Meson Exchange Research Articles

Neutrino emission in cold neutron stars: Bremsstrahlung and modified urca rates reexamined

Neutrino emission in cold neutron stars is dominated by the modified urca (murca) process and nucleon-nucleon bremsstrahlung. The standard emission rates were provided by Friman and Maxwell in 1979, effectively based on a chiral Lagrangian framework with pion and rho meson exchange, supplemented by Landau parameters to describe short-range interactions. We reevaluate these rates withinthe same framework, correcting several errors and removingunnecessary simplifications, notably the triangular approximation — where the Fermi momenta of protons and leptons negligible compared to that of neutrons — in MURCA, and quantify their importance.The impact of rho meson exchange, previously argued to cancel with interference effects, is actually quite relevant. Altogether, the cooling rates are reduced by as much as a factor 2. We provide comprehensive analytical formulas encompassing all contributions, designed for straightforward numerical implementation. Our results are particularly relevant for studies of physics beyond the standard model, where the emission of new particles — such as axions — is typically computed within the same framework we adopt here.

Heavy exotic hadrons near thresholds: [formula omitted] and its partners

Recent accelerator experiments have reported unexpected states known as exotic hadrons, whose properties cannot be explained by the conventional picture. In 2022, the LHCb collaboration reported the doubly charmed tetraquark Tcc+ which is a genuine exotic states whose minimal quark content is ccūd̄. We consider the Tcc state as a DD∗ hadronic molecule. The one meson exchange potentials are employed as for the hadron interactions, and a bound state properties is investigated. Furthermore, the superflavor symmetry predicts a new pentaquark state D̄Ξcc from Tcc, which is obtained by replacing a D(∗) meson with a Ξcc(∗) baryon. We also study a possible existence of the D̄Ξcc bound state, and its properties.

Pion gravitational form factors in the QCD instanton vacuum. I

The pion form factors of the QCD energy-momentum tensor (EMT) are studied in the instanton liquid model (ILM) of the QCD vacuum. In this approach, the breaking of conformal symmetry is encoded in the form of stronger-than-Poisson fluctuations in the number of instantons. For the trace of the EMT, it is shown that the gluonic trace anomaly term contributes half the pion mass, with the other half coming from the quark-mass-dependent σ term. The Q2 dependence of the form factors is governed by glueball and scalar meson exchanges. For the EMT, the spin-0 (trace) and spin-2 (traceless rank-2 tensor) form factors are computed at next-to-leading order in the instanton density using effective quark operators. Relations between the gluon and quark contributions to the EMT form factors are derived. The form factors are also expressed in terms of the pion light-front wave functions in the ILM. The results at the low resolution scale of the inverse instanton size are evolved to higher scales using the renormalization group equation. The ILM results compare well with those of recent lattice QCD calculations. Published by the American Physical Society 2024

Exploration of the LHCb Pc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P_c$$\\end{document} states and possible resonances in a unitary coupled-channel model

We extend our previous study of the interactions of D¯(∗)Λc-D¯(∗)Σc(∗)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{D}^{(*)} \\Lambda _c - \\bar{D}^{(*)}\\Sigma _c^{(*)}$$\\end{document} within an analytic, unitary, coupled-channel approach by including the J/ψp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J/\\psi p$$\\end{document} channel and performing fits to the J/ψp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J/\\psi p$$\\end{document} invariant mass distributions in the Λb0→J/ψpK-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _b^0 \\rightarrow J/\\psi p K^-$$\\end{document} decay by the LHCb Collaboration. We take into account the contributions of t-channel pseudoscalar and vector meson exchanges and u-channel baryon exchanges in this work, and a series of bound states and resonances with different spin-parities are dynamically generated. According to the results, four states have a significant impact on the physical observables, with two having a spin-parity of 1/2-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1/2^-$$\\end{document} and the other two having 3/2-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3/2^-$$\\end{document}. These states can be associated with the LHCb hidden-charm pentaquarks. We further provide the coupling strength between each pole and different channels, which provides some insights on how to search for them in future experiments. Moreover, we also search for poles in higher partial waves up to J=7/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J=7/2$$\\end{document} and find indications for the existence of several states with larger widths.

Meson Exchange Currents in the Clothed-Particle Representation: Calculation of the Deuteron Magnetic Form Factor

Meson Exchange Currents in the Clothed-Particle Representation: Calculation of the Deuteron Magnetic Form Factor

Molecular pentaquarks with hidden charm and double strangeness

We analyze theoretically the coupled-channel meson-baryon interaction with global flavor c¯cssn and c¯csss, where mesons are pseudoscalars or vectors, and baryons have JP=1/2+ or 3/2+. The aim is to explore whether the nonlinear dynamics inherent in the unitarization process within coupled channels can dynamically generate double- and triple-strange pentaquark-type states (Pcss and Pcsss, respectively), for which there is no experimental evidence to date. We evaluate the s-wave scattering matrix by implementing unitarity in coupled channels, using potential kernels obtained from t-channel vector meson exchange. The required PPV and VVV vertices are obtained from Lagrangians derived through appropriate extensions of the local hidden gauge symmetry approach to the charm sector, while capitalizing on the symmetry of the spin and flavor wave function to evaluate the BBV vertex. We find four different poles in the double strange sector, some of them degenerate in spin. For the triple-strange channel, we find the meson-baryon interaction insufficient to generate a bound or resonance state through the unitary coupled-channel dynamics. Published by the American Physical Society 2024

A study of U-isotope ground state properties with Covariant Energy Density Functional

Abstract In this paper we have systematically analyzed the ground state of uranium isotopes from 225 to 240. In our calculations, we used the covariant energy density functional of density dependent meson exchange interaction (DD-ME2) with separable pairing interaction (TMR). Using the multiple deformation constraint, we calculate the potential energy surface (PES) of the uranium isotopes for
both even-even and even-odd nuclei with quadrupole and octupole deformation. By comparison with experimental data and Hartree-Fock-Bogoliubov calculations with Gogny D1S, the ground state of the uranium isotopes is always preferred to reflection-asymmetric deformation with our calculation.

D(s)− mesons semileptonic form factors in four-flavor holographic QCD

We investigate semileptonic form factors of a D(s) meson from a modified soft-wall 4-flavor holographic model. The model successfully reproduces the masses and decay constants of various mesons, including ρ, K*, D*, Ds*, a1, K1, f1, D1, Ds1, π, K, η, D, and Ds. Moreover, we study the semileptonic decay processes D+→(π,K,η)l+νl and Ds+→(K,η)l+νl, associated with the vector meson exchange, as well as D(s)+→Kl+νl, associated with the vector and axial vector meson exchange. The form factors f+(q2) for D→π and D(s)→K decays agree excellently with experimental and lattice data, outperforming other theoretical approaches. The f+(q2) form factor for D+→η is compatible with experimental data, while a slight discrepancy is observed for Ds+→η at large q2. Additionally, we predict the vector form factors V(q2) and A1(q2) for D→K and Ds→K decays, respectively. The results agree well with other approaches and lattice data at maximum recoil (q2=0). Published by the American Physical Society 2024

Correlation function for the Tbb state: Determination of the binding, scattering lengths, effective ranges, and molecular probabilities

We perform a study of the B*+B0,B*0B+ correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in I=0 with a binding energy of about 21 MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each B*+B0,B*0B+ component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision. Published by the American Physical Society 2024

Modeling Double Charge Exchange processes occurring in Heavy Ion Reactions

Heavy ion induced double charge exchange reactions are treated as an incoherent sequence of two reactions driven by the exchange of charged mesons (double single charge exchange, DSCE). The process is described within a fully quantum mechanical distorted wave 2-step theory (2nd order DWBA). The DSCE reaction amplitudes are shown to be separable into superpositions of distortion factors, accounting for initial and final state ion-ion elastic interactions, and nuclear matrix elements (NMEs). Explicit expressions of projectile and target NMEs are derived within the QRPA theory. Reduction schemes for the DSCE transition form factors are described, analizing their momentum structure within the closure approximation. Formal analogies between the NMEs involved in DSCE reactions and in double beta decays are also pointed out. Results, obtained within this theoretical framework, are illustrated for the reaction 40Ca (18O, 18Ne)40Ar at 15.3 AMeV and compared to the data measured at INFN-LNS by the NUMEN Collaboration. Furthermore, preliminary results for reactions involving heavier systems, such as 76Se (18O, 18Ne)76Ge, are shown.

Double strangeness molecular-type pentaquarks from coupled channel dynamics

Abstract. The existence of the nucleonic pentaquark resonances Pc (4312), Pc(4380), Pc(4440) and Pc(4457), established by the LHCb collaboration, has been one of the major discoveries in hadron physics in the latest years. This has been followed by the discovery of pentaquarks with one unit of strangeness, Pcs(4338) and Pcs(4457). Most of these states can be understood as hadronic molecules, namely bound states of a sufficiently attractive meson-baryon interaction. A widely used model, based on unitarized meson-baryon amplitudes obtained from vector meson exchange interactions derived from the hidden gauge formalism, which predicted these states prior to their discovery, is also predicting the existence of pentaquarks with double strangeness content, at around 4500 MeV and 4600 MeV [1]. Our model also suggest that one of these double strangeness pentaquarks can be seen in the weak decay of the Eb baryon into J/ΨϕΞ. A detailed study of this reaction is still under investigation, but in these proceedings we shall show some preliminary results, which confirm the possibility of observing traces of S=-2 pentaquark in invariant mass spectra of J/ΨΞ pairs produced in the decays Ξb → J/ΨϕΞ.

Coordinate-space calculation of QED corrections to the hadronic vacuum polarization contribution to (g − 2)μ with SU(3) flavor symmetry

Lattice QCD (LQCD) has proven to be an important tool in understanding the tension between the experimental value for the anomalous magnetic moment of the muon (g − 2)μ and its prediction from the standard model. The lattice provides a non-perturbative method for evaluating the hadronic contributions to (g − 2)μ, which contributes the largest amount to the uncertainty of the theoretical prediction. Among these the hadronic vacuum polarization aμHVP is the dominant contribution. In order to match the uncertainty of the experiment, lattice QCD needs to reach sub-percent precision. This requires the calculation of QED corrections to aμHVP, which are represented by additional Feynman diagrams. We present a lattice calculation of the UV-finite (2+2) diagram at the SU(3) flavor symmetric point and compare this to the pseudoscalar meson exchange model with a vector-meson dominance parametrization of the transition form factor.

HYPERNUCLEI AND NEUTRON STARS WITH CHARGE SYMMETRY BREAKING HYPERONIC POTENTIAL

In this paper, we propose a method of taking charge symmetry breaking (CSB) in hypernuclei and neutron stars into account within the framework of the Hartree-Fock approach with Skyrme interaction. The parameters of the contribution of Λ𝑁-Skyrme force leading to CSB are derived from the corresponding parameters of the hyperon-nucleon interaction in the meson exchange models. Based on the obtained parameters, the effect of charge symmetry breaking on the hyperon binding energy in carbon hypernuclei is analyzed. The effect of charge symmetry breaking on the characteristics of neutron stars, such as their maximum mass and radii, is considered for the first time.

Hidden strange Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{c}$$\\end{document}-like molecular states

With the chiral unitary approach, we evaluate the hidden strange Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{c}$$\\end{document}-like molecular states of bc¯ss¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$b{\\bar{c}}s{\\bar{s}}$$\\end{document} systems B¯sD¯s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{B}}_{s}{\\bar{D}}_{s}$$\\end{document}, B¯s∗D¯s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{B}}_{s}^{*}{\\bar{D}}_{s}$$\\end{document}, B¯sD¯s∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{B}}_{s}{\\bar{D}}_{s}^{*}$$\\end{document}, and B¯s∗D¯s∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{B}}_{s}^{*}{\\bar{D}}_{s}^{*}$$\\end{document} coupled to the non-strange channels. The S-wave scattering amplitudes are calculated based on the vector meson exchange, four pseudoscalar mesons contact interactions, and four vector mesons contact interactions obtained from the extended local hidden gauge approach. We find six states below the threshold of the most relevant channel. The binding energies of these states are around 1–10 MeV and the widths are around 0.2–0.7 MeV. Our research is a supplement to the mass spectra of Bc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{c}$$\\end{document}-like states, which may be useful for the experimental search in the future.

Analysis of the γNΔ and ΔNπ interactions for pion photoproduction

In this paper we analyze for the first time the γNΔ excitation vertex from the point of view of the dynamics of the Δ field, Ψμ. That is, we look for the value of the Z parameter, present in all contact invariant Δ-field interaction Lagrangians and usually regarded as redundant, and shift it to contact background non-Δ resonant amplitudes (in this sense it is called “redundant”) by imposing that the Ψ0 has no dynamics, instead of readjusting the background coupling constants. We do this within an unitarized model that comprises the Δ-direct amplitude plus background contributions including the Δ-cross term, nucleon Born and meson exchange ones, already implemented in previous works of πN scattering, photo-production and weak-π production. Also we analyze the use of a πNΔ decay vertex interaction containing both first (I1) and second (I2) order derivative contributions, as required by renormalization and power counting considerations, in building the γN→Δ→πN amplitude, in contrast with other works where only I1 or I2 is adopted. It is shown that the description of the γN→πN process, following these prescriptions, is improved. This is a first step: we plan to introduce final state interactions (FSI) in the future, following our previous work in which FCI were introduced using the I1 interaction alone.

Combined analysis on nature of X(3960), chi _{c0}(3930), and X_0(4140)

In this work, a study of the D_s{bar{D}}_s interaction and its couplings to the channels D{bar{D}} and J/psi phi is performed in a quasipotential Bethe–Salpeter equation approach. The D_s^+{D}_s^- and D^+{D}^- invariant mass spectra in three-body B decays are investigated in order to understand the origin of X(3960), chi _{c0}(3930), and X_0(4140) structures reported at LHCb. With the help of effective Lagrangians, the potential kernel can be constructed with meson exchanges, from which the scattering amplitudes can be obtained. By inserting it into the three-body decay processes, the invariant mass spectra can be calculated with an additional Breit–Wigner resonance introduced. The D_s^+{D}_s^- invariant mass spectrum in the decay process B^+rightarrow D^+_sD^-_sK^+ is well reproduced, and the X(3960) structure can be explained as a molecular state from the D_s{bar{D}}_s interaction. The state also exhibits as a peak in the D^+{D}^- invariant mass spectrum in the decay B^+rightarrow D^+D^-K^+, however, it is too narrow to reproduce the experimental structure around 3930 MeV. The dip around 4140 MeV in the D_s^+{D}_s^- invariant mass spectrum can be reproduced by the additional resonance with interference effect. However, a small bump instead of a dip is produced from the D_s{bar{D}}_s-J/psi phi coupled-channel effect, which suggests that the X_0(4140) cannot be interpreted as the D_s{bar{D}}_s-J/psi phi coupling in the current model.

Molecular states in systems* *Supported by the Doctoral Program of Tian Chi Foundation of Xinjiang Uyghur Autonomous Region of China (51052300506), the NSFC and the Deutsche Forschungsgemeinschaftn(DFG, German Research Foundation) through the funds provided to the Sino-German Collaborative Research Center TRR110 “Symmetries and the Emergence of Structure in QCD” (NSFC 12070131001, DFG Project-ID 196253076 - TRR 110), the NSFC (11835015,

The possible hadronic molecules in systems with , and are investigated with interactions described by light meson exchanges. By varying the cutoff in a phenomenologically reasonable range of GeV, we find ten near-threshold (bound or virtual) states in the single-channel case. After introducing the coupled-channel dynamics of ----- systems, these states, except those below the lowest channels in each sector, move into the complex energy plane and become resonances in the mass range GeV. Their spin-parities and nearby thresholds are , , , , , , , , , and . The impact of the -term in the one-boson-exchange model on these states is presented. Setting GeV as an illustrative value, it is found that is a stable bound state (becoming unstable if the coupling to lower channels is turned on), and are physical resonances in cases where the -term is included or excluded, and the other seven states are physical resonances or "virtual-state-like" poles near thresholds, depending on whether the -term is included. In addition, the partial decay widths of the physical resonances are provided. These double-charm hidden-strangeness pentaquark states, as the partners of the experimentally observed and states, can be searched for in the final states in the future.

Amplitudes of 3H, 3He Two-Particle Photo-Breakup in Non-Local QED Approach

Three-nucleon systems are essential for the investigation of many-body forces in nuclear physics. Well-grounded parametrization of their vertex functions with further application for the calculation of cross-sections in nonlocal QED approach provides the ground for investigation of the variety of multi-particle systems. In present paper we describe the process of parametrization of two-particle photo-breakup amplitudes of three-nucleon systems (3H, 3He). We provide the general description of the wave function construction for three-nucleon systems as well as the parametrization of their vertex functions accounting two- and three-nucleon interactions based on meson exchange current formalism. In our calculations we account first and second order one-pion exchange terms and the term related to the exchange of ω and ρ mesons. The three-nucleon interaction potential is given as a sum of attraction (two-pion exchange) term andappropriate repulsive part. Based on the variational ”Urbana + Model VII” amplitudes we provide the results for energy dependence of differential cross-section of 3He(γ, p)d reaction at proton angle θ = 90◦ from the threshold up to Eγ = 40 MeV and compare theoretical predictions with the available experimental data. The investigation is also provided for angular cross-section distributions at high photon energies (Eγ = 305 ± 5 MeV; 365 ± 5 MeV; 450 ± 10 MeV and 675 ± 50 MeV). Correct description of 3H, 3He photo-disintegration processes in a unified approach based on the gauge nature of the electromagnetic field implies application of this model for other multi-particle systems.

Recent results on the analysis of the 48Ti(18O, 20Ne)46Ca reaction at 275 MeV

The 18O+48Ti reaction was studied at the energy of 275 MeV for the first time under the NUMEN and NURE experimental campaigns with the aim of investigating the complete reaction network potentially involved in the 48Ti→48Ca double charge exchange transition. Understanding the degree of competition between successive nucleon transfer and double charge exchange reactions is crucial for the description of the meson exchange mechanism. Into this context, angular distribution measurements for one- and two-nucleon transfer reactions for the system 18O+48Ti were performed at the MAGNEX facility of INFN-LNS in Catania. An overview of the status of the analysis for the two-proton transfer reaction will be given.

Possible molecular states from interactions of charmed strange baryons* *Supported by the National Natural Science Foundation of China (11675228)

In this study, we investigate possible molecular states composed of two charmed strange baryons from the interaction and their hidden-charm hidden-strange partners from the interaction. With the aid of heavy quark chiral effective Lagrangians, the interactions of charmed strange baryons are described with light meson exchanges. The potential kernels are constructed and inserted into the quasipotential Bethe–Salpeter equation. The bound states are produced from most interactions considered, which suggests that strong attractions exist widely between the charmed strange baryons. Experimental search for these types of molecular states is suggested in future high-precision measurements.