Narrow Results

There exist four pion nucleon coupling constants, $f_{{\pi }^{0}pp}$, $-f_{{\pi }^{0}nn}$, $f_{{\pi }^{+}pn}/\sqrt{2}$ and $f_{{\pi }^{-}np}/\sqrt{2}$ which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion–nucleon–nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination

We have analyzed the γp→pK⁺K^- reaction in the K⁺K^- effective mass region around the mass of the ϕ(1020) meson. The interference of the S-wave contribution with the P-wave has been studied. Both scalar resonances f₀(980) and a₀(980) have been taken into account. We obtained a good description of the available experimental data, in particular the mass distributions and the moments of the kaon angular distribution. Our calculations give values of the integrated S-wave total photoproduction cross section between 4 and 7 nb for the K⁺K^- effective mass range around the ϕ(1020) mass and at the laboratory photon energy near 5 GeV. These numbers favor lower experimental estimates obtained at DESY.

In the 90s of the last century high statistics experiments with fully equipped 4π detectors have lead to a better insight in the spectrum of hadrons. In particular the finding of crypto-exotic and J^PC exotic states tremendously improved the experimental situation in meson spectroscopy. All this was possible only with sophisticated analysis methods like the decomposition of measured phase-space distribution into partial waves and to express the partial waves in terms of complicated dynamical functions. This paper acts as an appetizer and gives an introduction about the concepts and formalisms involved.

We reported the observation of Y(2175) in ϕf₀(980) mass spectrum in J/ψ → ηϕf₀(980) with f₀(980) → π⁺π^-, the partial wave analysis results of J/ψ → γϕϕ, the measurement of , , and the observation of threshold enhancement in , based on 5.8 × 10⁷ J/ψ events collected at BESII. The measurement of ψ(2S) radiative decays with 1.4 × 10⁷ ψ(2S) events as well as the measurement of D decay branching fractions with 33 pb^-1 data collected at and around 3.773 GeV are also presented.

Diffractive dissociation reactions at COMPASS provide clean access to mesons with masses below ≈ 2.5 GeV/c². This paper presents a partial wave analysis of about 420 000 π^-Pb → π^-π^-π⁺Pb events at 190 GeV/c beam momentum and with four-momentum transfer t' ∈ [0.1,1] GeV²/c². The well-known a₁(1260), a₂(1320) and π₂(1670) mesons are resolved with high quality. Also the less established states π(1800) and a₄(2040) are seen. In addition, a resonance in the spin-exotic J^PC = 1^-+ wave is observed. A mass-dependent fit results in a mass and width of and , respectively, which is consistent with the disputed hybrid candidate π₁(1600).

To resolve the nonconvex optimization problem in partial wave analysis, this paper introduces a novel approach that incorporates fraction constraints into the likelihood function. This method offers significant improvements in the efficiency of pole searching within partial wave analysis.

New measurements of transverse target and beam-target asymmetries in pion photo-production were performed using the Crystal Ball at the Mainz Microtron MAMI. Preliminary results are discussed in the context of model-independent partial wave analyses for pseudo-scalar meson photo-production below E_cm = 2 GeV.

Based on 106×10⁶ ψ(3686) events collected with BESIII at BEPCII, partial wave analysis (PWA) of and are performed. Clear signals for N(1535) are observed and the mass, width and spin-parity are measured from . 7 N* intermediate resonances including two significant new resonances N(2300) and N(2570) are observed and the mass, width and spin-parity are also measured from .

We present a selection of recent results on light hadron spectroscopy from the BESIII collaboration. The topics include the full partial wave analysis on J/ψ radiative decays, including J/ψ → γηη and γωϕ. Besides, we also cover the topics about the resonance Y(2175) and η(1405).

The BESIII experiment in Beijing takes data in τ-charm domain since 2009. For the moment the world largest samples of J/ψ, ψ(3686), ψ(3770) and ψ(4040) data have been collected. Hadron spectroscopy is a unique way to access QCD, which is one of the most important physics goals of BESIII. Experimental search of new forms of hadrons and subsequent investigation of their properties would provide validation of and valuable input to the quantitative understanding of QCD. The key to success lies in high levels of precision during the measurement and high statistics in the recorded data set complemented with sophisticated analysis methods. Partial wave analysis (PWA) is a powerful tool to study the hadron spectroscopy, that allows one to extract the resonance's spin-parity, mass, width and decay properties with high sensitivity and accuracy. In this poster, we present the working PWA framework of BESIII – GPUPWA and the recent results of PWA of J/ψ → γηη. GPUPWA is a PWA framework for high statistics partial wave analyses harnessing the GPU parallel computing.

The 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab will enable a new generation of experiments in hadronic nuclear physics, seeking to address fundamental questions in our understanding of QCD. The existence of exotic states, suggested by both quark models and lattice calculations, would allow gluonic degrees of freedom to be explored, and may help explain the role played by gluons in the QCD interaction. This article will review the meson spectroscopy program being planned at the lab following the 12 GeV upgrade, utilising real and quasi-real photon beams in two of the lab's four experimental halls, whose distinct capabilities will enable an extensive set of spectroscopy experiments to be performed at the same facility.

We present a selection of recent results on light hadron spectroscopy from the BESIII collaboration. The topics include the full partial wave analysis on J/ψ radiative decays, including J/ψ → γηη and γωϕ. Besides, we also cover the topics about baryon spectroscopy, including the partial wave analysis of and .

The recent measurements of the reactions $pp\to pp{\pi }^0$ and $pn\to pp{\pi }^{-}$ by the ANKE collaboration at COSY are analyzed with the focus on the p-wave pion production amplitudes. These amplitudes are known to provide an important connection between $NN\to NN\pi$ and other low-energy few-nucleon reactions. The results of the recent partial wave analysis of the ANKE data are discussed and compared with the theoretical predictions.

We show that the photoproduction of resonances in the π⁺π⁻ system can be described by a combination of two production mechanisms: the long range production due to one pion exchange known in the literature as the Deck mechanism and the short range production related to exchanges of heavier particles and quark/gluon processes. The model with these components very well reproduces experimental mass distributions for partial waves S, P and D.

PAWIAN is a powerful, user-friendly and highly modular partial wave analysis software package with the aim to support analyses for a multitude of different cases in the field of hadron physics. Real data originating from the $\overline{p}p$ annihilation process and from e⁺e⁻ reactions are currently under investigation with PAWIAN. The software is written in C++ and follows an object-oriented approach with a wide range of flexibility. The software supports parallelization of the calculations and coupled channel analyses. The code allows to be easily extended for further decay models, complete amplitudes or other descriptions for the dynamics.

After an overview of the general features and capabilities of PAWIAN, some recent improvements concerning the treatment of analyticity as well as the extraction of pole parameters are discussed.

We reported the study of Y(2175) in J/ψ decays, the results from a partial wave analysis of and the observation of charged κ, based on 5.8×10⁷J/ψ events collected at BESII. We also reported the precision R values at the energy points of 2.60, 3.05 and 3.65 GeV/c² and the measurement of the line shape for the cross sections of e⁺e^- → hadrons in the energy range of 3.650 - 3.872 GeV/c². The status of BESIII running, as well as the preliminary results from BESIII are also presented.

The number of the baryon states observed in the analysis of the πN elastic data is significantly smaller than that predicted by all existing models of strong interactions at low energies. In the present paper we report the result of the analysis of the meson photoproduction data taken recently in a number of experimental facilities over the world. The combined analysis of the new data and the data on pion induced reactions reveals a set of new baryon states which escaped the identification in previous analyses of the elastic data. The performed analysis also allows us to determine a number of new properties of the known baryons with a good precision.