Sentence:  A total of 15,000 <WSD>beams</WSD> of neutrinos were fired over a period of 3 years from CERN towards Gran Sassoin Italy, 730km (500 miles) away, where they were picked up by giant detectors. 
Meaning of the word marked with <WSD> tags:  A ray or collection of approximately parallel rays emitted from the sun or other luminous body.