Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Magnetic moment of a single antiproton determined with greatest precision ever

19.01.2017

Physicists publish most accurate measurement of a fundamental property of the antiproton to date / Contribution to the matter-antimatter debate

As self-evident as it is that matter exists, its origins are just as mysterious. According to the principles of particle physics, when the universe was originally formed equal amounts of matter and antimatter would have been created, which then should have destroyed each other in a process that physicists call annihilation. But in reality, our universe shows a manifest imbalance in favor of matter.


BASE experiment using the CERN antiproton decelerator in Geneva: Visible in the image are the control equipment, the superconducting magnet that houses the Penning trap, and the antiproton transfer beam tube.

photo/©: Stefan Sellner, RIKEN

Therefore, scientists are looking for a small difference between a particle and its antiparticle that could explain why matter actually exists. The multinational Baryon Antibaryon Symmetry Experiment (BASE) collaboration at the CERN research center has set a new benchmark in this search by successfully measuring an important characteristic of the antiproton with the greatest accuracy ever achieved. The g-factor, a quantity that characterizes the magnetic moment, has been measured with a precision increased by a factor of six compared to previous results.

The idea that something like anti-matter must exist came up in the late 1920s. It was only a few years later that positrons, the antiparticles of electrons, were discovered. While positrons occur naturally on Earth, antiprotons, the antiparticles of protons, have to be artificially generated.

The Antiproton Decelerator storage ring at CERN produces cooled antiprotons in large quantities for a wide range of antimatter experiments. In the experiments carried out by the BASE group, of which Johannes Gutenberg University Mainz (JGU) is a member, single ultracold antiprotons are studied in an electromagnetic particle trap.

The system consists of three Penning traps. A reservoir trap stores a cloud of antiprotons for the experiment and supplies single particles to the co-magnetometer trap and the actual analysis trap. The purpose of the co-magnetometer trap is to continuously monitor the magnetic field. The analysis trap is surrounded by an extremely large magnetic field inhomogeneity of 300 Kilotesla per square meter.

This ultra-powerful magnetic field inhomogeneity is a fundamental requirement for detecting spin-flips, a method developed by Nobel Prize laureate Hans Georg Dehmelt in 1987 for measuring the magnetic moment of the electron and the positron. "However, the challenge in our case is much greater because the magnetic moment of the proton and the antiproton is about 660 times smaller in comparison," wrote the BASE scientists in a paper published in Nature Communications. The principle used to measure the magnetic moment of single protons was developed five years ago by a collaboration with a group at the Institute of Physics at Johannes Gutenberg University Mainz led by Professor Jochen Walz. With its high-precision measurement of the proton in 2014 the collaboration goes unchallenged as the top research team in this field.

G-factor measured with six times enhanced accuracy

The method used to analyze the antiproton employs the same principle. The g-factor was determined on the basis of six individual measurements with an uncertainty of just 0.8 parts per million. The value of 2.7928465(23) is six times more precise than the previous record achieved by another CERN research group in 2013. As recently as 2011, the magnetic moment of the antiproton was only known to an accuracy of three decimal places.

The new result is consistent with the g-factor of the proton as measured in Mainz in 2014, namely 2.792847350(9). "This means that within our experimental uncertainty, we cannot detect any difference between protons and antiprotons. At this level our measurement is consistent with the predictions of the Standard Model," stated Stefan Ulmer, coordinator of BASE at CERN and a former member of Walz' team at Mainz University.

Protons and antiprotons thus still appear to be mirror images of each other, meaning there is still no explanation of why matter actually exists at all and did not simply vaporize in the first moments of the Big Bang. The BASE collaboration intends to go a step further by increasing the precision of its measurements using a double Penning trap technique. This is a complex technique that was used for the Mainz proton measurements in 2014 and offers the potential of improving accuracy by a factor of 1,000.

"The asymmetry between matter and antimatter is so obvious that something must have happened which cannot yet be detected using the methods currently available to modern physics. So our main aim is to find approaches that can help solve this extraordinary puzzle," said Ulmer of the group's future plans. In addition to Johannes Gutenberg University Mainz, the other members involved in the research projects are the RIKEN research center in Japan, the Max Planck Institute for Nuclear Physics in Heidelberg, the Leibniz Universität Hannover and the GSI Helmholtz Center for Heavy Ion Research in Darmstadt.

Images:
http://www.uni-mainz.de/bilder_presse/08_physik_quantum_antiproton_01.jpg
BASE experiment using the CERN antiproton decelerator in Geneva: Visible in the image are the control equipment, the superconducting magnet that houses the Penning trap, and the antiproton transfer beam tube.
photo/©: Stefan Sellner, RIKEN

http://www.uni-mainz.de/bilder_presse/08_physik_quantum_antiproton_02.jpg
BASE experiment using the CERN antiproton decelerator in Geneva: Shown here are the superconducting magnet that houses the Penning trap and the antiproton transfer beam tube.
photo/©: Stefan Sellner, RIKEN

http://www.uni-mainz.de/bilder_presse/08_physik_quantum_antiproton_03.jpg
BASE Penning trap system that was used to measure the magnetic moment of the antiproton
photo/©: Georg Schneider, JGU

Publication:
Hiroki Nagahama et al.
Sixfold improved single particle measurement of the magnetic moment of the antiproton
Nature Communications, 18 January 2017
DOI: 10.1038/ncomms14084

Further information:
Prof. Dr. Jochen Walz
Quantum, Atomic, and Neutron Physics (QUANTUM)
Institute of Physics
Johannes Gutenberg University Mainz (JGU)
55099 Mainz, GERMANY
phone +49 6131 39-25976
fax +49 6131 39-25179
e-mail: Jochen.Walz@uni-mainz.de
http://www.quantum.physik.uni-mainz.de/members__ag_walz__jwalz.html.en

Dr. Stefan Ulmer
BASE spokesperson
CERN
1211 Geneva, SWITZERLAND
phone +41 75 411 9072
e-mail: stefan.ulmer@cern.ch
http://www.quantum.physik.uni-mainz.de/members__ag_walz__sulmer.html.en

Weitere Informationen:

http://www.nature.com/articles/ncomms14084 ;
http://base.web.cern.ch/ ;
http://www.quantum.physik.uni-mainz.de/ag_walz__index.html.en ;
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", 21 June 2011 ;
http://www.uni-mainz.de/presse/17364_ENG_HTML.php – press release "Magnetic moment of the proton measured with unprecedented precision", 6. June 2014

Petra Giegerich | idw - Informationsdienst Wissenschaft

More articles from Physics and Astronomy:

nachricht Researchers put a new spin on molecular oxygen
17.07.2019 | Osaka University

nachricht Harvesting energy from the human knee
17.07.2019 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

Im Focus: Modelling leads to the optimum size for platinum fuel cell catalysts: Activity of fuel cell catalysts doubled

An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...

Im Focus: The secret of mushroom colors

Mushrooms: Darker fruiting bodies in cold climates

The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Tracking down climate change with radar eyes

17.07.2019 | Earth Sciences

Researchers build transistor-like gate for quantum information processing -- with qudits

17.07.2019 | Information Technology

A new material for the battery of the future, made in UCLouvain

17.07.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>