170140
He then began experimental research under George Paget Thomson , and was one of the first to identify the K meson and its decay into three pion s , giving the most accurate , as of that time , estimate of its mass .
 George Paget Thomson
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 George Paget Thomson