Menu
Modern science
Soil Microbes Accelerate Global Warming

Bold New Approach to Wind 'Farm' Design May Provide Efficiency Gains

Soft Memory Device Opens Door to New Biocompatible Electronics

Most Elliptical Galaxies Are 'Like Spirals'

New Planets Feature Young Star and Twin Neptunes

Editing the Genome: Scientists Unveil New Tools for Rewriting the Code of Life

High Social Rank Comes at a Price, Wild Baboon Study Finds

Fossil Forensics Reveals How Wasps Populated Rotting Dinosaur Eggs

Monitoring Cellular Interactions at Nano-Scale in More Detail Than Ever Before

Non-Africans Are Part Neanderthal, Genetic Research Shows

Making Blood Sucking Deadly for Mosquitoes

Rising Oceans: Too Late to Turn the Tide?

Newly Developed Fluorescent Protein Makes Internal Organs Visible

NASA's Dawn Spacecraft Returns Close-Up Image of Giant Asteroid Vesta

Bacteria Use Batman-Like Grappling Hooks to 'Slingshot' On Surfaces, Study Shows

Mysterious Fossils Provide New Clues to Insect Evolution

Twisted Tale of Our Galaxy's Ring: Strange Kink in Milky Way

Engineering Excitable Cells for Studies of Bioelectricity and Cell Therapy

Ancient Footprints Show Human-Like Walking Began Nearly 4 Million Years Ago

Memories May Skew Visual Perception

Movement of Black Holes Powers Quasars, the Universe's Brightest Lights

First Artificial Neural Network Created out of DNA: Molecular Soup Exhibits Brainlike Behavior

Dolphins' 'Remarkable' Recovery from Injury Offers Important Insights for Human Healing

Cosmological Evolution of Dark Matter Is Similar to That of Visible Matter

Exoplanet Aurora: An Out-Of-This-World Sight

Fundamental Matter-Antimatter Symmetry Confirmed
An international collaboration including Max Planck Institute of Quantum Optics scientists has set a new value for the antiproton mass relative to the electron with unprecedented precision.

According to modern cosmology, matter and antimatter were created in equal amounts in the Big Bang at the beginning of the universe. Physicists are developing concepts to explain why the visible universe now seems to be made entirely out of matter. On the other hand, experimental groups are producing antimatter atoms artificially to explore the fundamental symmetries between matter and antimatter, which according to the present theories of particle physics should have exactly the same properties, except for the opposite electrical charge).

Now the independent research group “Antimatter Spectroscopy” of Dr. Masaki Hori, which is associated with the Laser Spectroscopy Division of Prof. Theodor W. Hänsch at the Max Planck Institute of Quantum Optics, has measured the mass of the antiproton relative to the electron with a precision of 1.3 parts per billion (Nature, 28 July 2011). For this they used a new method of laser spectroscopy on a half-antimatter, half-matter atom called antiprotonic helium. The result agreed with the proton mass measured to a similar level of precision, confirming the symmetry between matter and antimatter. The experiment was carried out at the European Laboratory for Particle Physics (CERN) in Geneva (Switzerland) in a project led by scientists from the Max Planck Institute of Quantum Optics and Tokyo University (Japan), and including the University of Brescia (Italy), the Stefan Meyer Institute (Vienna, Austria), and the KFKI Research Institute (Budapest, Hungary).

Physicists believe that the laws of nature obey a fundamental symmetry called “CPT” (this stands for charge conjugation, parity, and time reversal), which postulates that if all the matter in the universe were replaced with antimatter, left and right inverted as if looking into a mirror, and the flow of time reversed, this “anti-world” would be indistinguishable from our real matter world. Antimatter atoms should weigh exactly the same as their matter counterparts. If scientists were to experimentally detect any deviation, however small, it would indicate that this fundamental symmetry is broken. “Small” is the keyword here – it is essential to use the most precise methods and instruments available to make this comparison with the highest possible precision.

Antimatter is extraordinarily difficult to handle in the laboratory, because upon coming into contact with ordinary matter (even the air molecules in a room), it immediately annihilates, converting into energy and new particles. In 1997, researchers from the Max Planck Institute of Quantum Optics in cooperation with other European, Japanese, and American groups began construction of a facility called the Antiproton Decelerator (AD) at CERN. Here antiprotons produced in high-energy collisions are collected and stored in a vacuum pipe arranged in a 190-m-long racetrack shape. The antiprotons are gradually slowed down, before being transported to several experiments. The so-called ASACUSA1 (Atomic Spectroscopy and Collisions using Slow Antiprotons, named after a district in Tokyo) collaboration, of which Dr. Hori is one of the project leaders, sends the antiprotons into a helium target to create and study antiprotonic helium atoms.

Normal helium atoms consist of a nucleus with two electrons orbiting around it. In antiprotonic helium, one of these electrons is replaced by an antiproton, which finds itself in an excited orbit some 100 picometres (10-10 m) from the nucleus. Scientists fire a laser beam onto the atom, and carefully tune its frequency until the antiproton makes a quantum jump from one orbit to another. By comparing this frequency with theoretical calculations, the mass of the antiproton can be determined relative to the electron.

An important source of imprecision arises because the antiprotonic atoms jiggle around randomly according to their thermal energy, so that atoms moving towards the laser beam experience a different frequency compared to those moving away. This is similar to the effect that causes the siren of an approaching ambulance to change pitch as it passes you by. In their previous experiments of 2006, the MPQ / ASACUSA scientists used one laser beam, and this effect limited the precision of their measurement.

This time to go beyond this limit, a technique called “two-photon laser spectroscopy” was used. The atoms were struck by two laser beams travelling in opposite directions, with the result that the effect was partially cancelled, leading to a four to six times higher precision. The first laser caused the antiproton to make a quantum jump to a virtual energy level normally not allowed by quantum mechanics, so that the second laser could actually bring the antiproton up to the closest allowed state. Such a two-photon jump is normally difficult to achieve because the antiproton is heavy, but MPQ scientists accomplished it by building two ultra-sharp lasers and carefully choosing a special combination of laser frequencies. To do this, an optical frequency comb – a special device invented 10 years ago by the group of Prof. Theodor W. Hänsch to measure the frequency of light – was used.

The new measurements showed that the antiproton is 1836.1526736(23) times heavier than the electron, the parenthesis showing the 1-standard deviation imprecision. “We have measured the mass of the antiproton relative to the electron with a precision of 10 digits, and have found it exactly the same as the proton value known with a similar precision”, Masaki Hori explains. “This can be regarded as a confirmation of the CPT theorem. Furthermore, we learned that antiprotons obey the same laws of nonlinear quantum optics like normal particles, and we can use lasers to manipulate them. The two-photon technique would allow much higher precisions to be achieved in the future, so that ultimately the antiproton mass may be better known than the proton one.”

The Committee on Data for Science and Technology (CODATA) uses the results of this experiment as one of several input data to determine the proton-to-electron mass ratio, which in turn influences the values of many other fundamental constants.

Äë˙ ďĺ÷ŕňč

New Material Lets Electrons 'Dance' and Form New State

Cod Resurgence in Canadian Waters

Fundamental Matter-Antimatter Symmetry Confirmed

First True View of Global Erosion

NASA's WISE Finds Earth's First 'Trojan' Asteroid

Engineers Fly World's First 'Printed' Aircraft

Scientist Converts Human Skin Cells Into Functional Brain Cells

Rainforest Plant Developed 'Sonar Dish' to Attract Pollinating Bats

Sea Level Rise Less from Greenland, More from Antarctica, Than Expected During Last Interglacial

How Bats Stay On Target Despite the Clutter

Fall of the Neanderthals: Volume of Modern Humans Infiltrating Europe Cited as Critical Factor

Largest-Ever Map of Plant Protein Interactions

Some Plants Duplicate Their DNA to Overcome Adversity


Menu
Diamonds Pinpoint Start of Colliding Continents

Researchers Identify Seventh and Eighth Bases of DNA

Fool's Gold Gives Scientists Priceless Insight Into Earth's Evolution

Astronomers Discover Largest and Most Distant Reservoir of Water Yet

Major Step Toward Creating Faster Electronics Using Graphene

New Photonic Crystals Have Both Electronic and Optical Properties

Epigenetic 'Memory' Key to Nature Versus Nurture

Climate Change to Increase Yellowstone Wildfires Dramatically

Retinal Cells Thoughts to Be the Same Are Not, Biologist Says

Minority Rules: Scientists Discover Tipping Point for the Spread of Ideas

Mitochondria Share an Ancestor With SAR11, a Globally Significant Marine Microbe

Drug Shown to Improve Sight for Patients With Inherited Blindness

Elliptical Galaxies Are Not Dead

Hubble Constant: A New Way to Measure the Expansion of the Universe

Enceladus Rains Water Onto Saturn

Engineers Develop One-Way Transmission System for Sound Waves

Researchers Graft Olfactory Receptors Onto Nanotubes

New Invisibility Cloak Hides Objects from Human View

Bionic Microrobot Mimics the 'Water Strider' and Walks On Water

How Memory Is Lost: Loss of Memory Due to Aging May Be Reversible

Reservoirs of Ancient Lava Shaped Earth

Wave Power Can Drive Sun's Intense Heat

Social Deficits Associated With Autism, Schizophrenia Induced in Mice With New Technology

Tundra Fires Could Accelerate Climate Warming

Chandra X-Ray Observatory Images Gas Flowing Toward Black Hole