Underground Muon Intensities for Henderson DUSEL
Jeffrey Wilkes Dept of Physics, U. of Washington
for
Kregg PhilpottINT, U. of Washington
Henderson DUSEL Capstone Workshop 2006May 6, 2006 - Stony Brook, NY
Work Performed in Collaboration with Wick Haxton, Institute for Nuclear Theory, UW
Muon flux estimation● Muons primarily produced in atmosphere, from
decay of mesons produced by Galactic cosmic ray interactions
● At the surface, muon rate dependent on zenith angle (path length through atmosphere)
● Rate underground = rate at surface, attenuated by overburden in muon arrival direction
Ocean experiments are simpler… ● ...unfortunately mountains are not flat, even in
physics approximations Must fold in topography, from geodetic survey
mapsImage from http://www.unine.ch
dl
l=d sec()
dl
l = f (x,y)
Method● Muon flux at surface has been studied for decades
Good semi-analytic model available (Gaisser 2002)● Digital Elevation Maps (DEMs) available at 10m resolution for most of the USA, and < 90m resolution for most of the world
● For now, using simple 50 by 50 (zenith x azimuth) bins* and compute distance from surface to detector for each bin
● Multiply by mean rock density to get slant depth for each bin
Use R=10km as horizontal limit
*Runs take 1 day on a garden-variety PC
Flat surface● Benchmark: flux vs depth, summed over all arrival angles for flat surface topography
Henderson 3D view
● South-Looking View
● Continental Divide ~5km to the west (right)
● Take lab to be directly under peak of Harrison Mountain
Henderson Topography
● Continental Divide* is just beginning to show up on left edge of map; summits along the Divide have major effects on muon flux contours that follow
* Continental Divide = boundary between Mississippi River and Pacific Ocean watersheds
8100’ level (2500 mwe nominal)
Upper Campus 1
● Calculated flux under Harrison Mt. of 4.6093e-8 cm-2 s-1
● Equivalent Calculated depth of 2.7635 kmwe(for points directly under summit of Harrison Mt.)
7700’ level (3300 mwe nominal)
Upper Campus 2
● Calculated flux under Harrison Mt. of 2.7682e-8 cm-2 s-1
● Equivalent Calculated depth of 3.0698 kmwe
6750’ level (4200 mwe nominal)
Central Campus
● Calculated flux under Harrison Mt. of 8.7806e-9 cm-2 s-1
● Equivalent Calculated depth of 3.8088 kmwe
BTW, for comparison: Brand X, 4850’ depth
● Falling terrain to the Northeast means lower backgrounds obtained to the Southwest
● Calculated muon flux of 4.5141e-9 cm-2 s-1
● Equivalent Calculated Depth : 4.2651 kmwe
4900’ level (6000 mwe nominal)
Lower Campus● Calculated flux under Harrison Mt. of 1.1001e-9 cm-2 s-1
● Equivalent Calculated depth of 5.2879 kmwe
Comparisons
Summary
● Toolkit developed for calculations of muon flux vs (x,y,z) allows preliminary estimates of background at DUSEL experiment locations
● Uniform expression of muon flux in terms of depth below a flat surface allows comparisons in terms of equivalent depth parameter...
● Further info: contact Kregg Philpott, [email protected]