeley London Collaboration Meeting

2. 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

3. 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?

4. closest AMANDA strings The Verdict: • Yes! • up to 60% of flashes trigger AMANDA • Roughly 40 to 50% of the AMANDA events were string- triggered

5. What do the events look like? DOM 23 flashing

6. What do the events look like? DOM 23 flashing

7. Stuck String What do the events look like? 16 10 9

8. What do the events look like? DOM 23 z position

9. DOM 32 DOM 12 DOM 23 Up and Down String 21

10. 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

11. 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

12. what’s going on here? DOM 16 Up and Down String 21 Ryan’s dustlogger data for String 21 DOM 23

13. 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

14. 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

15. Ice Properties

16. maximum from previous graph dip from previous graph Ice Properties

17. 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

18. 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

19. 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?)