About YMEC

Search for emerging jets (CMS EXO-22-015)

The emerging jet signature search for jets where the constituents “emerge” some finite distance away from the hard scattering process. The efforts of searching for such signatures at CMS has been made public here, with this being my main graduate thesis. My own contributions to this work includes:

• Migration of the analysis code from the C++ based methods to the new array-based “coffea” framework.
• Re-evaluated the correctness of flavor inference and scale factor calculations required for background estimation. Because exotic signatures are prone to being sensitive to physics quantities that are not well modelled by simulation, the background estimation is nearly fully data driven.
• Handling the generation and validation of the new signal model. (The actual edits to the physics generator Pythia was done by Kevin).

HGCAL SiPM-on-Tileboard calibration test stand

Developing a test stand to allow for full SiPM dynamic range measurements for SiPMs mounted on large electronic tileboards. Results for this work in currently a paper in progress. My own contributions to this work includes:

• Design and assembly of the fast LED light source (sub-nanoseconds with non-specialized LED). The design was adapted from this paper.
• Design of supporting electronics for power/signal delivery and monitoring.
• Analysis code for extracting SiPM operation parameters from response function. First iteration was done in C++/RooFit, second iteration was done in zfit with support for GPU computation.
• Providing template for production calibration GUI, allowing for arbitrary code to be implemented by physicists without them needing to know external GUI software. First iteration was done with Python/ReactJS, second iteration was done with Python/Qt5, both aiming to as cross-platform as possible.

HGCAL SiPM-on-Tileboard light-yield simulation

Simulating the light-yield of the different scintillation tile optical and geometry parameters. The results of this study are documented as an internal CMS document. The source code for this project can be found here.

Search for excited top quark (CMS B2G-16-025)

The large mass of the top quark compared with all other standard model particles suggests that what we know as the top quark may not be a fundamental particle. This is a small team search effort to look for potential excited states of the top quark. My own contributions to the effort has been in the execution of the analysis code, as well as update all physics variables used for the search from the data collected in “LHC Run 1” (8TeV) to the LHC Run 2 (13TeV) standards. The final analysis result has been published, and the analysis source code can be found here.

bprime analysis kit development

The bprime analysis kit is a custom n-tuplizer for formatting CMS data into “easy-to-use” format. Aside from updating the physics variable calculation from Run 1 to Run 2 standards, as this work worked in parallel with the excited top quark analysis, I helped initialized the efforts to modularize of the code base for easier inclusion of alternate physic algorithms deployed in the LHC Run 2. Compare the commit before my first commit and my final commit.

I have worked with many flavors of numerical libraries to solve numerical computation required for physics analysis. Most of my work resolves around statistical methods, though I have worked with frequency analysis and time integral methods as well.

Some public example of my works regarding numerical methods

• C function pointer based libraries (using GSL):
  • A library used for quick-and-dirty methods of uncertainty propagation through numerical operations.
• C++/Python object-oriented libraries (such as CERN-ROOT)
  • A custom implementation of a PDF used to model SiPM responses
  • A more mixed repository of a full physics analysis.
• Array based libraries (such as numpy and awkward arrays):
  • Reimplementation of the SiPM response function using zfit+tensorflow for parallelized distribution fitting.
  • Mixed repository a full physics analysis (this repository requires a CERN account to access).