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Tampa APS Meeting April 2004 P. Gorham 1 UH ANITA monte carlo Peter Gorham University of Hawaii A N I T A

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Tampa APS Meeting April 2004 P. Gorham 2 UH ANITA MC Three independent sections: 1.anita_earthmodel.c: Use spherically symmetric shell-model of earth (PEM 2000, with ~12 layers incl core & crust) 1.5-3km ice layer (depending on neutrino energy) Interactions within ice accepted up to ~6 deg downgoing angle Gives weighted set of events vs. depth & zenith angle, w proper neutral/charged current ratios 2.anitamcE4.c: Take events from (1), generates flavor in 1:1:1 ratio (default) & determines effective y-factor, including largest 2ndary shower Both em & hadronic showers generated, along with ZHS angular distributions Ray-tracing done to determine angular distrubtion after refraction, Includes surface slope & roughness, frequency dependent attenuation Output is a library of ~1000-3000 sky-patterns of field strength vs. angle integrated for 4 ANITA frequency bands

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Tampa APS Meeting April 2004 P. Gorham 3 UH MC, cont. Two alternate detection & final MC integration programs in step 3: 3A. anitaVeffE4.c Reads in all 1000-3000 events from (2), applies antenna beam pattern, polarization, antenna absolute gain vs. frequency Received antenna voltage given additive thermal noise ANITA trigger applied to 1/2 array (1 side of antenna array) for all events at all possible azimuthal angles (over 2pi, not 4pi) at all radial locations out to horizon in a binned annular, uniform ice sheet below the payload. This is not “classic” MC integration, but a grid integral V*Omega=(Number of hits/Number of trials)*2*pi*V0 3B. anitaVeffE4R.c Same as (3A) but uses a “classic” MC integration, with random sampling of azimuthal angles and radial positions for events This avoids additional weighting calculations for uneven annular bins used in 3A These two methods agree to within 50%, constant with energy

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Tampa APS Meeting April 2004 P. Gorham 4 Events detected vs. distance Disagreement in peak of distribution at 1e20 eV –UCLA: 250km, UH: 350 km, no comparison yet at 3e18eV 3e18 eV

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Tampa APS Meeting April 2004 P. Gorham 5 Depth distributions Depth distributions consistent at 3e18 & 1e20 3e18 eV

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Tampa APS Meeting April 2004 P. Gorham 6 Depth vs. distance UH/UCLA depth vs. distance consistent at 1e20 (3e18 not available) 3e18 eV

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Tampa APS Meeting April 2004 P. Gorham 7 Flavor distributions Possible disagreement: more nu_es at low energy in UCLA MC

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Tampa APS Meeting April 2004 P. Gorham 8 Dip angle distributions Not enough statistics yet (UH) to tell, but peaks seems consistent

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Tampa APS Meeting April 2004 P. Gorham 9 Angular distributions UCLA (above) --calc. Separate from MC sequence? Check correspondence UH (right) from ray trace, but ray divergence not used (anymore) for effective Fresnel coefficient, needs further checking

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Tampa APS Meeting April 2004 P. Gorham 10 Details of angular dist. Seem to agree pretty well in shape & maximum (but only since last 5 days)

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Tampa APS Meeting April 2004 P. Gorham 11 Effective volume & limits Using UH ANITA-lite (left), UCLA (center) UH Veff*Omega for ANITAlite & ANITA (right)

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Tampa APS Meeting April 2004 P. Gorham 12 roughness Refraction gradient: very steep near TIR Any level of roughness will improve transmission near TIR- -very nonlinear UH MC: 1 degree rms increases Veff*Omega by factor of 2

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Tampa APS Meeting April 2004 P. Gorham 13 Effective volume vs. altitude One new study (just before I left): best Veff*Omega vs. payload altitude At 3e18: ~50-60Kft is better by about 55% (17/11) compared to balloon float Test runs indicate peak shifts lower at lower energies, higher at higher energies Surface Towers (<1km) prob. Not competitive compared to RICE-type array

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Tampa APS Meeting April 2004 P. Gorham 14 Summary

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