Muon Lifetime Experiment for

QuarkNet at SMU, June 9 – 13 2003

Jingbo Ye

1. Introduction to muon and muon lifetime.

2. How to measure muon lifetime.

3. The Readout Electronics Box and Assembly Issues.

4. Data and Data Analysis.

1. Introduction to muon and muon lifetime.

We live hereIs made of these:

The Universe’s fundamental building blocks.

As physicists, how do we measure these particles?

With facilities no single country can afford!

34 countries in ATLAS

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.

What is a lifetime?

N = N0 e –t/

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.

2. How to measure muon lifetime.

3. The Readout Electronics Box and Assembly Issues.

Congratulations on yesterday’s great job!

X(-4) X5 DiscVthrd

TDC(FPGA)

DC power unit

HV (-1200V)unit

What we do this afternoon:

1. Debug the boards, download the TDC code.2. Add the HV module. 3. Assemble the box into the box, connect the LEDs and connectors.4. Test on the detectors.

We should be able to finish before 5 PM.

The Detector:

Scintillation Detectors:Organic, liquid, plastic;Inorganic crystal (sodium iodide).

We use plastic, a good source is http://eljentechnology.com/ej-200.html with a quoted price of $372.

The may be used plastic scintillators from HEP and other experiments. If you have a good source, please let me know.

The cheapest (if new) is liquid scintillator. The following web page provides a good description on how to make such a detector yourself:

http://www.pma.caltech.edu/~ph77/labs/exp15.html

Another way to detect muons and electrons:cherenkov light.

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 0.768 MeV for electrons and 158.7 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 42o.

Light collection: PMT

A good source I know is http://www.burle.com/pdf/s83054f.pdf or s8349S.pdf with a quoted price of $215 for s83054f. The tubes come with a base attached.

I recommend this as a reading material for PMTs:http://www.burle.com/cgi-bin/byteserver.pl/pdf/Photo.pdf

A suggested muon detector based on water:

water

~50 to 100 cm~30 cm in DThe largest cooking pot will be a good starting object to work on.

muon

electron

If the container is conductive, try to insolate the PMT from the container by:

Tape the PMT.Leave a few cm air gap between the water surface and the PMT.

Last suggestion:

Check on the internet to see:

1. What is used in HEP experiments. They usually have a “public” link that describes the detector concepts much better than their “collaboration” links.

2. What other people have tried.

And then be creative! One can always try things out, as long as that is physically safe.

4. Data and Data Analysis.

Data format:

40010 1047328747 10 muons during this time40005 104732874840010 104732874940004 1047328750900 1047328750 one muon decay, 900*20 ns40005 104732875140007 104732875240008 104732902740006 104732902840006 104732902917280 1047329029 one muon decay,17280*20 ns40013 104732903040007 1047329031

For data analyses:

One can plot muon decay times and fit to

N = N0 e –t/ + Nb

To find out the lifetime. Here one needs to be careful about the flat background.

Expansion (upgrade) under consideration:

The muon box we have now provides:

1. High voltage to the PMT.2. PMT signal amplification and processing. 3. A timer (TDC) that records muon decay time w/ 20 ns

precision.4. A computer interface (via serial port and USB) and a DAQ

software.5. The absolute time stamp on each event relies on the PC

clock, which is only precise down to a few ms.

Next version:

1. Add a second channel, or maybe three channels to perform on-board co-incidence measurement.

2. Add a GPS time based absolute time stamp, w/ a precision down to 1 ns.

This will enable us to study shower profile with many detection units connected through internet. Please check by next year!