Exploring Vacuum Using World’s Highest-Intensity X-rays -Toward unknown fields- (Press Release)
- Release Date
- 30 Apr, 2014
- SACLA
The University of Tokyo
RIKEN
Key points
• We Explore unknown components (fields*3) in a vacuum and particle pairs predicted by quantum mechanics at the Spring-8 angstrom compact free-electron laser (SACLA) facility*2
• It is demonstrated that research of the elementary particle physics is possible using an intense and high-quality X-ray source and we establish the related key technologies, such as the collision of X-rays
• Demonstrating the important role of high-intensity X-rays in basic science for the first time in the world
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The most important implication of the discovery of Higgs particles,*1 for which the Nobel Prize for Physics in 2013 was awarded, was that it demonstrates that a vacuum is not an empty space but is filled with mysterious components, called the Higgs field. In addition to the Higgs field, several unknown components (fields) are expected to exist in a vacuum, such as the field causing the inflation of the universe and the field causing the reacceleration of the universe *4(Nobel Prize for Physics in 2011). A research group led by Shoji Asai (professor) of the Department of Physics, Graduate School of Science, The University of Tokyo, explored such unknown components (fields) in a vacuum at the Spring-8 angstrom compact free-electron laser (SACLA) facility*2. When finely focused X-rays are made to collide in the absence of an unknown field, the X-rays pass through each other and no reaction is induced; whereas in the presence of an unknown field, the X-rays are scattered and the direction and energy of the scattered X-rays change after scattering. Unfortunately, no scattering event was observed in this study. An upper limit of 1.7 × 10−24 m2 was found on the photon–photon scattering cross section.*5 In this study, the unknown field was explored with high sensitivity, which was realized by the development of a technique for colliding X-rays using two thin blades cut out from silicon single crystals. This was the first attempt to explore the unknown field using X-rays. The performance of SACLA is being improved; measurement with 25-digit higher sensitivity will be possible in the near future. SACLA has contributed to considerable achievements in the fields of materials science and life science. SACLA has also been demonstrated to be useful in fundamental physics such as through research on elementary particles and the universe. Publication: |
《Figures》
Virtual electrons and positrons are generated by the energy of X-ray collisions. They return to two X-rays in a short period of time permitted by quantum mechanics.
High-intensity X-rays generated at the SACLA facility are incident on two 0.6-mm-thick silicon blades (green line) from left to right in the figure. At the first silicon blade, the incident beams are split into transmitted and reflected beams. The two beams are further split into transmitted and reflected X-rays at the second silicon blade. The transmitted-reflected beam always collides with the reflected-reflected beam.
《Glossary》
*1 Higgs particle
The Higgs particle is a type of elementary particle that can explain why elementary particles have mass. For a detailed explanation, refer to the press release below. http://www.icepp.s.u-tokyo.ac.jp/~asai/work/NobelslideV2.pdf
*2 Spring-8 angstrom compact free-electron laser (SACLA) facility
The SACLA facility can be used to generate X-ray lasers by accelerating electrons to a high energy and controlling them. The SACLA facility is located in Harima and generates the world’s highest-performance X-ray free-electron laser. For details, refer to the following site.
http://xfel.riken.jp
*3 Fields
Physical quantities that exist spatially, such as electric fields, magnetic fields, and gravitational fields.
*4 Reacceleration of universe
The universe has been expanding since the Big Bang, and its rate of expansion is increasing. The Nobel Prize in Physics in 2011 was awarded for this discovery.
*5 Cross-section
A quantity with a dimension of area proportional to reaction rates
*6 Virtual electrons
Electrons that can exist only during a short period of time predicted by the uncertainty principle.*7 Particles that can be handled are called free electrons with an energy of 0.511 MeV. Quantum electrodynamics (QED) is the theory dealing with virtual electrons, free electrons, and photons.
*7 Uncertainty principle
Assuming that the energy uncertainty (unexplainable quantity) is ΔE and that Δt is a short period of time, then ΔE·Δt > h/4π (where h, called Planck’s constant, has a small value). If the period is very short (~10−21 s), electrons with an energy ~1 MeV different from their original energy can exist.
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For more information, please contact: Prof. Shoji Asai |
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