Presentation on theme: "Anita Simulation on the Mainland Amy Connolly April 9 th, 2005."— Presentation transcript:
Anita Simulation on the Mainland Amy Connolly April 9 th, 2005
Review of how our simulation works Pick balloon position Pick interaction point in ice within horizon Trace ray to balloon Pick neutrino direction at random, throw away events that can’t pass (if too far off Cerenkov Cone) All events given a weight that accounts for ‘s attenuation in Earth Volume of ice in horizon Bias in selection of direction Model Antenna response for ray’s hit angle Signal summed over frequency bins Model trigger including bandwidth slices and treatment of polarizations
Documentation on the elog (#17) Comments on that doc led to many improvements Signal modeling, trigger sim., n(z) function, some bugs Other new features since last meeting Geoid earth shape Secondary interactions Capability for reflected rays (Fenfang) Actual Anita-lite flight(shown Thursday,approx. -20% @ 10 19 ) Polarization vector rotated properly (few %) Use measured antenna gains instead of specs (-10%) Various bug fixes resulting from a few more sets of eyes looking at the code (largest- fresnel coeff. error factor of 10) Keeping log file (kept on CVS) listing each modification and the resulting % change at 10 19.5 eV for SM Since our last collaboration meeting…
Rays reflected from Rock-Ice Interface Due to uncertainties in reflection from rock (Steve will discuss this), not a default setting. But the capability is there with the flip of a switch. Fenfang added the capability of accounting for rays that are emitted downward and are detected after being reflected from ice-rock interface. Largest impact at high cross sections. Could open up large region of the sky!
Secondary Interactions Use Ped’s distributions generated from MMC for multiplicity, energy for each flavor, interaction type For a given neutrino: Pick # of interactions of each type from Poisson distribution For each interaction, grab energy (as fraction of neutrino energy) from Ped’s plots Keep only the interaction (primary or secondary) which contributes the strongest signal At 10 19.5, Sensitivity to increases by 50% Sensitivity to increases by nearly factor of 2
Direct Comparisons Between Simulations Have Begun Ice altitudegiven3.0 km3 km Ice surfacederived6359.755 km6360.9 km Payload height above icegiven37.0 km37-3=34 km Shower depthgiven500.0 m500 m Index of refraction, icegiven1.791.79 Cherenkov anglederived56.0456.04 deg Nadir angle to event surface exit pointchosen8080 deg Boresight ice intersection range derived237.94234 km Required angle of inc., ice-firn boundaryderived 33.6133.64 deg Refracted zenith anglederived82.11 82.64 deg
Comparisons Between Simulations (cont) Neutrino energyassumed 1.E191.E19eV yassumed1.001.00 Reference Energygiven1.E121.E12eV reference frequencygiven1.15E91.15E9Hz Boundaries of frequency bandsgiven same Peak field strength at 1m, band 1derived67.666.3 V/m Peak field strength at 1m, band 2derived122.8122.5 V/m Peak field strength at 1m, band 3derived248.3247.3 V/m Peak field strength at 1m, band 4derived444.6442.6 V/m Shower rays slant range to surfacederived600.3606.2 m Attenuation factor, band 1derived0.6930.636 Attenuation factor, band 2derived0.667(indep. of Attenuation factor, band 3derived0.619freq.) Attenuation factor, band 4derived0.513
Comparisons Between Simulations (cont) Refractive index of firn at surfacegiven1.3251.325 Angle of incidence below firn surfacederived48.39348.5 deg Firn transmission coefficientderived1.301.30 deg Modified surface trans. coeff. derived0.3250.27 Modified surface trans. coeff.derived0.2700.22 Transmitted field strength, ref. to d=1m, ch1 derived19.808 13.97 V/m Transmitted field strength, ref. to d=1m, ch2derived34.584 25.80 V/m Transmitted field strength, ref. to d=1m, ch3derived64.886 52.1 V/m Transmitted field strength, ref. to d=1m, ch4derived96.385 93.27 V/m
[V ] eff for Full ANITA Discrepancy either factor of ~30 in sensitivity at low energies OR ~1/2 order of magnitude in threshold Agreement at high energies looks promising
Nailing Down Source of Difference between MC’s a high priority Since we have shown close agreement for a given event, discrepancy (if not due to bugs) must come from an input distribution or function, such as: Ice map – compare effective ice depth, volume y Modeling Askaryan pulse Crust density profile Trigger simulation Antenna response Secondaries Comparing plots with Stephen’s may provide clues
Conclusions Simulation is benefiting from more people running the code, stretching it different ways More features being added Bugs being flushed out Given that we agree for a given event, I think discrepancy between two simulations most likely to be identified if we concentrate on input distributions/functions
Secondary Interactions Thanks to Fenfang for getting these numbers with the latest code yesterday.
The Askaryan Signal: Electric Field Electric field emitted at interaction: For salt (from personal communication w/ J. Alvarez Muniz in Fall 2003) C=1.10£10 -7, 0 =1300 MHz, » 1.5 Compare to ice (J. Alvarez Muniz, astro- ph/0003315) C=2.53£10 -7, 0 =1150 MHz, =1.44
The Askaryan Signal: Cone Width Width of Cerenkov cone (astro-ph/9706064, astro-ph/0003315, Phys.Lett.B434,396 (1998)): Material dependence Index of refraction Shower length
The Signal: Cone Width (cont) Phys.Lett.B434, 396(1998): Beyond parameterization ( >7), scaling by 7.5% per decade. Need theorists to come up with concise instructions for simulating the Askaryan signal, complete for all relevant media