Could we create dark matter? - Rolf Landua

譯者: Szu-Wen Kung 審譯者: Helen Chang

85% of the matter in our universe is a mystery.

宇宙有 85% 的物質仍未知

We don't know what it's made of, which is why we call it dark matter.

我們不清楚這些物質的成分 因此稱之為暗黑物質

我們能觀察到暗黑物質 在星團與其他天體上的重力

But we know it's out there because we can observe its gravitational attraction

on galaxies and other celestial objects.

所以知道暗黑物質的存在

We've yet to directly observe dark matter,

我們還無法直接觀察暗黑物質

but scientists theorize that we may actually be able to create it

不過科學家論述表示人類也許 能用世上最強大的粒子對撞機

in the most powerful particle collider in the world.

創造出暗黑物質

That's the 27 kilometer-long Large Hadron Collider, or LHC,

這是一台長 27 公里的 大強子對撞機或簡稱 LHC

in Geneva, Switzerland.

位於瑞士的日內瓦

So how would that work?

所以機器如何運作 ？

在 LHC 裡兩個質子束 以反方向旋轉

In the LHC, two proton beams move in opposite directions

and are accelerated to near the speed of light.

隨後加速近似光速

At four collision points, the beams cross and protons smash into each other.

在第四個撞擊點質子束相遇 質子互撞

Protons are made of much smaller components called quarks and gluons

質子是由更小的夸克和膠子所組成

In most ordinary collisions, the two protons pass through each other

在最普通的撞擊 兩個質子穿越彼此

without any significant outcome.

沒有產生重大的結果

However, in about one in a million collisions,

但每一百萬次裡的一次撞擊

two components hit each other so violently,

兩個質子會強力衝撞

that most of the collision energy is set free

釋放出絕大部分的衝撞能量

producing thousands of new particles.

產生上千個新粒子

It's only in these collisions that very massive particles,

只有在這類撞擊中才會 產生超大粒子

like the theorized dark matter, can be produced.

像是理論上的暗黑物質

The collision points are surrounded by detectors

撞擊點四周都是探測器

containing about 100 million sensors.

探測器內有約一億個感應器

如同大型 3D 照相機

Like huge three-dimensional cameras,

they gather information on those new particles,

探測器蒐集新粒子的資訊

including their trajectory,

包括軌跡

electrical charge,

電荷

and energy.

與能量

Once processed, the computers can depict a collision as an image.

處理運算後 電腦便能描繪出撞擊的影像

Each line is the path of a different particle,

每條線都是每個不同粒子的路徑

and different types of particles are color-coded.

還用顏色為不同型態的粒子編碼

Data from the detectors allows scientists to determine

探測器所蒐集的資料讓科學家能決定

what each of these particles is,

這些粒子是什麼

things like photons and electrons.

像是光子和電子

Now, the detectors take snapshots of about a billion of these collisions per second

探測器每秒大約拍攝十億次 這些碰撞的快照

to find signs of extremely rare massive particles.

以找出稀有大型粒子的跡象

To add to the difficulty,

難上加難的是

the particles we're looking for may be unstable

我們想尋找的粒子可能並不穩定

and decay into more familiar particles before reaching the sensors.

在感應器能覺察之前 就會衰變為我們較熟知的粒子

Take, for example, the Higgs boson,

以「希格斯玻色子」為例

a long-theorized particle that wasn't observed until 2012.

此長久來只存在理論上的粒子 直到 2012 年才被觀察到

The odds of a given collision producing a Higgs boson are about one in 10 billion,

要讓特定撞擊產生希格斯玻色子的 機率約是百億分之一

and it only lasts for a tiny fraction of a second

只存在須臾一秒

before decaying.

就衰變了

But scientists developed theoretical models to tell them what to look for.

不過科學家發展出理論架構 讓人知道該尋找甚麼

For the Higgs, they thought it would sometimes decay into two photons.

科學家原本認為希格斯玻色子 會衰變成兩個光子

So they first examined only the high-energy events

因此他們起初只檢視

包含雙光子的高能量事件

that included two photons.

But there's a problem here.

然而有個問題存在

There are innumerable particle interactions

無數個粒子互動

that can produce two random photons.

會隨機產生兩個光子

所以該如何將希格斯玻色子 與其他物質分離

So how do you separate out the Higgs from everything else?

The answer is mass.

答案是質量

The information gathered by the detectors allows the scientists to go a step back

探測器蒐集的資訊 能讓科學家退一步審思

and determine the mass of whatever it was that produced two photons.

判定產生兩個光子的那東西的質量

They put that mass value into a graph

科學家將質量值轉成圖表

and then repeat the process for all events with two photons.

然後在所有產生雙光子的事件 重複相同步驟

The vast majority of these events are just random photon observations,

絕大多數的事件 僅是觀察隨機產生的光子

what scientists call background events.

即科學家口中的背景事件

但當一個希格斯玻色子產生 並衰變為兩個光子時

But when a Higgs boson is produced and decays into two photons,

the mass always comes out to be the same.

產生的質量永遠一樣

Therefore, the tell-tale sign of the Higgs boson

因此希格斯玻色子的特徵

would be a little bump sitting on top of the background.

就是出現在背景上方的微小凸塊

It takes billions of observations before a bump like this can appear,

至少需進行數十億次的觀察 小凸塊才會出現

and it's only considered a meaningful result

且也只有當小凸塊 明顯比背景來得高

if that bump becomes significantly higher than the background.

得出的結果才有意義

In the case of the Higgs boson,

在希格斯玻色子的案例中

the scientists at the LHC announced their groundbreaking result

使用大強子對撞機的科學家 宣布突破性的結果

when there was only a one in 3 million chance

即只有三百萬分之一的機會

this bump could have appeared by a statistical fluke.

才能僥倖得出小凸塊出現的數據

So back to the dark matter.

回到暗黑物質

If the LHC's proton beams have enough energy to produce it,

若大強子對撞機的質子束 有足夠的能量產生暗黑物質

that's probably an even rarer occurrence than the Higgs boson.

可能會比希格斯玻色子的 出現更為罕見

So it takes quadrillions of collisions combined with theoretical models

所以需要千兆次的撞擊 並配合理論架構

to even start to look.

才能開始尋找

That's what the LHC is currently doing.

這也是大強子對撞機 目前正在進行的計畫

By generating a mountain of data,

藉由龐大資料的產生

we're hoping to find more tiny bumps in graphs

我們希望能在圖表中 找出更多微小凸塊

that will provide evidence for yet unknown particles, like dark matter.

期能為仍未知的粒子 如暗黑物質佐證

Or maybe what we'll find won't be dark matter,

也有可能我們找到的 不是暗黑物質

but something else

而是其他物質

that would reshape our understanding of how the universe works entirely.

這能夠完全改變人類 對宇宙運作的認知

That's part of the fun at this point.

那也是目前為止部分的研究樂趣

We have no idea what we're going to find.

到底會找到甚麼 我們仍一無所悉