Gerald Gabrielse | |
---|---|
Nationality | American |
Alma mater | Calvin College (B.S.) University of Chicago (Ph.D.) |
Known for | antimatter, precision measurement |
Awards | Davisson–Germer Prize (2002) George Ledlie Prize (2004) Inducted into the National Academy of Sciences (2007) Julius Edgar Lilienfeld Prize (2011) Trotter Prize (2014) Norman F. Ramsey Prize (2024) |
Scientific career | |
Fields | Physics |
Institutions | University of Washington Harvard University Northwestern University |
Doctoral advisor | Henry Gordon Berry |
Other academic advisors | Hans Dehmelt (postdoc) |
Doctoral students | Tanya Zelevinsky |
Website | cfp |
Gerald Gabrielse is an American physicist. He is the Board of Trustees Professor of Physics and director of the Center for Fundamental Physics at Northwestern University, and Emeritus George Vasmer Leverett Professor of Physics at Harvard University. He is primarily known for his experiments trapping and investigating antimatter, measuring the electron g-factor, [1] and measuring the electron electric dipole moment. [2] He has been described as "a leader in super-precise measurements of fundamental particles and the study of anti-matter." [3]
Gabrielse attended Trinity Christian College and then Calvin College, graduating with a B.S. (honors) in 1973. He then completed his M.S. (1975) and Ph.D. (1980) in physics from the University of Chicago under Henry Gordon Berry. Gabrielse became a postdoc at the University of Washington in Seattle in 1978 under Hans Dehmelt, [4] and joined the faculty in 1985. He became professor of physics at Harvard University in 1987, and the chair of Harvard's physics department in 2000.
In 2018, Gabrielse moved to Northwestern University, becoming the director of the newly created Center for Fundamental Physics at Low Energy. [5] [6] The center is the first of its kind to be dedicated to small-scale, tabletop fundamental physics experiments. [7]
Gabrielse was a pioneer in the field of low energy antiproton and antihydrogen physics by proposing the trapping of antiprotons from a storage ring, cooling them in collisions with trapped electrons, [8] and the use of these to form low energy antihydrogen atoms. [9] He led the TRAP team that realized the first antiproton trapping, [10] the first electron cooling of trapped antiprotons, and the accumulation of antiprotons in a 4 Kelvin apparatus. [11] The demonstrations and methods made possible an effort that grew to involve 4 international collaborations of physicists working at CERN's Antiproton Decelerator. In 1999, Gabrielse's TRAP team made the most precise test of the Standard Model's fundamental CPT theorem by comparing the charge-to-mass ratio of a single trapped antiproton with that of a proton to a precision of 9 parts in 1011. [12] The precision of the resulting confirmation of the Standard Model prediction exceeded that of earlier comparisons by nearly a factor of 106.
Gabrielse now leads the ATRAP team at CERN, one of the two teams that first produced slow antihydrogen atoms and suspended them in a magnetic trap. [13] [14] Both TRAP and ATRAP teams used trapped antiprotons within a nested Penning trap device to produce antihydrogen atoms slow enough to be trapped in a magnetic trap. The team made the first one-particle comparison of the magnetic moments of a single proton and a single antiproton. [15] [16] Their comparison, to a precision of 5 parts per million, was 680 times more precision than previous measurements. [17]
Gabrielse's group has been known to perform the most precise measurements of the electron magnetic moment by using a single trapped electron. These measurements are the most precise measurements of any single particle and are among the most stringent tests of the Standard Model. [18] Using the theory of quantum electrodynamics, a measurement of the electron magnetic moment can also be interpreted as a measurement of the fine structure constant. [19] In 2006, the group made its first measurement with an uncertainty of 0.76 parts per trillion, [20] which was 15 times more precise than a measurement that had stood for about 20 years. [21] This measurement was improved two years later by a factor of 2. [22] In 2023, the team improved upon the 2008 uncertainty by another factor of 2. [1]
In 2014, Gabrielse, as part of the ACME collaboration with John Doyle at Harvard and David DeMille at Yale, measured the electron electric dipole moment to over an order of magnitude over the previous measurement using a beam of thorium monoxide, [23] a result which had implications for the viability of supersymmetry. [24] In 2018, the ACME collaboration improved upon this upper limit by another order of magnitude. [25]
Gabrielse was also one of the discoverers of the Brown-Gabrielse invariance theorem, [26] relating the free space cyclotron frequency to the measureable eigenfrequencies of an imperfect Penning trap. The theorem's applications include precise measurements of magnetic moments and precise mass spectrometry. [27] It also makes sideband mass spectrometry possible, a standard tool of nuclear physics. [28]
Gabrielse has also invented a self-shielding superconducting solenoid that uses flux conservation and a carefully chosen geometry of coupled coils to cancel strong field fluctuations due to external sources. The device was responsible for the success of the precise comparison of antiproton and proton, and also enables magnetic resonance imaging (MRI) systems to locate changing magnetic fields from external sources, such as elevators. [29]
Gabrielse identifies himself as a scientist who is Reformed Christian. In an interview, he said:
I do not believe that science and the Bible are in conflict. However, it is possible to misunderstand the Bible and to misunderstand science. It is important to figure out what of each might be misunderstood. [30]
He has also delivered lectures on the relation between science and religion. In 2006 Gabrielse delivered a lecture titled "God of Antimatter" in the Faraday Institute for Science and Religion in Emmanuel College, Cambridge, discussing his research into antimatter as well as his personal experience with Christianity. [31] He was awarded the Trotter Prize in 2013. [32]
In modern physics, antimatter is defined as matter composed of the antiparticles of the corresponding particles in "ordinary" matter, and can be thought of as matter with reversed charge, parity, and time, known as CPT reversal. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. Minuscule numbers of antiparticles can be generated at particle accelerators; however, total artificial production has been only a few nanograms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling. Nonetheless, antimatter is an essential component of widely-available applications related to beta decay, such as positron emission tomography, radiation therapy, and industrial imaging.
The positron or antielectron is the particle with an electric charge of +1e, a spin of 1/2, and the same mass as an electron. It is the antiparticle of the electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more photons.
Antihydrogen is the antimatter counterpart of hydrogen. Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron and antiproton. Scientists hope that studying antihydrogen may shed light on the question of why there is more matter than antimatter in the observable universe, known as the baryon asymmetry problem. Antihydrogen is produced artificially in particle accelerators.
The antiproton,
p
, is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.
Samuel Chao Chung Ting is an American physicist who, with Burton Richter, received the Nobel Prize in 1976 for discovering the subatomic J/ψ particle.
ATHENA, also known as the AD-1 experiment, was an antimatter research project at the Antiproton Decelerator at CERN, Geneva. In August 2002, it was the first experiment to produce 50,000 low-energy antihydrogen atoms, as reported in Nature. In 2005, ATHENA was disbanded and many of the former members of the research team worked on the subsequent ALPHA experiment and AEgIS experiment.
The Antihydrogen Trap (ATRAP) collaboration at the Antiproton Decelerator facility at CERN, Geneva, is responsible for the AD-2 experiment. It is a continuation of the TRAP collaboration, which started taking data for the TRAP experiment in 1985. The TRAP experiment pioneered cold antiprotons, cold positrons, and first made the ingredients of cold antihydrogen to interact. Later ATRAP members pioneered accurate hydrogen spectroscopy and observed the first hot antihydrogen atoms.
In quantum electrodynamics, the anomalous magnetic moment of a particle is a contribution of effects of quantum mechanics, expressed by Feynman diagrams with loops, to the magnetic moment of that particle. The magnetic moment, also called magnetic dipole moment, is a measure of the strength of a magnetic source.
The gravitational interaction of antimatter with matter or antimatter has been observed by physicists. As was the consensus among physicists previously, it was experimentally confirmed that gravity attracts both matter and antimatter at the same rate within experimental error.
The PS210 experiment was the first experiment that led to the observation of antihydrogen atoms produced at the Low Energy Antiproton Ring (LEAR) at CERN in 1995. The antihydrogen atoms were produced in flight and moved at nearly the speed of light. They made unique electrical signals in detectors that destroyed them almost immediately after they formed by matter–antimatter annihilation.
The Antiproton Decelerator (AD) is a storage ring at the CERN laboratory near Geneva. It was built from the Antiproton Collector (AC) to be a successor to the Low Energy Antiproton Ring (LEAR) and started operation in the year 2000. Antiprotons are created by impinging a proton beam from the Proton Synchrotron on a metal target. The AD decelerates the resultant antiprotons to an energy of 5.3 MeV, which are then ejected to one of several connected experiments.
High-precision experiments could reveal small previously unseen differences between the behavior of matter and antimatter. This prospect is appealing to physicists because it may show that nature is not Lorentz symmetric.
Kam-Biu Luk is a professor of physics, with a focus on particle physics, at UC Berkeley and a senior faculty scientist in the Lawrence Berkeley National Laboratory's physics division. Luk has conducted research on neutrino oscillation and CP violation. Luk and his collaborator Yifang Wang were awarded the 2014 Panofsky Prize “for their leadership of the Daya Bay experiment, which produced the first definitive measurement of θ13 angle of the neutrino mixing matrix.” His work on neutrino oscillation also received 2016 Breakthrough Prize in Fundamental Physics shared with other teams. He also received a Doctor of Science honoris causa from the Hong Kong University of Science and Technology in 2016. Luk is a fellow of the American Physical Society, and the American Academy of Arts and Sciences.
Recycling antimatter pertains to recycling antiprotons and antihydrogen atoms.
The Antihydrogen Laser Physics Apparatus (ALPHA), also known as AD-5, is an experiment at CERN's Antiproton Decelerator, designed to trap antihydrogen in a magnetic trap in order to study its atomic spectra. The ultimate goal of the experiment is to test CPT symmetry through comparing the respective spectra of hydrogen and antihydrogen. Scientists taking part in ALPHA include former members of the ATHENA experiment (AD-1), the first to produce cold antihydrogen in 2002.
BASE, AD-8, is a multinational collaboration at the Antiproton Decelerator facility at CERN, Geneva. The goal of the Japanese and German BASE collaboration are high-precision investigations of the fundamental properties of the antiproton, namely the charge-to-mass ratio and the magnetic moment.
The rotating wall technique is a method used to compress a single-component plasma confined in an electromagnetic trap. It is one of many scientific and technological applications that rely on storing charged particles in vacuum. This technique has found extensive use in improving the quality of these traps and in tailoring of both positron and antiproton plasmas for a variety of end uses.
John Holmes Malmberg was an American plasma physicist and a professor at the University of California, San Diego. He was known for making the first experimental measurements of Landau damping of plasma waves in 1964, as well as for his research on non-neutral plasmas and the development of the Penning–Malmberg trap.
The Penning–Malmberg trap, named after Frans Penning and John Malmberg, is an electromagnetic device used to confine large numbers of charged particles of a single sign of charge. Much interest in Penning–Malmberg (PM) traps arises from the fact that if the density of particles is large and the temperature is low, the gas will become a single-component plasma. While confinement of electrically neutral plasmas is generally difficult, single-species plasmas can be confined for long times in PM traps. They are the method of choice to study a variety of plasma phenomena. They are also widely used to confine antiparticles such as positrons and antiprotons for use in studies of the properties of antimatter and interactions of antiparticles with matter.
The TRAP experiment, also known as PS196, operated at the Proton Synchrotron facility of the Low Energy Antiproton Ring (LEAR) at CERN, Geneva, from 1985 to 1996. Its main goal was to compare the mass of an antiproton and a proton by trapping these particles in the penning traps. The TRAP collaboration also measured and compared the charge-to-mass ratios of antiproton and proton. Although the data-taking period ended in 1996, the analysis of datasets continued until 2006.