Stephen Mrenna
Senior Scientist at Fermilab
Batavia, Illinois, United States
Summary
👤
Senior🎓
Top SchoolStephen Mrenna is a Senior Scientist with over 25 years of experience in particle physics and scientific software, currently based at Fermilab where he has led research on the CMS experiment at the LHC. He co-authored components of the widely used Pythia event generator and continues to contribute backend code to the CMS offline software, adding features like a Py8MassGun for specialized resonance decays. Trained with a PhD in Physics from Johns Hopkins, he blends deep theory and phenomenology with hands-on simulation and software engineering expertise. His career spans national labs and academia, producing both foundational physics tools and practical code used in large-scale experiments. Colleagues know him for solving “interesting problems” that require bridging complex physics models with robust, testable software implementations.
12 years of coding experience
19 years of employment as a software developer
Johns Hopkins UniversityBachelor of Science (B.S.), Physics, Bachelor of Science (B.S.), Physics at University of Notre Dame
Github Skills (5)
c-language10
high-energy-physics10
cprogramming-language10
cplus9
cpp9
Programming languages (4)
Github contributions (5)
cms-sw/cmssw
Feb 2014 - Jun 2021
CMS Offline Software
Role in this project:
Back-end Developer
Back-end DeveloperContributions:24 commits, 15 PRs, 67 comments in 7 years 4 months
Contributions summary:Stephen contributed to the CMS Offline Software by implementing and modifying components related to the Pythia8 event generator. The user added a new Py8MassGun class for generating specific particle decays and added a feature to allow for generic resonance decays. Further commits involved code formatting and refactoring within the Pythia8 interface. The user also made changes to the test configuration files.
cmscernweb-appc-plus-plusbackbonejs
smrenna/pythia8
Oct 2015 - Jun 2020
pythia8
Contributions:9 pushes, 7 branches in 4 years 8 months
python
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