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

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

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

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

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

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

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

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

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 m
photons all the way to ~400 m

15. Ice Properties

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

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?)