Among charmoniumlike $XYZ$ states, the $ψ(4220)$ and $ψ(4380)$ states have emerged as key candidates for exploring the charmonium spectrum. In this work, we propose a $4S$-$3D$ charmonium mixing scheme for the $ψ(4220)$ and $ψ(4380)$, induced by coupled-channel effects. By constructing a coupled-channel model, we identify the dynamical mechanism responsible for the large mixing angle observed in previous studies, which cannot be explained by conventional potential models alone. Our analysis reveals that the $DD_1$ channel significantly influences the lower state ($ψ(4220)$), while the $D^*D_1$ channel primarily affects the higher state ($ψ(4380)$). Furthermore, we investigate the two-body Okubo-Zweig-Iizuka (OZI)-allowed strong decay behaviors of these states, providing insights into their total widths. This study not only supports the $4S$-$3D$ mixing scheme but also offers a deeper understanding of the role of coupled channels in shaping the charmonium spectrum above 4 GeV. Our results align with experimental observations and provide a framework for interpreting future data on charmonium states.
The mechanism of channel coupling via decay products is used to study energy shifts, level mixing as well as the possibility of new near-threshold resonances in $c\bar c, b\bar b$ systems. The Weinberg eigenvalue method is formulated in the multichannel problems, which allows to describe coupled-channel resonances and wave functions in a unitary way, and to predict new states due to channel coupling. Realistic wave functions for all single-channel states and decay matrix elements computed earlier are exploited, and no new fitting parameters are involved. Examples of level shifts, widths and mi…
The measurement of possible Higgs sector CP-violation in the tau decay channels at the LHC is investigated. A CP-violating effect would manifest itself in these decay modes in characteristic spin-spin correlations of the tau lepton pairs which can be accessed using the momenta and impact parameters of the charged tau decay particles. We examine a CP-sensitive observable for a 125 GeV Higgs boson resonance in the gluon fusion channel at the LHC. Furthermore, we consider the distribution of this observable for the irreducible Drell-Yan background. By splitting these events into two categories we…
The mass spectrum and the two-body open-charm decays of the $J^{PC}=1^{--}$ charmonium states are studied with the coupled-channel effects taken into account. The coupled-channel-induced mixing effects among the excited vector charmonia are studied. Based on our calculations of the masses and the decay widths, we find that the tension between the observed properties of $Y(4260)/Y(4360)$ and their conventional charmonia interpretations could be softened.
Sensitivity of a neutrino factory to various mixing angles in a scheme with one sterile neutrino is studied using $ν_e\toν_μ$, $ν_μ\toν_μ$, $ν_e\toν_τ$ and $ν_μ\toν_τ$. While the "discovery-channel" $ν_μ\toν_τ$ is neither useful in the standard three flavor scheme nor very powerful in the sensitivity study of sterile neutrino mixings, this channel is important to check unitarity and to probe the new CP phase in the scheme beyond the standard neutrino mixing framework.
The usefulness of the $B_s^0 \to D_s^-a_1^+, D_s^- \to ϕπ^- \to K^+K^-π^-, a_1^+ \to ρ^0 π^+ \to π^+ π^- π^+$ decay chain is investigated for the $B_s$-reconstruction in the future ATLAS $B_s$-mixing experiment. It is shown that this decay channel is almost as suitable for this purpose as previously studied $B_s^0 \to D_s^-π^+$.
It is shown, using a track-level simulation, that the use of the $D_s^- \to K^{*0}K^-$ decay channel for $D_s^-$ reconstruction, in additioon with the previously studied $D_s^- \to ϕπ^-$ mode, enables two fold gain in the ATLAS $B_s^0$-mixing signal statistics through $B_s^0 \to D_s^-a_1$ $B_s^0$-decay channel. A new modification of the amplitude fit method is suggested for the $x_s$ determination. Some general aspects of the $B_s^0$-mixing phenomenon is illustrated by pictures of Casimir Malevich, Maurits Cornelis Escher and Salvador Dali.
It is shown that the hierarchical structure of the quark mass terms in the standard model suggests a new description of the flavor mixing. The latter is primarily a heavy quark mixing involving the t and b quarks, followed by a mixing exclusively in the u-channel or the d-channel. The complex phase describing CP violation arises only in the light quark sector. The Cabibbo angle is not a basic parameter, but results as a superposition of both the u-channel and d-channel mixing terms. The new description has a number of significant advantages in comparison with all descriptions previously used. …
We investigate how precisely the CP nature of the 125 GeV Higgs boson resonance h can be unraveled at the LHC in its decays to tau pairs. We use a method which allows to determine the scalar-pseudoscalar Higgs mixing angle in this decay mode. This mixing angle can be extracted from the distribution of a signed angle, which we analyze for the major charged-prong tau decays. For definiteness, we consider Higgs-boson production by gluon fusion at NLO QCD. We take into account also the irreducible background from Drell-Yan production at NLO QCD. We compute, for the signal and background reactions,…
The renormalization of a system of coupled scalars fields is analyzed. By introducing a momentum dependent mixing angle we diagonalize the inverse propagator matrix at any momentum $p^2$. The zeros of the inverse propagator matrix, \ie, the physical masses, are then calculated keeping the full momentum dependence of the self energies. The relation between this method and others previously published is studied. This idea is applied to the one-loop renormalization of the CP-even neutral Higgs sector of the Minimal Supersymmetric Model, considering top and bottom quarks and squarks in the loops. …
We investigate the potential (small) deviations from the unitarity of the mixing matrix that are expected to occur, because of mass splittings, in the Quantum Field Theory of non-degenerate coupled systems. We extend our previous analysis concerning mixing angles, which led to a precise determination of the Cabibbo angle, to the case of three generations of fermions. We show that the same condition for neutral currents of mass eigenstates, i.e. that universality of diagonal currents is violated with the same strength as the absence of non-diagonal ones, is satisfied: on one hand, by the three …
We introduce a momentum dependent mixing angle $α(p^2)$ which allow us to diagonalize at any external momentum $p$ the one-loop corrected inverse propagator matrix of two coupled scalar fields while keeping the full momentum dependence in the self energies. We compare this method with more traditional techniques applied to the diagonalization of coupled scalars at the one-loop level. This method is applied to the CP-even Higgs sector of the Minimal Supersymmetric Model, defining the momentum dependent mixing angle $α(p^2)$, and calculating the two CP-even Higgs masses and the mixing angle at t…
The new BES measurement on the two-body decays of J/psi and psi' into an axial-vector meson and a pseudoscalar meson is analyzed with the axial-K mixing including the one-photon annihilation contribution. A somewhat puzzling pattern of the K_1^+ K^- decay channels can be understood with no tight constraint on the mixing angle. The branching fractions of the K_1^0 K-bar^0 channels will be the cleanest source of information to determine the mixing angle from the 1^+ 0^- decays of J/psi and psi'.
The effect of scalar and vector meson mixing on the dilepton radiation from hot and dense hadronic matter is estimated in different isospin channels. In particular, we study the effect of $σ$-$ω$ and $ρ-a_0$ mixing and calculate the corresponding rates. Effects are found to be significant compared to standard $π$-$π$ and $K$-${\bar K}$ annihilations. While the mixing in the isoscalar channel mostly gives a contribution in the invariant mass range between the two-pion threshold and the $ω$ peak, the isovector channel mixing induces an additional peak just below that of the $ϕ$. Experimentally, …
From dispersion relation approach, a formalism that describes final state interaction among three particles in a coupled-channel system is presented in this work. Different representations of coupled-channel three-body formalism with only spinless particles in both initial and final states are derived.
We investigate the $D^0-\bar D^0$ mixing through the doubly Cabibbo suppressed (DCS) channel $D^0\to f_0(980)K^{*0}$ and its charge conjugate channel, in which the $K^{*0}$ meson is reconstructed in both $K^+π^-$ and $K_Sπ^0$ final state. Although the decay $D^0\to f_0(980)K^{*}$ has a small branching ratio, the final state mesons are relatively easy to identify. The $f_0(980)$ meson can be replaced by $π^+π^-$ in which $π^+π^-$ form an $S$-wave state, or a longitudinally polarized vector meson $ρ^0,ω$. All mixing parameters, including the mass difference and decay width difference, can be ext…
We discuss pure $q\bar{q}$ axial-vector mesons in the Tamm-Dancoff approximation of the Coulomb-gauge QCD model from NCSU. While recent studies have put emphasis in configuration mixing with open meson-meson channels, we here concentrate on the simpler closed-channel problem and follow the $1^+$ mixing through a wide range of quark masses. We also examine their radial excitations and discuss with them the concept of insensitivity to chiral symmetry breaking.
A dark sector containing a Higgs field and a dark photon coupled to visible photons via a small kinetic mixing is considered. The mass of the dark gauge boson becomes rescaled by the parameter involved in the kinetic mixing. We also calculate the total annihilation cross section for scalar Higgs interacting with an external field and show that exhibits Sommerfeld enhancement. The model can be extended to a $SU(3)\times SU(2)\times U(1)$ dark sector. The mass of the dark $Z$ boson increases due to the kinetic mixing.
Solutions to the atmospheric neutrino anomaly which smoothly interpolate between nu_mu -> nu_tau and nu_mu -> nu_s oscillations are studied. It is shown that, although the Super-Kamiokande data disfavor the pure nu_mu -> nu_s channel, one cannot exclude sizable amplitude for the nu_mu -> nu_s channel in addition to nu_mu -> nu_tau oscillations.
We consider the procedure of dressing of scalar and vector particles when there exists the off--diagonal loop connecting vector and scalar propagators. Instead of single Dyson equations for scalar and vector, we have in this case a system of three equations for coupled full propagators. Using the $π-a_1$ system as an example, we discuss the physical meaning of this effect and the renormalization procedure for coupled propagators. The considered effect of the unitary S~--~V mixing may exits also in the "Higgs boson~--~Z~(~W~)" system for extended electroweak models.
Data on open-charm channels collected by the Belle Collaboration are analysed simultaneously using a unitary approach based on a coupled-channel model in a wide energy range $\sqrt{s}=3.7÷4.7$ GeV. The resulting fit provides a remarkably good overall description of the line shapes in all studied channels. Parameters of 5 vector charmonium resonances are extracted from the fit.
A numerical analysis to the scalar form-factor in the $ππ$ and KK coupled--channel system is made by solving the coupled-channel dispersive integral equations, using the iteration method. The solutions are found not unique. Physical application to the $ππ$ central production in the $pp\to ppππ$ process is discussed based upon the numerical solutions we found.
The $ρρ$ scattering has been studied by two groups which both claimed a dynamical generated scalar meson, most likely to be $f_0(1370)$. Here we investigate the influence of coupled-channels of pseudoscalar mesons, i.e., $ππ$ and $\bar KK$, on this dynamical generated scalar state. With the coupled channel effect included, the pole and partial decay widths are found to be more close to PDG values for $f_0(1500)$.
Coupled-channel final-state-interaction effects for D and B weak decays into ππand K \bar{K} are discussed in a Regge framework. It is found that the inclusion of coupled-channel effects significantly affects the results obtained previously in a quasi-elastic approximation. It is also shown that in the isospin I=0 channel the inelastic final-state transitions (ππ)_{I=0} --> (K \bar{K})_{I=0} dramatically influence the phase of the B^0 --> (K \bar{K})_{I=0} amplitude.
Based on the Lippmann-Schwinger equation approach, a generalized Lüscher's formula in 1+1 dimensions for two particles scattering in both the elastic and coupled-channel cases in moving frames is derived. A 2D coupled-channel scattering lattice model is presented, the model represents a two-coupled-channel resonant scattering scalars system. The Monte Carlo simulation is performed on finite lattices and in various moving frames. The 2D generalized Lüscher's formula is used to extract the scattering amplitudes for the coupled-channel system from the discrete finite-volume spectrum.
We revisit the effect of the large stop mixing on the decay and production of the lightest SUSY Higgs at the LHC. We stress that whenever the inclusive 2-photon signature is substantially reduced, associated production, $Wh$ and $t\bar t h$, with the subsequent decay of the Higgs into photons is enhanced and becomes an even more important discovery channel. We also point out that these reductions in the inclusive channel do not occur for the smallest Higgs mass where the significance is known to be lowest. We show that in such scenarios the Higgs can be produced in the decay of the heaviest st…
We calculated the coupled channel photoproduction amplitudes of the scalar isovector resononace $a_0(980)$, which include the $πη$, $K^+K^-$ and $K^0\overline{K^0}$ intermediate states. Based on them we obtained the mass distribution in the $πη$ channel at photon energy $E_γ$=7 GeV, corresponding to energy accissible in new JLab experiments CLAS12 and GlueX. We also analyzed the shape of mass distribution as a function of the phase of the background amplitude.
The set of transition probabilities for a single neutrino emitted from a point source after passage through a turbulent supernova density profile have been found to be random variates drawn from parent distributions whose properties depend upon the stage of the explosion, the neutrino energy and mixing parameters, the observed channel, and the properties of the turbulence such as the amplitude C*. In this paper we examine the consequences of the recently measured mixing angle θ_13 upon the neutrino flavor transformation in supernova when passing through turbulence. We find the measurements of …
A low-energy non-unitary leptonic mixing matrix is a generic effect of a large class of theories accounting for neutrino masses. It is shown how the extra CP-odd phases of a general non-unitary matrix allow for sizeable CP-asymmetries in channels other than those dominant in the standard unitary case. The $ν_μ\to ν_τ$ channel turns out to be an excellent tool to further constrain moduli and phases. Furthermore, we clarify the relationship between our approach and the so-called "non-standard neutrino interactions" schemes: the sensitivities explored here apply as well to such constructions.
We study coupled channel effects upon isospin I=2 and I=0 $ππ$ S-wave interaction. With introduction of the $ππ\toρρ\toππ$ coupled channel box diagram contribution into $ππ$ amplitude in addition to $ρ$ and $f_2 (1270)$ exchange, we reproduce the $ππ$ I=2 S-wave and D-wave scattering phase shifts and inelasticities up to 2 GeV quite well in a K-matrix formalism. For I=0 case, the same $ππ\toρρ\toππ$ box diagram is found to give the largest contribution for the inelasticity among all possible coupled channels including $ππ\toωω\toππ$, $ππ\to K \bar{K}\toππ$. We also show why the broad $σ$ appea…
The $f_0(1710)$ was previously proposed to be dynamically generated state by interactions between vector mesons. We extend the study of $f_0(1710)$ by including its coupling to channels of pseudoscalar mesons within coupled-channel approach. The channels involved are $K^*\bar{K}^*,ρρ,ωω,ϕϕ, ωϕ,ππ,K\bar{K},ηη$. We show that the pole assigned to $f_0(1710)$ does not change much. Then we calculate the partial decay widths of $f_0(1710) \to K^*\bar{K}^* \to ππ,K\bar{K},ηη$ as the coupled channel dynamically generated state as well as assuming it to be pure $K^*\bar{K}^*$ molecule. In both cases th…
We study the $Λ(1520)$ resonance in a coupled channel approach involving the $πΣ(1385)$, $KΞ(1530)$, $\bar{K}N$ and $πΣ$ channels. Implementing unitarity in coupled channels, we make an analysis of the relative importance of the different mechanisms which contribute to the dynamical structure of this resonance. From experimental information on some partial wave amplitudes and constraints imposed by unitarity, we get a comprehensive description of the amplitudes and hence the couplings to the different channels. We test these amplitudes in different reactions like $K^-p\toΛππ$, $γp\to K^+K^-p$,…
We show that in see-saw models of neutrino mass a la SUSY SO(10), the observed large mixing in atmospheric neutrinos naturally leads to large b-s transitions. If the associated new CP phase turns out to be large, this SUSY contributions can drastically affect the CP violation in some of the B decay channels yielding the beta and gamma angles of the unitarity triangle. They can even produce sizeable CP asymmetries in some decay modes which are not CP violating in the standard model context. Hence the observed large neutrino mixing makes observations of low energy SUSY effect in some CP violatin…
We present a coupled channel partial wave analysis of nondiffractive S-wave pi+ pi- and K+ K- photoproduction focusing on the KK threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both pion-pion and kaon-antikaon channels. Our results indicate that these processes are experimentally measurable and valuable information on the f0(980) resonance structure can be obtained.
The resonance D*_sJ (2317) which is considered to be the 1^3P_0 state composed of charm and strange quarks has been discovered recently. The measured mass, which is about 160 MeV lower than the mass of the 1^3P_0 state obtained from the potential model calculation by Godfrey and Isgur, was considered surprisingly low and attracted a lot of theoretical investigations. We calculate the mass shift of the 1^3P_0 state by using the coupled channel e#ect. Our result shows that the coupled channel e#ect naturally explains the low mass of D*_sJ (2317).
In the hindered magnetic dipole transitions of heavy quarkonia, the coupled-channel effects originating from the coupling of quarkonia to a pair of heavy and anti-heavy mesons can play a dominant role. Here, we study the hindered magnetic dipole transitions between two $P$-wave bottomonia, $χ_b(n P)$ and $h_b(n^\prime P)$, with $n\neq n^\prime$. In these processes the coupled-channel effects are expected to lead to partial widths much larger than the quark model predictions. We estimate these partial widths which, however, are very sensitive to unknown coupling constants related to the vertice…
The decays eta, eta-prime -> pi^+ pi^- gamma are investigated within an approach that combines one-loop chiral perturbation theory with a coupled channel Bethe-Salpeter equation which satisfies unitarity constraints and generates vector mesons dynamically from composite states of two pseudoscalar mesons. It is furthermore shown that the inclusion of the eta-prime as a dynamical degree of freedom does not renormalize the Wess-Zumino-Witten term.
Based on the Hamiltonian formalism approach, a generalized Lüscher's formula for two particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice QCD computations.
We study the width of a two-body resonance in a coupled-channel system. We demonstrate how the width does not come only determined by the available phase space for its decay to the detection channel, but it greatly depends on the relative position of the mass of the resonance with respect to the masses of the coupled-channels generating the state. Our results are consistent with the experimental observation of narrow hadrons lying well above their lowest decay threshold.
We study the meson-baryon interaction with $J^P=1/2^-$ using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with $πN$, $ηN$, $KΛ$, $KΣ$, $ρN$ and $πΔ$ (d-wave). We fit the subtraction constants of each channel to the $S_{11}$ partial wave amplitude of the $πN$ scattering data extracted from experimental data. We find two poles that we associate to the $N^*(1535)$ and the $N^*(1650)$ resonances and show that the subtraction constants are all negative and of natural size. We calculate the branching ratios for the…
A local coupled-channels Kbar N-pi Sigma-pi Lambda potential is constructed, equivalently reproducing the scattering amplitude in chiral SU(3) dynamics. By analyzing the wave function of the Lambda(1405), we show the Kbar N dominance of the upper pole within the two-pole structure of the Lambda(1405). The resulting potential will be useful for investigating Kbar few-nucleon systems including their coupled channels.
The mixing of graviphotons and dark brane photons to the Standard Model hypercharge is analyzed in full generality, in weakly-coupled string theory. Both the direct mixing as well as effective terms that provide mixing after inclusion of SM corrections are estimated to lowest order. The results are compared with Effective Field Theory (EFT) couplings, originating in a hidden large-N theory coupled to the SM. The string theory mixing terms are typically subleading compared with the generic EFT couplings. The case where the hidden theory is a holographic theory is also analyzed, providing also s…
Spin-$\ffh$ resonance contributions in pion-nucleon scattering are investigated within the coupled channel $K$-matrix approach for c.m. energies up to $\sqrt s=$ 2 GeV. All previously studied $πN$, $2πN$, $ηN$, $K Λ$, $K Σ$, and $ωN$ final states are included. We find a significant improvement of $χ^2$ in almost all channels by inclusion of the spin-$\ffh$ states. The obtained coupling parameters are discussed.
The origin of the poles generated by chiral coupled-channel dynamics and applied to $\bar{K}N$ interactions is related to the nonzero diagonal couplings in the $πΣ$, $\bar{K}N$ and $KΞ$ channels. An evolution of the poles from the zero coupling limit and from a limit of restored SU(3) symmetry is discussed.
We demonstrate how an effective density of states can be derived from the S-matrix describing a coupled-channel system. Besides the locations of poles, the phase of the determinant of the S-matrix encodes essential details in characterizing the dynamics of resonant and non-resonant interactions. The density of states is computed for the two channel scattering problem ($ππ, K \bar{K}$, S-wave), and the influences from the various dynamical structures: poles, roots, branch cuts, and Riemann sheets, are examined.
A common feature of many string-motivated particle physics models is additional strongly coupled U(1)'s. In such sectors, electric and magnetic states have comparable mass, and integrating out modes also charged under U(1) hypercharge generically yields CP preserving electric kinetic mixing and CP violating magnetic kinetic mixing terms. Even though these extra sectors are strongly coupled, we show that in the limit where the extra sector has approximate N = 2 supersymmetry, we can use formal methods from Seiberg-Witten theory to compute these couplings. We also calculate various quantities of…
We review our recent efforts for determining resonance parameters associated with light-quark baryons ($N^*$, $Δ^*$, $Λ^*$, $Σ^*$) through comprehensive analyses of various meson production reactions off the nucleon within the ANL-Osaka dynamical coupled-channels approach.
We present the current status of a combined and simultaneous analysis of meson production reactions based on a dynamical coupled-channels (DCC) model, which is conducted at Excited Baryon Analysis Center (EBAC) of Jefferson Lab.
We give an overview of recent progress in the spectroscopic study of nucleon resonances within the dynamical coupled-channels analysis of meson-production reactions. The important role of multichannel reaction dynamics in understanding various properties of nucleon resonances is emphasized.
Dynamical coupled-channel approaches are a widely used tool in hadronic physics that allow to analyze different reactions and partial waves in a consistent way. In such approaches the basic interactions are derived within an effective Lagrangian framework and the resulting pseudo-potentials are then unitarized in a coupled-channel scattering equation. We propose a scheme that allows for a solution of the arising integral equation in discretized momentum space for periodic as well as twisted boundary conditions. This permits to study finite size effects as they appear in lattice QCD simulations…
We consider a unitary coupled channel model to describe the low energy proton-antiproton scattering and the lower Coulomb-like protonium states. The existence of deeper quasi-bound states of nuclear nature is found to be a consequence of the experimental data. The properties of these states as well as the protonium annihilation densities are described and the difference with respect to the optical models description are manifested.
Coupled-channel dynamics for scattering and production processes in partial-wave amplitudes is discussed from a perspective that emphasizes unitarity and analyticity. We elaborate on several methods that have driven to important results in hadron physics, either by themselves or in conjunction with effective field theory. We also develop and compare with the use of the Lippmann-Schwinger equation in near-threshold scattering. The final(initial)-state interactions are discussed in detail for the elastic and coupled-channel case. Emphasis has been put in the derivation and discussion of the meth…
