Nucleon Pole Research Articles

Photo-production of lowest state within the Regge-effective Lagrangian approach* *Supported by the National Natural Science Foundation of China (12192263, 12075288, 11735003, 11961141012), the Natural Science Foundation of Henan (222300420554, 232300421140), the Project of Youth Backbone Teachers of Colleges and Universities of Henan Province (2020GGJS017), the Youth Talent Support Project of Henan (2021HYTP002), the Open Project of Guangxi Key Laboratory of

Because the lowest state with quantum numbers spin-parity is far from being established experimentally and theoretically, we perform a theoretical study on the photo-production within the Regge-effective Lagrangian approach. Considering that couples to the channel, we study the contributions from the t-channel K exchange diagram. Moreover, the contributions from the t-channel exchange, s-channel nucleon pole, u-channel Σ exchange, and contact term are considered. The differential and total cross sections of the process are predicted with our model parameters. The results should help in experimentally searching for the state in the future.

Polarization phenomena in the reaction e++e−→N+N¯+π0 in the framework of the nonresonant mechanism

The dependence of the nucleon polarization in the reaction ${e}^{+}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}N+\overline{N}+{\ensuremath{\pi}}^{0}$ over different invariant variables is derived for the nonresonant mechanism. The nucleon polarization is expressed in terms of six invariant complex amplitudes, assuming the conservation of the hadron electromagnetic currents and the P invariance of the hadron electromagnetic interaction. An inclusive experimental setup when the proton (or the antiproton) and the pion are detected in coincidence is considered. Numerical estimations are performed for the so-called normal polarization in the energy range from threshold up to $s=16\text{ }\text{ }{\mathrm{GeV}}^{2}$, using selected parametrizations of the nucleon electromagnetic form factors in frame of a formalism derived in a previous work for the calculation of the unpolarized differential cross section.

General Analysis of the Reaction e^+ + e^- → N + Ñ + π^0

The general analysis of the reaction , in the case of longitudinally polarized electron beam, has been performed in the one-photon-nnihilation approximation, accounting for the polarization states of the final nucleon. This analysis is useful for the description of the continuum (non-resonant) and resonant (with different possible vector mesons or excited baryons in the intermediate virtual states of the Feynman diagrams) contributions. The conservation of the hadron electromagnetic currents and P-invariance of the hadron electromagnetic interaction were used to express the matrix element in terms of the six complex independent invariant amplitudes. The general structure of the hadronic tensor for the case of unpolarized final hadrons and polarized nucleon has been derived. The spin-independent part of the hadronic tensor is determined by five structure functions and the spin-dependent one by 13 structure functions. The transversal, longitudinal and normal components of the nucleon polarization four-vector are expressed by means of the four-vectors of the particle momenta. The five independent invariant variables which describe the reaction have been introduced. The limits of the changing of these variables have been considered. The kinematical double invariant variables regions are given in the figure. The kinematics, suitable to study the invariant mass distributions, is investigated.

Searching for strange hidden-charm pentaquark state Pcs(4459) in γp→K+Pcs(4459) reaction

We investigate the possibility of studying the strange hidden-charm pentaquark state $P_{cs}(4459)$ by photon-induced reactions on a proton target in an effective Lagrangian approach. The production process is described by the $t$-channel $K^{-}$ exchange, the $u$-channel $\Lambda$ exchange, the contract term, and the $s$- channel nucleon pole. Our theoretical approach is based on the assumption that $P_{cs}(4459)$ with $J^{P}=1/2^{-}$ or $J^{P}=3/2^{-}$ can be interpreted as a molecule composed of $\bar{D}^{*}\Xi_c$. Using the coupling constants of the $P^{J^P}_{cs}$ to $\gamma{}\Lambda$ and $K^{-}p$ channels obtained from molecule picture of the $P^{J^{P}}_{cs}(4459)$, the total cross-sections of the process $\gamma{}p\to{}P^{J^P}_{cs}K^{+}$ is evaluated. Our calculation indicates that the cross-section for $\gamma{}p\to{}P^{1/2^{-}}_{cs}K^{+}$ and $\gamma{}p\to{}P^{3/2^{-}}_{cs}K^{+}$ are of the order of 10.0 pb and 5.0 pb, respectively. In addition, we compute the cross-section by assuming $P_{cs}(4459)$ as a compact pentaquark and find it is quite different from the results of $\bar{D}^{*}\Xi_c$ molecule. Those results can be measured in future experiments, such as the Electron-Ion Collider in China and the United States. And can be used to test the nature of the $P_{cs}$.

Photoproduction of possible pentaquark states Λb0(5912) and Λb0(5920) in the γp→Λb0(*)B+ reactions

In this work, we report on a theoretical study of possible pentaquark states $\Lambda^0_b(5912)$ and $\Lambda^0_b(5920)$ in the $\gamma{}p\to{}\Lambda_b^{0(*)}B^+$ reactions within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole and $t$-channel $\bar{B}^{{*}-}$ exchange, the contact term contribution are also included. Our theoretical approach is based on the chiral unitary theory where the $\Lambda^0_b(5912)$ and $\Lambda^0_b(5920)$ resonances are dynamically generated. Within the coupling constants of the $\Lambda^0_b(5912)$ and $\Lambda^0_b(5920)$ to $\bar{B}p$ and $\bar{B}^{*}p$ channels obtained from chiral unitary theory, the total and differential cross sections of the $\gamma{}p\to{}\Lambda_b^{0(*)}B^+$ are evaluated. Our calculation indicates that the cross section for $\gamma{}p\to{}\Lambda_b^{0}(5912)B^{+}$ and $\gamma{}p\to{}\Lambda_b^{0}(5920)B^{+}$ reactions are of the order of 0.0164 nb and 0.00527 nb,respectively. If measured in future experiments, such as Electron-Ion Collider in China (EicC) or US(US-EIC), the predicted total cross sections and specific features of the angular distributions can be used to test the (molecular) nature of the $\Lambda^0_b(5912)$ and $\Lambda^0_b(5920)$ that they may be pentaquark states.

Model dependence of the polarization asymmetries in weak pion production off the nucleon

The work presents the study of the polarization observables in the single pion production (SPP) induced by the interaction of the muon neutrino (antineutrino) with nucleons. The SPP cross sections and spin asymmetries are computed within two phenomenological models. One is based on the nonlinear sigma model [E. Hernandez, J. Nieves, and M. Valverde, Phys. Rev. D 76, 033005 (2007)] and the other has origin in the linear sigma model [G. L. Fogli and G. Nardulli, Nucl. Phys. B160, 116 (1979)]. First, we show that the final nucleon polarization and target spin asymmetries are good observables to obtain information about the ${C}_{5}^{A}$ axial form factor. Second, we demonstrate that the nucleon polarization and the target spin asymmetries are sensitive to the relative phase between resonance and nonresonance amplitudes. We conclude that the polarization of the final nucleon and the target spin asymmetry are promising observables for testing SPP models, including studies of the axial content of $\mathrm{\ensuremath{\Delta}}(1232)$ resonance and unitarization procedures.

Role of the low-lying nucleon resonances in the pp¯→ψη reaction

Within the effective Lagrangian approach, we study the $p\bar{p} \rightarrow \psi\eta$ [$\psi\equiv\psi(3686)$, $J/\psi$] reaction at the low energy where the contributions from nucleon pole and low-lying nucleon resonances, $N(1520)$, $N(1535)$ and $N(1650)$ are considered. All the model parameters are determined with the help of current experimental data on the decay of $\psi \to p \bar{p} \eta$. Within the model parameters, the total and differential cross sections of the $p\bar{p} \rightarrow \psi\eta$ reaction are predicted. We show that the relative phases between different amplitudes of different nucleon resonance will change significantly the angular distributions of the $\bar{p} p \to \psi \eta$ reaction. Therefore, we conclude that these reactions are suitable to study experimentally the properties of the low-lying nucleon resonance and the reaction mechanisms. We hope that these theoretical calculations can be tested by future experiments.

Role of the Λ(1600) in the reaction

Role of the Λ(1600) is studied in the reaction by using the effective Lagrangian approach near the threshold. We perform a calculation for the total and differential cross sections by considering the contributions from the Λ(1600) and Λ(1670) intermediate resonances decaying into with decaying into . Additionally, the non-resonance process from u-channel nucleon pole is also taken into account. With our model parameters, the current experimental data on the total cross sections of the reaction can be well reproduced. It is shown that we really need the contribution from the Λ(1600) with spin-parity , and that these measurements can be used to determine some of the properties of the Λ(1600) resonance. Furthermore, we also plot the π0Λ invariant mass distributions which could be tested by the future experimental measurements.

On the existence of N*(890) resonance in S11 channel of πN scatterings

Low-energy partial-wave πN scattering data is reexamined with the help of the production representation of partial-wave S matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift is determined, with controlled systematic error estimates, by using the results of O(p3) chiral perturbative amplitudes obtained in the extended-onmass- shell scheme. In S11 and P11 channels, severe discrepancies are observed between the phase shift data and the sum of all known contributions. Statistically satisfactory fits to the data can only be achieved by adding extra poles in the two channels. We find that a S11 resonance pole locates at $$\sqrt {{z_r}} $$ = (0:895–0:081)–(0:164–0:023)i GeV, on the complex s-plane. On the other hand, a P11 virtual pole, as an accompanying partner of the nucleon bound-state pole, locates at $$\sqrt {{z_v}} $$ = (0:966–0:018) GeV, slightly above the nucleon pole on the real axis below threshold. Physical origin of the two newly established poles is explored to the best of our knowledge. It is emphasized that the O(p3) calculation greatly improves the fit quality comparing with the previous O(p2) one.

Ξ(1690)− production in the K−p→K+K−Λ reaction process near threshold

We investigate $\Xi(1690)^-$ production from the $K^-p\to K^+K^-\Lambda$ reaction within the effective Lagrangian approach at the tree-level Born approximation. We consider the $s$- and $u$-channel $\Sigma/\Lambda$ ground states and resonances for the $\Xi$-pole contributions, in addition to the $s$-channel $\Lambda$, $u$-channel nucleon pole, and $t$-channel $K^-$-exchange for the $\phi$-pole contributions. The $\Xi$-pole includes $\Xi(1320)$, $\Xi(1535)$, $\Xi(1690)(J^p=1/2^-)$,and $\Xi(1820)(J^p=3/2^-)$. We calculate the Dalitz plot density of $(d^2\sigma/dM_{K^+K^-}dM_{K^-\Lambda}$ at 4.2 GeV$/c$) and the total cross sections for the $K^-p\to K^+K^-\Lambda$ reaction near the threshold. The calculation results are in good agreement with previously acquired experimental data. Using the parameters from the fit, we present the total and differential cross sections for the two-body $K^-p\to K^+\Xi(1690)^-$ reaction near the threshold. In our calculation, a strong enhancement at backward $K^+$ angles is predicted because of the dominant $u$-channel contribution. We also demonstrate that the Dalitz plot analysis for $p_{K^-}=1.915 -- 2.065$ GeV/c enables us to access direct information regarding $\Xi(1690)^-$ production, which can be tested by future $K^-$ beam experiments. The possible spin-parity states of $\Xi(1690)^-$ are briefly discussed as well.

Photoproduction of f0(980) and f0(1500) resonances off a proton target

We study the $\gamma p \to p f_0$ [$f_0(980)$ and $f_0(1500)$] reaction close to threshold within an effective Lagrangian approach. The production process is described by $s$-channel nucleon pole or $t$-channel $\rho$ and $\omega$ exchange. The $K^0 \bar{K}^0$ invariant mass distributions of the $\gamma p\to f_0(980)p \to K^0 \bar{K}^0$ and $\gamma p\to f_0(1500)p \to K^0 \bar{K}^0 p$ reactions are investigated, where the two kaons have been separated in $S$ wave decaying from $f_0(980)$ and $f_0(1500)$. It is shown that the $s$-channel process is favored for the production of $f_0(980)$, while for the $f_0(1500)$ production, the experimental measurements can be described quite well by the $t$-channel process. It is expected that the theoretical results can be tested by further experiments at CLAS.

Polarization of Nucleons in the Deuteron Stripping Reaction on Nuclei

A general analytical expression has been obtained in the diffraction approximation for the polarization of nucleons arising in the deuteron stripping reaction on nuclei at intermediate energies of the incident particles. A tabulated density distribution of the target nucleus and a realistic wave function of the deuteron with correct asymptotic limits at large internucleon distances were used in the calculations. The nucleon-nucleus phase shifts were calculated in the Glauber formalism using the double folding potential. The calculated angular dependencies for the vector analyzing power $A_{y}$ of the reaction $^{3}\text{He}(\vec{d},p)^{4}\text{He}$ are found to be in satisfactory agreement with the corresponding experimental data.

Quark-antiquark asymmetry of helicity distributions in the nucleon sea

We study the helicity distributions of light flavor quark-antiquark ($q \bar{q}$) pairs in the nucleon sea. The valence quarks are handled by adopting the light-cone SU(6) quark-spectator-diquark model and the sea $q \bar{q}$ pairs are treated from statistical consideration by introducing the helicity suppression factors $l_q(x)$ and $\bar l_q(x)$ to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while $\Delta l_q(x)=l_q(x)-\bar l_q(x)$ represents a combined effect of helicity contribution due to sea $q \bar{q}$ pairs. From fitting the nucleon polarization asymmetries $A^N_1$ in inclusive deep inelastic scattering processes and the single-spin asymmetries $A^{W^{\pm}}_L$ in Drell-Yan type processes, we find a significant asymmetry between the quark and antiquark helicity distributions of the nucleon sea. Therefore the quark-antiquark asymmetry of helicity distributions of nucleon sea $q \bar{q}$ pairs, i.e., $\Delta q_s(x) \neq \Delta \bar q_s(x)$, plays an important role for a comprehensive understanding of the nucleon spin content.

POLARIZATION PHENOMENA IN PROCESS e⁺+e⁻ → N+Ñ+γ

The emission of the hard photon from the initial state is considered. The nucleon polarization and the differential cross sections for some experimental conditions have been calculated. The case of the emission of the collinear (with respect to the direction of the electron beam momentum) photon is considered separately. The differential cross section, the nucleon polarization, the correlation coefficients for both polarized nucleons (provided the electron beam is unpolarized or longitudinally polarized), the transfer polarization from the longitudinally polarized electron beam to the nucleon have been calculated. The photon energy distribution for the reaction e⁺e⁻ → h₁h₂γ where h₁ and h₂ are some hadrons for the case of the collinear photon, emitted in the initial state, has been calculated. As h₁h₂ final state we considered some channels, namely: two spinless mesons (for example,π⁺π⁻K⁺K⁻), two spin–one particles (for example, ρ⁺ρ⁻d⁺d⁻), and the channels πa₁ (1260) and Δ(1232)N . The photon energy distributions are calculated in terms of the form factors of the γ* → h₁h₂ transition (γ* is the virtual photon).

Status of the NICA project at JINR

The NICA (Nuclotron-based Ion Collider fAcility) is the new international research facility under construction at the Joint Institute for Nuclear Research (JINR) in Dubna. The main targets of the facility are the following: 1) study of hot and dense baryonic matter at the energy range of the maximum baryonic density; 2) investigation of nucleon spin structure and polarization phenomena; 3) development of JINR accelerator facility for high energy physics research based on the new collider of relativistic ions from protons to gold and polarized protons and deuterons as well with the maximum collision energy of √SNN ~11GeV (Au79+ +Au79+) and ~ 27 GeV (p+p). Two collider detector setups MPD and SPD are foreseen. The setup BM@N (Baryonic Matter at Nuclotron) is commissioned for data taken at the existing Nuclotron beam fixed target area. The MPD construction is in progress whereas the SPD is still at the beginning design stage. An average luminosity of the collider is expected at the level of 1027 cm-2 s-1 for Au79+ and 1032 cm-2 s-1 for polarized protons at 27 GeV. The status of NICA design and construction work is briefly described below.

Production of the charmoniumlike state Y(4220) through the pp¯→Y(4220)π0 reaction

The $Y(4220)$ production in the process of $p\bar{p} \to Y(4220)\pi^0$ is studied within the effective Lagrangian approach. We first study the $e^+e^-\to Y(4220) \to p\bar{p}\pi^0$ reaction at center-of-mass energy $4.258$ GeV with the assumption that the $Y(4220)$ is a $\psi(4S)$ state. We show that the inclusion of nucleon and nucleon resonance leads to a quite good description of the experimental data of $\pi^0 p$ and $\pi^0 \bar{p}$ invariant mass distributions. Then, the total and angular distributions of the $p\bar{p} \to Y(4220)\pi^0$ reaction are investigated. It is shown that the nucleon pole is dominant but the contributions from excited nucleon resonances are non-negligible. The $p\bar{p} \to Y(4220)\pi^0$ reaction is useful for studying the property of $Y(4220)$ and our calculated results may be tested at the forthcoming $\overline{\mbox{P}}$ANDA experiments.

Sivers effect in single spin asymmetry based on the covariant parton model

Sivers effect is describing the correlation between the transverse polarization of nucleon and the transverse momentum, [Formula: see text], of its unpolarized constituent partons. This effect is an outstanding subject and in this regard, a great deal in recent years has been considered from experimental and phenomenological points of view. It also plays an essential role to extend our understanding from nucleon structure. Semi-inclusive DIS (SIDIS) process provides us an opportunity to access to Sivers function which is dependent on transverse momentum of partons. In this paper, for the first time the covariant parton model is used to deliver us the [Formula: see text] and [Formula: see text] dependence part of Sivers function. Based on this model, this combinatory dependence is arising out from the HERAPDF parametrization group. In this paper the other required parametrized functions in Sivers function is also changed with respect to Ref. 1. The unknown parameters which exist in Sivers function can be extracted, doing a global fit over the recent available experimental data, including HERMES, COMPASS and JLAB collaborations for the single spin asymmetry (SSA) in [Formula: see text] and [Formula: see text] meson production as well as kaon production to constrain the evolved strange quark. This is done, considering advanced mathematical manipulations to overcome the difficulties which exist to compute the required multiple integrals and finally employing the CERN MINIUTE program to do a global fit. Our results for SSA are in good agreement with the available experimental data. For more confirmation a comparison between our results and the ones from Ref. 2 is also done.

Four-body calculation of H2(d,p)H3 and H2(d,n)He3 reactions above breakup threshold

Nucleon transfer reactions in deuteron-deuteron collisions at energies above the three- and four-body breakup threshold are described using exact four-body equations for transition operators that are solved in the momentum-space framework. Differential cross sections, analyzing powers, polarizations, and spin transfer coefficients are obtained using realistic two-nucleon potentials and including the Coulomb repulsion between protons. Overall good agreement between predictions and experimental data is found. Most remarkable discrepancies are seen around the minima of the differential cross section at higher energies and in the outgoing nucleon polarization at lower energies.

Sivers effect and the spin asymmetry in meson production

The transverse polarization of nucleon and the transverse momentum of its unpolarized constituent partons are correlated with each other. This can be fairly described by the Sivers effect. In recent years this effect is cynosure and produces privilege aspects from both theoretical and experimental views. To extend our knowledge from nucleon structure, this effect has an outstanding role. One way to obtain the Sivers function which is essentially depends on transverse momentum of partons, is to employ the Semi inclusive DIS (SIDIS) process. In this article a new parametrization for the concerned piece of Sivers function is used which is different with respect to what has been done in [M. Anselmino et al., Phys. Rev. D 72 (2005) 094007]. The required collinear PDF is getting from HERAPDF parametrization group. The unknown parameters which exist in Sivers function can be extracted, fitting the available experimental data for single spin asymmetry (SSA) in π+π− production. The final analytical results for SSA are in good agreement with the HERMES experimental data.

The Production of Neutral N∗(11052) Resonance with Hidden Beauty from π-p Scattering

We investigate the discovery potential of the predicted neutral hidden beauty N∗(11052) resonance through π-p scattering within an effective Lagrangian approach. Two reactions π-p→K-Σ+ and π-p→ηbn are studied in this work, with nucleon pole exchange as the background. It is found that the contributions of the N∗(11052) resonance give clear peak structures in the magnitude of 1 μb near the threshold of N∗(11052) in the total cross sections. The numerical results indicate that the center of mass energy W≃11–11.1 GeV would be the best energy window for searching the N∗(11052) resonance, where the N∗(11052) signal can be easily distinguished from the background. The COMPASS experiment at CERN’s Super Proton Synchrotron (SPS) with pion beam of ≃280 GeV will be an ideal platform for searching the super-heavy resonance with hidden beauty, which is promising for testing the theoretical results.