Physicists succeeded in the first direct high-precision measurement of a fundamental property of the proton / Results will contribute to a better understanding of the matter/antimatter asymmetry
One of the biggest riddles in physics is the apparent imbalance between matter and antimatter in our universe. To date, there is no explanation as to why matter and antimatter failed to completely annihilate one another immediately after the big bang and how the surplus matter was created that went on to form the universe as we know it. Experiments conducted at Johannes Gutenberg University Mainz (JGU) have contributed towards a resolution of this problem.
Double Penning trap used to measure the magnetic moment of the proton. The double Penning trap is made of gold-plated cylindrical trap electrodes; the individual trap electrodes are isolated from one another using sapphire rings. During measurements the trap is in an ultra-high vacuum. To the right of the image is the outer housing of a detection instrument which allows for the observation of single protons. The entire structure is about 20 centimeters long.
photo: Andreas Mooser, JGU
For the first time a direct and high-precision measurement of the magnetic moment of the proton has been conducted successfully. The magnetic moment is one of the fundamental properties of protons, which combine with neutrons to form the nucleus of atoms.
In principal, the method can also be used to measure the magnetic moment of an antiproton with a similarly high precision, making it possible to investigate matter/antimatter asymmetry. Related experiments are now being set up at the CERN research center in Geneva, Switzerland.
Years of preparation were necessary before the measurements were possible and the results obtained have far exceeded those of all previous attempts. In addition to Mainz University, the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, the Max Planck Institute of Nuclear Physics in Heidelberg, and the Japanese RIKEN research facility all took part in the experiment.
Using a double Penning trap, the researchers were able to determine the relevant parameter, the so-called 'g-factor,' with a precision of 3.3 x 10ˆ9. The result is 760 times more precise than all the results documented independently at Mainz University and Harvard University in 2012, and three-times more precise than the result obtained by an indirect measurement in 1972.
"Protons are like tiny rod magnets. They have a magnetic moment 24 magnitudes – equal to one millionth of a billionth of a billionth – weaker than a typical compass needle. This is the first time we have been able to measure anything on this scale," said Andreas Mooser, primary author of the study and a member of Professor Jochen Walz's research team at Mainz University.
The key to success proved to be the use of a double Penning trap, i.e., an electromagnetic particle trap, to isolate and evaluate a single free proton. An analysis trap serves to detect spin-quantum jumps of the proton, while in a precision trap precise frequency measurements are conducted.
It has proved possible in the past to use Penning traps to directly measure the magnetic moment of individual particles such as electrons and their antiparticle counterparts, positrons. But adapting this approach for use with protons is an enormous challenge as the magnetic moment of a proton is 660 times smaller than that of an electron.
The apparatus for the experiment needed to be far more sensitive. The collaborating partners were able to develop such a highly sensitive double Penning trap so that they could undertake the long-planned measurements.
Apart from the direct measurement performed in Mainz, the previous most precise measurements were obtained by means of an indirect method in 1972, where the hyper-fine structure of atomic hydrogen was measured and subsequently theoretical corrections were applied.
The principle of a direct measurement in a double Penning trap can also be used for the antiproton. "We can then compare the two results and test these against the fundamental predictions of the standard model," explained Stefan Ulmer, coordinator of the BASE joint project, which is currently setting up a corresponding experiment at CERN in Geneva.
Using the double Penning trap technique for the antiproton could enhance the precision of results obtained during the ATRAP project in 2013 by a factor of at least 1,000. Assuming that the measured values differ, this would represent an important step forward with regard to understanding the matter/antimatter asymmetry of our universe.
Andreas Mooser et al.
Direct high-precision measurement of the magnetic moment of the proton
Nature, 29 May 2014
Andreas Mooser et al.
Resolution of Single Spin Flips of a Single Proton
Physical Review Letters, 4 April 2013
Dr. Andreas Mooser
Quantum, Atomic and Neutron Physics (QUANTUM)
Institute of Physics
Johannes Gutenberg University Mainz (JGU)
D 55099 Mainz, GERMANY
phone +49 6131 39-25953
fax +49 6131 39-23438
http://www.nature.com/nature/journal/v509/n7502/full/nature13388.html (Abstract) ;
http://www.uni-mainz.de/presse/14236_ENG_HTML.php (press release „Quantum leap: Magnetic properties of a single proton directly observed for the first time”) ;
CORRECTION - 2nd paragraph, 3rd sentence:
Using a double Penning trap, the researchers were able to determine the relevant parameter, the so-called 'g-factor,' with a precision of 3.3 x 10ˆ9.
Petra Giegerich | idw - Informationsdienst Wissenschaft
Optical lenses, hardly larger than a human hair
29.06.2016 | Universität Stuttgart
Clandestine black hole may represent new population
28.06.2016 | International Centre for Radio Astronomy Research
3D printing revolutionized the manufacturing of complex shapes in the last few years. Using additive depositing of materials, where individual dots or lines...
R2D2, a joint project to analyze and development high-TRL processes and technologies for manufacture of flexible organic light-emitting diodes (OLEDs) funded by the German Federal Ministry of Education and Research (BMBF) has been successfully completed.
In contrast to point light sources like LEDs made of inorganic semiconductor crystals, organic light-emitting diodes (OLEDs) are light-emitting surfaces. Their...
High resolution rotational spectroscopy reveals an unprecedented number of conformations of an odorant molecule – a new world record!
In a recent publication in the journal Physical Chemistry Chemical Physics, researchers from the Max Planck Institute for the Structure and Dynamics of Matter...
Strands of cow cartilage substitute for ink in a 3D bioprinting process that may one day create cartilage patches for worn out joints, according to a team of engineers. "Our goal is to create tissue that can be used to replace large amounts of worn out tissue or design patches," said Ibrahim T. Ozbolat, associate professor of engineering science and mechanics. "Those who have osteoarthritis in their joints suffer a lot. We need a new alternative treatment for this."
Cartilage is a good tissue to target for scale-up bioprinting because it is made up of only one cell type and has no blood vessels within the tissue. It is...
Physicists in Innsbruck have realized the first quantum simulation of lattice gauge theories, building a bridge between high-energy theory and atomic physics. In the journal Nature, Rainer Blatt‘s and Peter Zoller’s research teams describe how they simulated the creation of elementary particle pairs out of the vacuum by using a quantum computer.
Elementary particles are the fundamental buildings blocks of matter, and their properties are described by the Standard Model of particle physics. The...
28.06.2016 | Event News
09.06.2016 | Event News
24.05.2016 | Event News
29.06.2016 | Life Sciences
29.06.2016 | Life Sciences
29.06.2016 | Earth Sciences