Matter and antimatter spin alike.Matter and antimatter antimatter: see antiparticle. antimatter Substance composed of elementary particles having the mass and electric charge of ordinary matter (such as electrons and protons) but for which the charge and related magnetic properties are opposite in sign. spin alike Physicists believe that matter and antimatter are precisely symmetric. That is, to every kind of subatomic particle there corresponds an antiparticle antiparticle, elementary particle corresponding to an ordinary particle such as the proton, neutron, or electron, but having the opposite electrical charge and magnetic moment. with exactly the same mass but with the opposite electric charge. Physicists frequently set up experiments to test this belief. One way of doing it involves the spins of electrons and positrons. Electrons and positrons have opposite polarity of electric charge, the electron's being negative, the positron's positive. However, the amount of electric charge, the mass and the amount of spin ought to be exactly the same. The latest of a series of experiments done at novosibirsk in the USSR USSR: see Union of Soviet Socialist Republics. used the interaction of electron and positron positron: see antiparticle. positron Subatomic particle having the same mass as an electron but with an electric charge of +1 (an electron has a charge of −1). It constitutes the antiparticle (see antimatter) of an electron. spins with the magnetic field of the VEPP-2M storage ring to test the sameness of the spins. Each electron or positron is a little magnet, producing a small magnetic field or, as physicists say, a magnetic moment. If the spins are exactly the same, so should be the strengths of the magnetic moments. As the magnetic moments of these particles interact with the magnetic field of the storage ring, their spins precess pre·cess intr.v. pre·cessed, pre·cess·ing, pre·cess·es To move in or be subjected to precession. [Back-formation from precession.] Verb 1. , or the spin axes describe a little circle. The experiment started with electrons and positrons with their spins all in one direction. The researchers forced the spin axes into a horizontal alignment by imposing an electric field that alternates at radio frequencies. Then they turned off the electric field, allowing the spins to precess freely in the magnetic field. Any difference in the size of the spins would cause a phase difference that would gradually build up. After one-tenth of a second, which is time enough for 3 million spin revolutions, the alternating electric field was turned on again. It repolarized the spins, but would have preserved any accumulated phase difference. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. a report in the January/February CERN CERN or European Organization for Nuclear Research, nuclear and particle physics research center straddling the French-Swiss border W of Geneva, Switzerland. COURIER, the experiment found that electron and positron spins are the same to 1 part in 100 million, supporting the long-held belief in matter-antimatter symmetry. |
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