Physicists nab the elusive glueball
物理学家捕捉到难觅的胶球
一种理论预言的粒子怎样成为实验发现？本文围绕“看见候选者—排除其他解释—检验理论”展开。既要读懂粒子名称与代词的关系，也要区分研究团队的确信和作者保留的判断。
原文来源：The Economist
学习目标
- 梳理胶子、夸克与胶球之间的关系
- 拆解报道倒装、关系从句和让步倒装
- 解释排除其他解释在论证中的作用
- 用准确的归属与限定语概括科学发现
中英对照阅读
A NEW SUBATOMIC particle has made the leap from theory to reality. So say the scientists of the Beijing Spectrometer III (BESIII), a Chinese physics experiment. Speaking on their behalf at the International Conference on High Energy Physics (ICHEP) on August 5th, Jin Shan, of Nanjing University, announced that the team have discovered a glueball—a hitherto hypothetical particle that is unlike any which physicists have seen before.
一种新的亚原子粒子实现了从理论到现实的跨越。 中国物理实验北京谱仪III（BESIII）的科学家们如此表示。 8月5日，南京大学的Jin Shan代表他们在国际高能物理会议（ICHEP）上发言，宣布团队发现了胶球——一种此前仅属假说、不同于物理学家以往见过的任何粒子的粒子。
The nuclei of atoms are held together by a phenomenon called the strong nuclear force. What better name, then, for the particle responsible for carrying this force than the “gluon”? Gluons interact with quarks, another type of fundamental particle, wrangling them into pairs and triplets to create protons, neutrons and other such “composite” particles. But gluons also interact with other gluons, raising the possibility of gluons gluing themselves together into a different kind of composite particle: the glueball.
原子核由一种称为强核力的作用维系在一起。 那么，对于负责传递这种力的粒子，还有什么名字比“胶子”更贴切呢？ 胶子与另一类基本粒子——夸克——相互作用，把它们聚合成对或成组三个，形成质子、中子以及其他这类“复合”粒子。 但胶子也与其他胶子相互作用，由此带来一种可能：胶子相互“粘”在一起，形成另一种复合粒子——胶球。
Physicists’ theories predict glueballs. Finding one is another matter, since those theories also suggest glueballs will be difficult to distinguish from the torrents of more mundane quark-based particles produced in machines like the Beijing Electron-Positron Collider II, to which BESIII is attached. Almost half a century of searching has left researchers empty-handed.
物理学家的理论预言胶球的存在。 找到一个却是另一回事，因为这些理论还表明，胶球很难与北京正负电子对撞机II等机器产生的大量更常见的夸克类粒子区分开来；BESIII就安装在这台对撞机上。 将近半个世纪的寻找让研究者始终一无所获。
No more, say the operators of BESIII. In 2011 a new particle, called X(2370), showed up in their detectors. It looked a lot like a glueball, but other interpretations were possible. So the team got to work on ruling them out. They have spent the intervening years analysing over 10bn processes in which X(2370) could play a role. The result—published online in July and presented at ICHEP by Dr Jin—is a complete picture of the new particle’s properties. The team is now convinced it is a glueball. “No other interpretation can explain all these properties simultaneously,” says Dr Jin.
BESIII的运行团队说，这种局面结束了。 2011年，一种名为X(2370)的新粒子出现在他们的探测器中。 它看起来很像胶球，但也存在其他可能的解释。 因此，团队着手排除那些解释。 在此后的这些年里，他们分析了超过100亿个X(2370)可能参与其中的过程。 所得成果于7月在线发表，并由Jin博士在ICHEP上介绍，完整描绘了这种新粒子的性质。 团队现在确信它是一个胶球。 Jin博士说：“没有其他解释能够同时说明所有这些性质。”
Detecting the glueball—if it has, indeed, been found—is not just a matter of physicists adding a new specimen to their by now extensive collection. Its discovery will provide valuable data to test the theory behind the strong force. That theory, good as it is, contains many mysteries. One is how the strong force generates mass—for gluons have no mass, but glueballs do. On the answering of such questions, the glueball’s discovery could tip the scales.
探测到胶球——如果确实已经找到它的话——并不只是物理学家往如今已相当庞大的收藏中添上一件新标本。 这一发现将为检验强力背后的理论提供宝贵数据。 这套理论虽好，却仍包含许多谜团。 其中一个谜团是强力如何产生质量——因为胶子没有质量，胶球却有。 在回答这类问题方面，胶球的发现可能推动天平倾斜。