Relativity Quantum Theory Antimatter 5-m平0 Paul A.M.Dirac (1928) 0 1 0 0 1 = 001 0 +im t = or 0 or 0 0 0 0 Electron:spin 1/2 Another spin-1/2 particle?? For v0,upper and lower components mix 1929:Positive electron=proton ??? 1931:m(e-)=m(e+)!Annihilation possible PDF文件使用"pdfFactory'” 试用版本创建www.fineprint..cn
PDF 文件使用 "pdfFactory" 试用版本创建 www.fineprint.cn
Negative Energy Rather than ignoring the negative energy state, as would be expected in classical physics,Dirac decided to deal with the problem in a quantum mechanical sense. The amplitude of a stream of particles can be represented by the plane wavefunction: Ae-i(Ei-px)Ih But this equation can also represent particles with negative energy and momentum travelling back in time. PDF文件使用"pdfFactory”试用版本创建w.fineprint.cn
Negative Energy qRather than ignoring the negative energy state, as would be expected in classical physics, Dirac decided to deal with the problem in a quantum mechanical sense. qThe amplitude of a stream of particles can be represented by the plane wavefunction: q But this equation can also represent particles with negative energy and momentum travelling back in time. i Et px h Ae- ( - )/ y = PDF 文件使用 "pdfFactory" 试用版本创建 3www.fineprint.cn 3
Positron Discovery A "Cloud Chamber"is capable of detecting Cloud Chamber charged particles as they pass through it. Photograph The chamber is surrounded by a magnet. The magnet bends positively charged particles in one direction,and negatively charged particles in the other direction. By examining the curvature above and below the lead plate,we can deduce: (a)the particle is traveling upward in this photograph. Lead Larger curvature (b)it's charge is positive plate of particle above plate Using other information about how far it means it's traveled,it can be deduced it's not a proton. moving slower Positron (lost energy as it It's a particle who's mass is same as electron passed through) but has positive charge POSITRON PDF文件使用"pdfFactory” 试用版本创建酸ffineprint.cn
Positron Discovery Lead plate Positron A “Cloud Chamber” is capable of detecting charged particles as they pass through it. The chamber is surrounded by a magnet. The magnet bends positively charged particles in one direction, and negatively charged particles in the other direction. By examining the curvature above and below the lead plate, we can deduce: (a) the particle is traveling upward in this photograph. (b) it’s charge is positive Using other information about how far it traveled, it can be deduced it’s not a proton. Cloud Chamber Photograph Larger curvature of particle above plate means it’s moving slower (lost energy as it passed through) It’s a particle who’s mass is same as electron but has positive charge è POSITRON ! 駿f
Expansion type cloud chamber Original Wilson chamber ▣Anderson used cloud chamber in a 15 kG magnetic field. The chamber was divided into two parts by a 6-mm lead plate. PDF文件使用"pdfFactory”试用版本创建ww.fineprint.cn
Expansion type cloud chamber Original Wilson chamber q Anderson used cloud chamber in a 15 kG magnetic field. q The chamber was divided into two parts by a 6-mm lead plate. PDF 文件使用 "pdfFactory" 试用版本创建 ÿwww.fineprint.cn
Tracks of particles in the cloud chamber PDF文件使用"pdfFactory”试用版本创建ww.fineprint.cn
Tracks of particles in the cloud chamber PDF 文件使用 "pdfFactory" 试用版本创建 ÿwww.fineprint.cn