Angular Correlation of Emitted Neutrons Due to Giant Dipole Resonance in Ultra Peripheral Collisions
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Authors
Kirchner, Kimberly
Issue Date
2008-05-29
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Thesis
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en_US
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Abstract
In an ultra peripheral collision with two gold ions, two virtual photons are exchanged, which excites the nuclei into a mutual giant dipole resonance (GDR) state. This excited state decays most often via neutron emission. The two emitted neutrons have an expected angular correlation based on the idea that the neutrons are emitted independently but with a common impact parameter. This thesis attempts to measure the expected angular correlation of emitted neutrons from mutual GDR excitation in ultrarelativistic gold-gold collisions at the Relativistic Heavy Ion Collider (RHIC). The Sodnialdal Tracker At RHIC (STAR) is the detector used to measure the angular correction. The neutrons emitted from mutual GDR excitation travel down the beamline and are detected in the Zero Degree Calorimeters (ZDC). In 2004 a Shower Max Detector (SMD) was installed in each of STAR’s ZDCs, which gives spatial information about the location of the neutron in the plane transverse to the beamline in each of the ZDCs. The Shower Max Detector consists of an array of vertical and horizontal slats which are used to locate where the neutron hit in the ZDC. Corrections needed to be made to the 2004 gold-gold ZDC SMD data for the pedestal and gain of the slats. To study the angular correlation specific selection criteria were applied to the data to ensure that there was only one neutron in each ZDC. This thesis will present the first experimental measurement of the predicted angular correlation between the two emitted neutrons at STAR.
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Creighton University
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Thesis-Kirchner.pdf