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Thomas Gutsche

Publications and source records attributed to Thomas Gutsche.

At least 109 records · Page 6Linked to original sources

Lepton flavor violating decays of vector mesons

We estimate the rates of lepton flavor violating decays of the vector mesons $ρ, ω, ϕ\to e μ$. The theoretical tools are based on an effective Lagrangian approach without referring to any specific realization of the physics beyond the standard model responsible for lepton flavor violation (\Lfv). The effective lepton-vector meson couplings are extracted from the existing experimental bounds on the nuclear $μ^--e^-$ conversion. In particular, we derive an upper limit for the \Lfv branching ratio ${\rm Br}(ϕ\to e μ) \leq1.3 \times 10^{-21}$ which is much more stringent than the recent experimental result ${\rm Br}(ϕ\to e μ) < 2 \times 10^{-6}$ presented by the SND Collaboration. Very tiny limits on \Lfv decays of vector mesons derived in this letter make direct experimental observation of these processes unrealistic.

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Relativistic constituent quark model with infrared confinement

We refine the relativistic constituent quark model developed in our previous papers to include the confinement of quarks. It is done, first, by introducing the scale integration in the space of alpha-parameters, and, second, by cutting this scale integration on the upper limit which corresponds to an infrared cutoff. In this manner one removes all possible thresholds presented in the initial quark diagram. The cutoff parameter is taken to be the same for all physical processes. We adjust other model parameters by fitting the calculated quantities of the basic physical processes to available experimental data. As an application, we calculate the electromagnetic form factors of the pion and the transition form factors of the omega and eta Dalitz decays.

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Meson wave function from holographic approaches

We discuss the light-front wave function for the valence quark state of mesons using the AdS/CFT correspondence. We consider two kinds of wave functions obtained in different holographic Soft-Wall approaches

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Quasielastic rho0 electroproduction on the proton at intermediate energy: Role of scalar and pseudoscalar meson exchange

We present a detailed analysis of rho(0) electroproduction at intermediate energy for quasi-elastic knockout kinematics. The approach is based on an effective Lagrangian which generates exchanges of scalar, pseudoscalar, axial-vector and tensor mesons. The specific role of mesons with different values for J(PC) is analyzed. We show that the pi(0) exchange amplitude and its interference terms with eta(eta') and f1 exchanges dominate in the transverse part of the cross section sigmaT. The main role plays the pi(0) to rho(0) M1 spin transition when coupling the virtual photons to the nucleon. In contrast, the longitudinal cross section sigmaL is generated by a series of scalar meson exchanges. To extract the dominant term more detailed information on the inner structure of scalar mesons is required. It turns out that recent data of the CLAS Collaboration on sigmaL and sigmaT can be described with reasonable accuracy if one proposes the quarkonium structure for the heavy scalar mesons (M > 1.3 GeV). On this basis the differential cross sections dsigmaL/dt and dsigmaT/dt are calculated and compared with the latest CLAS data.

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Possible hadronic molecule structure of the Y(3940) and Y(4140)

In the present article we report on evidence for hadronic molecule structures in the charmonium sector. In particular we discuss the Y(3940) and the recently observed Y(4140) as heavy hadron molecule states with quantum numbers $J^{PC} = 0^{++}$ or $2^{++}$. The Y(3940) state is considered to be a superposition of $D^{\ast +}D^{\ast -}$ and $D^{\ast 0} \overline{D^{\ast 0}}$, while the Y(4140) is a bound state of $D_s^{\ast +}$ and $D_s^{\ast -}$ mesons. We give predictions for both the strong Y(3940) to J/psi omega, Y(4140) to J/psi phi and radiative Y(3940)/Y(4140) to gamma gamma decay widths in a phenomenological Lagrangian approach. The results for the strong hidden charm decay modes clearly support the molecular interpretation of the Y(3940) and Y(4140), while our estimates for the radiative decays provide a sensitive test for the underlying meson structure of the two Y mesons discussed here. The alternative assignment of $J^{PC} = 2^{++}$ is also tested, giving similar results for the strong decay widths.

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Hadron Molecules

We discuss a possible interpretation of the open charm mesons $D_{s0}^*(2317)$, $D_{s1}(2460)$ and the hidden charm mesons X(3872), Y(3940) and Y(4140) as hadron molecules. Using a phenomenological Lagrangian approach we review the strong and radiative decays of the $D_{s0}^* (2317)$ and $D_{s1}(2460)$ states. The X(3872) is assumed to consist dominantly of molecular hadronic components with an additional small admixture of a charmonium configuration. Determing the radiative ($γJ/ψ$ and $γψ(2s)$) and strong ($J/ψ2π$ and $ J/ψ3π$) decay modes we show that present experimental observation is consistent with the molecular structure assumption of the X(3872). Finally we give evidence for molecular interpretations of the Y(3940) and Y(4140) related to the observed strong decay modes $J/ψ+ ω$ or $J/ψ+ ϕ$, respectively.

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Strong two-body decays of the Lambdac(2940)+ in a hadronic molecule picture

The Lambdac(2940)+ baryon with possible quantum numbers J(P) = 1/2+ and 1/2- is studied as a molecular state composed of a nucleon and D* meson. We give predictions for the strong two-body decay channels Lambdac(2940)+ to p D0, Sigmac(++) pi(-) and Sigmac(0) pi(+) where the sum of partial widths is consistent with current data for the case of J(P) = 1/2(+). The case of J(P) = 1/2(-) is shown to be ruled out.

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X(3872) as a molecular DD* state in a potential model

We discuss the possibility that the X(3872) can be a hadronic DD* bound state in the framework of a potential model. The potential is generated by the exchange of pseudoscalar, scalar and vector mesons resulting from the Lagrangian of heavy hadron chiral perturbation theory. The hadronic bound state configuration contains charged and neutral DD* components, while orbital S- and D-waves are included. Isospin symmetry breaking effects are fully taken into account. We show that binding in the DD* system with J(PC)=1(++) already exists for a reasonable value of the meson-exchange regularization parameter of Lambda around 1.2 GeV. We also explore the possibility of hadronic BB* bound states and show that binding can be achieved in the isoscalar limit for J(PC)=1(++) or 1(+-).

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Hadronic molecule structure of the Y(3940) and Y(4140)

We report on further evidence that the Y(3940) and the recently observed Y(4140) are heavy hadron molecule states with quantum numbers J(PC) = 0(++). The Y(3940) state is considered to be a superposition of D*(+)D*(-) and D*(0) barD*(0), while the Y(4140) is a bound state of Ds*(+) and Ds*(-) mesons. For the first time we give predictions for the strong Y(3940) to Jpsi omega, Y(4140) to Jpsi phi and radiative Y(3940)/Y(4140) to gamma gamma decay widths in a phenomenological Lagrangian approach. Results for the strong Jpsi V (V = omega, phi) decays clearly support the molecular interpretation of the Y(3940) and Y(4140).

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Semileptonic decays of double heavy baryons in a relativistic constituent three-quark model

We study the semileptonic decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. We present complete results on transition form factors between double-heavy baryons for finite values of the heavy quark/baryon masses and in the heavy quark symmetry limit which is valid at and close to zero recoil. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit.

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eta(1405) in a chiral approach based on mixing of the pseudoscalar glueball with the first radial excitations of eta and eta'

The supernumerous eta(1405) is considered a strong candidate for the pseudoscalar glueball. In a phenomenological chiral approach, we consider a mixing scenario of bare pseudoscalar (n bar n) and (s bar s) quarkonia with the glueball. We study the decay properties and point out the peculiarities of this scenario in order to support the possible identification of the J(PC) = 0(-+) glueball.

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Meson wave function from holographic models

We consider the light-front wave function for the valence quark state of mesons using the AdS/CFT correspondence, as has been suggested by Brodsky and Teramond. Two kinds of wave functions, obtained in different holographic Soft-Wall models, are discussed.

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The Scalars f0(980) and a0(980) as Hadronic Molecules

We discuss the hadronic molecule issue in the light and heavy meson sector. Thereby we use the radiative decays of the scalars f0(980) and a0(980) to study its possible molecular K barK structure. Further on we extend our formalism to mesons with open charm and strangeness, Ds0*(2317) and Ds1(2460), whose hadronic molecule interpretation is analyzed in weak decays with f0(980) in the final state.

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X(3872) as a hadronic molecule and its decays to charmonium states and pions

The X(3872) with quantum numbers J(PC) = 1(++) is considered as a composite hadronic state comprised of the dominant molecular D(0) D*(0) component and other hadronic pairs - D(+-) D*(-+), Jpsi omega and Jpsi rho. Applying the compositeness condition we constrain the couplings of the X(3872) to its constituents. We calculate two- and three-body hadronic decays of the X(3872) to charmonium states chi(cJ) and pions using a phenomenological Lagrangian approach. Next using the estimated X-Jpsi-omega and and X-Jpsi-rho couplings we calculate the widths of X(3872) to Jpsi + h, where h = pi(+) pi(-), pi(+) pi(-) pi(0), pi(0) gamma and gamma. The obtained results for the decay pattern of the X(3872) in a molecular interpretation could be useful for running and planned experiments.

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Weak decays of heavy hadron molecules involving the f0(980)

We study weak decays of the charm- and bottom-strange mesons Ds0*(2317), Ds1(2460), Bs0*(5725) and Bs1(5778) with f0(980) in the final state by assuming a hadronic molecule interpretation for their structures. Since in the proposed framework the initial and final states are occupied by hadronic molecules, the predictions for observables can provide a sensitive tool to further test the hadronic molecule structure in future experiments.

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Strong decays of radially excited mesons in a chiral approach

We study radial excitations of pseudoscalar and vector (q bar q) mesons within a chiral approach. We derive a general form for a chiral Lagrangian describing processes involving excited pseudoscalar and vector mesons. The parameters of the chiral Lagrangian are fitted using data and previous calculations in the framework of the 3P0 model. Finite-width effects are examined and predictions for mesons previously not discussed are given. Available experimental data is analyzed whenever possible. Possible hints for exotic mesons and open interpretation-issues are discussed.

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Strong and radiative decays of the scalars f0(980) and a0(980) in a hadronic molecule approach

We analyze the electromagnetic and strong decay properties of the light scalars a0(980) and f0(980) within a hadronic molecule interpretation. Both scalars are discussed within a covariant and gauge invariant model which also allows for finite size effects due to their spatially extended structure in the K Kbar-bound state picture. Allowing for f0-a0 mixing we also study its influence on the radiative decays f0/a0 to gamma gamma, f0/a0 to gamma omega, and f0/a0 to gamma rho as well as the phi production of the f0 and a0. Furthermore, we apply our formalism to describe the strong f0 to pi pi and a0 to pi eta decay properties.

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