In 1994, a team of physicists were colliding electrons head-on with protons at the DESY laboratory in Hamburg, Germany, when they saw an electron apparently turn into its heavier counterpart, a muon. Such a transformation is unheard of in the standard model. So what happened?

1994年，一组物理学家在德国汉堡的DESY实验室做电子迎头碰质子的实验。他们显然看到了一个电子变成了其较重的对应物，一个μ轻子。在标准模型中，这样的转变是前所未闻的。发生了什么？

One possibility is that the collisions created a heavyweight crossbreed known as a leptoquark. In the standard model, electrons and protons are very different sorts of particles, set apart by the forces they feel. Protons and the like are composites made when quarks combine under the influence of the strong force (see "Tetraquark"). Particles such as electrons and muons are elementary particles, collectively known as leptons, that do not feel the strong force at all.

一种可能性是，碰撞产生了一个重量级的称为轻子夸克的杂交。在标准模型中，电子和质子是种类截然不同的粒子，由它们感受到的相互作用将它们分开。质子和类似的粒子是夸克在强相互作用力的作用下复合而成的（请参阅"四夸克"）。如电子和μ轻子的粒子是基本粒子，统称为轻子，并不感受强相互作用力。

Grand unified theories aim to cut across such boundaries by rolling three of the four forces of nature into one. In some theories, when an electron hits a proton, as at DESY's HERA accelerator, leptoquarks can form and decay to a muon and a quark. "HERA seemed like a good place to make a leptoquark," says John Ellis, a theoretical physicist at King's College London.

大统一理论的目标是跨越这些界限，使自然界四种基本相互作用的三种融合为一种。在一些理论，当电子撞击一个质子时，例如在DESY的HERA加速器中，可以形成轻子夸克并衰减到一个μ轻子和夸克。"HERA似乎是一个产生轻子夸克的好地方"，伦敦大学国王学院的理论物理学家John Ellis说。

In the event, there were no further sightings, and the excitement faded. Yet the lure of grand unified theories remains - and the search for leptoquarks continues at the LHC today.

在这个事件中，进一步的观测事例的缺乏使大家的兴奋度下降。然而，大统一理论的诱惑一直存在——在大型强子对撞机上轻子夸克的寻找今天仍在继续。

• possibility [,pɔsə´biliti]   n.可能(性)；希望；前途   (初中英语单词)
• combine [kəm´bain]   v.(使)结合；联合企业   (初中英语单词)
• excitement [ik´saitmənt]   n.兴奋；骚动；煽动   (初中英语单词)
• laboratory [lə´bɔrətəri]   n.实验室；研究室(所)   (高中英语单词)
• apparently [ə´pærəntli]   ad.显然，表面上地   (高中英语单词)
• transformation [,trænsfə´meiʃən]   n.转化；转变；改造   (英语四级单词)
• elementary [,eli´mentəri]   a.基本的；初级的   (英语四级单词)
• hamburg [´hæmbə:g]   n.汉堡   (英语六级单词)