The standard model of particle physics—completed in 1973—is the jewel in the crown of modern physics. It predicts the properties of elementary particles and forces with mind boggling accuracy. Take the magnetic moment of the electron, for example, a measure of how strongly a particle wobbles in a magnetic field. The Standard Model gives the correct answer to 14 decimal places, the most accurate prediction in science. But the Standard Model is not perfect.

1973年完成的粒子物理學(xué)標(biāo)準(zhǔn)模型是現(xiàn)代物理學(xué)皇冠上的一顆寶石。它預(yù)測(cè)基本粒子和力的性質(zhì)的準(zhǔn)確性令人難以置信。以電子的磁矩為例，它是衡量一個(gè)粒子在磁場(chǎng)中擺動(dòng)強(qiáng)度的指標(biāo)。標(biāo)準(zhǔn)模型給出了小數(shù)點(diǎn)后14位的正確答案，這是科學(xué)上最準(zhǔn)確的預(yù)測(cè)。但是標(biāo)準(zhǔn)模型并不完美。

It cannot explain gravity, dark matter (mysterious stuff detectable only by its gravitational pull), or where all the antimatter in the early universe went. Physicists have spent much time, effort and money performing ever-more elaborate experiments in an effort to see where the Standard Model fails, in the hopes of finding a clue to the theory that will replace it.?

它無法解釋引力、暗物質(zhì)（只有通過引力才能探測(cè)到的神秘物質(zhì)），也無法解釋早期宇宙中所有反物質(zhì)的去向。物理學(xué)家們花費(fèi)了大量的時(shí)間、精力和金錢，進(jìn)行了越來越精細(xì)的實(shí)驗(yàn)，試圖找出標(biāo)準(zhǔn)模型的失敗之處，希望找到替代標(biāo)準(zhǔn)模型的理論線索。

But the Standard Model has fought back, stubbornly predicting the results of every experiment physicists have thrown its way. But that may perhaps be changing. In a paper published last week in Science, a team of researchers from the Fermi National Accelerator Laboratory (Fermilab) in America announced that the mass of an elementary particle called the w boson appears to be greater than the Standard Model predicts.

但是標(biāo)準(zhǔn)模型進(jìn)行了反擊，它固執(zhí)地預(yù)測(cè)物理學(xué)家們提出的每一個(gè)實(shí)驗(yàn)的結(jié)果。但這種情況可能正在改變。在上周《科學(xué)》雜志上發(fā)表的一篇論文中，美國費(fèi)米國家加速器實(shí)驗(yàn)室(簡(jiǎn)稱Fermilab)的一組研究人員宣布，一種名為w玻色子的基本粒子的質(zhì)量似乎比標(biāo)準(zhǔn)模型預(yù)測(cè)的要大。

The difference is small—only a hundredth of a percent—but the measurement’s precision exceeds that of all previous experiments combined. It places the odds that the result is spurious at only one in a trillion (“seven sigma” , in the statistical lingo), well above the one in 3.5m (five sigma) that physicists require to consider a finding robust.

差別很小，只有百分之一，但測(cè)量的精度超過了所有以前的實(shí)驗(yàn)的總和。它將結(jié)果不可信的幾率設(shè)定為一萬億分之一(用統(tǒng)計(jì)學(xué)術(shù)語來說就是“7西格瑪”)，遠(yuǎn)高于物理學(xué)家認(rèn)為這一發(fā)現(xiàn)可靠的350萬分之一(5西格瑪)。

The scientists at Fermilab analysed historical data from the Tevatron, a circular particle collider which was the most powerful in the world until the Large Hadron Collider (LHC) came online in 2009. between 2002 and 2011 (when it ran for the last time), the Tevatron produced approximately 4m w bosons in collisions between particles called quarks and their antimatter counterparts, antiquarks.

費(fèi)米實(shí)驗(yàn)室的科學(xué)家分析了Tevatron的歷史數(shù)據(jù)。Tevatron是一個(gè)圓形粒子對(duì)撞機(jī)，在2009年大型強(qiáng)子對(duì)撞機(jī)(LHC)投入使用之前，它是世界上最強(qiáng)大的粒子對(duì)撞機(jī)。在2002年到2011年(它最后一次運(yùn)行的時(shí)候)，Tevatron在夸克和它們的反物質(zhì)對(duì)位物反夸克之間的碰撞中產(chǎn)生了大約4m w的玻色子。

Using detailed recordings of the scattering trajectories of the menagerie of particles present in such collisions, the scientists could calculate the mass of the w boson with unprecedented accuracy. The finding has big implications. The w boson is a force-carrying particle. Together with its sibling the z boson, it mediates the weak nuclear force that governs radioactive decay.

利用這種碰撞中存在的大量粒子的散射軌跡的詳細(xì)記錄，科學(xué)家們可以以前所未有的精度計(jì)算出w玻色子的質(zhì)量。這一發(fā)現(xiàn)具有重大意義。玻色子是一種攜帶力的粒子。它和它的兄弟粒子z玻色子一起，調(diào)節(jié)控制放射性衰變的弱核力。

Unlike other force-carrying particles, however, the w and z bosons have mass—and a lot of it. The w boson is 90 times heavier than a hydrogen atom. The z boson is even more massive. What really distinguishes the w boson, however, is its ability to change the type—or “flavour”—of other elementary particles it comes across. For example, it can transform the electron (and two of its cousins, the muon and tau) into neutrinos.

然而，與其他攜帶力的粒子不同，w和z玻色子有質(zhì)量，而且質(zhì)量很大。w玻色子比氫原子重90倍。z玻色子的質(zhì)量更大。然而，真正區(qū)別w玻色子的是，它能夠改變遇到的其他基本粒子的類型或“味道”。例如，它可以將電子(以及它的兩個(gè)表親，muon 和tau)轉(zhuǎn)化為中微子。

It can also flip quarks from one type to another—up to down, top to bottom, and the whimsically named “strange” quark to a “charm” one. These protean powers mean that the mass of the w boson is linked to the mass of several other elementary particles. That allows scientists to use the w boson to calculate the mass of those other particles.

它還可以把夸克從一種類型翻轉(zhuǎn)到另一種類型，從上到下，從上到下，從上到下，把名字古怪的“奇怪”夸克翻轉(zhuǎn)到“迷人”夸克。這些千變?nèi)f化的能力意味著w玻色子的質(zhì)量與其他幾種基本粒子的質(zhì)量相聯(lián)系。這使得科學(xué)家可以使用w玻色子來計(jì)算其他粒子的質(zhì)量。

That is how they predicted the mass of the top quark (discovered in 1995) and the mass of the Higgs boson (discovered in 2012), before either particle had been detected. If the w boson is more massive than the Standard Model predicts, it implies that something else is tugging on it too—an as-yet-undiscovered particle or force. For particle physicists, that is an exciting prospect.

這就是他們?nèi)绾晤A(yù)測(cè)頂夸克(發(fā)現(xiàn)于1995年)和希格斯玻色子(發(fā)現(xiàn)于2012年)的質(zhì)量，在這兩個(gè)粒子被探測(cè)到之前。如果w玻色子的質(zhì)量比標(biāo)準(zhǔn)模型預(yù)測(cè)的要大，這就意味著還有其他的東西在拉著它——一種尚未發(fā)現(xiàn)的粒子或力。對(duì)于粒子物理學(xué)家來說，這是一個(gè)令人興奮的前景。

It is not the only one. In March 2021 scientists from CERN—Europe’s particle-physics laboratory—reported evidence that the bottom quark decays into electrons and muons in uneven numbers, contradicting the Standard Model. Only three weeks later, Fermilab announced that the magnetic moment of the muon appears to be greater than predicted by the Standard Model too.

它不是唯一的一個(gè)。2021年3月，歐洲核子研究中心粒子物理實(shí)驗(yàn)室的科學(xué)家報(bào)告稱，有證據(jù)表明，底部夸克衰變?yōu)閿?shù)量不均勻的電子和介子，這與標(biāo)準(zhǔn)模型相矛盾。僅僅三周后，費(fèi)米實(shí)驗(yàn)室宣布，介子的磁矩似乎也比標(biāo)準(zhǔn)模型預(yù)測(cè)的要大。

Like the mass of the w boson, the magnetic moment of the muon is partly determined by the properties of other particles. If it is greater than the Standard Model predicts, that hints at an as-yet-undiscovered particle or force too. Assuming, that is, the results are real. exciting as they were, neither result from 2021 crossed the 5-sigma threshold (they hit 3.1 and 4.2 sigma, respectively). That means further confirmation is necessary.

與w玻色子的質(zhì)量一樣，介子的磁矩部分取決于其他粒子的性質(zhì)。如果它比標(biāo)準(zhǔn)模型預(yù)測(cè)的要大，那就意味著還有一種尚未被發(fā)現(xiàn)的粒子或力。也就是說，假設(shè)結(jié)果是真實(shí)的。令人興奮的是，2021年的結(jié)果都沒有超過5西格瑪臨界值(分別達(dá)到了3.1和4.2)。這意味著需要進(jìn)一步確認(rèn)。

The more recent Tevatron result, though, contradicts the previous best measurement of the w boson mass, made in 2017 at the LHC. That was in close agreement with the Standard Model, presenting a puzzle. On the other hand, the latest Tevatron result aligns well with previous data provided by the Large Electron-Positron Collider, the LHC’s predecessor.

然而，最近的Tevatron結(jié)果與2017年LHC對(duì)w玻色子質(zhì)量的最佳測(cè)量結(jié)果相矛盾。這與標(biāo)準(zhǔn)模型非常接近，令人困惑。另一方面，Tevatron的最新結(jié)果與大型正電子對(duì)撞機(jī)(LHC的前身)提供的數(shù)據(jù)吻合得很好。

It is consequently the strongest evidence yet of the physics that must lie beyond the Standard Model. Anyone who prefers interesting errors over yet more dull confirmation will be hoping it holds up.

因此，這是迄今為止最有力的物理學(xué)證據(jù)，它必須超越標(biāo)準(zhǔn)模型。那些更喜歡有趣的錯(cuò)誤而不是更乏味的確認(rèn)的人會(huì)希望它能站得住腳。