自1964年首次提出以来，希格斯玻色子一直是解释基本粒子质量来源的关键。2012年，大型强子对撞机上的ATLAS和CMS实验证实了这一预测。此后，ATLAS合作组持续进行测量，特别是通过研究“壳外”希格斯玻色子产生过程，即希格斯玻色子质量远高于其典型值（125 GeV）时的产生。这种难以探测的现象，源于量子力学允许粒子暂时波动质量，能揭示希格斯玻色子寿命等更深层性质，并检验粒子物理标准模型的预测。ATLAS实验通过一种全新的数据解读方法，显著提高了对该过程的探测灵敏度，提供了2.5σ的证据，标志着对希格斯玻色子及高能粒子物理现象理解的重要进展。

⚛️ 希格斯玻色子是解释基本粒子质量起源的关键，其存在已由大型强子对撞机上的ATLAS和CMS实验于2012年证实，验证了该理论的预测。

💡 “壳外”希格斯玻色子产生过程的研究，即希格斯玻色子质量远高于其典型值（125 GeV）时的产生，是理解其性质的关键。这一现象源于量子力学允许粒子质量的暂时波动，有助于揭示希格斯玻色子的寿命等深层信息，并检验标准模型的预测。

📈 ATLAS实验通过采用一种全新的数据解读方法，显著提高了对“壳外”希格斯玻色子产生过程的探测灵敏度。在包含四个电子或缪子的事件中，该方法提供了2.5σ的证据，远超传统方法在同一信道下的0.8σ，标志着对希格斯玻色子及其相关高能粒子物理现象理解的重大进步。

First proposed in 1964, the Higgs boson plays a key role in explaining why many elementary particles of the Standard Model have a rest mass. Many decades later the Higgs boson was observed in 2012 by the ATLAS and CMS collaborations at the Large Hadron Collider (LHC), confirming the decades old prediction.  

This discovery made headline news at the time and, since then, the two collaborations have been performing a series of measurements to establish the fundamental nature of the Higgs boson field and of the quantum vacuum. Researchers certainly haven’t stopped working on the Higgs though. In subsequent years, a series of measurements have been performed to establish the fundamental nature of the new particle. 

One key measurement comes from studying a process known as off-shell Higgs boson production. This is the creation of Higgs bosons with a mass significantly higher than their typical on-shell mass of 125 GeV.  This phenomenon occurs due to quantum mechanics, which allows particles to temporarily fluctuate in mass.

This kind of production is harder to detect but can reveal deeper insights into the Higgs boson’s properties, especially its total width, which relates to how long it exists before decaying. This in turn, allows us to test key predictions made by the Standard Model of particle physics.

Previous observations of this process had been severely limited in their sensitivity. In order to improve on this, the ATLAS collaboration had to introduce a completely new way of interpreting their data (read here for more details).

They were able to provide evidence for off-shell Higgs boson production with a significance of 2.5𝜎 (corresponding to a 99.38% likelihood), using events with four electrons or muons, compared to a significance of 0.8𝜎 using traditional methods in the same channel.

The results mark an important step forward in understanding the Higgs boson as well as other high-energy particle physics phenomena.

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