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Why is impact parameter not directly measurable?

  1. Nov 3, 2015 #1
    I'm trying to understand a few things about the kinematics of collision processes.

    I guess it's because we calculate the scattered angle of the projectile and then back calculate to get a value for the impact parameter. Is this right?
     
  2. jcsd
  3. Nov 3, 2015 #2

    Vanadium 50

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    Are you talking about elementary particles or billiard balls?

    If the former, a direct measurement of impact parameter would require a trajectory that is good to 10^-16 meters or so over several meters. How do you propose to do that?
     
  4. Nov 3, 2015 #3
    Can you simplify you answer...
     
  5. Nov 3, 2015 #4

    Vanadium 50

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    Cab you answer my questions?
     
  6. Nov 3, 2015 #5

    mfb

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    For high-energy physics: Try to measure the position of a particle "somewhere in the accelerator" with a precision of 0.000000000000001 meters.
     
  7. Nov 4, 2015 #6

    ChrisVer

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    to be honest I don't get how you suggested that number (E-16 meters). Does it have anything to do with point-likeness?
     
  8. Nov 4, 2015 #7

    Vanadium 50

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    A proton is 10^-15 meters across. If you want to measure the impact parameter to 10%, you need to control the collision geometry to 10% of a proton radius, or about 10^-16 meters.
     
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