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Archive for the ‘High Energy Physics’ Category

James D. Bjorken:“Why Do We Do Physics? Because Physics Is Fun!”

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In this informal memoir, the author describes his passage through a golden age of elementary particle physics. It includes not only his career trajectory as a theoretical physicist but also his excursions into experimental physics and particle accelerator theory. While his successes are highlighted, some unsuccessful efforts are included in the narrative as well. Those “losers” were arguably as pleasurable as the less-frequent “winners.” Since retirement, the author has become interested in gravitation theory and cosmology—a new golden age. This activity is also briefly described ….. Read more at: https://www.annualreviews.org/doi/full/10.1146/annurev-nucl-101918-023359

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March 30, 2021 at 3:14 pm

Edward Witten: How Do Scientific Breakthroughs Happen?

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March 16, 2021 at 4:32 pm

Posted in High Energy Physics

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Antimatter and other deep mysteries

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Public lecture by Dr. Gerald Gabrielse
Our universe is made of matter. Yet the Big Bang produced essentially equal amounts of matter and antimatter according to our most fundamental understanding of the building blocks of nature. The inability of our fundamental theory to describe this basic feature of our universe is the great frustration of modern physics. In this one-hour lecture, held on Feb. 19, 2021, Dr. Gerald Gabrielse, Northwestern University, gives an introduction to antimatter and matter, explains the theoretical framework that explains particle interactions, and gives examples of attempts to solve the mystery of antimatter.

Dr. Gerald Gabrielse, a member of the National Academy of Science and the American Academy of the Arts and Sciences, is a Trustees Professor at Northwestern University. His vision, techniques and measurements started low-energy antiproton and antihydrogen research at the European laboratory CERN. He has made the most precise measurement of a property of an elementary particle, the electron’s magnet, to test the Standard Model’s most precise prediction. His test of whether the electron charge is spherical is one of the most sensitive tests for physics beyond the Standard Model.

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March 13, 2021 at 3:31 pm

Open Questions at the Physics Frontier with Steven Weinberg

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March 11, 2021 at 3:11 pm

Posted in High Energy Physics

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Elementary Particles: What are they? Substances, elements and primary matter

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D-M. Cabaret, T. Grandou, G-M. Grange, E. Perrier
The most successful “Standard Model” allows one to define the so-called “Elementary Particles”. Now from another point of view, philosophical, how can we think of them? Which kind of a status can be attributed to Elementary Particles and their associated quantised fields? Beyond the unprecedented efficiency and reach of quantum field theories the current paper attempts at understanding the nature of what we talk about, the enigmatic reality of the quantum world.
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Click to access 2103.05522.pdf

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March 10, 2021 at 8:33 pm

What are Elementary Particles?

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Wolfgang Bietenholz
We describe the very nature of the elementary particles, which our (visible) Universe consists of. We point out that they are not point-like, and we depict their ways of interacting. We also address puzzles that occur even in the absence of particles, in the vacuum.
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Click to access 2011.07719.pdf

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February 5, 2021 at 6:20 pm

The history of LHCb

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I. Belyaev, G. Carboni, N. Harnew, C. Matteuzzi. F. Teubert
In this paper we describe the history of the LHCb experiment over the last three decades, and its remarkable successes and achievements. LHCb was conceived primarily as a b-physics experiment, dedicated to CP violation studies and measurements of very rare b decays, however the tremendous potential for c-physics was also clear. At first data taking, the versatility of the experiment as a general-purpose detector in the forward region also became evident, with measurements achievable such as electroweak physics, jets and new particle searches in open states. These were facilitated by the excellent capability of the detector to identify muons and to reconstruct decay vertices close to the primary pp interaction region. By the end of the LHC Run 2 in 2018, before the accelerator paused for its second long shut down, LHCb had measured the CKM quark mixing matrix elements and CP violation parameters to world-leading precision in the heavy-quark systems. The experiment had also measured many rare decays of b and c quark mesons and baryons to below their Standard Model expectations, some down to branching ratios of order 10-9. In addition, world knowledge of b and c spectroscopy had improved significantly through discoveries of many new resonances already anticipated in the quark model, and also adding new exotic four and five quark states.
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Click to access 2101.05331.pdf

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January 15, 2021 at 10:11 pm

Posted in High Energy Physics

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The EFT-Hedron

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Nima Arkani-Hamed, Tzu-Chen Huang, Yu-tin Huang
We re-examine the constraints imposed by causality and unitarity on the low-energy effective field theory expansion of four-particle scattering amplitudes, exposing a hidden “totally positive” structure strikingly similar to the positive geometries associated with grassmannians and amplituhedra. This forces the infinite tower of higher-dimension operators to lie inside a new geometry we call the “EFThedron”. We initiate a systematic investigation of the boundary structure of the EFThedron, giving infinitely many linear and non-linear inequalities that must be satisfied by the EFT expansion in any theory. We illustrate the EFThedron geometry and constraints in a wide variety of examples, including new consistency conditions on the scattering amplitudes of photons and gravitons in the real world.
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Click to access 2012.15849.pdf

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January 1, 2021 at 9:42 am