Ian Ross Rose-Hulman Institute of Technology Mentor: Dr. Richard Teuscher University of Toronto ATLAS Group ATLAS Calorimeter: Cosmic Ray Commissioning

Overview Analysis of cosmic ray events provides valuable information about the status of detector modules and triggering mechanisms Identify and tag malfunctioning cells Ensure proper calibration and function of reconstruction software Primary focus is on the tile and liquid argon calorimeters

Analysis Process Data is stored in raw format, then converted to more amiable ntuple (through Athena) ntuple is examined for interesting events and malfunctioning cells (through Root) Events are reconstructed for further examination (through Atlantis, other event viewers)

Identifying Malfunctioning Cells A cell’s position (defined by the coordinates eta and phi) are plotted, along with the number of events for which the cell exceeds a designated energy. Cells that often report high (or low) energy content are often malfunctioning. These cells are checked against a database of known problem cells and reported if necessary.

Picking out Interesting Cosmic Events Malfunctioning cells are removed, and outlying energies typically indicate cosmic events Number of cosmic events were observed during this run Mostly brem hits, but also fireworks (cosmic air showers)

Hard Brem (Event 776 from Run 11000) Bad cell Bremsstrahlung hit Liquid Argon pulse Tile Calorimeter pulse Cosmic ray strikes detector and slows down, radiating energy as it does so

Fireworks (Event 3481 from Run 11000) Air shower event Cosmic ray collides with air particle, causing a cascade of energetic particles to shower over the detector Much rarer than Brem hits.

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