Anita Simulation on the Mainland

Amy Connolly

April 9th, 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 1019.5 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 1019.5 ,

Sensitivity to increases by 50%

Sensitivity to increases by nearly factor of 2

Direct Comparisons Between Simulations Have Begun

Ice altitude given 3.0 km 3 km

Ice surface derived 6359.755 km 6360.9 km

Payload height above ice given 37.0 km 37-3=34 km

Shower depth given 500.0 m 500 m

Index of refraction, ice given 1.79 1.79

Cherenkov angle derived 56.04 56.04 deg

Nadir angle to event surface exit point chosen 80 80 deg

Boresight ice intersection range derived 237.94 234 km

Required angle of inc., ice-firn boundary derived 33.61 33.64 deg

Refracted zenith angle derived 82.11 82.64 deg

Comparisons Between Simulations (cont)

Neutrino energy assumed 1.E19 1.E19 eVy assumed 1.00 1.00Reference Energy given 1.E12 1.E12 eVreference frequency given 1.15E9 1.15E9 Hz

Boundaries of frequency bands given samePeak field strength at 1m, band 1 derived 67.6 66.3 V/mPeak field strength at 1m, band 2 derived 122.8 122.5 V/mPeak field strength at 1m, band 3 derived 248.3 247.3 V/mPeak field strength at 1m, band 4 derived 444.6 442.6 V/m

Shower rays slant range to surface derived 600.3 606.2 mAttenuation factor, band 1 derived 0.693 0.636Attenuation factor, band 2 derived 0.667 (indep. ofAttenuation factor, band 3 derived 0.619 freq.)Attenuation factor, band 4 derived 0.513

Comparisons Between Simulations (cont)

Refractive index of firn at surface given 1.325 1.325Angle of incidence below firn surface derived 48.393 48.5 degFirn transmission coefficient derived 1.30 1.30 degModified surface trans. coeff. derived 0.325 0.27Modified surface trans. coeff. derived 0.270 0.22

Transmitted field strength, ref. to d=1m, ch1 derived 19.808 13.97 V/mTransmitted field strength, ref. to d=1m, ch2 derived 34.584 25.80 V/mTransmitted field strength, ref. to d=1m, ch3 derived 64.886 52.1 V/mTransmitted field strength, ref. to d=1m, ch4 derived 96.385 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

Backup Slides

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