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Experiment Research

E04-101: Measurement of the Parity-Violating Asymmetry in the N to Delta Transition

Nuclear physicists in the G-Zero collaboration are studying how particles called strange quarks contribute to the proton's properties. G-Zero is a multi-year experimental program designed to measure this using the weak force.

Strange quarks typically aren't permanent residents of the proton; however, they may visit the proton on occasion by popping into and out of existence in the "quark-gluon sea" � a seething mass of particles created out of energy from the strong force. What G-Zero scientists want to know is if and to what extent these ephemeral strange quarks contribute to the structure of proton.

One way to see these strange quarks is to measure them through the weak force. Electrons from JLab's CEBAF accelerator are sent into an experimental target, where some of these electrons will collide, or "interact," with the nuclei in the target. The electrons may interact with the nuclei either through the electromagnetic force or the weak force. G-Zero aims to take snapshots of the nucleus by measuring particles from each of these interactions and comparing them.

The data gathered for the G-Zero experiment will also be used to measure nucleons as they gain energy and become an "excited state" known as the Delta particle.

E04-101 Technical Paper (.pdf)