Air Shower Simulations for ANITA K. Belov UCLA

Goals Approach Estimate the energy of the UHECRs detected by ANITA using MC simulations Use well known (does not guarantee that they are correct) simulations tools Avoid using any parameterization for the air shower EM field

Tools used CORSIKA 6900/6960 COAST plug in for CORSIKA to provide the input for REAS simulation code REAS v2.59 New MC code for ANITA

CORSIKA simulations Showers are generated in flat in exponent spectrum from to eV. 10 energy bins/decade. Zenith angles from 25 to 89 degrees, 1 degree step 10 showers / energy and degree bin ~ 3000 showers thinning used ~ 3-4 weeks of computing time on Saxon cluster

REAS2 Modified REAS2.59 About 3 weeks of CPU time on Saxon cluster / energy decade. Each shower is split to allow no more than several hours CPU time / job. The trade off – huge number of files is generated.

REAS2 e-field REAS2 e-field spectrum for several angles off the shower axis deg off angle MHz microV/m/MHz

Other custom scripts used Modified reasplot to produce filtered version of REAS2 output Results in about 300K files / energy bin including condor scripts, outputs and logs. makeReasRootFile to process filtered REAS2 output into a single.root file Several parameters like energy, zenith angle, x max are stored for each shower. E-field (in microVolts/m/MHz) on the ground is stored as a Graph2D root object as a function of frequency and the angle off the shower axis (OffAngle), calculated individually for each shower. No parameterization is used. E-field spectra for several off angles for each shower is stored. Built in ROOT Graph2D interpolator can be used to obtain e-field at arbitrary frequency and off angle. ~ 10 hours script process time and < 10 MB final root file. Latest version of the REAS2 data file for ANITA is anita_reas_new9.root.

A new (yet another one) ANITA MC Fast MC code: 5x10 6 events / hour / CPU core Uses anita_reas root file for e-field input Payload is at fixed 37 km above the ice CR showers are thrown uniformly on the surface up to the horizon, flat in Phi (Azimuth angle) and flat in cos(theta). Flat in exponent spectrum For each CR event, the angle off the antenna axis, reflection off the ice and the distance to payload is calculated.

Antenna response and trigger Antenna is assumed to have uniform response in azimuth and gauss response in zenith (vertical direction)

Trigger The global trigger is used with acceptance curve from the ANITA- I paper also optimistically cut at 2.3 sigma SNR since we do not see events with SNR < ~ 3 sigma

Data-MC. V/m passed.

Data-MC. Distance to payload Deficit of distant events? Roughness might help to reach better agreement Red – Stephen’s data Black - MC

Data-MC. Zenith angle passed. Reconstructed zenith angle for the CR showers that pass the trigger. Red – Stephen’s data Black - MC

Off angle passed. Angle off the shower axis for events that pass the trigger REAS2 angular dependence looks too narrow.

Detector trigger efficiency See events at lower energies – Probably due to using oversimplified trigger. Red – Auger aperture

ANITA events expected Events / ANITA lifetime (17 days) Auger flux is extrapolated at lower and higher end.

To do To put the last nail into the REAS2 coffin: - Put real ANITA trigger - Add roughness to my reflection loss (~10% effect?) REAS3 is coming ?

Additional slides

Triggers at assa_1e17_condor.out:TRIGGER 0 vm assa_1e17_condor.out:TRIGGER 1 vm assa_1e17_condor.out:TRIGGER 2 vm assa_1e17_condor.out:TRIGGER 3 vm assa_1e17_condor.out:TRIGGER 4 vm assa_1e17_condor.out:TRIGGER 5 vm assa_1e17_condor.out:TRIGGER 6 vm assa_1e17_condor.out:TRIGGER 7 vm assa_1e17_condor.out:TRIGGER 8 vm assa_1e17_condor.out:TRIGGER 9 vm assa_1e17_condor.out:TRIGGER 10 vm assa_2e17_condor.out:TRIGGER 0 vm assa_2e17_condor.out:TRIGGER 1 vm assa_2e17_condor.out:TRIGGER 2 vm assa_2e17_condor.out:TRIGGER 3 vm assa_2e17_condor.out:TRIGGER 4 vm assa_2e17_condor.out:TRIGGER 5 vm assa_2e17_condor.out:TRIGGER 6 vm assa_3e17_condor.out:TRIGGER 0 vm assa_3e17_condor.out:TRIGGER 1 vm assa_3e17_condor.out:TRIGGER 2 vm assa_3e17_condor.out:TRIGGER 3 vm assa_3e17_condor.out:TRIGGER 4 vm assa_3e17_condor.out:TRIGGER 5 vm assa_3e17_condor.out:TRIGGER 6 vm assa_3e17_condor.out:TRIGGER 7 vm assa_3e17_condor.out:TRIGGER 8 vm assa_3e17_condor.out:TRIGGER 9 vm assa_3e17_condor.out:TRIGGER 10 vm assa_3e17_condor.out:TRIGGER 11 vm V noise RMS = 1.3 x V

Thrown spectrum

Thrown Zenith and azimuth angle of CR showers X-axis in degrees Direction theta from normal to the horizontal at the shower core location

Shower core location X- axis in degrees Latitude and longitude angles in payload coordinate system

Off angle thrown Angle in degrees between the shower axis “reflected” off the snow at the shower core and direction to the payload off the shower core