The discovery of the Higgs boson in 2012 was a significant achievement in the world of particle physics, filling in a crucial piece of the puzzle known as the Standard Model. However, despite this milestone, there are still unanswered questions lingering in the scientific community. What lies beyond the boundaries of the Standard Model? Where can we find the answers to the enigmas surrounding dark matter and the asymmetry between matter and antimatter in the universe?
One parameter that has the potential to shed light on new physics phenomena is the “width” of the W boson, the carrier of the weak force. The width of a particle is a direct reflection of its lifetime and how it decays into other particles. By observing how the W boson decays, scientists can gain insight into any unexpected pathways it may take, including decaying into previously undiscovered particles. Any deviations from the predicted values based on the Standard Model could be indicative of undiscovered phenomena.
A recent study published on the arXiv preprint server by the ATLAS collaboration has provided new insights into the width of the W boson. Previous measurements at CERN’s LEP collider and Fermilab’s Tevatron collider had yielded an average value of 2085 ± 42 MeV, in line with the Standard Model prediction of 2088 ± 1 MeV. However, using data from proton-proton collisions at the LHC, the ATLAS experiment measured the W-boson width to be 2202 ± 47 MeV. While slightly higher, this measurement still falls within 2.5 standard deviations of the Standard Model prediction.
To achieve this level of precision, the ATLAS physicists conducted a detailed analysis of the decays of the W boson into different particles, including electrons, muons, and neutrinos. By meticulously calibrating the detector’s response to these particles and accounting for background processes, they were able to improve the accuracy of the width measurement. Furthermore, the study relied on a combination of theoretical predictions and experimental validations to enhance the understanding of W-boson production and the inner structure of the proton.
The updated measurements of the W-boson mass and width by the ATLAS collaboration are consistent with the predictions of the Standard Model. As researchers continue to gather more data and refine their techniques, the precision of these measurements is expected to increase further. With advancements in theoretical predictions and a deeper understanding of parton distribution functions, physicists hope to reduce both the statistical and experimental uncertainties in future studies. This progress will enable scientists to conduct more rigorous tests of the Standard Model and potentially uncover new particles and forces that lie beyond our current understanding of the universe.