Study On Astrophysical Information About Galactic Dark Matter From Directional Direct Detection Experiments

Dark matter was noticed firstly at the beginning of the 1930 s.Up to now,there are enough evidences,mainly owing to astronomical observations and measurements,to believe that dark matter accounts for a great proportion of the total mass in the universe.Weak interacting massive particles(WIMPs)are the leading candidate for dark matter.The direct detection of the recoil energy deposited by the WIMP-nucleus scattering in a low background laboratory on Earth is the most promising direct detection method of WIMPs.For this kind of detecting method,the event rate,which is crucial to explore the nature of WIMPs,is related with the recoil energy.The event rate occurring elastic scattering between WIMPs and nucleus depends on the density of WIMPs,as well as the velocity distribution of WIMPs near the earth.In this work,we redefine the galactic coordinate system,the ecliptic coordinate system and equatorial coordinate system.We reconstruct the one–dimensional velocity distribution near the Earth by simulating the one–dimensional Maxwellian velocity distribution function of WIMP halo with the help of the redefined coordinate systems.More importantly,we also represent WIMPs velocity directional distribution in the rest frame of the Galaxy and in the equatorial coordinate system.At the same time,we also show the WIMPs velocity directional distribution on the Earth at different times when considering the rotation of the Earth around the Sun and its axis.The fitting WIMPs velocity distribution in the Earth frame almost matches with the well known shifted Maxwellian WIMP velocity distribution with little difference.What's more,the WIMPs velocity directional distribution in the galactic frame should be symmetrical by simulating the Maxwellian velocity distribution.The result totaly matches with the theoretical analysis,which gives support to the next work.The WIMPs velocity directional distribution in equatorial coordinate system shows asymmetric characteristics,indicating the WIMPs wind blowing towards the Earth.In the mean time,we present the WIMPs velocity direction distributions on Earth when the Earth rotate to any time in a year.The WIMPs velocity directional distributions on Earth at any moment of a day are also been shown through some technical treatment.The analysis of the WIMP velocity directional distributions on Earth provide basic theoretical basis for the directional direct experiments of detecting dark matter.