Data analysis, simulations, and reconstruction of antiproton annihilations in a silicon pixel detector
Appears in the following Collection
- Fysisk institutt 
AbstractThere are strong theoretical arguments in favor of the gravitational acceleration being identical for matter and antimatter, as anything else would violate the weak equivalence principle. The weak equivalence principle is the cornerstone of general relativity, and today there are no experiments contradicting it. However, it has never been experimentally verified that the gravitational acceleration of matter and antimatter is indeed identical. The AEgIS experiment at CERN aims at measuring the gravitational acceleration of antimatter to a precision of 1% by determining the fall of antihydrogen over the length of around 1 m. The proposed method will make use of a position sensitive detector to measure the annihilation point of antihydrogen. Such a detector must be able to tag an antihydrogen atom, measure its time of arrival, and reconstruct its annihilation point with high precision in the vertical direction. This thesis presents a detector response model for antiproton annihilations in a silicon detector equipped with the Timepix3 readout, in order to evaluate the possibility of using such a detector in the AEgIS experiment. Antiprotons from the Antiproton Decelerator at CERN were used to obtain data of direct annihilations on the surface of a Timepix3 detector. These data were used to develop and verify the detector response model. The work presented here includes all steps from data collection, simulation, and verification of the simulation. Clear tagging criteria for annihilation clusters were found, and a tagging efficiency of 50 ± 10%is achieved. By using the annihilation products to reconstruct the annihilation point a position resolution of 22 μm is achieved on a subset of the annihilation clusters. This thesis also includes a full simulation of the GRACE beam line that was build to improve the experimental conditions for testing detectors. The GRACE beamline can select out only the low energy antiprotons and direct them towards the detector. The simulation of the GRACE beamline evaluates the flux and energy of the antiprotons, and in most cases reproduced the energy distribution and flux within ± 30 %.
List of papers
|Paper I: A. Gligorova et al., "Comparison of Planar and 3D Silicon Pixel Sensors Used for Detection of Low Energy Antiprotons" in IEEE Transactions on Nuclear Science, vol. 61, no. 6, pp. 3747-3753, Dec. 2014. doi: 10.1109/TNS.2014.2368591. The paper is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1109/TNS.2014.2368591|
|Paper II: H. Holmestad, "Study of antiproton annihilation in silicon with a hybrid pixel detector using the TimePix3 readout," 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), San Diego, CA, 2015, pp. 1-3. doi: 10.1109/NSSMIC.2015.7581982. The paper is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1109/NSSMIC.2015.7581982|
|Paper III: S. Aghion et al., "Antiproton tagging and vertex fitting in a Timepix3 detector", 2018 JINST 13 P06004. doi: 10.1088/1748-0221/13/06/P06004. The article is included in the thesis. Also available at https://doi.org/10.1088/1748-0221/13/06/P06004|