Energy-dependent Partial-wave Analysis Research Articles

Renormalization of one-pion exchange in higher partial waves in chiral effective field theory for antinucleon-nucleon system* *Supported by the Doctoral Fund Project of Nanfang College, Guangzhou (2020BQ03)

The renormalization of the iterated one-pion exchange (OPE) has been studied in chiral effective field theory (χEFT) for the antinucleon-nucleon () scattering in some partial waves (Phys. Rev. C 105, 054005 (2022)). In this paper, we go further for the other higher partial waves but with total angular momenta . Contact interactions are represented by a complex spherical well in the coordinate space. Changing the radius of the spherical well means changing the cutoff. We check the cutoff dependence of the phase shifts, inelasticities, and mixing angles for the partial waves and show that contact interactions are needed at leading order in channels where the singular tensor potentials of OPE are attractive. The results are compared with the energy-dependent partial-wave analysis of scattering data. Comparisons between our conclusions and applications of χEFT to the nucleon-nucleon system are also discussed.

Renormalization of one-pion exchange in chiral effective field theory for antinucleon-nucleon scattering

The renormalization of iterated one-pion exchange (OPE) is studied in chiral effective field theory $(\ensuremath{\chi}\mathrm{EFT})$ for the antinucleon-nucleon $(\overline{N}N)$ system. The OPE potential is cut off at a certain distance and contact interactions are represented by a complex spherical well with the same radius. We investigate the dependence on the cutoff radius of the phase shifts, inelasticities, and mixing angles for the low partial waves in $\overline{N}N$ scattering. We show that renormalization requires additional contact interactions compared to the expectation based on naive dimensional analysis. Results after renormalization are compared with the state-of-the-art energy-dependent partial-wave analysis of $\overline{N}N$ data. We compare our conclusions with applications of $\ensuremath{\chi}\mathrm{EFT}$ to the nucleon-nucleon system.

Updated determination of N* resonance parameters using a unitary, multichannel formalism

Results are presented for an updated multichannel energy-dependent partial-wave analysis of $\pi N$ scattering. Our earlier work incorporated single-energy amplitudes for $\pi N \rightarrow \pi N$, $\gamma N \rightarrow \pi N$, $\pi N \rightarrow \pi\pi N$, $\pi N \rightarrow \eta N$, and $\pi N \rightarrow K \Lambda$. The present work incorporates new single-energy solutions for $\gamma p \rightarrow \eta p$ up to a c.m.\ energy of 1990~MeV, $\gamma p \rightarrow K^+ \Lambda$ up to a c.m.\ energy of 2230~MeV, and $\gamma n \rightarrow \eta n$ up to a c.m.\ energy of 1885~MeV, as well as updated single-energy solutions for $\pi N \rightarrow \eta N$, $\pi N \rightarrow K \Lambda$, and $\gamma N \rightarrow \pi N$. In this paper, we present and discuss the resonance parameters obtained from a combined fit of all these single-energy amplitudes. Our determined energy-dependent amplitudes provide an excellent description of the corresponding measured observables.

N(1520) 3/2(-) helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions.

New data on the polarization observables T, P, and H for the reaction γp→pπ(0) are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.

Polarization observables in low-energy antiproton-proton scattering

We investigate the polarization parameters in low-energy antiproton-proton elastic ($\bar{p}p\rightarrow\bar{p}p$) and charge-exchange ($\bar{p}p\rightarrow\bar{n}n$) scattering. The predictions for unmeasured observables are based on our new energy-dependent partial-wave analysis of all antiproton-proton scattering data below 925 MeV/$c$ antiproton laboratory momentum, which gives an optimal description of the existing database. Sizable and remarkable spin effects are observed, in particular for charge-exchange scattering. These result from the spin dependence of the long- and medium-range one- and two-pion exchange antinucleon-nucleon potential and the state dependence of the parametrized short-range interaction. We study the possibility of polarizing a circulating antiproton beam with a polarized proton target by exploiting the spin dependence of the $\bar{p}p$ total cross section. It appears feasible to achieve a significant transverse polarization of an antiproton beam within a reasonable time.

Partial-wave analysis of theπ−p→ηnandπ−p→K0Λreactions

We investigate the hadronic reactions {\pi}N {\to} {\eta}N and {\pi}N {\to} K{\Lambda} via single-energy partial-wave analyses in the c.m. energy range 1080 to 2100 MeV. Our results for the K{\Lambda} channel are consistent with prior works; however, for the {\eta}N channel our results differ significantly from previous energy-dependent partial-wave analyses that violate the S-matrix unitarity. We present the first (new) results of {\eta}N and K{\Lambda} partial-wave amplitudes constrained by a unitary energy-dependent model. We obtain excellent predictions of integrated cross sections for the two reactions from a global energy-dependent solution. Our results imply that the region just above S11 (1535) has a major contribution from P11 (1710) for {\pi}-p {\to} {\eta}n, whereas the large peak near 1700 MeV in {\pi}-p {\to} K0{\Lambda} is dominated by contributions from both S11 (1650) and P11 (1710).

Energy-dependent partial-wave analysis of all antiproton-proton scattering data below 925 MeV/c

We present a new energy-dependent partial-wave analysis of all antiproton-proton elastic and charge-exchange scattering data below 925 MeV/c antiproton laboratory momentum. The long-range parts of the chiral one- and two-pion exchange interactions are included exactly. The short-range interactions, including the coupling to the mesonic annihilation channels, are parametrized by a complex boundary condition at a radius of r=1.2 fm. The updated database, which includes significantly more high-quality charge-exchange data, contains 3749 scattering data. The fit results in chi^2_min/N_df=1.048, where N_df=3578 is the number of degrees of freedom. We discuss the description of the experimental data and we present the antiproton-proton phase-shift parameters.

Poles as the only true resonant-state signals extracted from a worldwide collection of partial-wave amplitudes using only one, well controlled pole-extraction method

Each and every energy dependent partial-wave analysis is parameterizing the pole positions in a procedure defined by the way how the continuous energy dependence is implemented. These pole positions are, henceforth, inherently model dependent. To reduce this model dependence, we use only one, coupled-channel, unitary, fully analytic method based on the isobar approximation to extract the pole positions from the each available member of the worldwide collection of partial wave amplitudes which are understood as nothing more but a good energy dependent representation of genuine experimental numbers assembled in a form of partial-wave data. In that way, the model dependence related to the different assumptions on the analytic form of the partial-wave amplitudes is avoided, and the true confidence limit for the existence of a particular resonant state, at least in one model, is established. The way how the method works, and first results are demonstrated for the S11 partial wave.

Partial wave analysis of πproduction in two-photon collisions at LEP

The reaction γγ → π+π-π0 with quasi-real photons is studied with a total integrated luminosity of 663pb^-1, collected by the L3 detector at LEP at center-of-mass energies from 183 to 209GeV. The results of an energy-dependent partial wave analysis in the mass region 1.1≤M(π+π-π0)≤2.2GeV are presented. The reaction is dominated by a 2(1320) formation. A strong signal consistent with the first radial excitation of the isovector tensor state, a 2(1700), is present and confirms the previous L3 observation. Its two-photon partial width is found to be $ \Gamma_{{\gamma\gamma}}^{}$ Br(3π) = 0.37+0.12 -0.08keV, the relative branching ratio of ρ(770)π to f 2(1270)π is 3.4±0.4. For all observed states the product of γγ partial width and 3π branching ratios is measured.

Measurement of the AbsolutenpScattering Differential Cross Section at 194 MeV

We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for np backscattering to better than +/-2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial-wave analyses. The present results are in good accord with the partial-wave analyses, but deviate systematically from other recent measurements.

Hyperon resonances in coupled channels and Crystal Ball data

The known resonance parameters of the Λ and Σ hyperons were determined almost entirely from energy-dependent partial-wave analyses of K ¯ N scattering data. Some of these analyses attempted to obtain a consistent set of parameters for reactions involving different final states ( K ¯ N , πΛ, πΣ), but unitarity was not enforced and various features (e.g., backgrounds) were not treated consistently. Now that K − p → neutrals data are beginning to be published by the Crystal Ball Collaboration, it is timely to take a fresh look at the strangeness −1 hyperons. First results are presented for a new unitary, multichannel description of several K ¯ N reactions.

Analysis of K0 s K0 s and π+ π– π0 final states in two photon collisions at LEP

The K0 s K0 s and π+ π– π0 final states in two-photon collisions are studied with the L3 detector at LEP. A full energy dependent partial wave analysis demonstrates that the two-photon mass spectra are dominated by the formation of tensor mesons. Their masses, widths and two-photon partial widths are determined.

Chiral two-pion exchange in the nucleon–nucleon interaction

After reviewing the method of energy-dependent partial-wave analysis of the two-nucleon scattering data, I report on recent work to include the two-pion-exchange interaction [1,2]. The chiral two-pion-exchange component of the long-range nucleon-nucleon interaction is derived from the effective chiral Lagrangian. Its presence and importance is demonstrated in the partial-wave analysis. The values of the chiral coupling constants c(i) (i = 1,3,4) are determined in a fit to the data, and agree well with those obtained previously from pion-nucleon scattering amplitudes.

Chiral Two-Pion Exchange and Proton-Proton Partial-Wave Analysis

The chiral two-pion exchange component of the long-range pp interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance, and determine the chiral parameters c_i (i=1,3,4). The values agree well with those obtained from pion-nucleon amplitudes.

Npscattering measurements at 162 MeV and theπNNcoupling constant

The differential $\mathrm{np}$ scattering cross section has been measured at 162 MeV in the angular range ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=72\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}180\ifmmode^\circ\else\textdegree\fi{}$, using the neutron beam facility at The Svedberg Laboratory in Uppsala. Special attention was paid to the absolute normalization of the data. In the angular range $150\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}180\ifmmode^\circ\else\textdegree\fi{}$, the data are steeper than those of most previous measurements and predictions from energy-dependent partial-wave analyses or nucleon-nucleon potentials. At $180\ifmmode^\circ\else\textdegree\fi{}$, the difference is of the order of 10\char21{}15%, an important change since this cross section is considered as a primary standard. It has also consequences for fundamental physics. Moreover, a value of the charged $\ensuremath{\pi}\mathrm{NN}$ coupling constant, ${g}_{{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}}^{2}=14.52\ifmmode\pm\else\textpm\fi{}0.26 {(f}_{{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}}^{2}=0.0803\ifmmode\pm\else\textpm\fi{}0.0014)$, is deduced from the data, using a novel extrapolation method. This is in good agreement with the classical text book value, but higher than those determined in recent partial-wave analyses of the nucleon-nucleon data base.

Energy-Dependent Partial-Wave Analysis of Pion-Deuteron Elastic Scattering in TL = 65 to 294 MeV Region

Energy-Dependent Partial-Wave Analysis of Pion-Deuteron Elastic Scattering in TL = 65 to 294 MeV Region

An energy-dependent partial-wave analysis of π+p → K +Σ+ between threshold and 2.35 GeV

An energy-dependent partial wave analysis of the reaction π +p → K + Σ + has been carried out between threshold and 2.35 GeV centre-of-mass energy using recently published, high statistical precision data. A single solution giving a satisfactory fit to the data has been found. In the region below 2 GeV the resonant features of the solution are compared with the QCD based model of Koniuk and Isgur. Above 2 GeV the states listed in the particle Data Group tables with two or more stars are observed but none of the dubious one-star states is confirmed. Significant SU(3) breaking is observed in some amplitudes.

Energy-dependent partial-wave analysis of the π+d→pp reaction in the region √s=2.09-2.42 GeV

A satisfactory description of available experimental data (1000 points) for the pi +d to pp process was obtained using a model including 3P1, 1D2 and 3F3 diproton resonances in the I=1 channel.

Phase shift analysis of the reaction K +N → KN below 1.6 GeV/ c

An energy-dependent partial wave analysis was made for the K + nucleon scattering in the energy range between 0.2 and 1.6 GeV/ c using the data including our new polarization data of K +n elastic and charge-exchange scattering. Counterclockwise Argand plots were found for the partial waves P 13, P 01 and D 03.

Quasiunique amplitude forI=0KNscattering below 1.89 GeV in center-of-mass system and implications for bag models

Quasiunique results are presented of an energy-dependent partial-wave analysis of $I=0$, $\mathrm{KN}$ scattering between 1.47 and 1.89 GeV in c.m. system. The data set used incorporates new results on the reaction ${K}_{L}^{0}p\ensuremath{\rightarrow}{K}_{S}^{0}p$ and new polarization measurements in ${K}^{+}n$ elastic and charge-exchange scattering as well as ${K}^{+}n$ elastic and charge-exchange differential cross sections. A careful analysis of the input hypotheses, notably the effects of different parametrizations with their different theoretical or phenomenological assumptions, is made. No obvious evidence is found for any exotic classical positive-strangeness baryon resonance. However, there is evidence for poles in the $P$ matrix for both $I=0$ and $I=1$, corresponding to confined quark states of bag models. Some predicted states are unobserved and an unpredicted state in $I=1$, ${S}_{1}(1.786 \mathrm{GeV})$, is observed.