My proposal was to develop a new event generator for high energy physics. An event generator is a program that uses the underlying theory of particle physics, called the Standard Model, to simulate results that are observed at particle colliders. One such collider is the Large Hadron Collider, currently operational at the CERN, the European Laboratory for Particle Physics. While several programs had been available that achieve such simulations in general, they were all limited in their accuracy.

The goal of my project was to use a theoretical technique (called soft-collinear effective theory) that I had developed in the past to increase the precision of such simulations.

The Early Career Award allowed me to pursue this ambitious project by hiring several young researchers to help develop the required theoretical technologies and write the very large software package required for this project. Over five years, we developed the theory and the simulation code required.

The resulting simulation package, called GENEVA (for GENerate EVents Analytically), implemented, for the first time, higher-order precision in a so-called logarithmic expansion and combined it with the most precise fixed-order calculations available to date. This makes GENEVA one of the most precise event generators available for certain observables.

Since the award ended in 2015, we have been working with experimental collaborations to make our simulation code accessible to their computing frameworks. It has been used in several experimental analyses. The project is still ongoing, and our collaboration is continuously expanding the processes that can be precisely simulated using GENEVA.


Christian W. Bauer is a senior staff scientist in the Theory Group of the Physics Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory.


The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.

For more information, please go to the Early Career Research Program.


GENEVA: An NLO Event Generator for the Large Hadron Collider

The objective of this project is to develop software tools that are crucial for physics discoveries in hadron collider experiments, e.g., LHC, that probe the fundamental properties of nature at the energy frontier. The project will improve on existing tools by implementing and incorporating the most accurate available theoretical calculations and predictions to simulate events that can be expected from the known Standard Model of particle physics.

One can then search for new physics by comparing data with the expected events. Without such tools, many signals of new physics (e.g., new particles, new fundamental forces, etc.) may not be revealed from the huge amount of data generated from these experiments.


S. Alioli, C.W. Bauer, C.J. Berggren, A. Hornig, F.J. Tackmann, C.K. Vermilion, J.R. Walsh, and S. Zuberi, “Combining higher-order resummation with multiple NLO calculations and parton showers in GENEVA.” J. High Energ. Phys.120 (2013). [DOI: 10.1007/JHEP09(2013)120]

S. Alioli, C.W. Bauer, C. Berggren, F.J. Tackmann, J.R. Walsh, and S. Zuberi, “Matching fully differential NNLO calculations and parton showers,” J. High Energ. Phys., 089 (2014). [DOI: 10.1007/JHEP06(2014)089]

S. Alioli, C.W. Bauer, C. Berggren, F.J. Tackmann, and J.R. Walsh, “Drell-Yan production at NNLL′+ NNLO matched to parton showers.” Phys. Rev. D 9, 094020 (2015). [DOI: 10.1103/PhysRevD.92.094020]