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Threshold cusps and triangle singularities in hadronic reactions

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TLDR
In this paper, a review of threshold cusps and various triangle singularities in hadronic reactions is presented, paying attention to their manifestations in phenomena related to exotic hadron candidates.
Abstract
The spectrum of hadrons is the manifestation of color confinement of quantum chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003, lots of new hadron resonant structures were discovered in the mass regions from light mesons to hadrons containing a pair of a heavy quark and an antiquark. Many of them are candidates of exotic hadrons, and they are usually observed as peaks in invariant mass distributions. However, the S-matrix also has kinematical singularities due to the on-shellness of intermediate particles for a process, such as two-body thresholds and triangle singularities, and they can produce peaks as well. On the one hand, such singularities may be misidentified as resonances; on the other hand, they can be used as tools for precision measurements. In this paper, we review the threshold cusps and various triangle singularities in hadronic reactions, paying attention to their manifestations in phenomena related to exotic hadron candidates.

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Journal ArticleDOI

An updated review of the new hadron states

TL;DR: In this article , an updated review of the recent experimental and theoretical progresses in the active field of hadron physics has been provided, including the recently observed open heavy flavor tetraquark states X(2900) and Tcc+(3875) as well as the hidden heavy flavor multiquark states.
Journal ArticleDOI

Coupled-channel approach to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>T</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>c</mml:mi></mml:mrow><mml:mo>+</mml:mo></mml:msubsup></mml:math> including three-body effects

- 24 Jan 2022 - 
TL;DR: In this article , a coupled-channel approach is applied to the charged tetraquark state (T}µµ+}$ recently discovered by the LHCb Collaboration.
Journal ArticleDOI

Landau equation and QCD sum rules for the tetraquark molecular states

TL;DR: In this article, it was shown that the Landau equation is of no use to study the Feynman diagrams in the QCD sum rules for the tetraquark molecular states; the fact is that the meson-meson scattering states cannot saturate the sum rules.
Journal ArticleDOI

Chiral perturbation theory for heavy hadrons and chiral effective field theory for heavy hadronic molecules

TL;DR: In this paper , an extensive review of the progress on the heavy hadronic molecular states within the framework of the chiral perturbation theory is presented, in which the same chiral dynamics not only govern the nuclei and forms the deuteron, but also dictates the shallow bound states or resonances composed of two heavy hadrons.
References
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Book

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TL;DR: The basic concepts of quantum mechanics Energy and momentum Schrodinger's equation Angular momentum Perturbation theory Spin The identity of particles The atom The theory of symmetry Polyatomic molecules Motion in a magnetic field Nuclear structure Elastic collisions Mathematical appendices.
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Observation of a Narrow Charmoniumlike State in Exclusive B±→K±π+π-J/ψ Decays

Suyong Choi, +175 more
TL;DR: In this article, a narrow charmonium-like state produced in the exclusive decay process B+/--->K+/-pi(+)pi(-)J/psi has been observed, which has a mass of 3872.0+/-0.6(stat)+/- 0.5(syst) MeV.
Book

The Analytic S-Matrix

TL;DR: In this paper, the authors present analytic properties of perturbation theory and asymptotic behavior of S-matrix theory with respect to perturbations and S-Matrix theory.
Journal ArticleDOI

Observation of $J/\psi p$ Resonances Consistent with Pentaquark States in $\Lambda_b^0 \to J/\psi K^- p$ Decays

Roel Aaij, +722 more
TL;DR: In this article, the pentaquark-charmonium states were observed in the J/ψp channel in Λ0b→J/K−p decays and the significance of these resonances is more than 9 standard deviations.
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