微中子偵測器可能發現超弦理論證據
South Pole Neutrino Detector Could Yield Evidences of String Theory
Diagram of IceCube. IceCube will occupy a volume of one cubic kilometer. Here we depict one of the 80 strings of opctical modules (number and size not to scale). IceTop located at the surface, comprises an array of sensors to detect air showers. It will be used to calibrate IceCube and to conduct research on high-energy cosmic rays. Author: Steve Yunck, Credit: NSF
東北大學以及加州大學 Irvine 分校的研究人員表示，科學家很快就會有額外次元存在的證據，以及超弦理論所預測的的特異情境出現。從南半球微中子偵測器，稱為 AMANDA 所傳來的早期結果顯示，來自於宇宙，鬼魅般的粒子可以用來當作探針，偵測超乎我們所熟悉的三次元以外的世界。
Researchers at Northeastern University and the University of California, Irvine say that scientists might soon have evidence for extra dimensions and other exotic predictions of string theory. Early results from a neutrino detector at the South Pole, called AMANDA, show that ghostlike particles from space could serve as probes to a world beyond our familiar three dimensions, the research team says.
到目前為止，尚未有超過一打的高能微中子被偵測到。然而，從電流偵測以以及能源範圍指出比 AMANDA 更大的後繼者，稱為 IceCube，目前仍建造中，可能會提供第一手關於超弦理論的證據，以及其他試圖建構我們目前所知宇宙的理論的證據。
No more than a dozen high-energy neutrinos have been detected so far. However, the current detection rate and energy range indicate that AMANDA's larger successor, called IceCube, now under construction, could provide the first evidence for string theory and other theories that attempt to build upon our current understanding of the universe.
一偏描述這項工作的文章，刊登於當期的 Physical Review Letters。作者包括：Luis Anchordoqui，東北大學物理系的副研究員；Haim Goldberg東北大學的物理系教授；Jonathan Feng 加州大學 Irvine 分校，物理與天文學系的副教授。
An article describing this work appears in the current issue of Physical Review Letters. The authors are: Luis Anchordoqui, associate research scientist in the Physics Department at Northeastern University; Haim Goldberg, professor in the Physics Department at Northeastern University; and Jonathan Feng, associate professor in the Department of Physics and Astronomy at University of California, Irvine.
Credit: NSF
他們表示，證據將來自於微中子與地球上其他物質如何產生交互作用。
The evidence, they say, would come from how neutrinos interact with other forms of matter on Earth.
Anchordoqui 表示：要找到支持超弦理論的證據，必須得知物質在極端能量下會有什麼交互作用產生。人造的加速器沒法辦到，但宇宙可以產生高能微中子。
“To find clues to support string theory and other bold, new theories, we need to study how matter interacts at extreme energies,” said Anchordoqui. “Human-made particle accelerators on Earth cannot yet generate these energies, but nature can in the form of the highest-energy neutrinos.”
在近十年來，新的理論被發展 - 例如超弦理論，額外次元以及超對稱 - 連結了二個 20 世紀最成功的理論，廣義相對論、量子力學之間的鴻溝。量子力學描述三個自然界的基本力：電磁力、強作用力（束縛原子核）、弱作用力（在放射線中可見到）。然而他與愛因斯坦的廣義相對論不相容，這個主要描述第四種力：重力。科學家希望能找到一個統一的理論，以量子來描述這四種力。
In recent decades, new theories have developed – such as string theory, extra dimensions and supersymmetry – to bridge the gap between the two most successful theories of the 20th century, general relativity and quantum mechanics. Quantum mechanics describes three of the fundamental forces of nature: electromagnetism, strong forces (binding atomic nuclei) and weak forces (seen in radioactivity). It is, however, incompatible with Einstein's general relativity, the leading description of the fourth force, gravity. Scientists hope to find one unified theory to provide a quantum description of all four forces.
科學家表示，統一的線索躺在極端能量中。在地球上，人類所製造的粒子加速器所產生的能量，已經讓電磁力以及弱作用力難以分辨。在下一代的加速器中，科學家預料會讓強作用力與弱作用力及電磁力難以分辨。但是，要見到重力與其他三力統一，必須要更高的能量。
Clues to unification, scientists say, lie at extreme energies. On Earth, human-made particle accelerators have already produced energies at which electromagnetic forces and weak forces are indistinguishable. Scientists have ideas about how the next generation of accelerators will reveal that strong forces are indistinguishable from the weak and electromagnetic at yet higher energies. Yet to probe deeper to see gravity's connection to the other three forces, still higher energies are needed.
Anchordoqui 以及他的同事表示，銀河系外的來源，可以當作終極的宇宙加速器。而來自這些地區的微中子，啪的一聲撞入質子可以將能源釋出到一個領域中，該領域就是超弦理論所能展示的第一個線索。
Anchordoqui and his colleagues say that extragalactic sources can serve as the ultimate cosmic accelerator, and that neutrinos from these sources smacking into protons can release energies in the realm where the first clues to string theory could be revealed.
微中子是與電子很類似的基本粒子，不過他們的質量超小，具有中性電荷，而且難與物質起作用。在宇宙中他們算是大量的粒子，每秒中都有數不清的數十億個微中子經過我們的身體。大部分的微中子都是來自於太陽的低能粒子。
Neutrinos are elementary particles similar to electrons, but they are far less massive, have neutral charge, and hardly interact with matter. They are among the most abundant particles in the universe; untold billions pass through our bodies every second. Most of the neutrinos reaching Earth are lower-energy particles from the sun.
由 NSF 所贊助的 AMANDA 嘗試要偵測落下的微中子，但同時也包括 "向上"穿越地球的。由於微中子難以產生交互作用，因此可以毫髮無損的穿越地球。從 "上" 與 "下" 穿越地球的微中子總數不清楚，然而除了特異的效應外，其他相關的偵測率我們倒是瞭如指掌。
AMANDA, funded by the National Science Foundation, attempts to detect neutrinos raining down from above but also coming "up" through the Earth. Neutrinos are so weakly interacting that some can pass through the entire Earth unscathed. The total number of "down" and "up" neutrinos is uncertain; however, barring exotic effects, the relative detection rates are well known.
AMANDA 在南極洲的冰層下，而 NSF 所投資的 IceCube 也有類似的設計，只不過他有六倍的偵測器，涵蓋在一立方公里的體積中。當微中子猛烈的轟入冰中的原子時，會發出一個短暫的、泄露祕密的藍色亮光；而且使用偵測器，科學家可以得知微中子打哪來，他的能量有多少。
AMANDA detectors are positioned deep in the Antarctic ice. The NSF-funded IceCube has a similar design, only it has about six times more detectors covering a volume of one cubic kilometer. A neutrino smashing into atoms in the ice will emit a brief, telltale blue light; and using the detectors, scientists can determine the direction where the neutrino came from and its energy.
The IceCube telescope and its predecessor, AMANDA, use optical sensors to locate the sources of high energy neutrinos. This picture shows the on-line display of neutrino event recorded by AMANDA. Author: Jodi Lamoureux, Credit: NSF
這項工作的關鍵是，科學家在比較所偵測到的 "上"、"下" 微中子，並且找尋偵測率之間的差異，這就是由新理論所預言的特異效應證據。
The key to the work presented here is that the scientists are comparing “down” to “up” detections and looking for discrepancies in the detection rate, evidence of an exotic effect predicted by new theories.
Jonathan Feng 表示，超弦理論以及其他理論可以使 "上"、"下" 微中子的相對數量產生偏差。舉例而言，額外的次元可能導致微中子建立一個超微小黑洞，那個黑洞馬上就會蒸發，而且在地球的大氣層以及南極的冰帽下產生壯麗的 "粒子雨"。這會增加 "往下" 微中子的數量。在此同時，所建立的黑洞會導致 "往上" 的微中子被地殼抓住，進而減少其數量。這個相對的 "上、下" 比率提供了新理論所預測微中子會產生偏差的證據。
“String theory and other possibilities can distort the relative numbers of 'down' and 'up' neutrinos,” said Jonathan Feng. “For example, extra dimensions may cause neutrinos to create microscopic black holes, which instantly evaporate and create spectacular showers of particles in the Earth's atmosphere and in the Antarctic ice cap. This increases the number of 'down' neutrinos detected. At the same time, the creation of black holes causes 'up' neutrinos to be caught in the Earth's crust, reducing the number of 'up' neutrinos. The relative 'up' and 'down' rates provide evidence for distortions in neutrino properties that are predicted by new theories.”
在宇宙中加速至地球上無法辦到的微中子，可以透過新物理偵測到其足印，Goldberg 表示，這些足印的主體，可以透過現今新一代人造對撞機複雜的實驗來展現。在前方那是一個令人相當振奮的高能物理時代。
“The neutrinos accelerated in the cosmos to energies unattainable on Earth can detect the 'footprint' of new physics,” said Goldberg. “The 'body' responsible for the footprint can then emerge through complementary experiments at the new generation of human-made colliders. On all fronts, it is an exciting era in high-energy physics.”
更多關於 AMANDA 與 IceCube 的資訊可以到 IceCube 的網站上發現：
More information about AMANDA and IceCube is available at the IceCube website, http://www.icecube.wisc.edu
Source: Northeastern University
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