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Text 4. A riddle inside a mystery inside a quark
(A NEW DEGREE OF SUBATOMIC COMPLEXITY)
Particle physicists around the world are not amused. They are distinctly sceptical about the suggestion that a group of their peers at Fermilab in Chicago, one of the field’s foremost laboratories, has discovered smaller particles within the quark, traditionally the indivisible building block of matter. What’s more, they are irritated that the team splashed the story in the media before its research is reviewed and published in a recognised journal. If the quark, itself too tiny to measure, is indeed built from smaller components,the Fermilab research represents the biggest discovery in particle physics since quarks themselves were discovered a quarter of a century ago.
John Baez, a leading physicist at the University of California, Riverside, speaks for many when he says: “If this were true, the consequences for physics would be revolutionary. For that very reason, we should treat these results with great caution until we get more evidence”.
It was a hundred years ago that J.J.Thomson found the first atomic particle; he showed that electrons were particles split off from supposedly fundamental atoms. Early in the 20th Century, Ernest Rutherford probed farther into atomic structure, and discovered something hard embedded inside the atom. It became clear that most of the mass of an atom is in this hard central nucleus, surrounded by a cloud of electrons; the size of the nucleus, compared with the size of the electron cloud, is like a grain of sand compared with the Albert Hall.
Further studies showed that the nucleus is made of positively-charged protons and zero-charged neutrons. But it was only at the end of the 1960s that a structure within these nuclear components was revealed. Researchers found that electrons fired at the protons occasionally bounced off at a large angle, a result that could be explained only by the presence of something hard within the particles.
In the 1970s, experiments of this kind established the standard model of particle physics. Each proton (and neutron) is made up of three quarks - two of one kind, and one of another (there are six different types of quark in all). The quarks inside a proton are held together by particles called gluons (because they “glue” particles together). The gluons operate like an elastic band: if two quarks are close together, the force between them is weak; but if they try to move apart, the “elastic band” stretches, building up a force that pulls them back into place. The theory describing this behaviour is called quantum chromodynamics, or QCD, and is regarded as a jewel in the crown of theoretical physics.
But QCD cannot seem to explain the results of experiments carried out at Fermilab over the past year, in which beams of protons were smashed head-on into beams of antiprotons (particles with the same mass but opposite charge).
Under these conditions, quarks do not have time to react and “notice” that they are locked up inside protons (the elastic bands do not have time to stretch) and the collisions take place directly between quarks moving in opposite directions. Furthermore, in some of the collisions, emerging particles are knocked sideways, as if they have struck something hard embedded within a quark.
QCD explains perfectly what happens down to a scale of one-thousandth the size of the proton. But when the collisions probe distances ten times smaller than this, QCD provides no explanation - there are 50 per cent more of these so-called “hard” collisions than the theory predicts.
The snag is that the discrepancy could still result from instrumental errors. It just might mean that there is something inside the quarks. But there are other possible explanations, and although all of them go beyond the standard model, most physicists at present seem to prefer the idea that quarks are indivisible.
John Ellis, theoretical physicist at CERN, the European nuclear research laboratory, says: “If the effect is real, and even if QCD cannot fit it, substructure is not the most conservative interpretation”. He stresses that other effects could be at work. One of the most intriguing is the possibility that a new kind of particle might be being created out of pure energy in these collisions.
But just suppose the results are taken at face value. One person not afraid to speculate on the implications is Don Page, a quantum cosmologist based at the University of Alberta, Edmonton. He points out that the quantum of length, the smallest length that could possibly exist, lies at the Planck scale, or one hundred, billion, trillion, trillionth of a metre. This is as much smaller than a proton as a proton is smaller than the Sun. “Perhaps”, he says, “there is a whole series of relatively basic structures at increasingly smaller sizes”, continuing the hierarchy of molecules, atoms, nuclei, protons and quarks that we know already. The consensus, though, is that it should all be taken with a pinch of salt - at least, for now.
John Gribbin. The Guardian, 1996
VOCABULARY AND COMPREHENSION EXERCISES
I. Translate these into your own language:
• particle physicists
• particle physics
• one of the field’s foremost laboratories
• indivisible building block of matter
• to splash the story in the media
• to publish the research in a recognised journal
• too tiny to measure
• John Baez speaks for many when he says
• for that very reason
• something hard embedded inside the atom
• to fire at the protons at a large angle
• to establish a model
• to go beyond the standard model
• to be taken at face value
II. Give synonyms of the following words and word combinations:
Suggestion, particle, consequences, tiny, to reveal, to operate, research
III. Give the situations from the text in which the following words and expressions are used:
a foremost laboratory a quark
tiny
to splash the story in media consequences
to treat the results
to split off from atoms to probe into
to establish the standard model to operate like
quantum chromodynamics
to explain the results of experiments collisions
to prefer the idea
IV. Comment on the structure of the following sentences:
• If the quark, itself too tiny to measure, is indeed built from smaller components, the Fermilab research represents the biggest discovery in particle physics since quarks themselves were discovered a quarter of a century ago.
• Researchers found that electrons fired at the protons occasionally bounced off at a large angle, a result that could be explained only by the presence of something hard within the particles.
V. Ask questions to which the following statements might be the answers:
• A group of physicists at Fermilab in Chicago has discovered smaller particles within the quark.
• The Fermilab research represents the biggest discovery in particle physics since quarks themselves were discovered.
• A hundred years ago J.J.Thomson found the first atomic particle.
• Early in the 20th century Ernest Rutherford probed farther into atomic structure.
• Most of the mass of an atom is in the hard central nucleus, surrounded by a cloud of electrons.
• The nucleus is made of positively-charged protons and zero-charged neutrons.
• In the 1970s experiments established the standard model of particle physics.
• The quarks inside a proton are held together by particles called gluons.
• The gluons operate like an elastic band.
• Quantum chromodynamics cannot explain the results of experiments.
VI. Arrange the items of the plan in a logical order according to the text.
1. The discoveries of the first atomic particle by J.J.Thomson and of the atomic structure by E.Rutherford.
• The standard model of particle physics.
• QCD and possible explanations of the experiments at Fermilab.
• The discovery of particles within the quark.
• The experiments at Fermilab in Chicago.
• The structure of the nucleus.
•
VII Agree or disagree with the following statements:
• A group of physicists at Fermilab in Chicago has discovered a new kind of energy in the quark.
• Particle physicists around the world are happy that the team splashed the story in the media.
• The Fermilab research represents the biggest discovery in particle physics since the first atomic particle was found by J.J.Thomson.
• Early in the 20th century Ernest Rutherford probed farther into atomic structure and discovered that most of the mass of an atom is in the hard central nucleus, surrounded by a cloud of electrons.
• Further studies showed that the nucleus is made of positively-charged protons and negatively-charged neutrons.
• In the 1950s, experiments established the standard model of particle physics.
• Each ptoron (and neutron) is made up of three quarks; and the quarks are held together by gluons.
• The gluons operate like an elastic band.
• Quantum chromodynamics, or QCD, is regarded as a jewel in the crown of experimental physics.
• QCD can easily explain the results of experiments carried out at Fermilab.
• In these experiments beams of electrons were smashed head-on into beams of antiprotons.
• In some of the collisions emerging particles are knocked sideways, as if they have struck something hard embedded within a quark.
• One of the most intriguing interpretations is the possibility that a new kind of particle might be created out of pure energy in the collisions.
• All of the explanations go beyond the standard model, and most physicists don’t like the idea that quarks are indivisible.
VIII. Answer the questions:
1. What has a group of particle physicists of Fermilab in Chicago discovered?
• Why are particle physicists around the world irritated?
• What does the Fermilab research represent if the quark is indeed built from smaller components?
• When were quarks themselves discovered?
• Who found the first atomic particle and when did it happen?
• When did Ernest Rutherford probe farther into atomic structure?
• When did experiments establish the standard model of particle physics?
• In what way are the quarks inside a proton held together?
• How do the gluons operate?
• How is the theory describing quarks and their behaviour called?
• Can you describe the experiments carried out at Fermilab?
• Does QCD explain the experiments carried out at Fermilab?
• What idea do most physicists seem to prefer to explain the experiments?
• What is the opinion of John Ellis?
• What is the opinion of Don Page?
IX. Write a summary in English (or in your own language).
• Give each paragraph a suitable title in English (or in your own language).
• Develop the titles of the paragraphs into topic sentences. Join the topic sentences together.
• Re-read your summary and make sure that the sentences are presented in a logical order.