## Theses and Dissertations

#### Title

Search For Solar Axions

1-1-2011

#### Document Type

Campus Access Dissertation

#### Department

Physics and Astronomy

#### Sub-Department

Physics

Peccei and Quinn proposed an elegant solution for restoring CP symmetry to the QCD Lagrangian \cite{PhysRevD.16.1791}. This method includes an additional global U(1) symmetry included in the QCD Lagrangian which is spontaneously broken at a high energy scale, fa. Breaking the symmetry generates a Nambu-Goldstone boson called the axion. Although there are various detection mechanisms that search for the axion, this thesis focuses on the the axio-electric effect. The axio-electric is similar to the photo-electric effect in that an axion is absorbed by an atom which subsequently emits an electron. The electron's energy is equivalent to the incoming axion energy minus the binding energy. The higher shell electrons immediately replenish the missing binding energy yielding a single energy peak at the incoming axion's energy. The 14.4 keV M1 transition of 57Fe is one possible axion source. The development of an optimum trigger algorithm has lowered the threshold for analysis in TeO2 bolometers to a few keV making an axion signature accessible to CUORE related R&D experiments such as the Chinese Crystal Validation Runs (CCVR) and Three Towers Test (TTT). These TeO2 crystal detectors have masses 750 and 790 grams, respectively. Each crystal has a stabilization heater and a germanium thermometer attached to its surface by an epoxy glue. The two previous experiments are R&D tests for the upcoming larger experiment, CUORE. CUORE will be made of 988 TeO2 crystals arranged in 19 towers with 13 floors each, each floor with 4 detectors. This thesis examined 87.01 kg·days of Three Towers data for an axion signal. A peak is observed in the region of interest with a statistical significance less than 1σ over the expected background fluctuations, yielding a total background rate of 0.185 ± 0.001 (Stat.) ± 0.006 (Syst.) Counts/kg/day at 95% C.L. This places an experimental limit on the coupling constant fa of $fa (S = 0.50)≥1.16\times106 GeV at 95% C.L. Projecting the TTT result to the CUORE mass and a five year run time we can expect a limit of$fa(S = 0.50)≥2.21\times106 GeV at 95% C.L. Improvements in granularity can strengthen the bound on \$fa by 8% and 25% for background reductions by a factor of 2 and 10, respectively.