Actually, CP symmetry is experimentally found to be violated for K- and B-mesons (see also §2.3). The most recognized model to explain a matter-dominant universe was proposed by Sakharov in 1967, 12) which requires three conditions: baryon number non-conserving processes, C- and CP-violations, and interactions under non-equilibrium conditions. What happened to all of the antimatter? 11) 8, 9) The possibility of a matter-antimatter patchwork universe was also discussed, 10) and it was concluded that the size of the patch would be comparable to that of the observable universe, i.e., a matter-antimatter symmetric universe is unfavored. For example, the AMS project, which measures various particles showering on Earth found eight antihelium events (six of them were compatible to 3 He ¯ and the rest of two were 4 He ¯), which were ∼10 −8 of helium events during the six years of continuous measurements. Every effort to find celestial antimatter has been unsuccessful until now, strongly indicating that the production and/or annihilation processes are asymmetric between matter and antimatter in some way. However, it looks like the present universe favors matter. The universe is believed to have contained the same amount of matter and antimatter at the moment of the Big Bang according to the best knowledge of the present elementary particle physics. Considering these, although speculative, CPT symmetry and WEP tests have been selected as the major subjects, which may also shine a light in the mystery of a matter-dominant universe (see e.g., Refs. It is also noted that the gravitational interaction is not in the scope of the SM. Examples of such discoveries include neutrino oscillation, 4) dark matter, and dark energy. On the other hand, recent important discoveries in this field of physics as well as astronomy are not well settled in the framework of the SM. The key property of p ¯ and H ¯ which enable to attack the above subjects is their stability, which exclusively enables one to conduct high-precision measurements.ĬPT symmetry is naturally concluded from the Standard Model (SM), the most successful theoretical framework of fundamental physics. 3) The field has been becoming active more than ever while growing its population and contributing to fundamental physics via high-precision measurements, which has been particularly true during the last 10 years.Ĭold antimatter science has two major topics: one is CPT symmetry tests that compare proton (p) and antiproton ( p ¯), hydrogen (H) and antihydrogen ( H ¯) as well as antiprotonic helium ( p ¯He +), where C, P and T refer to charge conjugation, parity, and time reversal, respectively the other one is the Weak Equivalence Principle (WEP) tests that measure the gravitational interaction between antimatter ( H ¯) and matter (the Earth). Cold antimatter science is thus a relatively young research field of physics that focuses primarily on fundamental physics, but at the same time on multidisciplinary science covering nuclear physics, atomic physics, plasma physics, as well as a basic study on cancer therapy. 2) It is expected to grow further waiting for the start of the operation of the Extra Low ENergy Antiproton ring (ELENA) in 2021 (see §4). The Low Energy Antiproton Ring (LEAR) at CERN, constructed in 1982 and operated until 1996, triggered a break for a cold antimatter science, 1) which flowered during the Antiproton Decelerator (AD) time. A new era of the cold antimatter physics will emerge soon including the transport of antiprotons to other facilities. An additional new post-decelerator, Extra Low ENergy Antiproton ring (ELENA), has been constructed and will be ready in 2021, which will provide 10–100 times more cold antiprotons to each experiment. Three collaborations joined the WEP tests inventing various unique approaches. Antiprotonic helium laser spectroscopy, which started during the Low Energy Antiproton Ring (LEAR) time, has reached a relative precision of 8 × 10 −10. The precisions of the antiproton and proton magnetic moments have improved by six orders of magnitude, and also laser spectroscopy of antihydrogen has been realized and reached a relative precision of 2 × 10 −12 during the AD time. ![]() Various groundbreaking techniques have been developed and are still in progress such as to cool antiprotons and positrons down to extremely low temperature, to manipulate antihydrogen atoms, to construct extremely high-precision Penning traps, etc. The central subjects are CPT symmetry tests and Weak Equivalence Principle (WEP) tests. The field of cold antimatter physics has rapidly developed in the last 20 years, overlapping with the period of the Antiproton Decelerator (AD) at CERN.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |