Measurement of lifetime for muons captured inside nuclei Advisors: Tsung-Lung Li Wen-Chen Chang Student: Shiuan-Hal Shiu 2007/06/27

Content Introduction Experimental Apparatus Analysis and Discussions Conclusion

Introduction

Flow Chart Physics motivation Physics events Detectors Electronic devices DAQ Data analysis Physics Results

Standard Model 6 quarks. 6 leptons. Force carrier particles.

The Four Interactions Force carrier GravitonPhotonGluon W,Z boson Action object Everything Charge particles Quarks, Gluons GluonsQuarks,Leptons Electroweakinteraction

Muon Muons were observed by Carl D. Anderson in Muons are denoted by μ− and antimuons by μ +. About 207 times mass as electron. (105.65Mev) Muon mean lifetime : μ sec Muon have 1 negative electric charge. Muon is a fermion with ½ spin.

Muon Decay Muon mean lifetime : μ sec Muon and antimuon decay:

Lepton Type Conservation Leptons are divided into three lepton families: 1. electron and electron neutrino 2. muon and muon neutrino 3. tau and tau neutrino

Fermi Coupling Constant G F The muon decay is purely leptonic. Its directly related to the strength of the weak interaction. Fermi coupling constant G F is a measurement of the strength of the weak force. The relationship between the muon lifetime τ free and fermi coupling constant G F : The new world average of muon lifetime is: μ sec. The new G F is: *10 -5 GeV 2.

Muon Source The muon is produced in the upper atmosphere by the decay of pions produced by cosmic rays The flux of sea-level muons is approximately 1 per minute per cm 2 The muon production height in the atmosphere is approximately 15km. If the muon traveling at the speed of light its still need 50 μ sec.

Muon Decay Time Distribution Muon decay is a typical process of radioactive decay. We call the muon lifetime is Random process

Muon Capture Muon capture is the capture of a negative muon by a proton. Ordinary muon capture (OMC): Radiative muon capture (RMC): In the past, one motivation for the study of muon capture on the proton is its connection to the proton's induced pseudoscalar form factor g P.

Capture process 1. Muon enter the matter 2. Electromagnetic interactions 3. Muonic atom formed 4. μ +p → n+ ν Captured by nuclei: μ +p → n+ ν only occur with negative charged muon In the order of nano-sec Muon capture Process e nucleus μ Matter μ

Muon Capture Time Distribution

Previous Result

Experiment Flow Chart

Experimental apparatus

Detector Physics 1. Charged particle passing 2. Slow down 3. Stop 4. Decay Scintillation detector PMT μ e μ

Measuring Muon Lifetime Scintillation detector PMT μ e

start: P1 P2 P3 stop: P3 PMT1 PMT3 TARGET PMT2 n p e μ μ Capture decay Free decay Pass through Detector Free decay n p e μ μ Capture decay

Electronic Device Block Diagram

Gate condition

Calibration of Experiment Apparatus Calibrate the PMT working voltage : Plateau measurement

Calibration of Experiment Apparatus

Calibrate the PMT working voltage : Coincidence plateau measurement Calibration of Experiment Apparatus

Calibrate the efficiency of data acquisition system Calibration of Experiment Apparatus

Data analysis

TDC Data Analysis In this experiment we use the TDC to save the pulse's timing information and try to fit the lifetime for free decay and capture decay.

TDC Data Analysis Procedure The end point of background fitting The start point of background fitting

Background (change end point) The 50ns/bin figure have a comparative little value with other figure.

Cu (change end point) The results are all less than world average. The 50ns/bin figure have a comparative little value with other figure.

Fe (change end point)

Al (change end point)

Change start point The start point of background fitting

Background (change start point) The 50ns/bin figure still have a comparative little value with other figure.

Cu (change start point) The first serveral points are less than world average. We select the 800ns to be the start point.

Fe (change start point) Fe data are all too less. We choose the 1000ns to be the start point.

Al (change start point) We choose the 1500ns to be the start point.

Background Fitting Result Background do not have any target the capture lifetime may come from the scintillation detector atom.

Cu Fitting Result

Fe Fitting Result

Al Fitting Result

ADC Data Analysis Procedure In this experiment we want to use the ADC to save the pulse's charge information and try to differentiate the free decay events and capture decay events by the information from ADC. 1. Analyze the ADC VS. TDC profile. 2. Comparing the probability of compatibility between two ADC distribution. 3. Making different ADC cut and analyze the TDC data for each ADC cut.

ADC VS. TDC Profile (TDC>10000)

ADC VS. TDC Profile (TDC>1000) From the figures we can find there are no obvious evidence to differentiate the capture events

Probability of Compatibility between two ADC Histogram (TDC<1000) Thistest is a statistical test of compatibility in shape between two histograms. The background ADC shape is the comparing base line

Probability of Compatibility between two ADC Histogram (TDC>1000)

Conclusion

Conclusion The TDC analysis result is listed on the table

All cut in 800 TDC Analysis with Different ADC Cut