W bosons mediate the weak interaction, one of the fundamental forces in physics. Because the Standard Model (SM) of particle physics places tight constraints on the mass of the W boson, measuring the mass puts the SM to the test. The Collider Detector at Fermilab (CDF) Collaboration now reports a precise measurement of the W boson mass extracted from data taken at the Tevatron particle accelerator (see the Perspective by Campagnari and Mulders). Surprisingly, the researchers found that the mass of the boson was significantly higher than the SM predicts, with a discrepancy of 7 standard deviations. —JS
今天关注到science封面的文章,
大意就是这次测量不是独立测量,是有依赖于现有的理论模型的,如果未来理论模型有所更新,可能会影响测量结果以及现有的标准模型对W质量的预言。
展示了不同的实验组对W玻色子质量的测量结果和精度
费米实验室的对撞机探测器
Tevatron 运行于1983 年到 2011 年,是一个长达6.3公里的环形装置,质子以高达 2 TeV的能量撞击反质子,这一能量大约是 W 玻色子质量的 25 倍。处于环路上的CDF探测器从2002年开始运行直到Tevatron关闭,在这些碰撞中寻找W玻色子的迹象。
[1] CDF Collaboration†‡ et al., “High-precision measurement of the W boson mass with the CDF II detector,” Science, vol. 376, no. 6589, pp. 170–176, Apr. 2022, doi: 10.1126/science.abk1781.