Search

We perform a systematic analysis of the J / ψ → γ π 0 π 0 and → γ K S 0 K S 0 partial waves measured by BESIII. We use a large set of amplitude parametrizations to reduce the model bias. We determine the physical properties of seven scalar and tensor resonances in the 1– 2.5 GeV mass range. These include the well known f 0 (1500) and f 0 (1710) , that are considered to be the primary glueball candidates. The hierarchy of resonance couplings determined from this analysis favors the latter as the one with the largest glueball component. [ABSTRACT FROM AUTHOR]

The production of η (′) π pairs constitutes one of the golden channels to search for hybrid exotics, with explicit gluonic degrees of freedom. Understanding the dynamics and backgrounds associated to η (′) π production above the resonance region is required to impose additional constraints to the resonance extraction. We consider the reaction π - p → η (′) π - p measured by COMPASS. We show that the data in 2.4 < m η (′) π < 3.0 GeV can be described by amplitudes based on double-Regge exchanges. The angular distribution of the meson pairs, in particular in the η ′ π channel, can be attributed to flavor singlet exchanges, suggesting the presence of a large gluon content that couples strongly to the produced mesons. [ABSTRACT FROM AUTHOR]

In light of recent experimental results, we revisit the dispersive analysis of the ω → 3 π decay amplitude and of the ω π 0 transition form factor. Within the framework of the Khuri–Treiman equations, we show that the ω → 3 π Dalitz-plot parameters obtained with a once-subtracted amplitude are in agreement with the latest experimental determination by BESIII. Furthermore, we show that at low energies the ω π 0 transition form factor obtained from our determination of the ω → 3 π amplitude is consistent with the data from MAMI and NA60 experiments. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: 10.1140/epjc/s10052-021-09420-1 [ABSTRACT FROM AUTHOR]

We give a detailed derivation of the Boltzmann equation, and in particular its collision integral, in classical field theory. We first carry this out in a scalar theory with both cubic and quartic interactions and subsequently in a Yang-Mills theory. Our method does not rely on a doubling of the fields, rather it is based on a diagrammatic approach representing the classical solution to the problem. [ABSTRACT FROM AUTHOR]

The quantum numbers and mass hierarchy of the glueballs observed in (2+1)-dimensional lattice QCD with gauge group SU( N) are shown to be in agreement with a constituent picture. The agreement is maintained when going from glueballs to gluelumps, and when the gauge group SO(2 N) is taken instead of SU( N). [ABSTRACT FROM AUTHOR]

Further progress in hadron spectroscopy necessitates the phenomenological description of three particle reactions. We consider the isobar approximation, where the connected part of the 3→3 amplitude is first expressed as a sum over initial and final pairs, and then expanded into a truncated partial wave series. The resulting unitarity equation is automatically fulfilled by the B-matrix solution, which is an integral equation for the partial wave amplitudes, analogous to the K-matrix parameterization used to describe 2→2 amplitudes. We study the one particle exchange and how its analytic structure impacts rescattering solutions such as the triangle diagram. The analytic structure is compared to other parameterizations discussed in the literature. We briefly discuss the analogies with recent formalisms for extracting 3→3 scattering amplitudes in lattice QCD. [ABSTRACT FROM AUTHOR]

We discuss the differences between several partial-wave analysis formalisms used in the construction of three-body decay amplitudes involving fermions. Specifically, we consider the decay Λb→ψpK-, where the hidden charm pentaquark signal has been reported. We analyze the analytical properties of the amplitudes and separate kinematical and dynamical singularities. The result is an amplitude with the minimal energy dependence compatible with the S-matrix principles. [ABSTRACT FROM AUTHOR]

The Khuri-Treiman formalism models the partial-wave expansion of a scattering amplitude as a sum of three individual truncated series, capturing the low-energy dynamics of the direct and cross channels. We cast this formalism into dispersive equations to study ππ scattering, and compare their expressions and numerical output to the Roy and GKPY equations. We prove that the Khuri-Treiman equations and Roy equations coincide when both are truncated to include only S- and P-waves. When higher partial waves are included, we find an excellent agreement between the Khuri-Treiman and the GKPY results. This lends credence to the notion that the Khuri-Treiman formalism is a reliable low-energy tool for studying hadronic reaction amplitudes. [ABSTRACT FROM AUTHOR]

Hadron decay chains constitute one of the main sources of information on the QCD spectrum. We discuss the differences between several partial wave analysis formalisms used in the literature to build the amplitudes. We match the helicity amplitudes to the covariant tensor basis. Hereby, we pay attention to the analytical properties of the amplitudes and separate singularities of kinematical and dynamical nature. We study the analytical properties of the spin-orbit (LS) formalism, and some of the covariant tensor approaches. In particular, we explicitly build the amplitudes for the B→ψπK and B→D¯ππ decays, and show that the energy dependence of the covariant approach is model dependent. We also show that the usual recursive construction of covariant tensors explicitly violates crossing symmetry, which would lead to different resonance parameters extracted from scattering and decay processes. [ABSTRACT FROM AUTHOR]