反氦原子的发现 学术报告ppt.pptx

Observation of the antimatter helium4 nucleusMing Shao, Center for Particle Physics and TechnologyWhy antimatter?The apparent /wiki/Baryon_asymmetryasymmetry of matter and antimatter in the /wiki/Visible_universevisible universe is one of the greatest /wiki/Unsolved_problems_in_physicsunsolved problems in physicsAntimatter matter!Big Bang initially produced matter antimatter in equal abundance – so does any primordial antimatter still persist in isolated regions of the cosmos?Clue to matter – antimatter asymmetryNature 451, 159 (2008)Search in Sky/SpaceAnti-helium 4 important!Finger print of anti-starCollisions at RHIC RHIC generates hot and dense matter, where matter antimatter decouple quickly:? Sweet spot between elementary particle collisions and Big Bang for anti-nuclei production.? Controlled, repeatable “little bangs”. Active production instead of “passive” searches.? Prove the existence (if any), provide a point of reference for future observations in cosmic radiation. Ideal factory for antinucleiFirst STAR results for antinucleiPRL 87, 262301 (2001)14 anti-3He based on 0.6M central AuAu at 130 GeVSTAR ExperimentSTAR Subsystem Status – 2010MTDEMC BarrelMRPC ToF Barrel + VPDEMC End CapFMSBBCFHCFPDTPCpp2pp’pp2pp’PMDFTPCtriggercomputingDAQ1000COMPLETEHLTHFTFGTOngoingRD2010 run provides ~ a billion events with greatly enhanced PIDFull ?? in azimuth at ~ 2 units in midrapiditySTAR Time-of-Flight From 2000 to 2009 … the STAR construction effort in China has been a complete scientific and technical success at every level, and the Chinese TOF team is to be highly congratulated. STAR TOF is the first large-scale detector of such type, and still keeps the world record of timing performance.Data Sample360 million minimum-bias (MB) collisions, 270 million central collisions and 170 million high tower calorimeter events at 200 GeV in 2010. 70 million MB events at 200 GeV in 2007.170 million MB events at 62 GeV in 2010.In total one billion Au+Au events sampledQu