particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

, true muonium is a theoretically predicted

exotic atom An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles of the same charge. For example, electrons may be replaced by other negatively charged particles such as muons (muonic atoms) ...

representing a bound state of an

muon A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...

and an antimuon (μ⁺μ⁻). The existence of true muonium is well established theoretically within the

Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...

. Its properties within the Standard Model are determined by

quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and spec ...

, and may be modified by physics beyond the Standard Model. True muonium is yet to be observed experimentally, though it may have been produced in experiments involving collisions of electron and positron beams. The ortho-state of true muonium (i.e. the state with parallel alignment of the muon and antimuon

spins The spins (as in having "the spins")Diane Marie Leiva. ''The Florida State University College of Education''Women's Voices on College Drinking: The First-Year College Experience"/ref> is an adverse reaction of intoxication that causes a state of v ...

) is expected to be relatively long-lived (with a lifetime of ), and decay predominantly to an e⁺e⁻ pair, which makes it possible for

LHCb The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the paramet ...

experiment at

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

to observe it with the dataset collected by 2025.

Experimental research

There are several experimental projects searching for the true muonium. One of them is the μμ-tron experiment (Myumutron) planned at the

Budker Institute of Nuclear Physics The Budker Institute of Nuclear Physics (BINP) is one of the major centres of advanced study of nuclear physics in Russia. It is located in the Siberian town Akademgorodok, on Academician Lavrentiev Avenue. The institute was founded by Gers ...

of the

Siberian Branch of the Russian Academy of Sciences The Siberian Branch of the Russian Academy of Sciences (SBRAS) was established by the Decree of the Government of the USSR which was based on the proposal of Mikhail Lavrentyev, Sergei Sobolev and Sergey Khristianovich in 1957 as a regional divis ...

(INP SB RAS), which has been under development since 2017. The experiment involves the creation of a special low-energy electron–positron

collider A collider is a type of particle accelerator which brings two opposing particle beams together such that the particles collide. Colliders may either be ring accelerators or linear accelerators. Colliders are used as a research tool in particle ...

, which will make it possible to observe the production of true muonium in collisions of electron and positron beams with an intersection angle of 75° with energies of 408 MeV. Thus, the

invariant mass The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, ...

of colliding particles will be equal to twice the mass of the muon (=105.658 MeV). To register the exotic atom (in the decay channel into an electron-positron pair), it is planned to create a specialized detector. Apart to the actual detection of true muonium, it is planned to isolate its various states and measure their lifetimes. In addition to experiments in the field of elementary particle physics, the collider created within the framework of the experiment is also of interest from the point of view of developing accelerator technologies for the

Super Charm-Tau factory Super Charm-Tau factory (SCT) is an electron–positron collider being designed and built by Budker Institute of Nuclear Physics in Novosibirsk. Its main goal is to study the CP-violation in the processes involving charmed hadrons, to investiga ...

planned at the INP SB RAS. The experiment was proposed in 2017 by , A. I. Milshtein, and , researchers at the INP SB RAS.

References

External links

Low-energy electron-positron collider to search and study (μ⁺μ⁻) bound state. A.V. Bogomyagkov, V.P. Druzhinin, E.B. Levichev, A.I. Milstein, S.V. Sinyatkin. BINP, Novosibirsk.
Hypothetical composite particles Onia {{particle-stub

Experimental research

See also

References

External links