Cosmic Muons

Cosmic rays from outer space turn into muons in the upper atmosphere.

Pass through 12''³ block of fancy plastic

• Emit brief (~ns) flash of light
• Viewed on both sides by photo-multipliers

Some Actually stop

• µ→eνν the es also emit a flash of light

If we can measure the Δt between flashes can measure how long the stopped muons last.

<u>Equipment</u>

• PMT need high voltage 2k V
• "fast electronics" to process & digitize signals
• TDC -> digital time -> histogram on computer

(Oscilloscope as debugger)

Lifetime of the muon is a big deal. Its how we measure the strength of the weak force! Existence of µs at sea level proof relativity is correct.