For the first time, scientists using the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) have observed the transition of one type of particle, the neutral D-meson, into its antimatter particle – a process known as ‘mixing’. The new observation will be used as a test of the Standard Model, the current theory that best describes the entire universe’s luminous matter and its associated forces.
UK BaBar spokesman, Fergus Wilson of the Rutherford Appleton Lab said "D-meson mixing was first predicted over three decades ago but it is such an elusive phenomenon that it has taken until today to see it. The observation of D-meson mixing is yet another outstanding achievement for the BaBar experiment. The BaBar collaboration continues to make ground-breaking measurements that challenge our understanding of how elementary particles behave."
"Achieving the large number of collisions needed to observe D-meson mixing is a testament to the tremendous capabilities of the laboratory's accelerator team," said SLAC Director Jonathan Dorfan. "The discovery of this long-sought-after process is yet another step along the way to a better understanding of the Standard Model and the physics beyond."
The PEP-II accelerator complex at SLAC, also known as the B Factory, allows the BaBar collaboration to study not only B-mesons but also several other types of particles including the D-meson. Mesons, of which there are about 140 types, are made up of fundamental particles called quarks, which can be produced when particles collide at high energy. A flurry of particles in a variety of combinations is produced when electrons and positrons smash together at high energy in the PEP-II collider facility. One of the most elusive results of this flurry is the transformation of one particle into its anti-particle in a process physicists call "mixing.” Neutral K-mesons, observed more than 50 years ago, were the first elementary particles to demonstrate this phenomenon. About 20 years ago, scientists observed mixing with the B-meson. Now, for the first time, the BaBar experimenters have seen the D-meson transform into its anti-particle, and vice versa.
"This is a very exciting moment for us, having found the missing puzzle piece for particle-antiparticle mixing," said BaBar Spokesman Hassan Jawahery, a physics professor at the University of Maryland.
D-meson mixing is remarkably rare. Of the BaBar experiment’s several billion recorded collisions, this study focuses on about a million events containing a D-meson decay that are candidates for this effect. The experimenters found about 500 events in which a D-meson had changed into an anti-D-meson before decaying.
By observing the rare process of D-meson mixing, BaBar collaborators can test the intricacies of the Standard Model. To switch from matter to antimatter, the D-meson must interact with “virtual particles," which through quantum fluctuations pop into existence for a brief moment before disappearing again. Their momentary existence is enough to spark the D-meson’s transformation into an anti-D-meson. Although the BaBar detector cannot directly see these virtual particles, researchers can identify their effect by measuring the frequency of the D-meson to anti-D-meson transformation. Knowing that quantity will help determine whether the Standard Model is sufficient or whether it must be expanded to incorporate new physics processes.
“It’s too soon to know if the Standard Model is capable of fully accounting for this effect, or if new physics is required to explain the observation,” said Jawahery. “But in the coming weeks and months we are likely to see an abundance of new theoretical work to interpret what we’ve observed.”
Some 600 scientists and engineers from 77 institutions in Canada, France, Germany, Italy, the Netherlands, Norway, Russia, Spain, the United Kingdom and the United States work on BaBar. SLAC is funded by the US Department of Energy’s Office of Science. UK involvement is funded by the Particle Physics and Astronomy Research Council (PPARC)
Julia Maddock | alfa
Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory
Unraveling the nature of 'whistlers' from space in the lab
15.08.2018 | American Institute of Physics
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
17.08.2018 | Life Sciences
17.08.2018 | Event News
17.08.2018 | Materials Sciences