particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

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exotic atom An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles.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

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 ''ħ'', but with a much greater mass. It is classified as a ...

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 Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

. Its properties within the Standard Model are determined by

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

, and may be modified by

physics beyond the Standard Model Physics beyond the Standard Model (BSM) refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the inability to explain the fundamental parameters of the standard model, the strong CP problem, neut ...

. True muonium is yet to be observed experimentally, though it may have been produced in experiments involving collisions of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

and

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

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") is an adverse reaction of Substance intoxication, intoxication that causes a state of vertigo and nausea, causing one to feel as if "spinning out of control", especially when lying down. It is most commonly as ...

) 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 a particle physics detector collecting data at the Large Hadron Collider at CERN. LHCb specializes in the measurements of the parameters of CP violation in the interactions of b- and c-hadro ...

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 Meyrin, western 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 (Mumutron) 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 Lavrentyev Avenue, Novosibirsk, Academician Lavrentiev ...

of the Siberian Branch of the Russian Academy of Sciences (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 that brings two opposing particle beams together such that the particles collide. Compared to other particle accelerators in which the moving particles collide with a stationary matter target, collid ...

, 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 ( = ). 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 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