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UH ANITA monte carlo Peter Gorham University of Hawaii

A N I T A. UH ANITA monte carlo Peter Gorham University of Hawaii. UH ANITA MC. Three independent sections: 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)

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UH ANITA monte carlo Peter Gorham University of Hawaii

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  1. A N I T A UH ANITA monte carloPeter GorhamUniversity of Hawaii

  2. UH ANITA MC • Three independent sections: • 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 • 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

  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

  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

  5. Depth distributions • Depth distributions consistent at 3e18 & 1e20 3e18 eV

  6. Depth vs. distance • UH/UCLA depth vs. distance consistent at 1e20 (3e18 not available) 3e18 eV

  7. Flavor distributions • Possible disagreement: more nu_es at low energy in UCLA MC

  8. Dip angle distributions • Not enough statistics yet (UH) to tell, but peaks seems consistent

  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

  10. Details of angular dist. • Seem to agree pretty well in shape & maximum (but only since last 5 days)

  11. Effective volume & limits • Using UH ANITA-lite (left), UCLA (center) • UH Veff*Omega for ANITAlite & ANITA (right)

  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

  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

  14. Summary

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