Physicists from CERN measured the width of the W boson for the first time at the LHC

When physicists discovered the Higgs boson at the Large Hadron Collider (LHC) in 2012, they provided the missing particle in the Standard Model of particle physics. But there are still many phenomena beyond the Standard Model that might reveal the secrets of the Universe. For example, these phenomena can explain the nature of dark matter, as well as the existing asymmetry in the amount of ordinary matter and antimatter. One of the keys to unlocking these mysteries is the width of the W boson, the particle that carries the weak force, one of nature’s fundamental forces. Using the ATLAS detector at the LHC, physicists measured the width of this particle for the first time and also updated its mass. The results of the study were published on the arXiv preprint server, writes Phys.

The width of the W boson is directly related to the lifespan of the particle and describes how it decays into other particles. If the decay occurs in a way that was not expected, that is, previously unknown particles arise as a result, then this will affect the value of the width of the W boson.

The Standard Model of particle physics accurately predicts the width of the W boson based on the weak force and the particle’s mass. Therefore, any deviation from the predicted values ​​will be an indication that unknown phenomena exist.

Previously, the width of the W boson had already been measured at other particle accelerators, but for the first time physicists obtained its value using the ATLAS detector at the LHC. The Standard Model predicts that the width of the W boson should be 2088 ± 1 megaelectronvolt. Past measurements showed an average value of 2085 ± 42 megaelectronvolts, which is still consistent with the Standard Model within uncertainties.

Using proton collisions at an energy of 7 teraelectronvolts at the LHC, physicists say they have obtained the most accurate value for the width of the W boson. It is 2202 ± 47 megaelectronvolts. Although this value is larger than predicted by the Standard Model, it is still consistent with its predictions in terms of standard deviations.

To get this value, physicists had to carefully analyze the decay of the W boson into an electron or muon, and a neutrino, which remains an invisible particle but leaves its mark when particles collide.

Also, during the study, scientists measured not only the width of the W-boson, but also updated the value of the mass of this particle. As the results showed, the mass of the W boson is 80367 ± 16 megaelectronvolts. This value turned out to be more accurate than physicists had previously obtained.

According to the authors of the study, the values ​​of both the width of the W boson and its mass are consistent with the predictions of the Standard Model of particle physics. Physicists believe that future measurements will provide even more accurate values ​​and reduce the level of errors. This in turn will help to better test the Standard Model and study new particles and unknown phenomena.