Partial Wave Analysis Research Articles

Scattering of e± from the neon isonuclear series over the energy range 1 eV–0.5 GeV

This work calculates the differential, integral and momentum transfer cross sections for the scattering of e± by the neutral neon over the energy range 1 eV–0.5 GeV and those of e− by the ions (Ne+–Ne10+) over the range 1 eV–1 keV. It also includes the estimation of the viscosity, inelastic, total and total ionization cross sections and Sherman function for the e±-atom systems over the same energy range. Our calculations involve two approaches, the optical potential model (OPM) and the nuclear structure approach (NSA), depending upon the collision energy. Both the approaches employ Dirac partial wave analysis but differ in the potentials. In OPM, a complex projectile-target optical potential, comprising static, exchange, polarization and imaginary components, is employed. In the NSA, only the nuclear potential is used, neglecting the screening of the electrons. Moreover, we have determined positions of critical minima, in energy and angle, from the analysis of elastic differential cross sections and Sherman function at different energies. Our results agree reasonably well with the available experimental data and other theoretical calculations.

Uncertainty quantification and falsification of chiral nuclear potentials

Are chiral theories at present describing experimental NN scattering data satisfactorily? Will the chiral approach offer a framework where fitting and selecting the existing np and pp data can be done without theoretical bias? While predictive power in theoretical nuclear physics has been a major concern in the study of nuclear structure and reactions, the Effective Field Theory (EFT) based on chiral expansions has emerged after Weinberg as a model-independent hierarchy for many-body forces and much progress has been achieved over the last decades. We review some of the issues involved which point to being close to the solution, but also that work remains still to be done to validate the theory. We analyze several examples including zero energy NN scattering and perturbative counter-term-free peripheral scattering where one would expect these methods to work best and unveil relevant systematic discrepancies when a fair comparison to the Granada-2013 NN-database and partial wave analysis based on coarse graining the interaction is undertaken.

Partial wave analysis of ψ(3686)→K+K−η

Using a sample of $(448.1\pm2.9)\times10^6$ $\psi(3686)$ events collected with the BESIII detector, we perform the first partial wave analysis of $\psi(3686)\rightarrow K^+K^-\eta$. In addition to the well established states, $\phi(1020)$, $\phi(1680)$, and $K_3^*(1780)$, contributions from $X(1750)$, $\rho(2150)$, $\rho_3(2250)$, and $K^*_2(1980)$ are also observed. The $X(1750)$ state is determined to be a $1^{--}$ resonance. The simultaneous observation of the $\phi(1680)$ and $X(1750)$ indicates that the $X(1750)$, with previous observations in photoproduction, is distinct from the $\phi(1680)$. The masses, widths, branching fractions of $\psi(3686)\rightarrow K^+K^-\eta$ and the intermediate resonances are also measured.

New data on [formula omitted] with polarized photons and protons and their implications for N⁎ → Nη decays

The polarization observables T,E,P,H, and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W=2400 MeV (T), 2280 MeV (E), 1620 MeV (P,H), or 1820 MeV (G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33±0.04 for N(1650)1/2− is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass JP=1/2−-resonances significantly.

Entanglement fidelity ratio for elastic collisions in non-ideal two-temperature dense plasma

The quantum diffraction and symmetry effects on the entanglement fidelity (EF) of different elastic electron–electron, ion–ion and electron–ion interactions are investigated in non-ideal dense plasmas. The partial wave analysis, an effective screened interaction potential including quantum mechanical diffraction and symmetry effects are employed to obtain the EF in a non-ideal dense plasma. We show that collision energy and temperatures of electron and ion have destructive effects on the entanglement in the system. In fact, by decreasing the temperature of plasma particles, the quantum effects become more prominent and the entanglement is elevated. Also, increase in the density of plasma leads to the enhancement of entanglement ratio. Additionally, some important characteristic parameters of the scattering such as differential, transport and total cross sections are calculated.

Astrophysical probes of inelastic dark matter with a light mediator

We consider an inelastic dark matter model, where a fermion is charged under a broken U(1) gauge symmetry, and introduce a tiny Majorana mass term to split the fermion into two states with the light one being a dark matter candidate. If the gauge boson is light, it can mediate both elastic and inelastic dark matter self-interactions in dark halos, leading to observational consequences. Using a numerical technique based on partial wave analysis, we accurately calculate the elastic and inelastic self-scattering cross sections. We assume a thermal freeze-out scenario and fix the gauge coupling constant using the relic density constraint. Then, we focus on six benchmark masses of dark matter, covering a wide range from $10~{\rm MeV}$ to $160~{\rm GeV}$ and map parameter regions where the elastic scattering cross section per unit mass is within $1~{\rm cm^2/g} - 5~{\rm cm^2/g}$, favored to solve small-scale issues of cold dark matter. If the heavy state can decay to the light state and a massless species, the inelastic up-scattering process can cool the halo and lead to core collapse. Taking galaxies with evidence of dark matter density cores, we further derive constraints on the parameter space. For dark matter masses below $10~{\rm GeV}$, the mass splitting must be large enough to forbid up scattering in the dwarf halo for evading the core-collapse constraint; while for higher masses, the up-scattering process can still be allowed. Our results show astrophysical observations can provide powerful tests for dark matter models with large elastic and inelastic self-interactions.

Partial wave analysis with OpenAcc

Partial wave analysis(PWA) is an important tool in hadron physics. Large data sets from the experiments in high precision frontier require high computational power. To utilize GPU cluster and the resource of super computers with various types of accelerator, we implement a software framework for partial wave analysis using OpenAcc, OpenAccPWA. OpenAccPWA provides convenient approaches for exposing parallelism in the code and excellent support for the large amount of existing CPU-based codes of partial wave amplitudes. It can avoid heavy workload of code migration from CPU to GPU. This proceeding will briefly introduce the software framework and performance of OpenAccPWA.

Recent results from the CBELSA/TAPS experiment at ELSA

In order to gain a better understanding of the dynamics inside the nucleon and of the non-perturbative regime of QCD, the nucleon excitation spectra and the properties of nucleon resonances are investigated. An essential experimental tool to achieve this goal is the study of different photoproduction reactions. Partial wave analyses are performed in order to obtain information about the contributing resonances. A complete experiment is needed to extract the underlying amplitudes unambiguously, which requires the measurement of carefully chosen single and double polarization observables in addition to the unpolarized cross section. The CBELSA/TAPS experiment in Bonn offers the possibility to measure several polarization observables using a linearly or circularly polarized photon beam and with a longitudinally or transversely polarized target. This contribution gives an overview of recently measured polarization observables in different final states. The impact of the new data is discussed.

Partial Wave Analysis of HADES Data for Two-Pion Production in Pion-Nucleon Reactions

Pion beams are important tools to study features of baryonic resonances and their decay channels because resonances are produced in s-channel at fixed mass equal to √s. In 2014 the HADES collaboration has performed systematic measurements in the second resonance region scanning around the mass of the N*(1520). Pion beams at four momenta (0.654, 0.686, 0.738 and 0.787 GeV/c) impinging on polyethylene and carbon targets have been used. With the use of the multichannel Partial Wave Analysis (PWA) the role of the N*(1520) resonance in conjunction with the intermediate ρ-meson production has been studied. Preliminary results at 0.654 GeV/c on exclusive production of two pions (ηπ+π- and pπ-π0) in the final state are presented.

Studying time-like electromagnetic baryonic transitions with HADES in pion induced reactions

A dedicated programme aiming at studying electromagnetic baryonic transitions in the time-like region has started at GSI using the pion beam and the High Acceptance Di-Electron Spectrometer (HADES) set-up. A pioneering experiment has been carried out in the second resonance region, at a center-of-mass energy of 1.49 GeV, using carbon and polyethylene targets, allowing for an analysis of the inclusivee+e-production and of the exclusive quasi-freeπ-p→ne+e-reaction, in complement to hadronic channels. Predictions for the Dalitz decay of N(1520) and N(1535) based on real photon couplings strongly underestimate thee+e-yield at invariant masses larger than 300 MeV/c2, which signals effects of time-like baryon transition form factors, in qualitative agreement with the Vector Dominance Models (VDM). A quantitative description of the observede+e-yield is achieved by taking into account the contribution from off-shellρs. The latter was provided by the preliminary results of a Bonn-Gatchina Partial Wave Analysis of the two-pion production channels, which were measured simultaneously in our experiment. A good agreement is also obtained using a covariant model for the time-like electromagnetic form factors for the N-N(1520) transition. The angular distributions for thee+e-production contain additional selective information on the spin structure of the different transitions. The measurements with the pion beam will be extended in future in the third resonance region. Hyperon Dalitz decay studies in proton induced reactions are also foreseen.

Scattering of e∓ from H2O

SynopsisTheoretical differential, elastic, total, momentum transfer, viscosity cross sections and spin-polarization for the elastic scattering of e∓ by H2 O molecule in the energy range 10 eV-10 keV have been calculated. These calculations have been carried out within the framework the Dirac partial wave analysis. We have employed a complex optical potential and additivity rule (AR) to compute the cross sections. Present results reasonably agree with available experimental data and other theoretical findings.

Cross section for γn→π0n measured at the Mainz A2 experiment

The $\gamma n \to \pi^0 n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195-1.553 GeV) and the pion c.m. polar production angles, ranging from 18 deg to 162 deg, making use of model-dependent nuclear corrections to extract pi0 production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883-MeV electron beam of the Mainz Microtron MAMI was used for the 0-meson production. Our accumulation of 3.6 x 10^6 $\gamma n \to \pi^0 n$ events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared to predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon decay amplitudes $N^* \to \gamma n$ at the resonance poles are determined for the first time.

Scattering of e± from N2 in the energy range 1 eV–10 keV

The differential, integrated elastic, inelastic, total, momentum transfer, viscosity, and ionisation cross sections for electron and positron scattering from the homonuclear diatomic nitrogen molecule over an incident energy range of 1 eV–10 keV are calculated using the additivity rule. Dirac partial wave analysis is employed to calculate the cross sections of the constituent atoms of molecules, using a complex optical model potential (OPM). Comparison of our results of the additivity rule with the available experimental data and other theoretical predictions is presented. Our findings produce reasonable results in intermediate and high energies.

Global parameterization of pi pi scattering up to 2 {mathrm {,GeV}}

We provide global parameterizations of pi pi rightarrow pi pi scattering S0 and P partial waves up to roughly 2 GeV for phenomenological use. These parameterizations describe the output and uncertainties of previous partial-wave dispersive analyses of pi pi rightarrow pi pi , both in the real axis up to 1.12 {mathrm {,GeV}} and in the complex plane within their applicability region, while also fulfilling forward dispersion relations up to 1.43 {mathrm {,GeV}}. Above that energy we just describe the available experimental data. Moreover, the analytic continuations of these global parameterizations also describe accurately the dispersive determinations of the sigma /f_0(500), f_0(980) and rho (770) pole parameters.

Tunneling optical resonances in light-droplet interactions: simulations of spaceborne cloud droplet observations.

A fruitful approach for light-droplet interaction in atmospheric optics, the quantum optical analogy combined with partial wave analysis, is used to characterize (location, width) very sharp tunneling optical resonances (TORs). For this purpose, a fast and flexible technique of computation, the transfer matrix method, has been developed; it is described herein. This paper proposes explicit calculations of TORs, considering isolated droplets and a droplet population, and so goes further than earlier studies. Applied in the context of POLDER observations, from the visible to the near infrared, it is shown that TORs enhance cross sections with respect to Mie's theory as currently computed in atmospheric optics. Precisely, for a typical warm cloud droplet population, this enhancement can reach almost 30% in the case of absorption. Scattering and extinction cross sections are also higher than those of Mie's theory, but to a lesser extent. As a conclusion, it is suggested that tunneling should be taken into account more explicitly when addressing light scattering by droplets. No scattering inversion technique is investigated in this paper, but for the time being, the results presented can be used as look-up tables (at least orders of magnitude) for practical computations in atmospheric remote sensing. Finally, the approach presented herein is proposed as a perspective to be used in different situations involving other spherical (or almost spherical) scatterers that otherwise should be addressed approximately.

Single-energy partial wave analysis for π0 photoproduction on the proton with fixed- t analyticity imposed

High precision data of the $\gamma p \to \pi^0 p$ reaction from its threshold up to $W=2$~GeV have been used in order to perform a single-energy partial wave analysis with minimal model dependence. Continuity in energy was achieved by imposing constraints from fixed-$t$ analyticity in an iterative procedure. Reaction models were only used as starting point in the very first iteration. We demonstrate that with this procedure partial wave amplitudes can be obtained which show only a minimal dependence on the initial model assumptions.

Hyperon I: Partial-wave amplitudes for K-p scattering

Early data on $K^-$ induced reactions off protons are collected and used in a coupled-channel partial wave analysis (PWA). Data which had been published in the form of Legendre coefficients are included in the PWA. In a {\it primary} fit using 3* and 4* resonances only, we observe some significant discrepancies with the data. In a systematic search for new $\Lambda$ and $\Sigma$ hyperon resonances, additional candidates are found. The significance of the known and of the additional resonances is evaluated. Seventeen resonances listed with 1* or 2* and one resonance listed with 3* in the Review of Particle Properties cannot be confirmed, five new hyperons are suggested. The partial-wave amplitudes deduced in this analysis are compared to those from other analyses.

Partial wave analysis for KΣ photoproduction on the nucleon valid from threshold up to W = 2.8 GeV

We have simultaneously analyzed the available kaon photoproduction data for the , , , and channels by using an isobar model constructed from the Feynman diagrammatic approach for the background terms and multipoles formulation for the resonance terms. The unknown coupling constants in the background terms as well as the helicity amplitudes and the kaon branching ratios of the resonance terms were extracted by fitting the calculated observables to nearly 8000 data points from the latest experimental measurements, including the recent and data from MAMI A2 collaboration. During the fitting process we used the data listed in the Review of Particle Properties of Particle Data Group as a guidance for the resonance properties. Since in the previous study the kaon branching ratio of the N(1710)P11 state was found to be relatively large and, as a consequence, a sizable spike appeared in the K+Σ− cross section near the threshold, in the present work we propose two isobar models, i.e. with and without this state. We have found that both models can nicely fit the data. Extensive comparisons between the result of model calculation and experimental data are presented in this paper. To investigate the role of each resonance in the present work the significance of each resonance is calculated and discussed. The present work indicates that the N(1895)S11 and Δ(1900)S31 as the important resonances in the KΣ photoproduction. We also present two examples of application of the presented isobar models, i.e. investigation of the nucleon resonance N(1535)S11 coupling to the KΣ channels and the contribution of KΣ channels to the Gerasimov–Drell–Hearn sum rule.

On the spin-observables in pseudoscalar meson photoproduction

Spin-observables in pseudoscalar meson photoproduction are discussed. This work is complementary to the earlier works on this topic. Here, the reaction amplitude is expressed in Pauli-spin basis which allows to calculate all the observables straightforwardly. We make use of the fact that the underlying reflection symmetry about the reaction plane can be most conveniently and easily exploited in this basis to help find the non-vanishing and independent observables in this reaction. The important issue of complete experiments is reviewed. By expressing the reaction amplitude in Pauli-spin basis, many sets of eight observables—distinct from those found in earlier works from the amplitude in transversity basis—capable of determining the reaction amplitude up to an overall phase are found. It is also shown that some of the combinations of the spin observables are suited for studying certain aspects of the reaction dynamics. We, then, carry out a (strictly) model-independent partial-wave analysis, in particular, of the peculiar angular behavior of the beam asymmetry observed in photoproduction very close to threshold (Levi Sandri et al 2015 Eur. Phys. J. A 51 77). This work should be useful, especially, for newcomers in the field of baryon spectroscopy, where the photoproduction reactions are a major tool for probing the baryon spectra.

Partial-wave analysis of J/ψ→K+K−π0

A partial-wave analysis of the decay $J/\psi \to K^+K^-\pi^0$ has been made using $(223.7\pm1.4)\times 10^{6}$ $J/\psi$ events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from $K^*_2(1430)^\pm$, $K^*_2(1980)^\pm$ and $K^*_4(2045)^\pm$ decaying to $K^\pm\pi^0$. The two latter states are observed in $J/\psi$ decays for the first time. Two resonance signals decaying to $K^+K^-$ are also observed. These contributions can not be reliably identified and their possible interpretations are discussed. The measured branching fraction $B(J/\psi \to K^+K^-\pi^0)$ of $(2.88\pm0.01\pm0.12)\times10^{-3}$ is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.