Salem Ritenour with Corbin Covault (project started January 2006)
Cosmic Ray Showers: Detectors, Simulation, and Reconstruction
The arrival of cosmic rays into earth’s atmosphere poses a variety of scientific conundrums. One can examine these problems by devising methods of deducing the Entergy, arrival direction, and composition of the rays. Our approach will be to examine the effects of particle interaction during cosmic ray showers. Such rays might penetrate an atom through the electron region causing minimal deflection. In the event that the ray strikes a nucleus, it will become deflected and energy will be released due to the collision, causing the genesis of secondary particles. One expects this procedure to repeat numerous times before the shower reaches the ground. Furthermore, the angle of incidence of the particles with respect to the ground introduces measurement uncertainties via the variance in the dispersion of the front of particles. This angle can, in principle, lead one to a particular region of space to which the rays originated, provided that a significant portion of the rays were not severely deflected before entering the atmosphere, most likely due to the presence of a magnetic field.
Although still under construction, the Pierre Auger project is capable of acquiring data via detectors comprising photomultiplier tubes housed in water tanks on the plains of Argentina. Moving near the speed of light in air, the secondary particles will exceed the local speed of light in water upon entering the tank due to the difference in indices of refraction between air and water. A flash of light will result, which the detectors will record. If a significant number of detectors report a flash within a few nanoseconds, it can be deduced with fair certainty that a cosmic ray shower occurred. Through examining the differences in timing and pulse-height data from each individual detector, one can infer the arrival direction of the shower.
An important step toward building such detectors is the testing of the Tank Power Control Board, which is capable of evenly distributing power gathered from solar cells throughout the day and night. The High Energy Astrophysics group at Case Western Reserve University is undertaking the testing of such boards for the entire Auger Project. We will further examine the technical specifications of the boards in hope of specifying more precise error bounds for their operating properties. Detailed tolerance testing and analysis will assist in discerning to what extent variations in the specifications would have upon reconstructed quantities such as energy and arrival direction.
In the event that the examination of the power control boards is completed in due time, we will extend the research to consider other uncertainties in timing determinations at individual detector stations. This might include errors in data relay such as GPS timing drifts, miscalculated timing offsets, spurious or missed triggers, and/or event mismerging. For each of these examples, we will develop numerical simulations and compare them to actual data in order to minimize the impact of these errors on uncertainties in arrival directions.