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10 pages, 1113 KiB

Open AccessArticle

Identifying D Mesons from Radiative W Decays at the Large Hadron Collider

by Evelin Bakos, Nicolo de Groot and Nenad Vranjes

Symmetry 2023, 15(10), 1948; https://doi.org/10.3390/sym15101948 - 20 Oct 2023

Cited by 1 | Viewed by 1208

In this paper, we present two machine learning algorithms to identify D mesons produced in a colour singlet state from radiative W boson decays at the LHC. The combined network algorithm is able to identify D mesons via its hadronic decays with an efficiency of 47% while suppressing a background of quark and gluon jets by a factor of 100. Using the developed algorithm, we perform a prospective study for the measurement of

B (W \to D_{s} γ)

. Full article

(This article belongs to the Section Physics)

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64 pages, 5437 KiB

Open AccessEditor’s ChoiceReview

Emergence of Hadron Mass and Structure

by Minghui Ding, Craig D. Roberts and Sebastian M. Schmidt

Particles 2023, 6(1), 57-120; https://doi.org/10.3390/particles6010004 - 11 Jan 2023

Cited by 58 | Viewed by 24793

Abstract

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale-invariant. Thus, if the Standard Model is truly a part of the theory of Nature, then the proton mass is an emergent feature of QCD; and emergent hadron mass (EHM) must provide the basic link between theory and observation. Nonperturbative tools are necessary if such connections are to be made; and in this context, we sketch recent progress in the application of continuum Schwinger function methods to an array of related problems in hadron and particle physics. Special emphasis is given to the three pillars of EHM—namely, the running gluon mass, process-independent effective charge, and running quark mass; their role in stabilising QCD; and their measurable expressions in a diverse array of observables. Full article

(This article belongs to the Special Issue Strong Interactions in the Standard Model: Massless Bosons to Compact Stars)

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71 pages, 2928 KiB

Open AccessEditor’s ChoiceReview

Radiative Corrections to Semileptonic Beta Decays: Progress and Challenges

by Chien-Yeah Seng

Particles 2021, 4(4), 397-467; https://doi.org/10.3390/particles4040034 - 28 Sep 2021

Cited by 18 | Viewed by 4952

Abstract

We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the [...] Read more.

O (G_{F} α)

radiative corrections. The latter are expressed as compact hadronic matrix elements that allow systematic non-perturbative analysis such as dispersion relation and lattice QCD. This brings substantial improvements to the precision of the electroweak radiative corrections in semileptonic decays of pion, kaon, free neutron and

J^{P} = 0^{+}

nuclei that are important theory inputs in precision tests of the Standard Model. Unresolved issues and future prospects are discussed. Full article

(This article belongs to the Special Issue Beta-Decay Processes in Nuclear Systems)

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29 pages, 476 KiB

Open AccessArticle

Sterile Neutrinos as Dark Matter: Alternative Production Mechanisms in the Early Universe

by Daniel Boyanovsky

Universe 2021, 7(8), 264; https://doi.org/10.3390/universe7080264 - 25 Jul 2021

Cited by 2 | Viewed by 2622

Abstract

We study various production mechanisms of sterile neutrinos in the early universe beyond and within the standard model. We obtain the quantum kinetic equations for production and the distribution function of sterile-like neutrinos at freeze-out, from which we obtain free streaming lengths, equations of state and coarse grained phase space densities. In a simple extension beyond the standard model, in which neutrinos are Yukawa coupled to a Higgs-like scalar, we derive and solve the quantum kinetic equation for sterile production and analyze the freeze-out conditions and clustering properties of this dark matter constituent. We argue that in the mass basis, standard model processes that produce active neutrinos also yield sterile-like neutrinos, leading to various possible production channels. Hence, the final distribution function of sterile-like neutrinos is a result of the various kinematically allowed production processes in the early universe. As an explicit example, we consider production of light sterile neutrinos from pion decay after the QCD phase transition, obtaining the quantum kinetic equation and the distribution function at freeze-out. A sterile-like neutrino with a mass in the keV range produced by this process is a suitable warm dark matter candidate with a free-streaming length of the order of few kpc consistent with cores in dwarf galaxies. Full article

(This article belongs to the Special Issue keV Warm Dark Matter (ΛWDM) in Agreement with Observations in Tribute to Héctor J. De Vega)

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28 pages, 438 KiB

Open AccessReview

Soft Anomalous Dimensions and Resummation in QCD

by Nikolaos Kidonakis

Universe 2020, 6(10), 165; https://doi.org/10.3390/universe6100165 - 1 Oct 2020

Cited by 12 | Viewed by 1943

Abstract

I discuss and review soft anomalous dimensions in QCD that describe soft-gluon threshold resummation for a wide range of hard-scattering processes. The factorization properties of the cross section in moment space and renormalization-group evolution are implemented to derive a general form for differential resummed cross sections. Detailed expressions are given for the soft anomalous dimensions at one, two, and three loops, including some new results, for a large number of partonic processes involving top quarks, electroweak bosons, Higgs bosons, and other particles in the standard model and beyond. Full article

(This article belongs to the Section High Energy Nuclear and Particle Physics)

35 pages, 2694 KiB

Open AccessEditor’s ChoiceArticle

Empirical Consequences of Emergent Mass

by Craig D. Roberts

Symmetry 2020, 12(9), 1468; https://doi.org/10.3390/sym12091468 - 7 Sep 2020

Cited by 76 | Viewed by 4962

Abstract

The Lagrangian that defines quantum chromodynamics (QCD), the strong interaction piece of the Standard Model, appears very simple. Nevertheless, it is responsible for an astonishing array of high-level phenomena with enormous apparent complexity, e.g., the existence, number and structure of atomic nuclei. The source of all these things can be traced to emergent mass, which might itself be QCD’s self-stabilising mechanism. A background to this perspective is provided, presenting, inter alia, a discussion of the gluon mass and QCD’s process-independent effective charge and highlighting an array of observable expressions of emergent mass, ranging from its manifestations in pion parton distributions to those in nucleon electromagnetic form factors. Full article

(This article belongs to the Special Issue Chiral Symmetry in Physics)

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