R. Cady

Dethinning extensive air shower simulations

We describe a method for restoring information lost during statistical thinning in extensive air shower simulations. By converting weighted particles from thinned simulations to swarms of particles with similar characteristics, we obtain a result that is essentially identical to the thinned shower, and which is very similar to non-thinned simulations of showers. We call this method dethinning. Using non-thinned showers on a large scale is impossible because of unrealistic CPU time requirements, but with thinned showers that have been dethinned, it is possible to carry out large-scale simulation studies of the detector response for ultra-high energy cosmic ray surface arrays. The dethinning method is described in detail and comparisons are presented with parent thinned showers and with non-thinned showers.

Measurement of ultra-high energy cosmic rays by telescope array (ta)

The Telescope Array (TA) is a large scale ground experiment in Utah, USA for the measurement of extensive air showers from the ultra-high energy cosmic rays. Its construction is completed in March, 2008 and the data taking started.

Using CORSIKA to quantify Telescope Array surface detector response

Historically, studies of surface detector response have been severely limited by the inability to simulate charge density fluctuations at the distance scale of individual detector units. We present a twoprong solution. First, we have developed an interface script that allows us to simulate a cosmic ray shower, using CORSIKA, that runs in parallel on many computers simultaneously. In doing this no changes have been made to the CORSIKA program. In this ”parallel mode” a very large number of computers can be used. This has allowed us to simulate 100 non-thinned CORSIKA showers in energy decade centered at 10 eV. Second, we have developed an algorithm (called ”dethinning”) that enables us to reconstruct the information lost using the CORSIKA thinning option. The input to this algorithm is the list of weighted particles produced by CORSIKA, run with thinning, and the output is individual particles distributed in space and time as if no thinning had been used in the CORSIKA generation. We validate the algorithm by comparison with the non-thinned parallel showers mentioned above. We can then convolve a library of dethinned CORSIKA events with the Telescope Array (TA) surface detector response and simulate the surface detector’s data. We will present estimates of the aperture and resolution of the TA surface detector array.