Benjamin Nachman

Postdoc, Lawrence Berkeley National Laboratory
Research Fellow
Dates of Visit: Jan. 9May 31, 2018

Benjamin Nachman's primary interest is in the fundamental properties and applications of high energy jet fragmentation. Quarks and gluons are the fundamental building blocks of matter responsible for most of the visible energy density in the universe. However, we cannot observe them directly, due to the confining nature of the strong force. Particle colliders try to probe the highest energy reactions involving quarks and gluons happening at the smallest distance scales ever studied in a terrestrial laboratory. The observable consequence of quarks and gluon production in these reactions are jets: collimated streams of particles traveling at nearly the speed of light. There is a wealth of information encoded in the distribution of energy inside jets. The use of this jet substructure information for tagging the origin of jets in order to search for new particles has gained significant attention since the startup of the Large Hadron Collider (LHC). This has exposed fundamental questions about the theoretical and experimental limits of jet substructure. Experimentally, one of the most important challenges is the reconstruction of charged particle trajectories (tracks) inside jets. Charged particles are measured with much finer precision than neutral particles and thus are critical for resolving the structure of jets. Nachman's research program targets track reconstruction inside jets from many levels. One of the most exciting aspects of this work is the designing of a readout chip for the upgraded ATLAS pixel detector at the LHC. Over the next years, we must design a chip that must cope with extreme rates (GHz/cm^2), data volumes (Gbps/cm^2), and radiation damage (GRad). The readout from the pixel detector is the input to charged particle tracking, and therefore the design choices we make will have a significant implication on physics analysis in the future.

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