arXiv subjects

Stephen R. Cotanch

Publications and source records attributed to Stephen R. Cotanch.

At least 19 recordsLinked to original sources

arXiv2013

Coulomb gauge model for hidden charm tetraquarks

The spectrum of tetraquark states with hidden charm is studied within an effective QCD Coulomb gauge Hamiltonian approach. Of the four independent color schemes, two are investigated, the $(q\bar{c})_1(c\bar{q})_1$ singlet-singlet (molecule) and the $(qc)_3(\bar{q}\bar{c})_3$ triplet-triplet (diquark), for selected $J^{PC}$ states using a variational method. The predicted masses of triplet-triplet tetraquarks are roughly a GeV heavier than the singlet-singlet states. There is also an interesting flavor dependence with $(q\bar{q})_1(c\bar{c}_1)$ states about half a GeV lighter than $(q\bar{c})_1(\bar{q}c)_1$. The lightest $1^{++}$ and $1^{--}$ predictions are in agreement with the observed X(3872) and Y(4008) masses, respectively, suggesting they both have a $ωJ/ ψ$ rather than $D^*\bar D^*$ molecular type structure. This is consistent with observed $X$, $Y$ decays to $π^\pm J/ ψ$ and not $D^*\bar D^*$ .

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arXiv2010

Coulomb Gauge Model for Exotic Hadrons

Hadron structure advances provided by the Coulomb gauge model are summarized. Highlights include a realistic description of the vacuum and meson spectrum with chiral symmetry and dynamical flavor mixing, accurate hyperfine splittings for light and heavy systems, glueball and hybrid meson predictions in agreement with lattice QCD, and tetraquark results providing an understanding of the observed pi_1(1400) having unconventional quantum numbers.

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arXiv2010

Coulomb Gauge QCD and the Excited Hadron Spectrum

We discuss progress in understanding the light and heavy quark excited hadron spectrum from Coulomb gauge QCD. For light quark systems we highlight the insensitivity to spontaneous chiral symmetry breaking, which predicts Wigner parity-degeneracy in the highly excited hadron spectrum and allows the quark mass momentum dependence to be experimentally probed. For heavy quark meson decays we invoke the Franck-Condon principle, a consequence of small velocity changes for heavy quarks, to extract qualitative, but model independent, structure insight from the momentum distribution of the decay products.

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arXiv2008

Coulomb gauge approach to scalar hadrons

The Coulomb gauge model, involving an effective QCD Hamiltonian in the Coulomb gauge, is applied to scalar hadrons. Mass predictions are presented for both conventional q-qbar meson and q-qbar-q-qbar tetra-quark states. Mixing matrix elements between these states were also computed and diagonalized to provide a reasonable description of the scalar spectrum below 2 GeV.

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arXiv2008

Franck-Condon principle for heavy-quark hadron decays

The Franck-Condon principle governing molecular electronic transitions is utilized to study heavy-quark hadron decays. This provides a direct assessment of the wavefunction of the parent hadron if the momentum distribution of the open-flavor decay products is measured. Model-independent results include an experimental distinction between quarkonium and exotica (hybrids, tetraquarks...), an off-plane correlator signature for tetraquarks and a direct probe of the sea quark orbital wavefunction relevant in the discussion of 3S_1 or 3P_0 decay mechanisms.

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arXiv2008

Meson and tetra-quark mixing

The mixing between q-qbar meson and qqbar-qqbar tetra-quark states is examined within an effective QCD Coulomb gauge Hamiltonian model. Mixing matrix elements of the Hamiltonian are computed and then diagonalized yielding an improved prediction for the low-lying J^{PC} = 0^{+/- +}, 1^{--} isoscalar spectra. Mixing effects were found significant for the scalar hadrons but not for the 1^{--} states, which is consistent with the ideal mixing of vector mesons. A perturbative assessment of the exact QCD kernel is also reported.

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arXiv2007

Light 1-+ exotics: molecular resonances

Highlights in the search for nonconventional (non qqbar) meson states are the pi_1(1400) and pi_1(1600) exotic candidates. Should they exist, mounting theoretical arguments suggest that they are tetraquark molecular resonances excitable by meson rescattering. We report a new tetraquark calculation within a model field theory approximation to Quantum Chromodynamics in the Coulomb gauge supporting this conjecture. We also strengthen this claim by consistently contrasting results with exotic state predictions for hybrid (q qbar g) mesons within the same theoretical framework. Our findings confirm that molecular-like configurations involving two color singlets (a resonance, not a bound state) are clearly favored over hybrid or color-exotic tetraquark meson (q qbar q qbar atoms) formation. Finally, to assist needed further experimental searches we document a useful off-plane correlator for establishing the structure of these exotic systems along with similar, but anticipated much narrower, states that should exist in the charmonium and bottomonium spectra.

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arXiv2006

QCD Coulomb Gauge Approach to Exotic Hadrons

The Coulomb gauge Hamiltonian model is used to calculate masses for selected J^{PC} states consisting of exotic combinations of quarks and gluons: ggg glueballs (oddballs), q bar{q} g hybrid mesons and q bar{q} q bar{q} tetraquark systems. An odderon Regge trajectory is computed for the J^{--} glueballs with intercept much smaller than the pomeron, explaining its nonobservation. The lowest 1^{-+} hybrid meson mass is found to be just above 2.2 GeV while the lightest tetraquark state mass with these exotic quantum numbers is predicted around 1.4 GeV consistent with the observed pi(1400).

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arXiv2006

QCD Coulomb gauge approach to hybrid mesons

An effective Coulomb gauge Hamiltonian, H_eff, is used to calculate the light (u-ubar-g), strange (s-sbar-g) and charmed (c-cbar-g) hybrid meson spectra. For the same two parameter H_eff providing glueball masses consistent with lattice results and a good description of the observed u,d,s and c quark mesons, a large-scale variational treatment predicts the lightest hybrid has J^{PC}=0^{++} and mass 2100 MeV. The lightest exotic 1^{-+} state is just above 2200 MeV, near the upper limit of lattice and Flux Tube predictions. These theoretical formulations all indicate the observed 1^{-+} pi_1(1600) and, more clearly, pi_1(1400) are not hybrid states. The Coulomb gauge approach further predicts that in the strange and charmed sectors, respectively, the ground state hybrids have 1^{+-} with masses 2125 and 3830 MeV, while the first exotic 1^{-+} states are at 2395 and 4020 MeV. Finally, using our hybrid wavefunctions, dimensional counting rules and the Franck-Condon principle, novel experimental signatures are presented to assist light and heavy hybrid meson searches.

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arXiv2006

The BES f_0(1810): a new glueball candidate

We analyze the f_0(1810) state recently observed by the BES collaboration via radiative J/ψdecay to a resonant ϕωspectrum and confront it with DM2 data and glueball theory. The DM2 group only measured ωωdecays and reported a pseudoscalar but no scalar resonance in this mass region. A rescattering mechanism from the open flavored KKbar decay channel is considered to explain why the resonance is only seen in the flavor asymmetric ωϕbranch along with a discussion of positive C parity charmonia decays to strengthen the case for preferred open flavor glueball decays. We also calculate the total glueball decay width to be roughly 100 MeV, in agreement with the narrow, newly found f_0, and smaller than the expected estimate of 200-400 MeV. We conclude that this discovered scalar hadron is a solid glueball candidate and deserves further experimental investigation, especially in the K-Kbar channel. Finally we comment on other, but less likely, possible assignments for this state.

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arXiv2006

Soft gluons are heavy and rowdy

We study dynamical mass generation in pure Yang-Mills theory and report on a recently developed ansatz that exactly solves the tower of Dyson-Schwinger equations in Landau gauge at low Euclidean momentum, featuring enhanced gluon-gluon vertices, a finite ghost-gluon vertex in agreement with an old argument of Taylor, and an IR suppressed gluon propagator. This ansatz reinforces arguments in favor of the concept of a gluon mass gap at low momentum (although the minimum of the gluon's dispersion relation is not at zero momentum). As an application, we have computed the spectrum of oddballs, three-gluon glueballs with negative parity and C-parity. The three body problem is variationally solved employing the color density-density interaction of Coulomb gauge QCD with a static Cornell potential. Like their even glueball counterparts, oddballs fall on Regge trajectories with similar slope to the pomeron. However their intercept at t=0 is smaller than the omega Regge trajectory and therefore the odderon may only be visible in experimental searches (for example at BNL) with higher -t than conducted to date at DESY.

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arXiv2005

Many Body Methods and Effective Field Theory

In the framework of pionless nucleon-nucleon effective field theory we study different approximation schemes for the nuclear many body problem. We consider, in particular, ladder diagrams constructed from particle-particle, hole-hole, and particle-hole pairs. We focus on the problem of finding a suitable starting point for perturbative calculations near the unitary limit (k_Fa)->infinity and (k_Fr)-> 0, where k_F is the Fermi momentum, a is the scattering length and r is the effective range. We try to clarify the relationship between different classes of diagrams and the large g and large D approximations, where g is the fermion degeneracy and D is the number of space time dimensions. In the large D limit we find that the energy per particle in the strongly interacting system is 1/2 the result for free fermions.

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arXiv2005

Oddballs and a Low Odderon Intercept

We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature JPC (P=C= -1) glueball states (oddballs). The trajectory intercept is clearly smaller than the pomeron and even the omega trajectory's intercept which provides an explanation for the nonobservation of the odderon in high energy scattering data. To further support this result we compare to glueball lattice data and also perform calculations with an alternative model based upon an exact Hamiltonian diagonalization for three constituent gluons.

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arXiv2005

Tensor Glueball Photoproduction and Decay

Using vector meson dominance (VMD), tensor glueball photoproduction cross sections, asymmetries and widths are calculated. The predicted hadronic VV' decays are comparable for different vector meson (V = rho, omega and phi) channels with the omega phi width the largest but the radiative omega gamma and phi gamma decays are suppressed relative to rho gamma by over a factor of 2. This decay profile is distinct from typical meson branching rates and may be a useful glueball detection signature. Results are compared to a previous VMD scalar glueball study.

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arXiv2004

Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange

Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both S and D waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the pi-rho mass difference. A reasonable description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the pi mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The eta_b mass is predicted to be around 9400 MeV consistent with other theoretical expectations and above the unconfirmed 9300 MeV candidate. Finally, for comparison with lattice results, the J reliability parameter is also evaluated.

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arXiv2004

RPA Vector Meson Leptonic Widths

Recent J = 0 (para) baryonium interpretations of the BES narrow resonance data near the e^-e^+ -> p anti-p threshold suggests the existance of ortho baryonium. To assist future searches we study J = 1 states, especially vector meson leptonic decays, and report RPA calculations for both light and heavy mesons using a Coulomb-gauge QCD-inspired model. Since the phi(1880) is the only missing model state, other discovered J = 1 particles in this region are ortho baryonium candidates.

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arXiv2004

Goldberger-Treiman constraint criteria for hyperon coupling constants

The generalized Goldberger-Treiman relation is combined with the Dashen-Weinstein sum rule to provide a constraint equation between the g(KSigmaN) and g(KLambdaN) coupling constants. A comprehensive examination of the published phenomenological and theoretical hyperon couplings has yielded a much smaller set of values, spanning the intervals 0.80<=g(KSigmaN)/Sqrt(4Pi)<=2.72 and -3.90<=g(KLambdaN)/Sqrt(4Pi)<=-1.84, consistent with this criteria. The SU(3) and Goldberger-Treiman hyperon couplings satisfy the constraint along with predictions from a Taylor series extrapolation using the same momentum variation as exhibited by g(PiNN).

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arXiv2004

Glueball enhancements in p(gamma,VV)p through vector meson dominance

Double vector meson photoproduction, p(gamma, G -> VV)p, mediated by a scalar glueball G is investigated. Using vector meson dominance (VMD) and Regge/pomeron phenomenology, a measureable glueball enhancement is predicted in the invariant VV = rho rho and omega omega mass spectra. The scalar glueball is assumed to be the lightest physical state on the daughter pomeron trajectory governing diffractive vector meson photoproduction. In addition to cross sections, calculations for hadronic and electromagnetic glueball decays, G -> V V' (V,V'= rho, omega, phi, gamma), and gamma_v V -> G transition form factors are presented based upon flavor universality, VMD and phenomenological couplings from phi photoproduction analyses. The predicted glueball decay widths are similar to an independent theoretical study. A novel signature for glueball detection is also discussed.

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