since scientists working on Qweak performed a limited measurement back in 2013, Greg Smith from Jefferson Lab told Gizmodo. But that was essentially a preliminary run with 4 percent of the data. This new paper is the whole shebang.
So, what use is the weak charge? It’s an important test of fundamental physics.
The current state of particle physics is sort of like a partially explored cave with a shadowy regions. We think we understand the structure of the cave, but there could be entirely new chambers hiding in the shadows. After all, calculations suggest that the Standard Model of only describes 4 percent of all of the universe’s mass and energy, with mysterious dark matter and dark energy taking up the rest. That means the cave system could be far larger than physicists think. These experiments offer fundamental measurements to compare against theoretical predictions. If things are different, that could shine light on a new part of the cave.
This new measurement was basically what predictions said it should be. “It is very consistent with the theory,” said Maxim Perelstein, a Cornell theoretical physicist who was not involved with the study. “The more measurements we have that are precise and agree, the better constraints we can put on theories extending the Standard Model.”
It’s like you’re exploring the cave and you find a wall where you thought there might be a tunnel. For example, “for a very popular type of dark matter model, there is a ‘dark photon’ that can mediate the interaction between the dark matter and Standard Model particles,” Mu-Chun Chen, professor of physics and astronomy at the University of California, Irvine, told Gizmodo. “From Qweak, one can place a limit on the mass of the dark photon.”
These results also offered the physicists another chance to measure the “weak mixing angle.” At high enough energies, the weak force and electromagnetism merge into a combined “electroweak” force. The weak mixing angle is an important number that relates these two forces once they separate, and Qweak offered some of the most precise measurements of this value yet.
