Nav: Home

Searching for disappeared anti-matter: A successful start to measurements with Belle II

March 25, 2019

The Belle II detector got off to a successful start in Japan. Since March 25, 2019, the instrument has been measuring the first particle collisions, which are generated in the modernized SuperKEKB accelerator. The new duo produces more than 50 times the number of collisions compared to its predecessor. The huge increase in evaluable data means that there is not a greater chance of finding out why there is an imbalance between matter and anti-matter in the Universe.

In the Belle II experiment, electrons and their anti-particles, the positrons, are brought to collision. This results in the generation of B mesons, couples consisting of a quark and an anti-quark. During earlier experiments (Belle and BaBar), scientists were able to observe that B mesons and anti-B mesons decay at different speeds (1).

This phenomenon is known as CP violation (2). It offers an orientation when it comes to the question of why the Universe contains almost no anti-matter - even though after the Big Bang, both forms of matter must have been present in equal quantities.

Will Belle II discover new physics?

"However, the asymmetry observed to date is too small to explain the lack of anti-matter," says Hans-Günther Moser from the Max Planck Institute for Physics. "That's why we're looking for a more powerful mechanism that has remained unknown to date that would burst the boundaries of the 'standard model of particle physics' that has been used to date. However, to find this new physics and to provide statistical evidence for it, physicists must collect and evaluate far more data than they have done to date."

With this task in mind, the former KEK accelerator and Belle - which were operational from 1999 to 2010 - have been fully modernized. They are now being run under the names Belle II and SuperKEKB. The key new development is the 40-fold increase in luminosity, the number of particle collisions per area unit.

For this purpose, scientists and technicians have significantly reduced the profile of the particle beam; at the same time, it will be possible to double the number of shot particle bunches in the future. The probability that the particles might actually hit each other is thus considerably increased. In this way, scientists will have 50 times the amount of data available for evaluation in the future.

High-precision recording of particle tracks

However, the additional amount of data presents major challenges when it comes to the quality of the analysis provided by the detector. After the particle collision, the B mesons decay by just 0.1 millimeters on an average flight. This means that the detectors have to work very quickly and precisely. This is ensured by a highly sensitive pixel vertex detector, a large part of which was developed and built at the Max Planck Institute for Physics and the semiconductor laboratory of the Max Planck Society. The detector has 8 million pixels overall, and delivers 50,000 images per second.

"Several special technologies are built into the pixel vertex detector," Moser explains. "When new particle packages are fed into the SuperKEKB, which initially generates a very large background, we can blind the detector for about 1 microsecond. This means that non-relevant signals can be blocked out." Also, the detector sensors are no thicker than a human hair, with widths of just 75 micrometers. The physicists hope that in this way, they can prevent particles from being scattered while passing through matter.

The start of the measurement operation will mark the end of a major construction project. For nine years, scientists and engineers have been working on the conversion and modernization of the detector. The run that has now begun will continue until 1st July 2019. The SuperKEKB and Belle II will restart in October 2019 after a brief pause for maintenance.
-end-
(1) In 2008, the Japanese professors Makoto Kobayashi and Toshihide Maskawa won the Nobel Prize for Physics for this discovery.

(2) Charge/Parity

(3) The pixel vertex detector was developed and built by 11 research institutions: Excellence Cluster Universe, DESY, Semiconductor Laboratory of the Max Planck Society, Ludwig-Maximilians-Universitaet Muenchen, Karlsruhe Institute for Technology, Max-Planck Institute for Physics, Technical University of Munich, University of Bonn, Giessen University, University of Goettingen, Heidelberg University.

Charge/Parity

The pixel vertex detector was developed and built by 11 research institutions: Excellence Cluster Universe, DESY, Semiconductor Laboratory of the Max Planck Society, Ludwig-Maximilians-Universitaet Muenchen, Karlsruhe Institute for Technology, Max-Planck Institute for Physics, Technical University of Munich, University of Bonn, Giessen University, University of Goettingen, Heidelberg University.

Contact:

Dr. Hans-Guenther Moser
Max Planck Institute for Physics
+49 89 32354-248
moser@mpp.mpg.de

Max Planck Institute for Physics

Related Physics Articles:

Diamonds coupled using quantum physics
Researchers at TU Wien have succeeded in coupling the specific defects in two such diamonds with one another.
The physics of wealth inequality
A Duke engineering professor has proposed an explanation for why the income disparity in America between the rich and poor continues to grow.
Physics can predict wealth inequality
The 2016 election year highlighted the growing problem of wealth inequality and finding ways to help the people who are falling behind.
Physics: Toward a practical nuclear pendulum
Researchers from Ludwig-Maximilians-Universitaet (LMU) Munich have, for the first time, measured the lifetime of an excited state in the nucleus of an unstable element.
Flowers use physics to attract pollinators
A new review indicates that flowers may be able to manipulate the laws of physics, by playing with light, using mechanical tricks, and harnessing electrostatic forces to attract pollinators.
Physics, photosynthesis and solar cells
A University of California, Riverside assistant professor has combined photosynthesis and physics to make a key discovery that could help make solar cells more efficient.
2-D physics
Physicist Andrea Young receives a 2016 Packard Fellowship to pursue his studies of van der Waals heterostructures.
Cats seem to grasp the laws of physics
Cats understand the principle of cause and effect as well as some elements of physics.
Plasma physics' giant leap
For the first time, scientists are looking at real data -- not computer models, but direct observation -- about what is happening in the fascinating region where the Earth's magnetic field breaks and then joins with the interplanetary magnetic field.
Nuclear physics' interdisciplinary progress
The theoretical view of the structure of the atom nucleus is not carved in stone.

Related Physics Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".