Antimatter  

In General > s.a. CPT symmetry; equivalence principle; particles and experimental particle physics.
* Motivation: It is used to study CPT violations, its coupling to gravity and the equivalence principle, and high-energy astrophysical and cosmological phenomena.
*
History: 1930, Prediction by P A M Dirac of antiparticle counterparts of the known particles; 1932, Discovery by C D Anderson of the e+; 1955, Discovery of the \(\bar p\); 1993, ..., 1999, NASA Bess project, a balloon looking for antimatter in cosmic rays; 1996, Anti-H obtained, but quickly annihilated; 2000, Plans to produce and store anti-H; 2001, Precise determination of \(\bar p\) charge and mass by Japanese-European collaboration at the CERN Antiproton Decelerator (values agree with those for p within 6 × 10–8); 2005, anti-H produced at 2400 K, way too hot for precise spectroscopy; 2011, Anti-H trapped for 1000 seconds.
@ General references: Schiff PRL(58) [positive m]; Peach PW(91)dec [baryon asymmetry]; Greenland CP(97); Tarlé & Swordy SA(98)apr [cosmic]; Weiss ed-99 [e+]; Zichichi RNC(01) [review]; Massó & Rota PLB(04)ap [gravitational field]; Eades pw(05)oct [antiprotonic He]; Baker & Halvorson BJPS(10)#1 [nature, and algebraic quantum field theory]; Close 09.
@ Matter-antimatter asymmetry: Kusenko et al PRL(15) [and Higgs field relaxation].
@ Anti-H: Eades et al PW(93)jul; Charlton et al PRP(94); Hall & Gabrielse PRL(96) + pn(96)nov; news pw(04)aug; Holzscheiter et al PRP(04) [including CPT and equivalence principle]; Collins SA(05)jun; Charlton & Hangst pw(05)oct; Charlton et al CP(08) [precision tests]; news sn(10)nov [dozens of atoms trapped]; Enomoto et al PRL(10) [towards spectroscopy]; news phot(11)apr [trapped for 1000 s]; Amsler et al IJMPA(14) [ATHENA experiment]; news pw(16)dec [optical spectrum].
@ Other examples and applications: Gsponer & Hurni phy/05 [weapons]; news pw(11)mar, physorg(11)apr [anti-He/alpha particles]; Hori et al Sci(16)nov + news pt(16)nov [antiprotonic He and the \(\bar p\) mass].
> Related topics: see Action at a Distance; proton [antiproton].
> Online resources: CERN page [2011.05].

In Gravity, Astrophysics and Cosmology
* On Earth: Antiparticles do not survive long; They are produced in high-energy interactions or arrive to Earth from sources within the Milky Way galaxy.
* Matter-antimatter asymmetry: The fact that in the observable universe (not just on Earth and nearby, but also on cosmological scales) there seems to be an imbalance, with a lot more matter than antimatter; Possible explanations include a breaking of CP symmetry at primordial high temperatures (this field is being actively studied in particle physics), the existence of regions in the universe where antimatter dominates (2012, This is an open problem, but data make the possibility appear less and less likely), or the presence of an electric dipole moment in a fundamental particle; > s.a. Wikipedia page.
* Masses: Experimentally, \(m_p = m_{\bar p}\) within \(10^{-10}\) (1998, Gabrielse et al).
@ General references: Villata a1003/GRG, Hajdukovic IJTP(10), Villata EPL(11)-a1103 [repulsion between matter and antimatter?]; Menary a1207 [gravitational interactions between matter and antimatter]; Dufour et al AHEP(15)-a1409-conf [free fall and gravitational quantum states]; Dolgov a1411-conf [possible signatures, rev].
@ Astrophysics, observations: news bbc(11)aug [antiproton belt discovered around the Earth]; Abe et al PRL(12)mar [limits on the cosmic antihelium abundance].
@ Cosmology, observations: Canetti et al NJP(12)-a1204 [matter-antimatter asymmetry in the early universe]; > s.a. matter in cosmology.
> Related topics: see cosmic rays [antiprotons]; early universe; interference [atom interferometers]; quantum-gravity phenomenology.


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