Study On The Lifetime And Flux Of The Muon Of Atmospheric Cosmic Ray On The Earth's Surface

Cosmic ray is the high-energy particle flux from the cosmic space.It'll interact with the atmospheric nuclei,like nitrogen,oxygen,hydrogen and so on,and produce lots of the secondary particles when goes through the earth's atmosphere,this phenomenon is named the extensive air shower.The secondary particles are absorbed by the earth medium when passing the earth,and most of them decay in the process of the flight because of the short lifetime,so they can't arrive to the earth's surface.But the muon of the secondary particles have longer lifetime,large momentum and high velocity,it can fly to the earth's surface due to the relativity effect.Thus,about 90%of the component in the secondary cosmic ray particles on the earth's surface is the muon.The majority of the cosmic ray secondary particles are the positive charge,they will deflect due to the influence of the earth's magnetic field when arrive to the earth's surface.In the south and north,lower the latitude,higher energy and the more little flux when the secondary particles enter the earth.In the east and west,the cut-off stiffness in the west is little,the flux is large.It formed east-west effect and north-south effect of the cosmic ray on the earth's surface.Though people have know the theory that the magnetic field of the earth influence the cosmic ray on the earth's surface,the experimental data is lacking,and the data come from the large cosmic ray detection arrays,so that the development of the cosmic ray on the earth's surface is slowing.Aim at the above problem,this thesis simulates the cosmic ray on the earth's surface,and uses the small cosmic ray detector measure the lifetime of the muon and the flux.The specific work is as follows:Firstly,simulate the composition and energy of the particles of the cosmic ray on the earth's surface by CORSIKA.We can know that 86%of the particles of the earth's surface is muon according to the simulation,the average energy is 2.85 Gev,it is consist with the theory.In addition,we simulate the flux of the cosmic ray by CORSIKA,the result show that the cosmic ray has the effect of east-west and north-south.Secondly,measure the average lifetime of the muon in the plastic scintillator.We improve the accuracy through deducting the background come from the accidental coincidence between the incoming muon,the coincidence between the muon and the electronics noise,and using the integral fitting formula,the average lifetime of the muon in the plastic scintillator increased from 2140±28.6 ns to 2154.4±8.3 ns,the difference is only 1.94%from the theoretical value.Thirdly,remodel the equipment of CRP3,extend the angle of the detector,enhance the measure accuracy of the cosmic ray flux.Using the equipment,we measure the zenith angle distribution of the muon.The count of the muon dependent on the zenith angle is accord with the empirical formula,I(?)=Io cos??,and the angle dependent on alpha is agree with the theory within the allowable range of the error.We test the effect of east-west and north-south of the cosmic ray flux in the area of Wuhan on the earth's surface for the first time,there are 0.78%asymmetries in the east and west,and 8.2%asymmetries in the north and south.Fourthly,propose the scheme that heighten the measure accuracy of the flux further,and analyse the scheme in detail and carry out.The scheme adopt the multi-wire proportional chamber of the two dimension readout to set up the telescope system,every chamber can give the position,so we can revert the particle' track.Since the position resolution of the chamber is the millimeter level,we can improve the accuracy substantially and reduce the test time relative to the equipment of CRP3.