Search For Isolated Fractionally Charged Particles

Determining the mass and electric charge of the falling fluid drops.

• The terminal velocity of a fluid drop falling in air in an electric field is determined by its radius, charge and mass.
  
  
• Since the density of our test fluid is known we need to determine only the charge and mass.
  
  
• By taking measurements of the terminal velocity of the same fluid drop with two different E field values, two equations can be obtained to solve for the values of the drop's charge and mass.
  
  
• The charge measurement accuracy is limited in our apparatus by Brownian motion. For 6 micron diameter drops a measurement accuracy of 1/100 e has been obtained.
  

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October 13, 1998
Stanford Linear Accelerator Center
Website maintenance: erlee@SLAC.stanford.edu