вЂњBut the fact that NA64 reached an experimental sensitivity that is better than the current accuracy of the direct measurements of a e, and of recent high-precision measurements of the п¬Ѓ ne-structure constant, is amazing.вЂќ These contributions are too small to explain the current anomaly in the electronвЂ™s anomalous magnetic moment, says NA64 spokesperson Sergei Gninenko. The result sets new bounds on the e вЂ“X interaction strength and, as a result, on the contributions of X bosons to a e: X bosons with a mass below 1 GeV could contribute at most between one part in 10 15 and one part in 10 13, depending on the X-boson type and mass. The result sets new bounds on the e вЂ“X interaction strengthДЄnalysing data collected in 2016, 20, corresponding to about 3 Г— 10 11 electrons-on-target, the NA64 team found no evidence for such events. NA64 searches for X bosons by directing 100 GeV electrons generated by the SPS onto a target, and looking for missing energy in the detector via electronвЂ“nuclei scattering e вЂ“Z в†’ e вЂ“ZX. Given experimental constraints on its decay modes involving Standard Model particles, it is presumed to decay predominantly invisibly, for example into dark-sector particles.

The generic X boson could be a sub- GeV scalar, pseudoscalar, vector or axial- vector particle. Motivated by this inconsistency, the NA64 collaboration at CERN set out to investigate whether new physics вЂ“ in the form of a lightweight вЂњX bosonвЂќ вЂ“ might be influencing the electronвЂ™s behaviour. Though with a much lower significance, a similar puzzle may also be emerging for the anomalous magnetic moment of the electron, a e.Дepending on which of two recent independent measurements of the fine-structure constant is used in the theoretical calculation of a e вЂ“ one obtained at Berkeley in 2018 or the other at KastlerвЂ“Brossel Laboratory in Paris in 2020 вЂ“ the Standard Model prediction stands 2.4Пѓ higher or 1.6Пѓ lower than the best experimental value, respectively. Recent measurements bolstering the longstanding tension between the experimental and theoretical values of the muonвЂ™s anomalous magnetic moment generated a buzz in the community. Exploration The NA64 set up is being used to search for new particles that might account for the electron g-2 and ATOMKI anomalies.

Boson x speedrun 100