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Text 5 . Heart of the Matter
(A PARTICLE “FACTORY” FOR PROBING A
SEMINAL ASYMMETRY)
On one side of the Atlantic at least, these are nxious days for particle physicists. Letters in Physics Today and other journals agonize over the future of the field. A poor economy has kept the Superconducting Super Collider (SSC) teetering on the edge of political death.
Many physicists fear that their discipline, acking experimental results may become lost in a mathematical wasteland. Yet there are signs of vitality. On October 4, 1993 the Department of Energy announced its intention to build a facility at the Stanford Linear Accelerator Center (SLAC) for probing one of the fundamental mysteries of modern physics, a phenomenon called CP (for charge parity) violation.
The roots of the CP-violation puzzle reach back to experiments done more than 30 years ago showing that matter and antimatter are linked by deep symmetries. Any process energetic enough to create particles will produce an equal number of antiparticles. When particles and antiparticles collide, they vanish in a burst of pure radiation. Moreover, antiparticles generally behave like oppositely charged, mirror images of their particle counterparts (if a particle spins clockwise, for example, its antiparticle will spin counterclockwise), obeying what came to be known as charge-parity conservation.
By the early 1960s many physicists had concluded that CP conservation was a stricture as absolute as the conservation of energy. They were therefore stunned in 1963, when experiments by Val L.Fitch and James W.Cronin showed that not all interactions follow the charge-parity rule. Fitch and Cronin found that particles called K mesons transmute into their antiparticles slightly less often than the antiparticles change into K mesons.
Some theorists viewed CP violation as an unsightly deviation from the overall symmetry of physics, but the Soviet physicist Andrei Sakharov realized it might solve what was emerging as a central problem in cosmology. The primordial explosion in which the universe was conceived should have spawned matter and antimatter in equal proportions. Over time, each particle should have encountered its antiparticle, and eventually all matter would be replaced with a glimmer of gamma rays. The obvious question is, how is it that so much matter managed to survive and so little antimatter?
In 1968 Sakharov suggested that CP violation might hold the key to this puzzle, which is sometimes called matter-antimatter asymmetry. During the big bang, Sakharov speculated, an asymmetry related to the effects, observed by Fitch and Cronin, could have led to the production of slightly more particles than antiparticles.
Sakharov’s proposal served as the seed for a thriving field of inquiry. Unfortunately, experimentalists have been unable to test the suggestions rigorously. “K mesons can’t pin down the CP-violation mechanism”, says Karl Berkelman of Cornell University. Physicists have therefore pinned their hopes for understanding CP violation on the B meson, which Jonathan M.Dorfan of Stanford calls the K meson’s “heavy brother”.
B mesons are similar to K mesons, except that they are composed of bottom quarks rather than lighter strange quarks. Theorists estimated a decade ago that to study CP violation fully will require generating B mesons in amounts well beyond the capability of any current accelerator. Thus was the idea for the “B factory” born.
The Stanford facility will generate B mesons by boosting electrons and their antimatter twins, positrons, to high energies and then smashing them together. In addition to solving the CP-violation mystery, the B factory could lead to a deeper understanding of the forces of nature.
John Horgan. Scientific American, 1993
Vocabulary and Comprehension Exercises
I. Translate these into your own language:
• anxious
• particle physics
• to teeter on the edge of political death
• to lack experimental results
• signs of vitality
• to build a facility
• to probe
• charge parity (CP)
• CP violation
• CP conservation
• to be linked by
• to vanish in a burst of pure radiation
• to follow the rule
• K meson
• to transmute
• antiparticles
• to emerge as a central problem
• primordial explosion
• to spawn matter and antimatter in equal proportions
• to survive
• to pin down the CP-violation mechanism
• to be similar to
• bottom quarks
• strange quarks
• to lead to a deeper understanding
III. Give synonyms of the following words and word combinations:
To be anxious, to probe, to produce, to transmute, to vanish, to view, facility.
IV. Find the sentences in the text in which the following words and expressions are used:
• particle physicists
• lacking experimental results
• to build a facility
• to probe
• CP-violation puzzle
• to be linked by
• to vanish in a burst of pure radiation
• to behave
• to follow the charge-parity rule
• to transmute into
• an unsightly deviation
• a central problem in cosmology
• to spawn matter and antimatter in equal proportions
• to hold the key to this puzzle
• the Big Bang
• to pin down the CP-violation mechanism
• to pin the hopes on the B meson
• to be similar to
• to generate B mesons
• a deeper understanding
V. Comment on the structure of the following sentences:
• The roots of the CP-violation puzzle reach back to experiments done more than 30 years ago showing that matter and antimatter are linked by deep symmetries.
• Any process energetic enough to create particles will produce an equal number of antiparticles.
• Moreover, antiparticles generally behave like oppositely charged, mirror images of their particle counterparts (if a particle spins clockwise, for example, its antiparticle will spin counterclock wise), obeying what came to be known as charge-parity conservation.
• During the big bang, Sakharov speculated, an asymmetry related to the effects observed by Fitch and Cronin, could have led to the production of slightly more particles than antiparticles.
• The Stanford facility will generate B mesons by boosting electrons and their antimatter twins, positrons, to high energies in separate rings and then smashing them together.
VI. Ask questions to which the following statements might be the answers:
• Letters in Physics Today and other journals agonize over the future of particle physics.
• A poor economy has kept the Superconducting Super Collider (SSC) teetering on the edge of political death.
• On October 4, 1993 the Department of Energy announced its intention to build a facility for probing CP-violation.
• Matter and antimatter are linked by deep symmetries.
• Any process energetic enough to create particles will produce an equal number of antiparticles.
• By the early 1960s many physicists had concluded that CP conservation was a stricture as absolute as the conservation of energy.
• They were stunned in 1963, when experiments by Fitch and Cronin showed that not all interactions follow the charge-parity rule.
• Some theorists viewed CP-violation as an unsightly deviation from the overall symmetry of physics.
• The primordial explosion should have spawned matter and antimatter in equal proportions.
• In 1968 Sakharov suggested that CP-violation might hold the key to matter-antimatter asymmetry.
VII. Agree or disagree with the following statements:
• These are anxious days for particle physicists.
• A poor economy has kept the Superconducting Super Collider (SSC) teetering on the edge of political death.
• Many physicists are sure that their discipline will never become lost in a mathematical wasteland.
• In November the Department of Energy announced its intention to build a facility at the Stanford Linear Accelerator Center (SLAC).
• The physicists are going to probe one of the fundamental mysteries of modern physics, a phenomenon called CP-violation.
• The roots of the CP-violation puzzle reach back to experiments done more than 100 years ago.
• Matter and antimatter are linked by deep symmetries.
• When particles and antiparticles collide, they eject light.
• By the early 1960s many physicists had concluded that CP conservation was a stricture as absolute as the conservation of energy.
• The experiments of Val Fitch and James Cronin showed that all interactions follow the charge-parity rule.
• Some theorists viewed CP-violation as an unsightly deviation from the overall symmetry of physics but Andrei Sakharov considered it to be a law.
• Experimentalists have been able to test Sakharov’s suggestion rigorously.
VIII. Arrange the items of the plan in a logical order according to the text.
• - Sakharov’s suggestion.
• - The roots of the CP-violation puzzle.
• - Anxious days for particle physicists.
• - K mesons and B mesons.
• - CP conservation.
• - A new facility for probing CP violation.
IX. Answer the questions:
• Why are these days anxious for particle physicists?
• What do many physicists fear?
• What are the signs of vitality?
• What is CP-violation?
• How old is the CP-violation puzzle?
• What happens when particles and antiparticles collide?
• In what way do antiparticles generally behave?
• Who conducted the experiments that showed that not all interactions follow the charge-parity rule?
• What did Fitch and Cronin find?
• How did some theorists view CP-violation?
• To what puzzle might CP-violation hold the key, in the opinion of Sakharov?
• Can K mesons pin down the CP violation mechanism?
• On what have physicists pinned their hopes?
• What quarks are B mesons composed of?
• What is the main principle of acting of the Stanford facility?
X. 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.