Measurement of the Muon’s Lifetime & Cosmic Ray Flux J.C.Xu Q.Y.Tang

Content 1 、 Introduction 2 、 Measurement &Result 3 、 Discussion & Improvement

3 、 The muon is an unstable subatomic particle with a mean lifetime of 2.2 µs. 1 、 Introduction——What’s Muon? 2 、 Muons are produced in copious amounts in high-energy interactions in normal matter. These interactions usually produce pi mesons initially, which most often decay to muons. 1 、 The muon is an elementary particle similar to the electron, but with a much greater mass. it is not thought to be composed of any simpler particles.

Is made of these: The Universe’s fundamental building blocks. 1 、 Introduction—— What’s Muon?

But if we consider the Einstein's theory of relativity: So it could reach the ground surface. 1 、 Introduction——What’s Muon? Muon travels at a speed slightly below that of light, if we observe muon in static reference frames ， muon could travel 600m （ far below the thickness of the atmosphere within its lifetime.

Can we at least measure one of those fundamental particle parameters in a classroom? At ground level, we have mostly muons from these cosmic showers. The questions is what can we measure and how do we measure. Muons decay and its lifetime is a fundamental particle parameter. So let’s measure muon lifetime.

Our Detector  e By measuring the time difference muon entrance and the electron production, we can calculate the muon lifetime . So we need a detector to count a double pulse. 1 、 Introduction—How to Measure Muon Lifetime?

1 、 Introduction—How to Measure Muon Lifetime?

X(-4) X5 Disc V thrd TDC (FPGA) 1 、 Introduction—How to Measure Muon Lifetime?

1 、 Introduction—How to Measure Muon Lifetime?

Threshold:400mV Time:10min HV muon count 、 Measurement &Results——Explore

HV: 400V Time: 10min thres hold muon count 、 Measurement &Results——Explore

CH1CH2Effect 11 Coincidence Counting 10Muon Lifetme 01Muon Lifetime 00 Anti-coincidence Counting Coincidence Counting: The entangled particles are vastly outnumbered by non-entangled particles which are also detected; patternless noise that drowns out the entangled signal. In a two detector system, a coincidence counter alleviates this problem by only recording detection signals that strike both detectors simultaneously. This ensures that the data represents only entangled particles. 2 、 Measurement &Results——Flux

sigma+sigma-measured E E Vertical W W sigma+sigma-measured N N Vertical S S 、 Measurement &Results——Flux

sigma+sigma-measured E E Vertical W W sigma+sigma-measured N N Vertical S S 、 Measurement &Results——Flux

For data analyses ， plot muon decay times and fit to 1 ） elapsed time: 16h40m 2 、 Measurement &Results—Muon Lifetime

2 ） elapsed time: 7d23h33m 2 、 Measurement &Results—Muon Lifetime

Data format:  10 muons during this time  one muon decay, 900*20 ns  one muon decay,17280*20 ns 、 Measurement &Results——Data Analysis

--Lengthen the time duration for the experiment --Increase the size of the muon detector to collect more data --Deploy multiple detectors in different locations to form a controlled experiment --Better ways to analyse the data Improvement 3 、 Discussion & Improment

In a medium with an index of refraction of n the light velocity is c/n. When a charged particle traverses the medium with velocity larger than the light velocity, so called Cherenkov light is emitted. The minimum energy of the particle with this velocity (called "Cherenkov threshold energy'') is MeV for electrons and MeV for muons. Cherenkov light is emitted in a cone of half angle  from the direction of the particle track. In water this angle is about 42 o. 3 、 Discussion & Improment Another way to detect muons and lectrons:cherenkov light

A suggested muon detector based on water water muon electron 3 、 Discussion & Improment

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Reference 1.“A compact apparatus for muon lifetime measurement and time dilation demonstration in the undergraduate labrotory.” T.Conan, T.Liu and J.YE.J.Ye Am.J.Phys.74,161(2006) 2.“Studies of the performance of the ATLAS detector using cosmic-ray muons.” The ATLAS Collaboration, Nov Published in Eur.Phys.J.C71:1593, “Cosmic Ray Muons an the Muon Lifetime.”University of Florida- department of Physics,Published in Advanced Physics Laboratory, October 14, 2013