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

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 ~ sky-patterns of field strength vs. angle integrated for 4 ANITA frequency bands

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 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

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

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

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

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

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

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

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)

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)

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

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

Tampa APS Meeting April 2004 P. Gorham 14 Summary