Chiral perturbation theory

In the past decade many charmonium-like states were observed experimentally. Especially those charged charmoniumlike Z c states and bottomonium-like Z b states can not be accommodated within the naive quark model. These charged Z c states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.

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“…[283,284,285,286,287] for the case of three flavors, and was extended to the case of four flavors in Refs. [249,250], where…”

Section: Dynamically Generated Resonancementioning

confidence: 99%

The hidden-charm pentaquark and tetraquark states

et al. 2016

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“…Finally, we add the diagrams where the last effective vertex is connected to the outgoing pseudoscalars through the kernel. This extra contribution is given by the form factor G ν of the factorized element 8) shown in Fig. A(a), which we have separated into transverse and longitudinal parts.…”

Section: Appendix C: Summation Of General Two-body Topologiesmentioning

confidence: 99%

“…We will use the latter in order to include kaon interactions in our study. Chiral Perturbation Theory (χPT) [5,6,7,8,9] describes the physical low-energy amplitudes as an expansion in powers of quark masses and momenta over a characteristic chiral scale Λ χ ≃ 4πf π ∼ 1 GeV, with f π = 92.4 MeV the pion decay constant.…”

Section: Introductionmentioning

confidence: 99%

Rho meson properties in the chiral theory framework

Sanz-Cillero

Pich

2003

Eur. Phys. J. C

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We study the mass, width and couplings of the lightest resonance multiplet with I (J P C ) = 1 (1 −− ) quantum numbers. Effective field theories based on chiral symmetry are employed in order to describe the form factor associated with the two-pseudoscalar matrix element of the QCD vector current. The bare poles of the intermediate resonances are regularized through a Dyson-Schwinger-like summation. We explore the role of the resonance width in physical observables and make a coupled-channel analysis of final-state interactions. This provides many interesting properties, as the pole mass M pole ρ = 764.1 ± 2.7 +4.0 −2.5 MeV. At energies E ∼ > 1 GeV, a second 1 (1 −− ) resonance multiplet is considered in order to describe the data in a more consistent way. From the phenomenologically extracted resonance couplings, we obtain the chiral coupling L r 9 (µ 0 ) = (7.04 ± 0.05−0.27 ) · 10 −3 , at µ 0 = 770 MeV, and show how the running with the scale µ affects the resonance parameters. A 1/N C counting is adopted in this work and the consistency of the large-N C expansion is tested. Finally, we make an estimation of the contribution from diagrams with resonances in crossed channels.

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“…The pions have masses corresponding to the explicit breakdown of the chiral symmetry. The pion physics, the effective theory of QCD, has been well established as the chiral perturbation theory (see, e.g., [8][9][10] and references therein), which is a cutoff theory below the scale 4πf π with f π being the pion decay constant. It is known that perturbative unitarity is violated in pion-pion scatterings above the cutoff in the effective theory.…”

Section: Introductionmentioning

confidence: 99%

New resonance scale and fingerprint identification in minimal composite Higgs models

et al. 2015

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Composite Higgs models are an intriguing scenario in which the Higgs particle is identified as a pseudo Nambu-Goldstone boson associated with spontaneous breaking of some global symmetry above the electroweak scale. They would predict new resonances at high energy scales, some of which can appear at multi-TeV scales. In such a case, analogies with pion physics in QCD that a sizable phase shift is predicted in pion-pion scattering processes might help us to evaluate scales of the resonances. In this paper, we discuss two complementary approaches to investigate the compositeness scale in minimal composite Higgs models. First, we discuss the bound on vector boson scattering from perturbative unitarity, and we evaluate the phase shift of the scattering amplitude, assuming that the same fitting function can be applied as the case in the pion physics.We then obtain the relation between possible phase shifts and promising new resonance scales. We also investigate the possibility to measure the phase shift at LHC and the future hadron colliders.Second, we classify deviations in Higgs coupling constants from the standard model predictions in various kinds of the minimal composite Higgs models. We then discuss a possibility to discriminate a specific minimal composite Higgs model from the other models with extended Higgs sectors by utilizing deviation patterns in the Higgs boson couplings by future precision measurements.

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Chiral perturbation theory

Cited by 470 publications

References 242 publications

The hidden-charm pentaquark and tetraquark states

The hidden-charm pentaquark and tetraquark states

Rho meson properties in the chiral theory framework

New resonance scale and fingerprint identification in minimal composite Higgs models

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