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For example , in regions of high dark matter density ( e.g. , the centre of our galaxy ) two dark matter particles could annihilate to produce gamma rays or Standard Model particle–antiparticle pairs .
 location: Standard Model
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 location: Standard Model