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Archive for the ‘High Energy Physics’ Category

Open Questions at the Physics Frontier with Steven Weinberg

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March 11, 2021 at 3:11 pm

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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

How to record a ghost particle

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December 4, 2020 at 12:40 pm

Edward Witten: Feynman Diagrams in String Theory

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November 28, 2020 at 9:47 am

Reflections on a Revolution

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John Iliopoulos, reply by Sheldon Lee Glashow
In response to “The Yang–Mills Model” (Vol. 5, No. 2).

To the editors:

It is an honor and a pleasure to comment on Sheldon Lee Glashow’s magisterial essay on the Yang–Mills model. His essay is all the more special for describing one of the greatest chapters in the history of physics, the story of a beautiful mathematical concept transformed into a theory for all seasons, the Standard Model of particle physics. It was of course Glashow who played a central role in the electroweak part of the story by coming up with his masterpiece, the SU(2) × U(1) gauge theory. And with the added masterstroke from Steven Weinberg, his high-school buddy, as he reminds us, we now have not just a theory of all relevant particle interactions at today’s energies, but also a theory of the origin of the masses of elementary particles. Simply, mass turned into a dynamical variable, the knowledge of which enables us to unambiguously predict the associated Higgs boson decay into the relevant particles. And we know with certainty that the W and Z bosons, predicted by Glashow, and the third-generation fermions receive their masses from the Higgs mechanism….
Read more at https://inference-review.com/letter/reflections-on-a-revolution

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October 2, 2020 at 5:18 pm