physics

Mu to E Gamma

Mu to E Gamma is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mu to E Gamma rather than just read about it. In short: The Mu to E Gamma (MEG) is a particle physics experiment dedicated to measuring the decay of the muon into an electron and a photon, a decay mode which is heavily suppressed in the Standard Model by lepton flavour conservation, but enhanced in supersymmetry and grand unified theories. It is located at the Paul Scherrer Institute and began taking data September 2008.

Key takeaways

Mu to E Gamma belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mu to E Gamma to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mu to E Gamma from memory before moving on to harder problems.

Reference excerpt

The Mu to E Gamma (MEG) is a particle physics experiment dedicated to measuring the decay of the muon into an electron and a photon, a decay mode which is heavily suppressed in the Standard Model by lepton flavour conservation, but enhanced in supersymmetry and grand unified theories. It is located at the Paul Scherrer Institute and began taking data September 2008.

MEG Results In May 2016 the MEG experiment published the world's leading upper limit on the branching ratio of this decay:

B ( μ + → e + γ ) < 4.2 × 10 − 13 {\displaystyle \mathrm {B} (\mu ^{+}\to e^{+}\gamma )<4.2\times 10^{-13}}

at 90% confidence level, based on data collected in 2009–2013. This improved the MEG limit from the prior MEGA experiment by a factor of about 28.

MEG II Result The MEG collaboration presented an upgrade plan for the MEG II experiment in 2014, and data taking begun in 2021 after significant detector and electronics upgrades.

In October 2025 the MEG II collaboration published the latest result using data from 2021 and 2022.

Combined with the MEG result, this yields in a new upper limit on the branching ratio of

B ( μ + → e + γ ) < 1.5 × 10 − 13 {\displaystyle \mathrm {B} (\mu ^{+}\to e^{+}\gamma )<1.5\times 10^{-13}}

More data being taken in 2023-2026 with much higher statistics will result in an even better limit to be published in the future.

Apparatus MEG and MEG II uses a continuous muon beam (3 × 107/s) incident on a plastic target. The experiment searches for a back-to-back positron and monochromatic photon (52.8 MeV). A liquid xenon scintillator with photomultiplier tubes measure the photon energy, and a drift chamber in a magnetic field detects the positrons. All detectors are read out by the MIDAS DAQ system. More experiments are planned to explore rare muon transitions, such as Comet (experiment), Mu2e and Mu3e.

References

External links MEG-II experiment record on INSPIRE-HEP "MEG home page".

Worked examples

Example 1 — a first encounter with Mu to E Gamma

Start with the simplest possible case. Write down what Mu to E Gamma claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mu to E Gamma before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mu to E Gamma ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mu to E Gamma

In research: Mu to E Gamma appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mu to E Gamma in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mu to E Gamma is common in secondary-school and first-year university syllabi. It links to neighbouring topics Particle experiments, Particle physics stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Mu to E Gamma outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Mu to E Gamma in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mu to E Gamma means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mu to E Gamma out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mu to E Gamma in simple terms?

Why does Mu to E Gamma matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mu to E Gamma?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mu to E Gamma.