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Prof. Dr. Deliang Yao

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Guest Editor

School of Physics and Electronics, Hunan University, Changsha 410082, China
Interests: hadron physics; S-matrix theory and dispersion relations; chiral effective field theories; in particular baryon chiral perturbation theory

Dr. Zhi Yang

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Guest Editor

School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
Interests: hadron physics; exotic states

Special Issue Information

Dear Colleagues,

One of the most challenging problems in particle physics is understanding the color confinement mechanism encountered in the non-perturbative regime of quantum chromodynamics (QCD). Since quarks and gluons are confined to form color-neutral hadrons, a feasible and efficient method is to scrutinize the relevant hadron spectroscopy with modern experimental data by employing various theoretical approaches.

Great progress has been made in recent years. With the development of experimental techniques and the accumulation of statistics, a large number of new states have been discovered by collaborations such as BaBar, Belle, BESIII and LHCb. Most of them are beyond conventional quark model expectation and usually dubbed exotic states. Meanwhile, high-precision measurements have also shed new light on the properties of traditional meson and baryon states. Furthermore, new scientific projects such as EiC, EicC and STCF, etc., have been proposed, aiming to explore traditional baryons, baryon excitations, new mesons, as well as QCD exotics with high statistics and high precision in the energy regions of interest.

The recent experimental developments have also triggered the renaissance of theoretical studies of hadron spectroscopy. Efforts have been mainly devoted either to unveiling the nature of the newly observed exotic states or to gaining more insights into the properties and inner structures of the traditional hadrons. Pertinent explanations and novel predictions can be achieved by making use of lattice QCD, non-relativistic QCD, chiral effective field theories, QCD sum rules, chiral quark models and other phenomenology models. With the help of general S-matrix arguments, such as analyticity, unitarity and crossing symmetry, solid conclusions can be drawn on hadron interactions and appropriate paradigms can be established in the classification of hadrons.

The aim of this Special Issue is to gather contributions and recent progress on exotic hadrons and candidates, traditional meson and baryon states, hadron structure and compositeness, hadron decay, production and interactions. It will also serve as a topic collection for both experimentalists and theoreticians, so that the discussion of open problems and possible future developments in hadron spectroscopy can be stimulated.

Prof. Dr. Deliang Yao
Dr. Zhi Yang
Guest Editors

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Keywords

exotic states and candidates
meson spectroscopy
baryon spectroscopy
hadron structure
hadron decay and production
hadron–hadron interactions

Published Papers (3 papers)

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Research

Jump to: Review

12 pages, 373 KiB

Open AccessArticle

Mission Target: Tetraquark Mesons of Flavour-Cryptoexotic Type

by Wolfgang Lucha

Universe 2023, 9(8), 358; https://doi.org/10.3390/universe9080358 - 31 Jul 2023

Viewed by 1108

Abstract

Currently, flavour-cryptoexotic tetraquarks form the most common sort of all experimentally established exotic multiquark hadrons. This note points out a few promising concepts that should help improve theoretical (but, for several reasons, not quite straightforward) analyses of this kind of states; among others, their scope of application encompasses the strong interactions in the limit of (arbitrarily) large numbers of colours, and equally analytical and nonperturbative approaches to multiquark states. Full article

(This article belongs to the Special Issue Recent Progress in Hadron Spectroscopy)

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10 pages, 418 KiB

Open AccessArticle

ϕ(2170) Decaying to ϕππ and ϕ

K \bar{K}

by Yun-Hua Chen

Universe 2023, 9(7), 325; https://doi.org/10.3390/universe9070325 - 9 Jul 2023

Cited by 1 | Viewed by 639

Abstract

Within the framework of dispersion theory, we study the the processes

e^{+} e^{-} \to ϕ (2170) \to ϕ π π (K \bar{K})

. The strong pion–pion final-state interactions, especially the

K \bar{K}

coupled channel in [...] Read more.

Within the framework of dispersion theory, we study the the processes

e^{+} e^{-} \to ϕ (2170) \to ϕ π π (K \bar{K})

. The strong pion–pion final-state interactions, especially the

K \bar{K}

coupled channel in the S wave, are taken into account in a model-independent way using the Omnès function solution. Through fitting the experimental data of the

π π

and

ϕ π

invariant mass distributions of the

e^{+} e^{-} \to ϕ (2170) \to ϕ π^{+} π^{-}

process, the low-energy constants in the chiral Lagrangian are determined. The theoretical prediction for the cross sections’ ratio

σ (e^{+} e^{-} \to ϕ (2170) \to ϕ K^{+} K^{-}) / σ (e^{+} e^{-} \to ϕ (2170) \to

ϕ π^{+} π^{-})

is given, which could be useful for selecting the physical solution, when the fit to the

e^{+} e^{-} \to ϕ K^{+} K^{-}

cross-section distribution is available in the future. Our results suggest that above the kinematical threshold of

ϕ K \bar{K}

, the mechanism

e^{+} e^{-} \to ϕ K^{+} K^{-}

, with the kaons rescattering to a pion pair, plays an important role in the

e^{+} e^{-} \to ϕ π^{+} π^{-}

transition. Full article

(This article belongs to the Special Issue Recent Progress in Hadron Spectroscopy)

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Review

Jump to: Research

45 pages, 2330 KiB

Open AccessReview

Vector Quarkonia at the LHC with Jethad: A High-Energy Viewpoint

by Francesco Giovanni Celiberto

Universe 2023, 9(7), 324; https://doi.org/10.3390/universe9070324 - 7 Jul 2023

Cited by 6 | Viewed by 899

Abstract

In this review, we discuss and extend the study of the inclusive production of vector quarkonia,

J / ψ

and

Υ

, emitted with large transverse momenta and rapidities at the LHC. We adopt the novel ZCW19

^{+}

determination of fragmentation functions to [...] Read more.

In this review, we discuss and extend the study of the inclusive production of vector quarkonia,

J / ψ

and

Υ

, emitted with large transverse momenta and rapidities at the LHC. We adopt the novel ZCW19

^{+}

determination of fragmentation functions to depict the quarkonium production mechanism at the next-to-leading level of perturbative QCD. This approach is based on the nonrelativistic QCD formalism well adapted to describe the formation of a quarkonium state from the collinear fragmentation of a gluon or a constituent heavy quark at the lowest energy scale. We rely upon the

NLL / {NLO}^{+}

hybrid high-energy and collinear factorization for differential cross-sections, where the collinear formalism is enhanced by the BFKL resummation of next-to-leading energy logarithms arising in the t-channel. We employ the method to analyze the behavior of the rapidity distributions for double-inclusive vector quarkonium and inclusive vector quarkonium plus jet emissions. We discover that the natural stability of the high-energy series, previously seen in observables sensitive to the emission of hadrons with heavy flavor detected in the rapidity acceptance of LHC barrel calorimeters, becomes even more manifest when these particles are tagged in forward regions covered by endcaps. Our findings present the important message that vector quarkonia at the LHC via hybrid factorization offer a unique chance to perform precision studies of high-energy QCD, as well as an intriguing opportunity to shed light on the quarkonium production puzzle. Full article

(This article belongs to the Special Issue Recent Progress in Hadron Spectroscopy)

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Published Papers (3 papers)

Research

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