Douglas Bryman

Professor

Research Classification

Science and Knowledge

Research Interests

Experimental Particle Physics
Applied physics
physics

Relevant Degree Programs

 

Research Methodology

Experimental physics
CERN SPS
CERN NA62
TRIUMF PIENU
TRIUMF
CERN

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Master's students
Doctoral students
2019
2020

Particle physics experiments at CERN, Geneva.

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2019)
A high-precision measurement of the pion branching ratio (2017)

The pion decay branching ratio is an importantobservable in the Standard Model of particle physics. The value of thebranching ratio has been calculated within the Standard Model tobe (1.2352 ± 0.0002) ×10^−4. The PIENU experiment at TRIUMFaims to measure this quantity to a precision of
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Study of Pi plus → e plus Nu e decay (2012)

The pion branching ratio (R^π = [formula omitted] ) is an auspicious observable for a test of the standard model of particle physics (SM). Rπ has been calculated within this framework with high precision because the strong interaction dynamics cancel out in the ratio and the structure dependence only appears through electroweak corrections. Since the discovery of the electronic pion decay in 1958, Rπ was measured with increasing precision and confirmed the SM value of RπSM = 1.2352(2) x 10⁻⁴. However, the current experimental precision is 20 times worse than the theoretical one leaving a large window for potential new physics at “high-mass" scales (up to ∽1000 TeV).The PIENU experiment aims at measuring Rπ with an improved precision by a factor larger than 5 over the previous experiment at TRIUMF (Rπexp = (1.2265 ± 0:0056) x 10⁻⁴) in order to confront the theoretical prediction at the 0.1% level. The result presented in this thesis focuses on a fraction of the data taken since the beginning of physics data taking in 2009. A blind analysis has been implemented in order to avoid a human bias. With this set of data, the procedure is established for the final analysis. An improvement by a factor 1.17, dominated by statistical uncertainty, has been reached in the branching ratio precision. If added to the current Particle Data Group value, the result of this analysis reduces the uncertainty on the branching ratio by ∽25%.

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The Measurement of the Rare Decay K-plus to Pi-plus, Neutrino and Anti-neutrino (2009)

No abstract available.

Master's Student Supervision (2010 - 2018)
Studies for the PIENU experiment and on the direct radiative capture of muons in zirconium (2014)

The branching ratio of pions decaying to positrons and muons R = (π→eυ + π→eυγ)/(π→μυ + π→μυγ) has been calculated with very high precision in the Standard Model of particle physics. So far, the theoretical value of R = 1.2352(1) x 10-⁴ is 40 times more precise than the current experimental value of R = 1.230(4) x 10-⁴. To test this variable with respect to deviations from the Standard Model, the experimental precision needs to be improved, which is why the PIENU experiment aims at a precision of less than 10-³, i.e. an improvement of an order of magnitude over the current precision. At this level, mass scales ∼ TeV/c² can be probed for evidence of new pseudo-scalar interactions. The data collected with the experimental setup also allows for a search of sterile neutrinos. When determining the branching ratio, various systematic corrections are applied. The largest among these is due to electro-magnetic shower leakage out of the calorimeters and radiative decays. It was calculated to be (2.25 ± 0.06) % in this thesis.In the second part of the thesis, an experiment on the direct radiative capture of muons in zirconium is described. One theoretical extension to the Standard Model involves a new light and weaklyinteracting particle in the muon sector which does not conserve parity. This can be studied experimentally with polarized muons that undergo the direct radiative capture into the 2S state of a medium mass target nucleus. During this capture, longitudinal muon polarization is conserved and the muons instantly undergo the 2S-1S transitionemitting a second photon. Studying the angular distribution of this second photon indicates whether or not the process is parity violating, which would manifest physics beyond the Standard Model. The direct radiative capture of a muon into an atom in the 1S or 2S state has not been observed yet. Therefore, data was taken in 2012 to studythe radiative capture of muons in zirconium. The analysis method of this data set is described with a blind analysis technique.

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Electric field calculation and ionization signal simulation in liquid xenon detectors for PET (2012)

Electric field calculations and ionization signal simulations in a liquid xenon detector for Positron Emission Tomography have been performed. The electric field was calculated using Opera 3D, a Finite Element Method application software. The uniformity of the electric field inside of the detector was evaluated by calculating the deviation of drifting electrons under the applied electric field. The ionization signals of the detector have been simulated. The comparison between simulation results and measurement signals was made.

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Simulations of a high-resolution micro-PET system based on liquid xenon. (2011)

The capabilities and system performance of a high-resolution micro-PET system based on liquid xenon have been studied. Monte-Carlo simulations of scintillation events within a single sector of a twelve-sector prototype have been performed, and the results have been analyzed using Neural Network algorithms. The ability of the system to distinguish interaction points using scintillation information has been analyzed and presented. Monte-Carlo simulations of a full scale prototype have also been performed using NEMA standard mouse and rat phantoms. A novel scatter suppression scheme based on weighted Line of Response data is presented, and the effects on scatter fraction and background noise are analyzed.

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