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Workgroup Practical Activities: Cosmic Rays

Workgroup Practical Activities: Cosmic Rays. Ela, Helena, Jef, Leo,. Carlos. Thanks to Jack, Stacy and Tom. Content. 1/ PowerPoint presentation for Teachers and Students 2/ Determination of the speed of muons 3/ Correlation between flux and distance.

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Workgroup Practical Activities: Cosmic Rays

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  1. Workgroup Practical Activities: Cosmic Rays Ela, Helena, Jef, Leo, Carlos Thanks to Jack, Stacy and Tom

  2. Content 1/ PowerPoint presentation for Teachers and Students 2/ Determination of the speed of muons 3/ Correlation between flux and distance

  3. 1/ PowerPoint presentation for Teachers and Students See: PowerPoint presentation for Teachers and Students.ppt

  4. 2/ Determination of the speed of muons Setup

  5. We looked for coincidences  hit?  time-window of 192 ns  2nd hit?  coincidence!

  6. BUT ... This can also happen: plate 1 plate 2 Probability???  1st part of the experiment: determination of probability  (2st part of the experiment: determination of speed)

  7. 1st part of the experiment: We determined: (average) number of hits on CH1 (per minute) (average) number of hits on CH2 (per minute) (average) number of coincidences (per minute) Results: CH1: 1150 hits / min CH2: 4074 hits / min Number of coincidences: 90 / min

  8. Statistical analysis CH1: 1150 hits / min Poissondistribution: P (k, λ) = Prob of at least 1 hit on CH1 in 192 ns = 3,68 x10-6 Prob of at least 1 hit on CH2 in 192 ns = 1,30 x10-5

  9. Prob of at least1 hit on CH1 AND on CH2 in 192 ns: 3,68 x10-6 x 1,30 x 10-5 = 4,78 x 10-11 1 coinc in 0,67 s 1 coinc in 1 h 07 min 90 coinc per minut

  10. ‘ALL’ coincidences are caused by particles going through both plates

  11. 2nd part of the experiment: When there was a coincidence, we determined: • the channel number • the time of the rising edge (t1 and t2) We calculated t2 - t1.

  12. Results: v = (1,88 ± 1,20) x 108 m/s

  13. Analysis Expected distribution: Distribution we got:

  14. Possible explanations: 1: not all the muons travel with the ‘same’ speed 2: the error on the time-differences Time-diff ≈ ** ns ± 2 ns Average = 3.422 ns ± 2.187 ns

  15. How to improve the experiment? If we could measure the time-differences as accurate as the distance, we should have an error on the speed as low as 0,020 x 108 m/s!

  16. Useful and practicable? + - Opportunity of • use of statistics - equipment • experiment from mod.phys. - curriculum • deep analysis of setup, method, results • start of CR-project • work with high-tech equipment

  17. 3/ Correlation: number of coincidences and distance between two detectors

  18. Table and graph of results

  19. Analyzing data

  20. The exponent is rather strange: - 1.3118 Possible explanations: - during time of measurement, there is not only one shower, but also others, so that there is no fixed relationship (e.g. NOC ~ x-2 ) To investigate this, we have to repeat the experiment and check whether the exponent remains the same, and if not, to see if these numbers are distributed at random. - background

  21. After subtracting background from the results

  22. Now we got for the exponent -1.9417 -1.94 ≈ - 2 NOC ~ 1 / x² ??? It was only one experiment with 7 measurement points, that is not enough to find the ‘real’ correlation. More measurements in different conditions are advised.

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