Effective Lagrangian Approach Research Articles

Neutrino charge radius and electromagnetic dipole moments via scalar and vector leptoquarks

The one-loop contribution of scalar and vector leptoquarks (LQs) to the electromagnetic properties (NEPs) of massive Dirac neutrinos is presented via an effective Lagrangian approach. For the contribution of gauge LQs to the effective neutrino charge radius defined in Bernabeu et al. (Phys Rev Lett 89:101802, 2002. https://doi.org/10.1103/PhysRevLett.89.101802 [Erratum: Phys Rev Lett 89:229902 (2002)]), we considered a Yang–Mills scenario and used the background field method for the calculation. Analytical results for nonzero neutrino mass are presented, which can be useful to obtain the NEPs of heavy neutrinos, out of which approximate expressions are obtained for light neutrinos. For the numerical analysis we concentrate on the only renormalizable scalar and vector LQ representations that do not need extra symmetries to forbid tree-level proton decay. Constraints on the parameter space consistent with current experimental data are then discussed and it is found that the scalar R~2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\widetilde{R}}_2$$\\end{document} and the vector U1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$U_1$$\\end{document} representations could yield the largest LQ contributions to the NEPs: for LQ couplings to both left- and right handed neutrinos of the order of O(1) and a LQ mass of 1.5-2 TeV, the magnetic dipole moment (MDM) of a Dirac neutrino with a mass in the eV scale can be of the order of 10-9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-9}$$\\end{document}–10-10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-10}$$\\end{document}μB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu _B$$\\end{document}, whereas its neutrino electric dipole moment (EDM) can reach values as high as 10-20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-20}$$\\end{document}–10-19\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-19}$$\\end{document} ecm. On the other hand, the effective NCR can reach values up to 10-35\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-35}$$\\end{document} cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} even if LQs do not couple to right-handed neutrinos, in which case the EDM vanishes and the contribution to the MDM would be negligible.

Propagator Zeros and Lattice Chiral Gauge Theories.

Symmetric mass generation (SMG) has been advocated as a mechanism to render mirror fermions massive without symmetry breaking, ultimately aiming for the construction of lattice chiral gauge theories. It has been argued that in an SMG phase, the poles in the mirror fermion propagators are replaced by zeros. Using an effective Lagrangian approach, we investigate the role of propagator zeros when the gauge field is turned on, finding that they act as coupled ghost states. In four dimensions, a propagator zero makes an opposite-sign contribution to the one-loop beta function as compared to a normal fermion. In two dimensional Abelian theories, a propagator zero makes a negative contribution to the photon mass squared. In addition, propagator zeros generate the same anomaly as propagator poles. Thus, gauge invariance will always be maintained in an SMG phase, in fact, even if the target chiral gauge theory is anomalous, but unitarity of the gauge theory is lost.

Search for the anomalous quartic gauge couplings through Z γ production at e − e + colliders

Spontaneous breaking of the electroweak symmetry of the standard model (SM) sets the constraints on triple and quartic gauge couplings. Therefore, the measurement of multiboson production in e − e + collisions allows us to directly test the predictions of the SM and to indirectly probe new physics beyond the SM. In this paper, we focus on the process e − e + → e − Z γ e + with Z boson decaying into neutrinos to study the anomalous quartic gauge couplings using the effective Lagrangian approach at the compact linear collider (CLIC). We obtain the sensitivities on the anomalous f T,i /Λ4 (i = 0, 2, 5, 6, 7, 8, 9) couplings taking into account the systematic uncertainties of 3, 5% at 95% Confidence Level for the CLIC with TeV. Our results show that the sensitivities on some anomalous couplings without systematic errors are up to two orders of magnitude better than the current experimental limits. Considering a realistic systematic uncertainty such as 5% from possible experimental sources, the sensitivity of all anomalous quartic couplings becomes worse by about 10% compared to those without systematic uncertainty for the CLIC.

Analysis of data for γp → f 1(1285)p photoproduction* *Partially supported by the National Natural Science Foundation of China (12175240, 12147153, 11635009, 12305097, 12305137), the Fundamental Research Funds for the Central Universities, and the China Postdoctoral Science Foundation (2021M693141, 2021M693142)

The photoproduction of the meson off the proton target is investigated within an effective Lagrangian approach. The t-channel ρ- and ω-exchange diagrams, u-channel nucleon-exchange diagram, generalized contact term, and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data. Three different models, that is, the Feynman, Regge, and interpolated Regge models, are employed, where the t-channel reaction amplitudes are constructed in Feynman, Regge, and interpolated Regge types, respectively. The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data for . Nevertheless, in the Regge model, when any one of the , , , , , , , , and resonances is considered, the data can be well described. The resulting resonance parameters are consistent with those advocated in the Particle Data Group (PDG) review. Further analysis shows that, in the high-energy region, the peaks of differential cross sections at forward angles are dominated by the contributions from t-channel ρ- and ω-exchange diagrams, while in low-energy region, the s-channel pole diagrams of resonances also provide significant contributions to the cross sections.

Pionic transitions from Zc(4020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)$$\\end{document} to D wave charmonia

In the present work, we investigate the charmed meson loops contributions to the pionic transitions from Zc(4020)+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)^+$$\\end{document} to the D wave triplets charmonia by using an effective Lagrangian approach. Our estimations indicate that the predicted branching fraction of Zc(4020)+→π+ψ(13DJ),J=(1,2,3)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)^+ \\rightarrow \\pi ^+ \\psi (1^3D_J), \\ J=(1,2,3)$$\\end{document} are much smaller than the one of Zc(4020)+→π+hc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)^+ \\rightarrow \\pi ^+ h_c $$\\end{document}. Thus, searching Zc(4020)±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)^\\pm $$\\end{document} in the π±ψ(13DJ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm \\psi (1^3D_J) $$\\end{document} invariant mass distributions is impossible. Thus, the observed peak structures at 4.04 and 4.13 GeV in the π±ψ(3770)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm \\psi (3770)$$\\end{document} invariant mass distributions should not come from the contributions of Zc(4020)±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)^\\pm $$\\end{document}, and further precise experimental measurements of the e+e-→π+π-ψ(3770)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^+ e^- \\rightarrow \\pi ^+ \\pi ^- \\psi (3770)$$\\end{document} process are needed to decode the nature of these two peak structures.

Investigations on the light hadron decays of Zb(10610) and Zb(10650)

The light hadron decay processes of $Z_b(10610)/Z_b(10650)$ provide us a way to study their nature and decay mechanism. In this work, we evaluate the branching ratios of $Z_b(10610)/Z_b(10650) \to VP$ ($V$ and $P$ stand for light vector and pseudoscalar mesons, respectively) using an effective Lagrangian approach, in which the contributions of intermediate bottomed meson triangle loops are considered. In our calculations, the $Z_b(10610)$ and $Z_b(10650)$ are regarded as $B\bar{B}^*+c.c.$ and $B^*\bar{B}^*$ molecular states, respectively. The predicted branching ratios of $Z_b(10610)\rightarrow VP$ are about in the order of $10^{-2}$, while the branching ratios of $Z_b(10650)\rightarrow VP$ are in the order of $10^{-3}$. Furthermore, the dependence of these ratios between different decay modes of $Z_b(10610)/Z_b(10650)$ on the mixing $\eta-\eta^\prime$ angle $\theta_P$ is investigated, which may be a good quantity for the experiments. It is hoped that the calculations here could be tested by future experiments.

Effective-Lagrangian study of ψ′(J/ψ)→VP and the insights into the ρπ puzzle

Within the effective Lagrangian approach, we carry out a unified study of the $J/\psi (\psi')\to VP$, $J/\psi \to P\gamma$ and relevant radiative decays of light-flavor hadrons. Large amount of experimental data, including the various decay widths and electromagnetic form factors, are fitted to constrain the numerous hadron couplings. Relative strengths between the strong and electromagnetic interactions are revealed in the $J/\psi \to VP$ and $\psi' \to VP$ processes. The effect from the strong interaction is found to dominate in the $J/\psi \to \rho\pi$ decay, while the electromagnetic interaction turns out to be the dominant effect in $\psi' \to \rho\pi$ decay, which provides an explanation to the $\rho\pi$ puzzle. For the $J/\psi\to K^{*}\bar{K}+\bar{K}^{*}K$ and $\psi' \to K^{*}\bar{K}+\bar{K}^{*}K$, the former process is dominated by the strong interactions, and the effects from the electromagnetic parts are found to be comparable with those of strong interactions in the latter process. Different $SU(3)$ breaking effects from the electromagnetic parts appear in the charged and neutral channels for the $\psi' \to K^{*}\bar{K}+\bar{K}^{*}K$ processes explain the rather different ratios between $B(\psi'\to K^{*+}K^{-}+K^{*-}K^{+})/B(J/\psi\to K^{*+}K^{-}+K^{*-}K^{+})$ and $B(\psi'\to K^{*0}\bar{K}^{0}+\bar{K}^{*0}K^{0})/B(J/\psi\to K^{*0}\bar{K}^{0}+\bar{K}^{*0}K^{0})$.

Estimation of coupling constants for D-meson, charmed, and light baryons in effective Lagrangian approach and quark model

We estimate coupling constants for effective Lagrangians of D-meson, charmed, and light baryons from charmed baryon decay processes. First, we calculate decay widths for the processes $$\varLambda _{c} \rightarrow D^{*}N$$ , $$\varLambda _{c} \rightarrow DN$$ , $$\varSigma _{c} \rightarrow D N$$ , $$\varSigma _{c} \rightarrow D \varDelta $$ , and $$\varSigma _{c} \rightarrow D^{*} \varDelta $$ in effective Lagrangian method and quark model picture with $$^{3}P_{0}$$ model. By employing the coupling constants for $$D^{*} \varLambda _{c} N$$ interaction from several literatures, the strength parameter $$\lambda $$ for $$^{3}P_{0}$$ quark model is fixed in the decay process $$\varLambda _{c} \rightarrow D^{*}N$$ . Then, the coupling constants for the effective Lagrangians of $$D\varLambda _{c}N$$ , $$D\varSigma _{c}N$$ , $$D\varSigma _{c}\varDelta $$ , and $$D^{*}\varSigma _{c}\varDelta $$ interactions are estimated in the decay channels $$\varLambda _{c} \rightarrow DN$$ , $$\varSigma _{c} \rightarrow D N$$ , $$\varSigma _{c} \rightarrow D \varDelta $$ , and $$\varSigma _{c} \rightarrow D^{*} \varDelta $$ , respectively. Then, the coupling constants for $$D\varSigma _{c}N$$ , $$D^{*}\varSigma _{c}N$$ , and $$D^{*}\varSigma _{c}^{*}\varDelta $$ interactions are calculated from heavy-quark and large- $$N_c$$ sum rules. The coupling constants from this study will be useful for further studies of charm hadrons.

The π−p→a0−ηp reaction in an effective Lagrangian model

In this work, we perform a study of the ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{a}_{0}^{\ensuremath{-}}\ensuremath{\eta}p$ reaction within an effective Lagrangian approach and isobar model. In our model, we consider the excitation of the ${N}^{*}$ and ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances in the intermediate states and background terms. Based on our model, it is found that this reaction is dominated by the production of the $N(1535)$ in the near threshold region. And the contributions from other well-established ${N}^{*}$ or ${\mathrm{\ensuremath{\Delta}}}^{*}$ resonances only play minor roles. Besides, we discuss the possibility of verifying the existence of a narrow nucleon resonance $N(1685)$/$N(1700)$ proposed by some recent works in the present reaction. With adopting different quantum numbers, we find that it may contribute significantly in this reaction. Thus this reaction may provide a good platform to study the properties of nucleon resonances, e.g., $N(1535)$ and $N(1685)$/$N(1700)$, which couple strongly with the $\ensuremath{\eta}N$ channel. To compare with future experiments, the predictions of the total cross sections, the angular distributions, and invariant mass spectrums of final particles are also presented. Furthermore, the off-shell effects due to high-spin states are also discussed.

Production rates of Ds+Ds− and DD¯ molecules in B decays

Motivated by the recent discovery of a charmonium $X(3960)$ in $B$ decays by the LHCb Collaboration, the likely existence of two bound/virtual states (denoted by $ X_{s\bar{s}}$ and $ X_{q\bar{q}}$) below the $D_{s}^{+}D_{s}^{-}$ and $\bar{D}D$ mass thresholds has been re-examined recently. In this work, we employ the effective Lagrangian approach to calculate their production rates in $B$ decays utilizing triangle diagrams. Our results show that the production yields of $B^{+}\to X_{s\bar{s}} K^{+}$ and $B^{+}\to X_{q\bar{q}} K^{+}$ are of the order of $10^{-4}$, in agreement with the relevant experimental data, which indicates that, if the $D_{s}^{+}D_{s}^{-}$ and $\bar{D}D$ bound states indeed exist, they can be detected in $B$ decays. Moreover, we calculate the production rate of $B^{+}\to X(3960) K^{+}$ assuming that $X(3960)$ is a resonant state of $D_{s}^{+}D_{s}^{-}$ and find that it is also of the order of $10^{-4}$ but a bit smaller than that as a $D_s^+D_s^-$ bound state.

The production of singly charmed pentaquark {bar{c}} q qqq from bottom baryon

In the paper, we study the production of pentaquark bar{c}q qqq from singly bottom baryon. The tensor representations of pentaquark bar{c}q qqq are completed at first. Under the light quark symmetry analysis, we decompose the singly charmed pentaquarks into 6, 15 and 15' multiple states, and deduce the representations of these states. Then we construct the production Hamiltonian of the multiple states in proper order. For completeness, we systematically study the production channels of pentaquark states, including the possible production amplitudes and decay relations between different channels, concurrently, the widths of selected channels are worked out with the effective Lagrangian approach. Ultimately, we expect that the chosen channels will be fairly valuable supports for future search experiments.

Searching for X_{0}(2900) and X_{1}(2900) through the kaon induced reactions

Within an effective Lagrangian approach, a theoretical study of the K^{+}p rightarrow Sigma _{c}^{++}X_{0}(2900) and K^{+}p rightarrow Sigma _{c}^{++}X_{1}(2900) reactions is carried out to search for the exotic states X_{0}(2900) and X_{1}(2900). The production process is described by the t-channel D^{-} meson exchange. The numerical results show that the total cross sections may reach up to about 0.5 nb and 25 nb for the productions of X_0(2900) and X_1(2900) , respectively. The predicted differential cross sections are sensitive to the scattering angles and have strong forward enhancements. The cross sections for the K^{+}n rightarrow Lambda _{c}^{+}X_{0,1} are also calculated and found to be larger than that in K^{+}p collisions by more than one order of magnitude. The results are helpful to the possible experimental measurements with kaon beam.

Radiative decays of the neutral Zc(3900) and Zc(4020)

We study the radiative decays $Z_c(3900)/Z_c(4020) \to \gamma \chi_{cJ}(\gamma\chi_{cJ}^\prime)$ ($J=0, 1, 2$), with the assumption that the $Z_c(3900)$ and $Z_c(4020)$ couple strongly to $D\bar D^* +c.c$ and $D^*{\bar D}^*$ channel, respectively. By considering the contributions of intermediate charmed mesons triangle loops within an effective Lagrangian approach, it is shown that the calculated partial widths of $Z_c(3900) \to \gamma \chi_{cJ}$ are about a few hundreds keVs, while the obtained partial widths $Z_c(4020) \to \gamma \chi_{cJ}$ are about tens of keVs. The predicted partial widths of $Z_c(3900)\to\gamma\chi_{c0,1}^\prime$ are less than 1 keV, which mainly due to the very small phase space. For $Z_c(4020)\to\gamma\chi_{c0,2}^\prime$, the calculated partial widths are usually smaller than 1 keV. For the $Z_c(4020)\to\gamma\chi_{c1}^\prime$ process, the obtained partial widths can reach up to the order of 10 keV. Furthermore, the dependence of these ratios between different decay modes on the masses of $Z_c(3900)$ or $Z_c(4020)$ are also investigated, which may be a good quantity for the experiments. It is hoped that these calculations here could be tested by future experiments.

A study of the elastic πN scattering at finite baryon density

In this work, we investigate the elastic [Formula: see text] scattering for the [Formula: see text] channel dominated by the [Formula: see text] resonance at finite baryon density for the symmetric nuclear matter, employing the effective Lagrangian approach at the tree-level Born approximation. The quark-meson coupling (QMC) model is employed to describe the medium modifications for the in-medium baryon properties that are constructed at the quark level, such as the nucleon and [Formula: see text] masses, and [Formula: see text] full decay width. We first reproduce the experimental data of the cross-section in a vacuum and we then analyze various physical observables including the total and differential cross-sections and proton-spin asymmetry in a medium. It turns out that suppression and broadening on the peak of the in-medium cross-section becomes more significant at higher baryon density due to the increase of the decay width in the nuclear medium. Also, we find that beyond the [Formula: see text]-resonance region [Formula: see text] GeV, the elastic cross-section scattering is almost independent of the density. Results for the in-medium [Formula: see text] resonance will be relevant and useful for the relativistic heavy-ion collisions (RHICs).

Study of B, B_s mesons using heavy quark effective theory

Inspired by the lower statistical information in the bottom sector, in this paper, we calculate the masses and the strong decays of excited B and B_s mesons in the framework of heavy quark effective theory (HQET). Using an effective chiral Lagrangian approach based on heavy quark spin-flavor and light quark chiral symmetry, we explore the flavor independent parameters varDelta _F^{(c)} = varDelta _F^{(b)} and lambda _F^{(c)} = lambda _F^{(b)} to calculate the masses of experimentally unknown bottom mesons. Our predictions are consistent with the available experimental results and other theoretical studies. Their strong decay to the ground state bottom mesons plus light pseudoscalar mesons is calculated in terms of the square of the couplings g_H, g_S, g_T, g_X, g_Y, and g_R. The weighted average value of the couplings g_H, g_S and g_T is obtained in the charm sector (Phys. Rev. D 86: 054024, 2012) by fitting the calculated decay widths with experimental measurements, which will be used in the present study to analyze the strong decays of excited open bottom mesons. Moreover, the ratio of the decay rates is also predicted, which can be countered with future experimental data.

Elastic α−C12 scattering at low energies with the resonant 22+ and 23+ states of O16

The elastic $\alpha$-$^{12}$C scattering for $l=2$ at low energies is studied in an effective Lagrangian approach. We explicitly include two resonant $2_2^+$ and $2_3^+$ states of $^{16}$O in the scattering amplitudes and construct an $S$ matrix assuming that three amplitudes, the non-resonant part of the amplitude which has the sub-threshold $2_1^+$ state of $^{16}$O and those of the two resonant states, are represented by the summation of corresponding parts of the phase shift. Then, we fit the parameters in the $S$ matrix to the phase shift data by imposing three conditions at very low energies where the phase shift data are not available. By using the fitted parameters, we calculate the asymptotic normalization coefficients (ANC) of the $2_1^+$ state of $^{16}$O and find that the previously reported small and large values of the ANC can be reproduced depending on the imposed conditions, but we obtain large error bars for the large ANC values which are reported from the $\alpha$ transfer reactions.

Production of Z_{cs} in B and B_s decays

In the present work, we investigate the productions of Z_{cs}^+ in B^+ and B_s^0 decays, where Z_{cs}^+ is assigned as a D_s^{+} {bar{D}}^{*0} + D_s^{*+}{bar{D}}^0 molecular state. By using an effective Lagrangian approach, we evaluate the branching fractions of B^0_srightarrow K^- Z^+_{cs} and B^+rightarrow phi Z^{+}_{cs} via the triangle loop mechanism. The estimated branching fractions of B^0_srightarrow K^- Z^+_{cs} and B^+rightarrow phi Z^{+}_{cs} are of the order of 10^{-4} and 10^{-5}, respectively. The ratio of these two branching fractions is estimated to be about 4, which indicate that the B_s^0 rightarrow K^pm Z^mp _{cs} rightarrow K^+ K^- J/psi may be a better process of searching Z_{cs} and accessible for further experimental measurements of the Belle II and LHCb Collaborations.

Nucleon and Δ resonances in γn→K+Σ− photoproduction

The most recent data on beam asymmetries $\mathrm{\ensuremath{\Sigma}}$ and beam-target asymmetries $E$ from the CLAS Collaboration, together with the previous data on differential cross sections and beam asymmetries from the CLAS and LEPS Collaborations, for the $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ reaction are studied based on an effective Lagrangian approach in the tree-level Born approximation. The $t$-channel $K$ and ${K}^{*}(892)$ exchanges, the $u$-channel $\mathrm{\ensuremath{\Sigma}}$ exchange, the interaction current, and the exchanges of $N$, $\mathrm{\ensuremath{\Delta}}$, and their excited states in the $s$ channel are considered in constructing the reaction amplitudes to describe the available experimental data. The reaction mechanisms of $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ are analyzed, and the associated resonances' parameters are extracted. The numerical results show that the $\mathrm{\ensuremath{\Delta}}$ exchange and the $N(1710)1/{2}^{+}$, $N(1880)1/{2}^{+}$, $N(1900)3/{2}^{+}$, and $\mathrm{\ensuremath{\Delta}}(1920)3/{2}^{+}$ resonance exchanges in the $s$ channel dominate the $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{+}{\mathrm{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ reaction in the lower energy region, and the $t$-channel ${K}^{*}(892)$ exchange plays a crucial role at forward angles in the higher energy region.

The effect of hidden-charm strange pentaquarks Pcs on the K− p → J/ψ Λ reaction

We present a recent investigation on the production of Pcs (4459) in the K− p → J/ψΛ reaction, using both the effective Lagrangian and Regge approaches. We assume six different spin and parity assignments, i.e., 1/2± , 3/2± and 5/2± to the newly found Pcs. The total and differential cross sections for the K− p → J/ψΛ reaction are calculated. We examine the dependence of the results on the different assignments of JP for Pcs.

Photoproduction in an effective Lagrangian approach * *Partially supported by the National Natural Science Foundation of China (12175240, 11475181, 11635009), the Fundamental Research Funds for the Central Universities, the China Postdoctoral Science Foundation (2021M693141, 2021M693142), and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (Y7292610K1)

A gauge-invariant model is constructed for the reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction. In addition to the t-channel K and exchanges, s-channel nucleon exchange, and interaction current, the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the s-channel exchange are required to describe the most recently measured total cross-section data for from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the reaction near the threshold as a result of gauge invariance. The t-channel K exchange contributes significantly, while the contributions from the t-channel exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy GeV. The predictions of the differential cross sections for are presented and discussed, which can provide theoretical guidance for future experiments.